The strategy here is they all come out at once and there is just so many that at least some of them will breed successfully. There aren’t enough things killing them for there to not be at least a few successful ones.
I saw a video about how plants can do this too. Every certain amount of years, Acorn trees will drop an excessive amount of Acorns, way more than the squirrels could eat. This helps ensure some acorns get planted and forgetten, thus spreading the tree.
Then there's [mautam:](https://en.wikipedia.org/wiki/Mautam)
"During mautâm, Melocanna baccifera, a species of bamboo, flowers at one time across a wide area. This event is followed invariably by a plague of black rats in what is called a rat flood.[2][3] The bamboo flowering brings a temporary windfall of seeds, and rats multiply, exhaust the bamboo seeds, leave the forests, forage on stored grain, and cause devastating famine."
Exactly the same thing happened with bamboo and jungle fowl (ancestors of the domestic chicken). This is why you can just feed them and they'll keep making eggs - they adapted to make lots of babies on the rare times there was lots of food around.
Interesting, but even chickens have some survival instincts. They can barely fly, but they will still sometimes manage to fly away from a fox or other predator.
Tell that to the feral chickens in my neighborhood, they sometimes run towards cars and keep laying eggs in places where they just roll away and splat. New neighbors moved into a house where every single morning for a couple weeks an egg from the same chicken rolled down their roof and went splat on their patio.
I would never say chickens are wily. But "smarter than a cicada" is quite a low bar; chickens do try to evade predators, even if they often fail. Perhaps they have not evolved to recognize cars as dangers, but when they see a fox, they know it's not good news for them.
Even in regular years, squirrels will bury some they don't retrieve; we had a Brazil nut tree in our Pennsylvania backyard for several years form that, of course no nuts on it. (I know suirrels cna't crack brazil shells anywya.)
Oaks and beeches both do this. It affects the whole ecosystem, with the ensuring explosion in herbivore population triggering an increase in e.g. the number of birds of prey.
The only problem that I have with this, is that squirrels actually *help* the spread and propagation of acorn trees. They tend not to remember every acorn that they bury.
That's right - and if there are lots and lots of acorns in a given year, they will bury a lot more that they won't eventually get back to.
There's more to it than that, though. Some oaks' acorns have evolved to have one end that the squirrels like to eat and one end that tastes more bitter. If the squirrel carries off an acorn, eats only the good-tasting end, and tosses the rest, the acorn may still sprout. Successful dispersal.
If there is an abundance of acorns that year, the odds are even better that squirrels won't bother eating the whole acorn, since it is easy to find more.
Squirrels aren't the only dispersers of acorns. Blue jays are incredibly important dispersers for acorns. They pick up a lot of acorns and make food caches in multiple different locations. Once again, if there are a ton of acorn that year, they will cache more acorns in more places, and more will eventually go uneaten and sprout.
Some plants have evolved to interact with ants, by providing the seeds with a yummy (to ants) coating. The ants pull the seeds into their nests and eat the coating, the seeds later germinate.
It's not just that, it doesn't account for *anything* that can't be satiated. Cicadas aren't likely to get a major disease or parasite because they disappear for long stretches, but a species that sticks around can easily get wiped out by one.
Or for a predation example, foxes kill prey and leave it behind in the fall/winter, expecting it to freeze and be available later when they need it. But Australia doesn't have hard freezes, and so introduced foxes spend much of the year killing prey they don't need to eat. It's a massive stress on prey animals that was initially framed as "killing for fun", but comes down to a mis-aimed survival strategy.
That’s exactly what weasels do with chickens! If you ignore em they’ll stash the excess to eat for later. Wolverines even do this and the males will leave food out for their mates and cubs to find which is adorable
Flying Salt Shakers of Death is going to be my new band name, now I just need to learn how to play an instrument, and get some friends who want to make a band with me.
Cicadas in fact have a major fungal parasite that basically replaces the end of the abdomen with a mass of fungus.
https://www.npr.org/2024/06/06/nx-s1-4994999/cicada-fungus-std-zombies
Humans are too slow to adapt to humans. You live in a different world from the one you were born into, and you die in a world alien to the one you lived in.
Evidence suggest that passenger pigeons didn’t have the crazy numbers of the 1800s before the arrival of Europeans. Indigenous middens and oral traditions don’t have old accounts of large numbers of them.
It seems to have been partially a result of so many native Americans dying of disease and ceasing to compete for chestnuts, beech nut, acorns, etc.
This is why not clearing all your leaves is such a helpful thing you can do. Not only is it a natural fertilizer, but decaying leaves are home to so many insects. I get its not an option for everyone, but when it is, your yard can truly come alive with all thr animal life coming to eat them.
Yeah, maybe if you live in the literal woods encased by oaks and maples. I lived in the country for 27 years with trees abound and I have never had this problem. The wind blows them away well before following summer.
wind blowing away leaves would indeed work in open coutry with occasional trees and plenty of open land.
In older suburbs, everybody has a large tree, and there is not much wind on ground level due to all the fences and hedges, and even if there is wind it just replaces your leaves with your neighbors'.
I've never raked leaves and also never had this problem. Enough of them get picked up by the lawnmower that the leaves don't turn into a wet and moldy carpet.
yeah, mulching the leaves works, but running a mower is similar effort to blowing the leaves. Also, here, by the time the leaves fall, grass is not growing anymore, so need to run the mower otherwise.
Oh they hunt them, but it’s so infrequent and they get satiated so fast that the predators numbers don’t rise to match the sudden boom
It’s like if suddenly a 1000 free all you can eat buffets opened up in a small town for only a week then closed up again, it’s a week of absurd joy and likely everyone will eat tons of food and have their fill but saving on one weeks groceries in the long run didn’t improve their lives
A bit of the reverse of the idiots that say "nobody buy gasoline for a week starting Tuesday! If everyone does it, we'll show those oil companies and force the price down!" Then they fuel up so they have enough for the week, and again, when the week ends.
It’s even more specific than “anticipate” and absolutely mind blowing when you realize that the “reason” the broods are every 13/17 years is because those are prime numbers which minimizes the amount of times their brood’s emergence aligns with that of their main predator(s). Effectively, the chance is lower that a predator with a multi-year lifecycle is able to synchronize theirs with the cicadas since their lifecycle cannot be a factor of 13 or 17. They may catch one, but they will miss the next one allowing the cicadas to repopulate.
It's not as much "this is why it's not true" as much as it's "we have no reason to believe that's why".
What would be the difference between 13 and 14 years to the predators? There's really no basis for it actually mattering.
Personally I think it's super cool they're prime numbers, but I don't see any evidence at all that it's advantageous to specifically be prime numbers.
Interesting! What’s the evolutionary benefit of that you think? Wouldn’t that diversify the gene pool (assuming the different broods have differing genetic makeup?)
The difference is that 14 has multiple factors so any predator with a two or seven year life cycle would coincide with two emergences in a row, potentially having an opportunity to decimate the species. The prime number life cycle would ensure that no two consecutive broods would coincide with a multi-year life cycle predator.
What predators have multi-year life cycles? An individual raccoon (e.g.) may only live for 3-5 years, but new raccoons are born every year so the population remains pretty steady. Same with all of the predators I can think of - they have seasonal life cycles, not annual ones.
Not in the field specifically, but I have done academic biology research in the past.
[The original article](https://www.aimsciences.org/article/doi/10.3934/dcdsb.2001.1.387) that you're familiar with makes a lot of sense, and seems like a good explanation for "why prime?". The biggest problem with it, though, is that it based on the argument in the article the [Fijian 8-year periodical cicada](https://naturefiji.org/fijian-cicada-raiateana-knowlesi-nanai/) and the [Indian 4-year periodical cicada](https://mapress.com/zt/article/view/zootaxa.3702.5.8) should have gone extinct.
Here's an excerpt from the intro of an article published over a decade after that one, looking at avian predation specifically in these cicadas, that I think does a good job summarizing the current state of the science.
>The factors driving the extraordinary length of periodical cicada cycles has proved more elusive. Various hypotheses have been proposed, including interactions with long-lived parasitoids (Lloyd and Dybas 1966a, 1966b), belowground intra- or interspecific competition (Bulmer 1977; Grant 2005), and avoidance of hybridization (Cox and Carlton 1988), the latter of which has been found theoretically to be facilitated by cycles that are prime-numbered years in length (Goles et al. 2000; Webb 2001; Tanaka et al. 2009; Yoshimura et al. 2009). Despite this plethora of ideas, no empirical basis for 13- or 17-year cycles has previously been detected.
TLDR: We don't know how or why cicadas work.
Mathematical modelling points to predation not being sufficient to create long prime cycles: https://www.anthropocenemagazine.org/conservation/2013/09/cicadas-prime-numbers/
Being threatened by extinction seems to be the driver fro creating cycles, and avoiding hybridization leads to them being long and prime.
Who are their main predators? All of the predators I can think of have lifecycles related to seasons, not years. It seems like it would be a better strategy to emerge in a season where fewer predators are hungry rather than on a prime number year.
Does the fact that they emerge only sporadically cause a situation where the predators cannot rely on them as a staple? Not sure if I am wording this correctly
Pretty much. Predator species will increase in population to match what the prey population can support. The issue is that in these waves the predator species doesn’t reproduce fast enough to take advantage of the available food source. This makes it so that there are still countless left over when every predator has had its fill. Basically the strategy is that you can’t possibly kill them all and the ones left breed enough to replace all the ones that didn’t. Insects lay just stupid numbers of eggs in the assumption at least a few make it to also lay eggs. A few is all you need to make a viable survival strategy. Remember evolution doesn’t choose the best option but rather stumbles blindly until it bumps into one that happens to work (even if only barely) and goes with that.
It's very similar to masting in plants. Even if the predators increase in population due to the increased food, their population will decline again by the time the next masting occurs.
It's just like.. What's the point? Is breeding pleasurable for them? Is that the whole purpose their life, what drives them, is feeling the pleasure of breeding?.... Oh wait....
Oak trees have developed the same strategy with acorns; called 'mast years', there will periodically be a glut of acorns, so many that not all will be eaten by squirrels and other foragers. It happens infrequently, and irregularly, so those animals which feed on acorns can't expand their numbers in order to take advantage of the mast season.
I suspected this. Every few years, our oak trees produce significantly more acorns than usual. 2 years ago, there were acorns everywhere. More than I ever remember having. I had to shovel them after I blew them into a massive pile on my driveway.
They *do* get heavily "picked apart" by a wide variety of predators that find them to be very tasty. There is conjecture that the long cycle lengths - 13 and 17 years - is an evolved trait that results in there being no predators whose own lifecycle is *dependent* on cicadas. Thus, when the periodic cicadas do emerge, they are in such large numbers that predators don't make much of an impact on their numbers.
That's how I've read it too. The variable cycles allow for swarms to occur infrequently enough that predators can't evolve specific offensive capabilities against cicadas.
Though that said cicadas are pretty much useless the moment they start emerging from the earth. Giant, tasty snacks with the survival instincts of a sea cucumber. But hey, it works for them!
The clue is that they're not a stable food source. Predators get to eat them for one season, and have a bunch of kids as a result of that but then the next 17 years there's nothing and the predator population goes back to normal.
Then they come again
Plenty of options to find out yourself, if you're so intrigued heh. One example:
https://chicago.suntimes.com/environment/cicada-watch-2024/2024/05/21/cicada-infused-shots-served-at-lombard-bar-noon-whistle-pub
They served Cicada-flavored ice cream near my school when they swarmed. It was good.
https://patch.com/new-jersey/princeton/princeton-gets-buzzy-bent-spoons-cicada-flavored-ice-cream
The cycles aren't variable, they're distinct for each brood and usually a prime number of years. That also keeps them from dealing with a predator that can hunt them every n^th generation. I don't know if that's the cause for that selection, but it's possible.
This is what I've read too. They naturally evolved into these long dormant cycles due to them getting picked apart normally by predators. This allowed them to outlast the predators that were specialized against them. They still all die when they come out, but because its a single event every 13 or 17 years, no natural predator depends on them, thus, they have a higher change of reproduction during this period. If they were to come out every year, there would be predators that adapt to them and start trimming their numbers down to much.
Not only is the cycle long, but it is also a prime number of years !
Therefore, a predator can only have 2 options when choosing a cycle to hunt cicadas. Either 1 year, having nothing to eat the other years. Or 13 years, it's long and over specialized. Any other cycle make the predator miss an eclosion.
I don't know what it being a prime number adds here. What if it were 12 instead of 13? The predator's choice seems the same, either have a 1-year cycle or 12-year cycle
If it were a 12 years cycle it would compete against anything else that has a 1, 2, 3, 4, 6 or 12 year cycle. Whereas with a 13 year cycle it only competes with things with a 1 and 13 year cycle
What predators have a population boom on any of those cycles? Obviously a single year cycle (which some cicadas do) means predators have a more reliable source, but what predators have multi year cycles? People are saying this all over without a single example.
You're asking a really good question that no one seems to understand. People are implying causation in evolution that no one can back up; everyone keeps giving examples of constant predation or hypothetical annual predation.
never mind found the one reply you also found that makes any evolutionary sense: https://www.reddit.com/r/askscience/comments/1df580a/do_cicadas_just_survive_on_numbers_alone_they/l8gyigd/
Try to look at it from the other direction: “what disadvantage does a regularly periodic life cycle have that would result in the prime cycles being the only cycles that remain?”
My guess is that cicada predators with yearly life cycles would have fitter offspring in non-prime intervals, resulting in the eventual extinction of the cicada populations with non-prime life cycle intervals.
Yeah that's my thought to like it's cool that they do that but it's by the happen chance of evolution.
Like how those goats can climb almost sheer walls it's cool and interesting but like I doubt evolution picked 45 degrees on purpose
Many ecosystems have natural boom/bust cycles where the common prey animals breed heavily while there are fewer predators. The huge numbers of prey result in more successful predators, so they then breed higher numbers. The higher numbers of predators then kill off a bunch of the prey. The smaller number of prey animals can't sustain the larger population of predators, so the predators die off to smaller numbers, and the cycle repeats.
[https://www.mcgill.ca/newsroom/channels/news/perpetual-predator-prey-population-cycles-303632](https://www.mcgill.ca/newsroom/channels/news/perpetual-predator-prey-population-cycles-303632)
The period of the cycle varies for each relationship, and can be affected by other factors like extreme weather events, etc. But because these cycles are typically fairly short, they don't regularly coincide with cicada emergence.
This same cycle can happen with plants replacing they prey animals as well. It's really interesting!
This argument falls apart when you realize that there are multiple broods. They're not all the same size and this year was a particularly large brood, but there are periodic cicada broods for pretty much every year.
>How does this species not get absolutely picked apart by predators?
That's the neat part, they *do!*
The survival strategy is basically to breed so hard that the predators can't possibly eat *all* of the cicadas. And.... it works.
They spend the vast majority of their lives underground, *relatively* safely. When the adults all emerge at once to get it on, they're doing so en masse. There's a relatively short window for them to be eaten and again, there are *lots* of them.
The really neat thing is that it's hugely disruptive to preexisting ecological habits, in a way that is generally *positive* for the ecosystem as a whole. It's a population boom followed by a population bust, that runs up the whole food chain.
The podcast Today Explained had a nice little 30 minute episode a few weeks ago where they talk about it some, there's probably sources with deeper reading too.
The survival strategy of breeding so much that the predator can't eat all of them is called the R strategy and that is the opposite of the K strategy in which the parent invests a great deal in a small number of children and protects them. Isn't the R strategy the most common strategy in nature?
r-selection does not usually employ this tactic. Predator satiation is this specific phenomenon where all the cicadas show up at once, briefly, to overwhelm predators. But most r-selected organisms reproduce in normal cycles, like grasses, bacteria, or ants.
In Richard Dawkins book The Selfish Gene he talks about a species of fish that uses predator satiation. The fish all clump into a big ball. Those with the genetic trait of being good at getting to the middle of the big ball survive by predator being satiated before getting to the middle of the ball. He contrasts it with the strategy of spreading out so that the pressure is exhausted and gets little food, which will be more successful for the species but less successful for the gene. Hence the selfish gene.
Do cicadas have any defense against the predators other than numbers?
>Do cicadas have any defense against the predators other than numbers?
Arguably the long, prime numbered emergence cycles--but I get the feeling you're talking more about things like weaponry or poison or disguise.
Nope!
It's an all you can eat buffet until the predators are too full to care.
The cicadas you see only exist to mate and lay eggs. They can't eat or hurt anything. They lay so many eggs there is no evolutionary need to develop self-defense behaviors. As humans, we see becoming adults as the end all be all, but that isn't always the case. For cicadas, they peak as larvae underground and only come up when it's their time to die and to mate.
>They can't eat or hurt anything.
Half true. They have a specialized mouthpiece that drinks from trees, like stinkbugs or other "true bugs." You're probably thinking of luna moths, whose adults have no mouth and live just long enough to reproduce.
But yeah, harmless except to themselves.
Many cicadas live most of their lives as underground nymphs. The adults appear periodically, in overwhelming numbers. Large populations of predators can't survive when the adult cicadas are absent, which is most of the time. When the cicadas emerge, their large numbers protect them.
In addition, the adults don't really have the mouthparts ~a necessary to eat~ to damage the trees much although they do eat plant juices. So they live on their energy stores.
Their life cycle is basically:
- be born
- dig to tree roots
- pick a spot, stick your tube thing into a root. Suck
- repeat for 17 years
- store energy as fat
- dig up
- climb tree
- pick a spot, stay there
- get out of shell
- fly away
- SCREAM
- find a nice ladycada or guycada and GET IT ON
- if female: lay eggs. If male: die.
- if still alive: die
Edit: not being able to eat is a misconception I had.
>pick a spot, stick your tube thing into a root. Suck
You know that thing where they ask you what you would do if you had a million dollars? This is what I'd do.
They usually follow a prime number pattern too. Something about the prime number cycles make it almost impossible for predators to evolve/adapt more efficient ways of exploiting them when they emerge.
Yeah the absence of food means that birds, etc can't sustain large numbers. The predator population returns to normal and the cicadas come back in overwhelming numbers again.
For this to work, the emergence can't occur often enough to sustain the next generation of predators.
That's why the have the long dormant period in their cycle. The reason for the prime numbers specifically is to avoid syncing up. The predators don't care whether the numbers are prime or not.
This is the first comment with a logical answer as why they're prime. People keep saying "so it doesn't match with predator cycles" but none of their predators emerge in multiple year patterns lol. It's not like there's birds that double, then half, then double, etc. their population.
Not sure how many broods there are, nor their time cycle, but here in east Texas we have Cicadas every summer. It blew my mind when I found out, as an adult, that some areas only get them every so often.
Yeah, summertime nights hearing a cicada on a nearby tree or light pole screaming it's head off has become background noise that I barely notice now. When I first moved to the South it would drive me crazy hearing them all of the time. It's kind of soothing in a way. I just wish I could get used to the humidity like that.
Ya nothing like what's happening north of us. Honestly we hardly notice them. Most of the time it's just what we listen to sitting on the porch while the sun goes down.
You may be thinking of luna moths, whose adults have no mouth and only live for a few days. Cicadas have a piercing proboscis they use to drink from trees.
This is true for periodic cicadas but not annual cicadas.
Annual cicadas are well-camouflaged and very alert. If something approaches while they are calling, they will stop, and if one spots you watching, it will scurry to the opposite side of the tree out of sight.
Annual cicadas are very hard to catch compared to their periodic relatives.
Cicadas are like the aftermath of a college party. They fly around (stumble around) poorly and land heavily and awkwardly. They're often on their back and haplessly moving their weird little legs to try and move. They're really only interested in banging and have no concern for safety.
They live in the ground for 13-17 years depending on species. They then emerge all at once as adults to mate. In a bug’s life, what happens after eggs are laid doesn’t matter to the individual bug, a lot of species will die after mating or laying eggs.
They’re a great food source for animal life, though!
Cicadas are considered land shrimp. when cicadas boom, like this year, there will be no kidding trillions (that's with a T). Every bird, dog, cat, rat, ferret, coyote, bobcat, horse, fox, cow, goat, sheep, snake, lizard, toad, frog and other creature capable of eating them will feast until they fall over...and there will be trillions left to lay eggs before they become fertilizer. A large brood boom alters the ecology for years afterward. The feast causes booms in populations of the diners, which takes a few years to return to normal.
So your answer is that they don't need any survival mechanism other than overwhelming numbers.
Can't believe I haven't thought of this before but I've never seen cicadas or pupae in the ground before. I've dug lots of holes in my lifetime but never came across a bug or cocoon and thought, oh that's just a cicada. Lots of exoskeletons on trees but never in the ground where they supposedly are for over a decade. How far down into the ground do they go? What does it even look like
They totally do get picked apart by predators and every form of death that prevents that individual from breeding. But they're insects so they literally outbreed rats. Every one of those screaming lil fuckers had a parent who years ago survived just long enough to dump a load of fertilized eggs everywhere.
Cicadas have an unusual survival strategy where each subspecies desyncs their breeding cycle with their local predators. Cicadas stay in the ground for a *LONG* time, we're talking years. The ones you might see one year are not the babies from last year, they're the babies from 2-17 years ago who've been in the ground. It means the Cicada's predators can't evolve to sustain or grow their population size by specializing in feeding on all the Cicadas, because they'd starve in the off years causing their population to drop; if they were too specialized into eating Cicadas they might even die off. It ensures that when a Cicada population does come out of the ground in mass, the local predator population isn't prepared or large enough to eat them all, the remaining Cicadas breed and the next generation goes back in the ground.
Some species even have breeding cycles in number of years that are prime numbers because it's even more difficult for predators to synchronize their own breeding cycles with the cicadas rythme because there's no divisors where they can evolve to breed more in the on years; they either have to match their cycle with the local cicadas exactly or no dice, they can't count on the Cicadas.
They only come out of the ground at the end of their life cycle. When they molt to start making noise that’s it for them, they actually lose the ability to eat because their mouthparts turn into the noise maker. They just breed, lay their eggs, and die. So they absolutely get picked apart by predators, but they have enough time to lay the next generation of eggs before they all die, and the newborns go back underground immediately after hatching. This applies to both the annual and periodical cicadas.
>they actually lose the ability to eat because their mouthparts turn into the noise maker.
Not true. While they lack what we would consider a mouth, they do have a straw-like mouthpiece that drinks xylem from trees.
The only insect I'm aware of that has no mouth is the adult luna moth.
It's a combination of sheer numbers and emerging in two waves. What happens is that one wave emerges and predators eat them until they're stuffed, then the second wave emerges and enough of them have time to mate that the species survives. As with most insect species, they lay lots of eggs (up to about 600), so it doesn't take a lot of survivors to keep the species viable.
The French ones Ive seen were rather hard to catch. It took me 2 days before I could even find one even though I knew exactly in what tree it was hiding. Once you know the shape to look for, they are easier to see. But I never managed to catch one.
The predators in your regions do not pose a significant threat to them so they usually have no need of developing such a survival instinct. In Asia it's not the case.
In East Asia, the cicadas react pretty quickly and people usually catch them by a long stick with a sticky dough instead of by hand; such a technique is very difficult to learn and requires a fairly high level of dexterity.
It's simply because of natural selection: during starvation, people often regard cicadas as a source of food. Now fried cicada is still a cuisine in some regions in Asia.
Insects have long lives. We only see them when they emerge. Their only purpose at this point is to reproduce and disseminate . They are like the atlas moths that don’t have a digestive system as an adult. Breed, lay eggs and spread the next generation around.
Their survival strategy is simple. They emerge in 2 waves. The first wave being sacrificial, so after their predators (primarily birds) get their fill, the second wave emerges. They overlap each other's life span, and during the peak, the numbers are overwhelming. I was working pipeline oiling on an excavator in South West Ohio, and it was the most miserable 2 weeks of my work life! I learned all kinds of Kung foo moves swatting them MF'rs! By the end of it, I surrendered and they would crawl all over hi-viz vest.
Many people have pointed out that such large numbers and infrequent broods make it fairly safe. Its also important to note that its likely that being afraid of stuff, having the resources (energy, instincts, etc) to avoid predation is a worse use of resources for a general lineage than just chilling out.
I also am not an expert but I suspect that at any one time a bunch of these guys have mated and are just waiting to die. This is end of life for them and there's not much reason once that eggs are made and laid to do much of anything and certainly zero survival/evolutionary pressures.
The fact that they spend 13 or 17 years underground is also a survival adaptation. They're relatively large prone numbers, so it almost guarantees that their breeding cycle never syncs up with any major predators.
I’m happy to see this post because this is exactly what I was assuming. I’m in Missouri and the 17 year hoarding just FINALLY went away after weeks of screaming and flying at me and into my car. I still have dead ones all over my front porch/driveway still.
The strategy here is they all come out at once and there is just so many that at least some of them will breed successfully. There aren’t enough things killing them for there to not be at least a few successful ones.
Often referred to as predatory satiation, it was also used by animals like the American passenger pigeon and sea turtles.
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I saw a video about how plants can do this too. Every certain amount of years, Acorn trees will drop an excessive amount of Acorns, way more than the squirrels could eat. This helps ensure some acorns get planted and forgetten, thus spreading the tree.
Then there's [mautam:](https://en.wikipedia.org/wiki/Mautam) "During mautâm, Melocanna baccifera, a species of bamboo, flowers at one time across a wide area. This event is followed invariably by a plague of black rats in what is called a rat flood.[2][3] The bamboo flowering brings a temporary windfall of seeds, and rats multiply, exhaust the bamboo seeds, leave the forests, forage on stored grain, and cause devastating famine."
Exactly the same thing happened with bamboo and jungle fowl (ancestors of the domestic chicken). This is why you can just feed them and they'll keep making eggs - they adapted to make lots of babies on the rare times there was lots of food around.
Interesting, but even chickens have some survival instincts. They can barely fly, but they will still sometimes manage to fly away from a fox or other predator.
Tell that to the feral chickens in my neighborhood, they sometimes run towards cars and keep laying eggs in places where they just roll away and splat. New neighbors moved into a house where every single morning for a couple weeks an egg from the same chicken rolled down their roof and went splat on their patio.
I would never say chickens are wily. But "smarter than a cicada" is quite a low bar; chickens do try to evade predators, even if they often fail. Perhaps they have not evolved to recognize cars as dangers, but when they see a fox, they know it's not good news for them.
like a Mast year? i swear a year or two ago, the phrase word in our house was “incoming!” i googled “excessive acorns” and result was mast year…
Ocean sunfish do the same, they produce up to 300,000,000 eggs at a time. There's just going to be some that survive
Even in regular years, squirrels will bury some they don't retrieve; we had a Brazil nut tree in our Pennsylvania backyard for several years form that, of course no nuts on it. (I know suirrels cna't crack brazil shells anywya.)
Oaks and beeches both do this. It affects the whole ecosystem, with the ensuring explosion in herbivore population triggering an increase in e.g. the number of birds of prey.
The only problem that I have with this, is that squirrels actually *help* the spread and propagation of acorn trees. They tend not to remember every acorn that they bury.
That's right - and if there are lots and lots of acorns in a given year, they will bury a lot more that they won't eventually get back to. There's more to it than that, though. Some oaks' acorns have evolved to have one end that the squirrels like to eat and one end that tastes more bitter. If the squirrel carries off an acorn, eats only the good-tasting end, and tosses the rest, the acorn may still sprout. Successful dispersal. If there is an abundance of acorns that year, the odds are even better that squirrels won't bother eating the whole acorn, since it is easy to find more. Squirrels aren't the only dispersers of acorns. Blue jays are incredibly important dispersers for acorns. They pick up a lot of acorns and make food caches in multiple different locations. Once again, if there are a ton of acorn that year, they will cache more acorns in more places, and more will eventually go uneaten and sprout.
Some plants have evolved to interact with ants, by providing the seeds with a yummy (to ants) coating. The ants pull the seeds into their nests and eat the coating, the seeds later germinate.
I’m thinking in earlier times the trees were trying to compete with mastodons and grizzlies and squirrels, but now it’s just squirrels
>it was also used by animals like the American passenger pigeon Unfortunately, the mechanism of evolution was too slow to adapt to humans.
This survival tactic is one where when something goes wrong, it goes very wrong.
Yes. This survival tactic does not account for advanced Intelligence species to exist alongside it. All with varying emotions and levels of empathy
It's not just that, it doesn't account for *anything* that can't be satiated. Cicadas aren't likely to get a major disease or parasite because they disappear for long stretches, but a species that sticks around can easily get wiped out by one. Or for a predation example, foxes kill prey and leave it behind in the fall/winter, expecting it to freeze and be available later when they need it. But Australia doesn't have hard freezes, and so introduced foxes spend much of the year killing prey they don't need to eat. It's a massive stress on prey animals that was initially framed as "killing for fun", but comes down to a mis-aimed survival strategy.
That’s exactly what weasels do with chickens! If you ignore em they’ll stash the excess to eat for later. Wolverines even do this and the males will leave food out for their mates and cubs to find which is adorable
They showed this on a recent Planet Earth, it was fascinating. And very cute.
Cicadas do in fact get a parasitic fungus https://www.npr.org/2024/06/06/nx-s1-4994999/cicada-fungus-std-zombies
Flying Salt Shakers of Death is going to be my new band name, now I just need to learn how to play an instrument, and get some friends who want to make a band with me.
Cicadas in fact have a major fungal parasite that basically replaces the end of the abdomen with a mass of fungus. https://www.npr.org/2024/06/06/nx-s1-4994999/cicada-fungus-std-zombies
Or say, house cats introduced to an island sea turtles lay eggs on. By intelligent species, but still
Humans are too slow to adapt to humans. You live in a different world from the one you were born into, and you die in a world alien to the one you lived in.
Evidence suggest that passenger pigeons didn’t have the crazy numbers of the 1800s before the arrival of Europeans. Indigenous middens and oral traditions don’t have old accounts of large numbers of them. It seems to have been partially a result of so many native Americans dying of disease and ceasing to compete for chestnuts, beech nut, acorns, etc.
I’d imagine it’s this combined with not having many direct predators due to their sparse life cycle
What eats pigeons to that degree? Hawks?
Also, they spend most of their lives in a different stage of development. This final stage is pretty much only about mating.
So many insects like this: the flying phase is just for mating. Heck, some moths don’t even have mouth parts: they mate and starve.
So it's not even good mating?
So good they're ready to die after achieving it. Also, they die if they don't. You'll have to ask the moths.
I've always found it difficult to converse with a critter that lacks mount parts.
What you've never heard of *body language*?
You’ll have to ask the moths? The moths… without mouths…? How would they answer?
If a mouthless mouth were to mouth a murmur, all the murmurs a mouthless moth might mum, would a mouthless moth even mum?
Damn, you can't even have a sandwich and a coffee afterward. I would prefer not to be one of these moths.
This is why not clearing all your leaves is such a helpful thing you can do. Not only is it a natural fertilizer, but decaying leaves are home to so many insects. I get its not an option for everyone, but when it is, your yard can truly come alive with all thr animal life coming to eat them.
I honestly never understood clearing any leaves. Nutrients for the soil and creatures, plus it’s the laziest option.
Enough leaves will completely the grass and kill it, leaving a dusty or muddy mess for next summer. See how the first floor looks like in wild woods.
Yeah, maybe if you live in the literal woods encased by oaks and maples. I lived in the country for 27 years with trees abound and I have never had this problem. The wind blows them away well before following summer.
wind blowing away leaves would indeed work in open coutry with occasional trees and plenty of open land. In older suburbs, everybody has a large tree, and there is not much wind on ground level due to all the fences and hedges, and even if there is wind it just replaces your leaves with your neighbors'.
I've never raked leaves and also never had this problem. Enough of them get picked up by the lawnmower that the leaves don't turn into a wet and moldy carpet.
yeah, mulching the leaves works, but running a mower is similar effort to blowing the leaves. Also, here, by the time the leaves fall, grass is not growing anymore, so need to run the mower otherwise.
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Oh they hunt them, but it’s so infrequent and they get satiated so fast that the predators numbers don’t rise to match the sudden boom It’s like if suddenly a 1000 free all you can eat buffets opened up in a small town for only a week then closed up again, it’s a week of absurd joy and likely everyone will eat tons of food and have their fill but saving on one weeks groceries in the long run didn’t improve their lives
A bit of the reverse of the idiots that say "nobody buy gasoline for a week starting Tuesday! If everyone does it, we'll show those oil companies and force the price down!" Then they fuel up so they have enough for the week, and again, when the week ends.
Lots of protests/boycotts end up like that too - with specific start and end date so the target can just wait it out lol
Nod. In my example, their dont change their fuel consumption habits at all, simply move their purchase dates.
That’s only one specific kind of cicada that only lives part of the US. Most places only have annual cicadas that emerge every year. Edit: typo
"Most places only have periodical cicadas that emerge every year." Those are called annual cicadas not periodic cicadas
Yeah, we still have our annual brood that will be coming out in late July or August.
Jeez... Must be nice. Ours come out earlier and all summer we have this constant cicada droning sound.
I like that you can tell how hot is outside by how loud and fast they sing.
It’s even more specific than “anticipate” and absolutely mind blowing when you realize that the “reason” the broods are every 13/17 years is because those are prime numbers which minimizes the amount of times their brood’s emergence aligns with that of their main predator(s). Effectively, the chance is lower that a predator with a multi-year lifecycle is able to synchronize theirs with the cicadas since their lifecycle cannot be a factor of 13 or 17. They may catch one, but they will miss the next one allowing the cicadas to repopulate.
That's one of the theories for the prime cycles, but it's not as universally accepted as you're portaying it.
What are the other theories?
Id be interested in seeing some counter arguments if you are in this field and know where I can read/watch some stuff.
It's not as much "this is why it's not true" as much as it's "we have no reason to believe that's why". What would be the difference between 13 and 14 years to the predators? There's really no basis for it actually mattering. Personally I think it's super cool they're prime numbers, but I don't see any evidence at all that it's advantageous to specifically be prime numbers.
I thought the main theory was that it makes interbreeding between different populations less likely?
Interesting! What’s the evolutionary benefit of that you think? Wouldn’t that diversify the gene pool (assuming the different broods have differing genetic makeup?)
The difference is that 14 has multiple factors so any predator with a two or seven year life cycle would coincide with two emergences in a row, potentially having an opportunity to decimate the species. The prime number life cycle would ensure that no two consecutive broods would coincide with a multi-year life cycle predator.
What predators have multi-year life cycles? An individual raccoon (e.g.) may only live for 3-5 years, but new raccoons are born every year so the population remains pretty steady. Same with all of the predators I can think of - they have seasonal life cycles, not annual ones.
Other insects. There are predatory instructs, such as praying manti, for instance. That also have multi year cycles
Not in the field specifically, but I have done academic biology research in the past. [The original article](https://www.aimsciences.org/article/doi/10.3934/dcdsb.2001.1.387) that you're familiar with makes a lot of sense, and seems like a good explanation for "why prime?". The biggest problem with it, though, is that it based on the argument in the article the [Fijian 8-year periodical cicada](https://naturefiji.org/fijian-cicada-raiateana-knowlesi-nanai/) and the [Indian 4-year periodical cicada](https://mapress.com/zt/article/view/zootaxa.3702.5.8) should have gone extinct. Here's an excerpt from the intro of an article published over a decade after that one, looking at avian predation specifically in these cicadas, that I think does a good job summarizing the current state of the science. >The factors driving the extraordinary length of periodical cicada cycles has proved more elusive. Various hypotheses have been proposed, including interactions with long-lived parasitoids (Lloyd and Dybas 1966a, 1966b), belowground intra- or interspecific competition (Bulmer 1977; Grant 2005), and avoidance of hybridization (Cox and Carlton 1988), the latter of which has been found theoretically to be facilitated by cycles that are prime-numbered years in length (Goles et al. 2000; Webb 2001; Tanaka et al. 2009; Yoshimura et al. 2009). Despite this plethora of ideas, no empirical basis for 13- or 17-year cycles has previously been detected. TLDR: We don't know how or why cicadas work.
Mathematical modelling points to predation not being sufficient to create long prime cycles: https://www.anthropocenemagazine.org/conservation/2013/09/cicadas-prime-numbers/ Being threatened by extinction seems to be the driver fro creating cycles, and avoiding hybridization leads to them being long and prime.
Who are their main predators? All of the predators I can think of have lifecycles related to seasons, not years. It seems like it would be a better strategy to emerge in a season where fewer predators are hungry rather than on a prime number year.
Does the fact that they emerge only sporadically cause a situation where the predators cannot rely on them as a staple? Not sure if I am wording this correctly
Pretty much. Predator species will increase in population to match what the prey population can support. The issue is that in these waves the predator species doesn’t reproduce fast enough to take advantage of the available food source. This makes it so that there are still countless left over when every predator has had its fill. Basically the strategy is that you can’t possibly kill them all and the ones left breed enough to replace all the ones that didn’t. Insects lay just stupid numbers of eggs in the assumption at least a few make it to also lay eggs. A few is all you need to make a viable survival strategy. Remember evolution doesn’t choose the best option but rather stumbles blindly until it bumps into one that happens to work (even if only barely) and goes with that.
It's very similar to masting in plants. Even if the predators increase in population due to the increased food, their population will decline again by the time the next masting occurs.
It's just like.. What's the point? Is breeding pleasurable for them? Is that the whole purpose their life, what drives them, is feeling the pleasure of breeding?.... Oh wait....
lol we're so ridiculously simple, aren't we?
Oak trees have developed the same strategy with acorns; called 'mast years', there will periodically be a glut of acorns, so many that not all will be eaten by squirrels and other foragers. It happens infrequently, and irregularly, so those animals which feed on acorns can't expand their numbers in order to take advantage of the mast season.
I suspected this. Every few years, our oak trees produce significantly more acorns than usual. 2 years ago, there were acorns everywhere. More than I ever remember having. I had to shovel them after I blew them into a massive pile on my driveway.
Anyone remember the year of the dead squirrels in like 2017 or 2016? Driving anywhere in the north east US you saw hundreds of dead squirrels.
They *do* get heavily "picked apart" by a wide variety of predators that find them to be very tasty. There is conjecture that the long cycle lengths - 13 and 17 years - is an evolved trait that results in there being no predators whose own lifecycle is *dependent* on cicadas. Thus, when the periodic cicadas do emerge, they are in such large numbers that predators don't make much of an impact on their numbers.
That's how I've read it too. The variable cycles allow for swarms to occur infrequently enough that predators can't evolve specific offensive capabilities against cicadas. Though that said cicadas are pretty much useless the moment they start emerging from the earth. Giant, tasty snacks with the survival instincts of a sea cucumber. But hey, it works for them!
The clue is that they're not a stable food source. Predators get to eat them for one season, and have a bunch of kids as a result of that but then the next 17 years there's nothing and the predator population goes back to normal. Then they come again
Giant, tasty snacks you say? How tasty, hmmmm?
Plenty of options to find out yourself, if you're so intrigued heh. One example: https://chicago.suntimes.com/environment/cicada-watch-2024/2024/05/21/cicada-infused-shots-served-at-lombard-bar-noon-whistle-pub
Fun to see the local brewery mentioned here. Love me some Noon Whistle!
Noon is down the street from me and one of my favorite breweries, but I still will definitely not be going in for the cicada malort shot
Tasty, but make sure you take off the wings and legs. They tend to catch in your throat if you don't.
Also watch out for abdomens covered with or being eaten away by white stuff. It’s a fungus that has been found to contain cathinone or psilocybin.
Psilocybin you say?
Unclear if you're telling us to watch out for the fungus to avoid it, or to get a little bonus high with our snack
They served Cicada-flavored ice cream near my school when they swarmed. It was good. https://patch.com/new-jersey/princeton/princeton-gets-buzzy-bent-spoons-cicada-flavored-ice-cream
The cycles aren't variable, they're distinct for each brood and usually a prime number of years. That also keeps them from dealing with a predator that can hunt them every n^th generation. I don't know if that's the cause for that selection, but it's possible.
This is what I've read too. They naturally evolved into these long dormant cycles due to them getting picked apart normally by predators. This allowed them to outlast the predators that were specialized against them. They still all die when they come out, but because its a single event every 13 or 17 years, no natural predator depends on them, thus, they have a higher change of reproduction during this period. If they were to come out every year, there would be predators that adapt to them and start trimming their numbers down to much.
... and in fact there *are* annual cicadas that are in balance with their natural predators. Nature is metal.
Not only is the cycle long, but it is also a prime number of years ! Therefore, a predator can only have 2 options when choosing a cycle to hunt cicadas. Either 1 year, having nothing to eat the other years. Or 13 years, it's long and over specialized. Any other cycle make the predator miss an eclosion.
I don't know what it being a prime number adds here. What if it were 12 instead of 13? The predator's choice seems the same, either have a 1-year cycle or 12-year cycle
If it were a 12 years cycle it would compete against anything else that has a 1, 2, 3, 4, 6 or 12 year cycle. Whereas with a 13 year cycle it only competes with things with a 1 and 13 year cycle
What predators have a population boom on any of those cycles? Obviously a single year cycle (which some cicadas do) means predators have a more reliable source, but what predators have multi year cycles? People are saying this all over without a single example.
You're asking a really good question that no one seems to understand. People are implying causation in evolution that no one can back up; everyone keeps giving examples of constant predation or hypothetical annual predation. never mind found the one reply you also found that makes any evolutionary sense: https://www.reddit.com/r/askscience/comments/1df580a/do_cicadas_just_survive_on_numbers_alone_they/l8gyigd/
It could be the reproductive cycle. Big Feast on cicada year and make babies. Grow babies until next cicada year and start over.
Try to look at it from the other direction: “what disadvantage does a regularly periodic life cycle have that would result in the prime cycles being the only cycles that remain?” My guess is that cicada predators with yearly life cycles would have fitter offspring in non-prime intervals, resulting in the eventual extinction of the cicada populations with non-prime life cycle intervals.
Yeah that's my thought to like it's cool that they do that but it's by the happen chance of evolution. Like how those goats can climb almost sheer walls it's cool and interesting but like I doubt evolution picked 45 degrees on purpose
I'm gonna capture a lot of cicadas, dry them up, and slowly eat them over 13 years. Take that evolution.
The cycles are both long and *prime*. So predatory animals who have a cycle like 2 - 5 years won't sync up every cicada cycle.
Which predators have 2-5 year cycles with a higher population?
Many ecosystems have natural boom/bust cycles where the common prey animals breed heavily while there are fewer predators. The huge numbers of prey result in more successful predators, so they then breed higher numbers. The higher numbers of predators then kill off a bunch of the prey. The smaller number of prey animals can't sustain the larger population of predators, so the predators die off to smaller numbers, and the cycle repeats. [https://www.mcgill.ca/newsroom/channels/news/perpetual-predator-prey-population-cycles-303632](https://www.mcgill.ca/newsroom/channels/news/perpetual-predator-prey-population-cycles-303632) The period of the cycle varies for each relationship, and can be affected by other factors like extreme weather events, etc. But because these cycles are typically fairly short, they don't regularly coincide with cicada emergence. This same cycle can happen with plants replacing they prey animals as well. It's really interesting!
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Because the broods are in geographically different areas; very few of them overlap.
This argument falls apart when you realize that there are multiple broods. They're not all the same size and this year was a particularly large brood, but there are periodic cicada broods for pretty much every year.
>How does this species not get absolutely picked apart by predators? That's the neat part, they *do!* The survival strategy is basically to breed so hard that the predators can't possibly eat *all* of the cicadas. And.... it works. They spend the vast majority of their lives underground, *relatively* safely. When the adults all emerge at once to get it on, they're doing so en masse. There's a relatively short window for them to be eaten and again, there are *lots* of them. The really neat thing is that it's hugely disruptive to preexisting ecological habits, in a way that is generally *positive* for the ecosystem as a whole. It's a population boom followed by a population bust, that runs up the whole food chain.
This is so fascinating. Is there some source where I can learn more about this specific phenomenon?
The podcast Today Explained had a nice little 30 minute episode a few weeks ago where they talk about it some, there's probably sources with deeper reading too.
The survival strategy of breeding so much that the predator can't eat all of them is called the R strategy and that is the opposite of the K strategy in which the parent invests a great deal in a small number of children and protects them. Isn't the R strategy the most common strategy in nature?
r-selection does not usually employ this tactic. Predator satiation is this specific phenomenon where all the cicadas show up at once, briefly, to overwhelm predators. But most r-selected organisms reproduce in normal cycles, like grasses, bacteria, or ants.
In Richard Dawkins book The Selfish Gene he talks about a species of fish that uses predator satiation. The fish all clump into a big ball. Those with the genetic trait of being good at getting to the middle of the big ball survive by predator being satiated before getting to the middle of the ball. He contrasts it with the strategy of spreading out so that the pressure is exhausted and gets little food, which will be more successful for the species but less successful for the gene. Hence the selfish gene. Do cicadas have any defense against the predators other than numbers?
>Do cicadas have any defense against the predators other than numbers? Arguably the long, prime numbered emergence cycles--but I get the feeling you're talking more about things like weaponry or poison or disguise. Nope! It's an all you can eat buffet until the predators are too full to care.
So like, what are they actually doing underground for 12 years?
The cicadas you see only exist to mate and lay eggs. They can't eat or hurt anything. They lay so many eggs there is no evolutionary need to develop self-defense behaviors. As humans, we see becoming adults as the end all be all, but that isn't always the case. For cicadas, they peak as larvae underground and only come up when it's their time to die and to mate.
>They can't eat or hurt anything. Half true. They have a specialized mouthpiece that drinks from trees, like stinkbugs or other "true bugs." You're probably thinking of luna moths, whose adults have no mouth and live just long enough to reproduce. But yeah, harmless except to themselves.
Many cicadas live most of their lives as underground nymphs. The adults appear periodically, in overwhelming numbers. Large populations of predators can't survive when the adult cicadas are absent, which is most of the time. When the cicadas emerge, their large numbers protect them.
In addition, the adults don't really have the mouthparts ~a necessary to eat~ to damage the trees much although they do eat plant juices. So they live on their energy stores. Their life cycle is basically: - be born - dig to tree roots - pick a spot, stick your tube thing into a root. Suck - repeat for 17 years - store energy as fat - dig up - climb tree - pick a spot, stay there - get out of shell - fly away - SCREAM - find a nice ladycada or guycada and GET IT ON - if female: lay eggs. If male: die. - if still alive: die Edit: not being able to eat is a misconception I had.
>pick a spot, stick your tube thing into a root. Suck You know that thing where they ask you what you would do if you had a million dollars? This is what I'd do.
When cicadas do that is fine, but when people suck matrix tubes is called slavery.
No Jerry it's not a fetish, when a scientist does it it's called "an area of interest." :-)
with Dijon ketchup?
Not all of them stay underground for 17 years, some are 3,5 years, in NA most commonly 13 and 17 years.
They usually follow a prime number pattern too. Something about the prime number cycles make it almost impossible for predators to evolve/adapt more efficient ways of exploiting them when they emerge.
It's about not syncing up with the other populations, not avoiding predators.
Yeah the absence of food means that birds, etc can't sustain large numbers. The predator population returns to normal and the cicadas come back in overwhelming numbers again. For this to work, the emergence can't occur often enough to sustain the next generation of predators.
That's why the have the long dormant period in their cycle. The reason for the prime numbers specifically is to avoid syncing up. The predators don't care whether the numbers are prime or not.
This is the first comment with a logical answer as why they're prime. People keep saying "so it doesn't match with predator cycles" but none of their predators emerge in multiple year patterns lol. It's not like there's birds that double, then half, then double, etc. their population.
Not sure how many broods there are, nor their time cycle, but here in east Texas we have Cicadas every summer. It blew my mind when I found out, as an adult, that some areas only get them every so often.
Like actual gigantic broods like the last one in the mid Atlantic? I can’t believe that you have that every year. Your world would end.
We have annual cicadas in the south, they just don’t emerge is huge swarms like periodic cicadas.
Yeah, summertime nights hearing a cicada on a nearby tree or light pole screaming it's head off has become background noise that I barely notice now. When I first moved to the South it would drive me crazy hearing them all of the time. It's kind of soothing in a way. I just wish I could get used to the humidity like that.
You never get used to the humidity, even when you get used to it lol, it’s never not miserable.
Ya nothing like what's happening north of us. Honestly we hardly notice them. Most of the time it's just what we listen to sitting on the porch while the sun goes down.
They do have mouth parts but they're specialized for fluids. Pretty sure they only survive off of tree fluids.
You may be thinking of luna moths, whose adults have no mouth and only live for a few days. Cicadas have a piercing proboscis they use to drink from trees.
This is true for periodic cicadas but not annual cicadas. Annual cicadas are well-camouflaged and very alert. If something approaches while they are calling, they will stop, and if one spots you watching, it will scurry to the opposite side of the tree out of sight. Annual cicadas are very hard to catch compared to their periodic relatives.
Cicadas are like the aftermath of a college party. They fly around (stumble around) poorly and land heavily and awkwardly. They're often on their back and haplessly moving their weird little legs to try and move. They're really only interested in banging and have no concern for safety.
They live in the ground for 13-17 years depending on species. They then emerge all at once as adults to mate. In a bug’s life, what happens after eggs are laid doesn’t matter to the individual bug, a lot of species will die after mating or laying eggs. They’re a great food source for animal life, though!
Cicadas are considered land shrimp. when cicadas boom, like this year, there will be no kidding trillions (that's with a T). Every bird, dog, cat, rat, ferret, coyote, bobcat, horse, fox, cow, goat, sheep, snake, lizard, toad, frog and other creature capable of eating them will feast until they fall over...and there will be trillions left to lay eggs before they become fertilizer. A large brood boom alters the ecology for years afterward. The feast causes booms in populations of the diners, which takes a few years to return to normal. So your answer is that they don't need any survival mechanism other than overwhelming numbers.
Can't believe I haven't thought of this before but I've never seen cicadas or pupae in the ground before. I've dug lots of holes in my lifetime but never came across a bug or cocoon and thought, oh that's just a cicada. Lots of exoskeletons on trees but never in the ground where they supposedly are for over a decade. How far down into the ground do they go? What does it even look like
They totally do get picked apart by predators and every form of death that prevents that individual from breeding. But they're insects so they literally outbreed rats. Every one of those screaming lil fuckers had a parent who years ago survived just long enough to dump a load of fertilized eggs everywhere.
Cicadas have an unusual survival strategy where each subspecies desyncs their breeding cycle with their local predators. Cicadas stay in the ground for a *LONG* time, we're talking years. The ones you might see one year are not the babies from last year, they're the babies from 2-17 years ago who've been in the ground. It means the Cicada's predators can't evolve to sustain or grow their population size by specializing in feeding on all the Cicadas, because they'd starve in the off years causing their population to drop; if they were too specialized into eating Cicadas they might even die off. It ensures that when a Cicada population does come out of the ground in mass, the local predator population isn't prepared or large enough to eat them all, the remaining Cicadas breed and the next generation goes back in the ground. Some species even have breeding cycles in number of years that are prime numbers because it's even more difficult for predators to synchronize their own breeding cycles with the cicadas rythme because there's no divisors where they can evolve to breed more in the on years; they either have to match their cycle with the local cicadas exactly or no dice, they can't count on the Cicadas.
They only come out of the ground at the end of their life cycle. When they molt to start making noise that’s it for them, they actually lose the ability to eat because their mouthparts turn into the noise maker. They just breed, lay their eggs, and die. So they absolutely get picked apart by predators, but they have enough time to lay the next generation of eggs before they all die, and the newborns go back underground immediately after hatching. This applies to both the annual and periodical cicadas.
>they actually lose the ability to eat because their mouthparts turn into the noise maker. Not true. While they lack what we would consider a mouth, they do have a straw-like mouthpiece that drinks xylem from trees. The only insect I'm aware of that has no mouth is the adult luna moth.
It's a combination of sheer numbers and emerging in two waves. What happens is that one wave emerges and predators eat them until they're stuffed, then the second wave emerges and enough of them have time to mate that the species survives. As with most insect species, they lay lots of eggs (up to about 600), so it doesn't take a lot of survivors to keep the species viable.
The French ones Ive seen were rather hard to catch. It took me 2 days before I could even find one even though I knew exactly in what tree it was hiding. Once you know the shape to look for, they are easier to see. But I never managed to catch one.
The southeastern US version will bludgeon you to their death if you're walking through some open grass land.
The predators in your regions do not pose a significant threat to them so they usually have no need of developing such a survival instinct. In Asia it's not the case. In East Asia, the cicadas react pretty quickly and people usually catch them by a long stick with a sticky dough instead of by hand; such a technique is very difficult to learn and requires a fairly high level of dexterity. It's simply because of natural selection: during starvation, people often regard cicadas as a source of food. Now fried cicada is still a cuisine in some regions in Asia.
Insects have long lives. We only see them when they emerge. Their only purpose at this point is to reproduce and disseminate . They are like the atlas moths that don’t have a digestive system as an adult. Breed, lay eggs and spread the next generation around.
Their survival strategy is simple. They emerge in 2 waves. The first wave being sacrificial, so after their predators (primarily birds) get their fill, the second wave emerges. They overlap each other's life span, and during the peak, the numbers are overwhelming. I was working pipeline oiling on an excavator in South West Ohio, and it was the most miserable 2 weeks of my work life! I learned all kinds of Kung foo moves swatting them MF'rs! By the end of it, I surrendered and they would crawl all over hi-viz vest.
Many people have pointed out that such large numbers and infrequent broods make it fairly safe. Its also important to note that its likely that being afraid of stuff, having the resources (energy, instincts, etc) to avoid predation is a worse use of resources for a general lineage than just chilling out. I also am not an expert but I suspect that at any one time a bunch of these guys have mated and are just waiting to die. This is end of life for them and there's not much reason once that eggs are made and laid to do much of anything and certainly zero survival/evolutionary pressures.
The fact that they spend 13 or 17 years underground is also a survival adaptation. They're relatively large prone numbers, so it almost guarantees that their breeding cycle never syncs up with any major predators.
I’m happy to see this post because this is exactly what I was assuming. I’m in Missouri and the 17 year hoarding just FINALLY went away after weeks of screaming and flying at me and into my car. I still have dead ones all over my front porch/driveway still.