Lemmings? Or?

December 27, 2019 1:45 PM

Biological MeFites, my friend who is writing a novel asks: "Are there examples in nature of self-culling in plants, animals, or bacteria? It could be war, could be suicide, could be contraception - anything which might keep a species from hitting the wall of carrying capacity or environmental degradation."
posted by exceptinsects to Science & Nature (11 answers total)

Bears mate in the spring/summer but the blastocyst waits until fall and will not implant if momma bear didn't gain enough weight before hibernation.
posted by muddgirl at 1:58 PM on December 27, 2019 [3 favorites]

A more general definition: embryonic diapause. It's not just bears.

Oh, and you know the bit about lemmings is a myth, right?
posted by SPrintF at 2:32 PM on December 27, 2019 [2 favorites]

Rabbit does can absorb a fetus back into their bodies. (Right? I think I learned that from Watership Down.)
posted by kerf at 2:46 PM on December 27, 2019 [2 favorites]

Quorum sensing in microbes.

Embryonic cannibalism in sharks.
posted by porpoise at 4:31 PM on December 27, 2019 [1 favorite]

Response by poster: Oh, and you know the bit about lemmings is a myth, right?

Yep, just hoping to entice some knowledgeable people to correct me with better info! :-D
posted by exceptinsects at 4:59 PM on December 27, 2019

There’s a lot this novelist is missing. Write what you know, right?

Examples abound. One thing not mentioned so far is the notion of self thinning. Lots of crops and wild plants do this as a matter of course.

Carrying capacity is not a wall so much as a rubber band. Ecosystem engineers alter carrying capacity of several organisms.

Also facilitation and keystone species can be said to counteract “hitting the wall” as you put it. Rather than degrade their environment some species enrich it and create niche opportunities.

Finally many organisms will alter fecundity allocation based on present resources, and fecundity selection also alters how species adapt to scarcity and abundance.
posted by SaltySalticid at 4:59 PM on December 27, 2019 [2 favorites]

Well, trees are the most readily seen example. The giants shade out the newborns. Especially in conifers. No light, no life. You have to wait for a tree to fall down before a sprout will grow.
posted by sanka at 6:58 PM on December 27, 2019 [2 favorites]

How about the way that chicks will all wait to be born at the same time? The eggs get laid over the course of a few days but they all hatch at once because they start peeping in the shell and use the peeping to synchronize when they will come out of the shells.

Failing that what about cell death, that only rarely fails, and when it does you get cancer cells?
posted by Jane the Brown at 7:50 PM on December 27, 2019

I'm not sure if this fits your criteria, but a lot of animals die when they reproduce, instead of living on and creating many seasons of offspring. A female octopus, for example, dies once she has brooded her egg cache.
posted by effluvia at 11:31 PM on December 27, 2019 [1 favorite]

Some species of salamander are more likely to produce "cannibal" variants if their environment becomes overcrowded or food is scarce:

https://www.reed.edu/biology/professors/srenn/pages/teaching/web_2006/AMGJTG_Cannibals/competitive.html
posted by justkevin at 6:38 PM on December 28, 2019

Infanticide, hierarchy, ostracism, and war/territoriality in meerkats.

Note that if your friend suggests that this evolved for the good of the species rather than as individual-level selection with a species-positive side effect, they'll be wading into one of the nastier debates in biology.
posted by clawsoon at 3:35 AM on January 2, 2020