Cannibalism is now recognized to be widespread and to contribute broadly to the self-regulation of many populations

Don't try this yourself please! 😄

"Eating your own kind is fairly common throughout the animal world, from single-celled amoebas to salamanders ... report in a new review in Ecology. But not as many species snack on their brethren as one might expect—and the team has detailed the reasons why.

First off, cannibalism is risky. ...

Cannibalism is also dicey from a disease perspective. Many pathogens are host specific, so if a cannibal devours an infected companion, it risks picking up the same disease. Different populations of humans have found this out the hard way multiple times. ...

Finally, cannibalism is a terrible way to pass down one’s genes. ...

Although cannibalism is far from ideal, certain conditions appear to make the risky behavior worthwhile. ... if you’re starving, you’ve got to protect your survival, ...

In their review, ... pinpoint specific hormones—octopamine in invertebrates and epinephrine in vertebrates—that appear to be linked to increasing rates of cannibalism. As conditions become crowded and food becomes scarce, the amounts of these hormones spike and “hangry” animals attack whatever they can snatch with jaws, legs, or pincers. ...
The study also highlights how certain conditions make some young amphibians such as tiger salamanders and spadefoot toads turn into supercannibals.  ...
Other creatures, such as the highly invasive cane toad, take the opposite approach. When hungry cannibals are lurking, vulnerable toad larvae accelerate their growth and development, tacking on mass to become too big to scarf down. ..."

From the abstract:

"Cannibalism, once viewed as a rare or aberrant behavior, is now recognized to be widespread and to contribute broadly to the self-regulation of many populations. Cannibalism can produce endogenous negative feedback on population growth because it is expressed as a conditional behavior, responding to the deteriorating ecological conditions that flow, directly or indirectly, from increasing densities of conspecifics. Thus, cannibalism emerges as a strongly density-dependent source of mortality. In this synthesis, we review recent research that has revealed a rich diversity of pathways through which rising density elicits increased cannibalism, including both factors that (a) elevate the rate of dangerous encounters between conspecifics and (b) enhance the likelihood that such encounters will lead to successful cannibalistic attacks. These pathways include both features of the autecology of cannibal populations and features of interactions with other species, including food resources and pathogens. Using mathematical models, we explore the consequences of including density-dependent cannibal attack rates on population dynamics. The conditional expression of cannibalism generally enhances stability and population regulation in single-species models but also may increase opportunities for alternative states and prey population escape from control by cannibalistic predators."

Why some animals turn cannibal | Science | AAAS Study finds good reasons to go after your comrades—and some bad ones, too

Pathways to the density-dependent expression of cannibalism, and consequences for regulated population dynamics (open access)