Honey, I ate the kids: The sweet side of filial cannibalism

Credit: CC0 Public Domain

As you bite into a chocolate bunny or egg this weekend, consider this: rabbits often eat their own young, and hens their own eggs.

In fact, eating or abandoning has been documented in a variety of mammal and —as well as fish, insects and spiders. Hunger and are among the many reasons proposed for this counterintuitive survivor of natural selection.

Now researchers at the University of Tennessee and the University of Oxford suggest that in some cases, filial cannibalism and offspring abandonment might even be considered forms of parental care. Published in Frontiers in Ecology and Evolution, their mathematical model shows that when overcrowding threatens offspring survival—which often occurs due to spread of infection or competition for resources—sacrificing a few so the most can live becomes the ultimate form of tough love.

Putting all your eggs in one basket

To understand the role of overcrowding or 'offspring density' in the survival benefit of filial cannibals, the researchers focused on species that lay .

"Communal egg laying is common in a range of fish, insects, reptiles, and amphibians," says senior author Dr. Hope Klug, Associate Professor at the University of Tennessee, Chattanooga. "This makes it easier to protect, clean, incubate and feed the eggs—but can also increase , and competition for food and oxygen."

Offspring density has been found to affect egg survival, and in some cases abandonment or cannibalism, in many of these species.

"For example, in the beaugregory damselfish, fathers were more likely to eat eggs under low oxygen conditions," notes Klug. "Such cases have led the to the hypothesis that eating or abandoning offspring may be an adaptation to improve overall survival of offspring by reducing their density."

Model parents eat their offspring

Klug and colleagues created a to test this hypothesis.

"The model introduced an imaginary individual with a mutation for filial cannibalism or offspring abandonment, into a population of generic egg-laying animals," explains lead author Dr. Mackenzie Davenport, also of the University of Tennessee.

As in the group's previous models, the gene for cannibalism spread throughout the population if it gave parents extra calories.

But for the first time in this model, they found that when offspring mortality increases with egg laying density, both filial cannibalism and offspring abandonment result in increased fitness.

"Under these conditions, the mutants were able to outcompete and replace the generic population," reports Davenport.

This was the case even when cannibal parents were given little or no energy benefit from the extra food—or when abandoned offspring were assumed to die.

"Our findings suggest that surprisingly, filial cannibalism and offspring abandonment can function as forms of parental care, by increasing total offspring survival."

Live fast, die young, be prepared to abort

"The fitness benefit of offspring abandonment and filial also increases as adult death rate increases, particularly for the case of ," adds co-author Prof. Michael Bonsall of the University of Oxford.

In other words: if you've got fewer shots at reproducing, you'll need to be ruthless in protecting your brood. But if offspring mortality is density dependent, why produce so many eggs in the first place?

"It is not always possible for parents to predict the environment that their offspring will end up in," explains Bonsall. "Factors like , oxygen availability, diseases presence and predation, might change in an unpredictable manner. Likewise, in many fish and other animals females deposit their eggs in the nests or territories of males and leave, so cannot predict an optimal laying density given that additional females might subsequently add eggs to the nest."

"It's up to empiricists now to test these models in a variety of species," the authors conclude.

Explore further

Should I eat the kids? When to care for, abandon, or eat your offspring

More information: Frontiers in Ecology and Evolution, DOI: 10.3389/fevo.2019.00113 , https://www.frontiersin.org/articles/10.3389/fevo.2019.00113/full
Provided by Frontiers
Citation: Honey, I ate the kids: The sweet side of filial cannibalism (2019, April 16) retrieved 15 October 2019 from https://phys.org/news/2019-04-honey-ate-kids-sweet-side.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Apr 16, 2019
Only humans are stupid enough to ignore instincts on how to improve the race. To their eventual detriment.

Apr 16, 2019
Birds do it. Rabbits do it. Expectant rabbits will even absorb their unborn fetuses rather than bring them into overcrowded warrens.

Humans have been living with chronic overpopulation ever since they became able to hunt the predators that were hunting them. Humanity congealed into tribes for the purpose of securing and protecting resources. Competition among tribes led to ever more complex social structures, technological advancement, and bigger brains. We became a domesticated species with all sorts of unnatural behaviors meant to serve the tribe.

But the human animal still struggled with overpopulation. We have homosexuality, bestiality, various non-procreative alternatives to vent our tropical urges to mate year round. We have eating disorders which return women to a prepubescent state. We have infanticide before and after birth. And yes, we have cannibalism in our repertoire of tools to reduce growth to sustainable levels.

Apr 16, 2019
Our struggles with endemic overpopulation have been cultural as well as biological. The farther north a species resides, the more seasonal its reproduction naturally becomes. Northern tribes adopted the rites of spring, the June wedding, rites of passage, contraception. Neanderthal gestation was probably aligned with the seasons which is why it was overwhelmed and extincted by the tropical cromags.

Group selection favored tribes with greater internal order and stability coupled with external aggression. Religions emerged which maximized the human repro rate for the purposes of outgrowing and overwhelming the competition, while still maintaining internal stability. The result was fetid, squalid cities, infectious diseases from living in close contact with animals, and chronic malnutrition from eating grasses.

Apr 16, 2019
Chronic overpopulation meant that war was always a constant. Northern tribes found that they could avoid conflict by managing growth, and their religions reflected this tendency. But they were no match for the tropical religions that exploited and maximized the growth rate of the tropical human animal, and were extincted just like neanderthal.

"On Île de la Cité, the historic heart of ancient Paris, a pagan altar once lay buried beneath the public square that stands before the Cathedral of Our Lady of Paris. An earlier Gallo-Roman temple stood beneath the cathedral itself, and this had replaced an even earlier shrine sacred to the ancient gods of Lutetia."

Burn baby burn.

Apr 16, 2019
How "disappointing".
Humanity's -- ray of darkness --, relegated to 2nd, 3rd, 4th spots on the thread. His age is finally catching up to his incessant misanthropy. He obviously did not inherit it from his parents and that's a pity. For the forum could have been so much brighter.

Apr 16, 2019
The preceding commentators offer themselves as proof of the failure of Big Brain evolution.

I have long-held that Humans egotistically defining themselves as
"Homo Sapient"
is evidence for our racial level of stupid.
The correct term would designate people as
Homo Anthropophagus.

Apr 17, 2019
How stupid and ignorant for the author to suggest that we think of Cannibalism on the day of Easter, the day that we celebrate Life. Truly this world is a crooked place.

Apr 17, 2019
But are modern people fit for human consumption? I mean, we have to have some standards. I only want to eat certified organic people.

Apr 17, 2019
Oh Bart, you are being such a hypocrite.
worshiping a primitive stuporstition of sanguinary practices.
Your comment is perfectly placed among the commentators to this article.

Apr 18, 2019
How stupid and ignorant for the author to suggest that we think of Cannibalism on the day of Easter, the day that we celebrate Life. Truly this world is a crooked place.
But bart dont you know that the eucharist is only the adaptation of an ancient cannibal rite, you know, to attract the rubes?

Catholics consume the actual blood and flesh of another human being. Other xians take communion and only pretend. Easter - the day you all celebrate the torture murder of another human being because it's your selfish way of living forever. Your symbol of life is that little torture murder instrument you wear around your neck.

Cannibalism, human sacrifice, jesus the scapegoat, martyrdom, worshipping dead saints and keeping their body parts in reliquaries above your altars... these things are all taboo except when they are included in ones own religion arent they?

Apr 18, 2019
15 hours ago
Comment posted by a person you have ignored ... show comment
Hey there willis dont you wish you had some actual content to post like otto always does? Instead of just pretense and silly mangled words that is?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more