As you bite in 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 offspring has been documented in a variety of mammals and bird species-as well as fish, insects and spiders. Now scientists at the University of Tennessee and the University of Oxford suggest that in some cases filial cannibalism and offspring abandonment may 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 the spread of infection or competition for resources-sacrificing a few so the most can live will become 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 focus on species that lay eggs
"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. "It's found that it affects 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. "These cases have led to the hypothesis that eating or abandoning offspring may be an adaptation to improve the overall survival of offspring by reducing their density."
Model parents eat their offspring
Klug and colleagues Created a mathematical model 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
"Under these conditions, the mutants were able to outcompete and replace the generic population", reports Davenport.
This was the case with the newborns. "Even if the cannibal parents were given little or no energy from supplementary food, or if abandoned offsprings were supposed to die."
"Our findings suggest that, surprisingly, filial cannibalism and offspring abandonment can act as forms of parenting by increasing total offspring survival. "
Live fast, die young, without being ready to abort
" The fitness of the offspring abandonment and filial cannibalism also increases as adult death rate increases, especially for the case of filial cannibalism, "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. "It's not always possible for parents to predict the environment that their offspring will end up in," explains Bonsall. "Factors like food availability, oxygen availability, disease presence and predation may change in an unpredictable way. Similarly, in many fish and other animals, females can deposit their eggs in the nests or territories of males and leaves, so they can not predict the optimum lay density Given that additional females might later add eggs to the nest. "
" It's up to empiricists now to test these models in a variety of species, "the authors conclude.
Should I eat the kids? When to care for, abandon, or eat your offspring
Frontiers in Ecology and Evolution DOI: 1
Honey, I ate the kids: The sweet side of filial cannibalism (2019, April 16)
retrieved on April 16, 2019
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