As you bite into a chocolate bunny or egg this weekend, consider this: rabbits often eat their own young, and their own eggs.
In fact, eating or abandoning offspring has been documented in a variety of mammal and bird species — as well as fish, insects and spiders. Hunger and quality control are among the reasons proposed for this intuitive survivor of natural selection.
Now researchers at the University of Tennessee and the University of Oxford suggest that in some cases, branch 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 branch cannibals, the researchers focused 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. "This makes it easier to protect, clean, incubate and feed the eggs ̵
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 beagregory damselfish, fathers were more likely to eat eggs under low oxygen conditions," notes Klug. "Such cases have led 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 mathematical model to test this hypothesis.
"The model introduced an imaginary individual with a mutation for branch cannibalism or offspring abandonment, into a population of generic egg-laying animals," said lead author Dr. Mackenzie Davenport, also of the University of Tennessee
As in the group's previous models, the genes for cannibalism spread throughout the population with the gift of extra calories
But for the first time in this model, they found that When offspring mortality increases with egg laying density, both branch cannibalism and offspring abandonment result in increased fitness. [Undertheseconditionsthemutantswereabletooutcompeteandreplacethegenericpopulation"reportsDavenport
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, branch cannibalism and offspring abandonment can function as forms of parental care, at increasing total offspring survival. "
Live fast, young, be prepared to abort
" The fitness benefit of offspring abandonment and branch cannibalism also increases as adult death rate increases, especially for the case of branch 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 bread. 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," Bonsall explains. "Factors like food availability, oxygen availability, diseases presence and predation, might change in and unpredictable less. Likewise, in many fish and other animals their eggs are in the nests or territories of males and leaves, so cannot predict and optimal laying density. given that additional females might add add to the nest. "" It is 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: 10.3389 / fevo.2019.00113, https://www.frontiersin.org/articles/10.3389/fevo.2019.00113/full
Honey, I ate the kids: The sweet side of branch cannibalism (2019, April 16)
retrieved April 16, 2019
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