FILIAL cannibalism 鈥� eating one鈥檚 own offspring 鈥� is hardly the most caring thing a parent can do, but ironically may have helped the evolution of parental care.
That鈥檚 the message from a computer model which analysed how cannibalism and parental caring could evolve. 鈥淲hat comes out is that they can co-evolve for different reasons, under different conditions,鈥� says Michael Bonsall at the University of Oxford, who developed the model with Hope Klug of the University of Florida at Gainesville.
The pair devised a hypothetical egg-laying species, with hatchlings that developed into juveniles -which could benefit from care 鈥� before reaching adulthood. At the start of the simulation, neither cannibalism nor parental care existed in the population. The researchers then observed what happened when they introduced 鈥渕utants鈥� into the population that cannibalised or cared for their offspring, or both. The researchers could also vary the environment.
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When food was scarce, the population opted either for cannibalism or caring, but not both. When food was plentiful, both strategies evolved together. 鈥淲e studied how these traits 鈥榠nvaded鈥� the original population under a range of conditions,鈥� says Bonsall (The American Naturalist, ).
They found that cannibalism and parental care often co-evolved and become dominant in the population, but through different mechanisms. Sometimes, it paid the parent to eat some eggs or juvenile offspring, for example. 鈥淚f you produce too many babies, you can鈥檛 care for them all,鈥� says Bonsall. 鈥淪o do they all die, or do you eliminate some and get a smaller number through to adulthood?鈥� Parents eating their young also acquired energy to help them rear survivors.
In some simulations, parents tucked into the weakest and most disease-prone offspring to give the strongest more of a chance to survive. 鈥淭here are many examples of this in nature, such as sand gobies, burying beetles and wolf spiders (pictured).鈥�
The model also shows how cannibalism could speed up the evolution of traits such as egg maturation. If parents eat eggs, this favours the evolution of eggs that mature faster, as the first to hatch are less likely to get eaten.
Evolution 鈥� Learn more about the struggle to survive in our comprehensive special report.
