CANNIBALS are rare in the animal kingdom partly because eating your relatives
makes you sick, say researchers in the US who have tested the idea for the first
time.
For years, biologists have wondered why cannibalism is rare. In theory,
eating your own kind can give nutritional and competitive advantages, although
communities of cannibals might also have a tendency to wipe themselves out. One
answer, they reckoned, was that animals avoid cannibalism to stop the spread of
species-specific pathogens.
To test this theory, a team led by David Pfennig of the University of North
Carolina at Chapel Hill created 鈥渄iseased鈥� larvae of the cannibalistic tiger
salamander, Ambystoma tigrinum, and of another tadpole species,
Ambystoma texanum, by exposing them to tanks infected with their natural
pathogens, such as Clostridium species. Diseased and healthy larvae of
both species were then given as food to 24 slightly larger and more mature tiger
salamander larvae.
Advertisement
The larvae that ate diseased larvae of their own species grew less quickly
and were less likely to survive metamorphosis than all the other animals,
Pfennig鈥檚 team will report in a forthcoming issue of Animal Behaviour.
鈥淐annibalism may be more rare because you risk getting pathogens or parasites,鈥�
says Pfennig. 鈥淭hey coevolve with their host.鈥�