By Susan Milius
Bluegill sunfish have provided an unusually tidy test of the much-discussed prediction that animal dads’ diligence in child care depends on how certain they are that the offspring really are their own.
When researchers presented male bluegills with phony evidence of cuckoldry, the dads slacked off on nest defense, says Bryan Neff of the University of Western Ontario in London, Canada. Later, reassured of their paternity, the fish grew fiercely protective, Neff reports in the April 17 Nature.