PERSPECTIVES W

should parents do when they detect indications of more preda-tors nearby that might eat their babies? This scenario is commonly faced by parents in the wild, and the consequences are important. The number of offspring that organisms produce has a major infl uence on fi tness and, when averaged across a popu-lation, affects whether this population will increase or decrease. Offspring production thus has critical implications for evolution via fitness, and ecology and conservation via demography. On page 1398 of this issue, Zanette et al. ( 1) show that the fear of preda-tion can, by itself, strongly affect the numbe