HOW SHOULD PARENTS RESPOND TO A REDUCTION IN LITTER SIZE ABANDONMENT OR EXTRA CARE

Although natural selection may favour the evolution of an optimal broo d size, unpredictable environmental factors can intervene to render th e brood either considerably larger or smaller than this optimum. The q uestion therefore arises as to how parents should respond to unusually large or small litters. Solutions to this problem which involve aband onment of the offspring or brood reduction, for example by infanticide , have received most theoretical and empirical attention. For small ma mmalian litters, however, evidence that parents employ these behaviour al strategies is sparse. I suggest that, under certain conditions, an alternative to abandonment and infanticide of small litters in mammals is an increase in total parental care above that seen in larger litte rs. Evidence is presented which supports this possibility. This strate gy may allow parents to compensate for the loss of offspring by produc ing a small number of high quality individuals. It is most likely to o ccur when opportunities for rapid rebreeding are limited, and when inc reases in parental care have strong effects on offspring quality. Inte rest in abandonment and infanticide has diverted attention away from t his alternative parental response to small litters. Studies of this re sponse are encouraged, not least because they will focus attention on the poorly understood relationship between parental care and offspring quality.