Brood success in variable environments: Implications for parental care allocation

Abstract

A model is developed which makes predictions about intraspecific variation in parental care patterns. The model assumes that animals can respond to predictable changes in conditions for rearing offspring, and can adjust the amount of parental care they provide. The following predictions are made: (1) Where the environment or the parent's condition varies predictably, animals should provide more care to successive broods under improving conditions, and less care under deteriorating conditions. (2) In stochastic environments, variation in brood success during the period of parental care should have a predictable effect on subsequent brood-care. (3) In non-uniform environments or populations, parents facing higher than average mortality risks of types independent of parental effort should increase care provided for current offspring. Parents whose mortality risks result from parental effort should provide less care for their offspring. These predictions are assessed in relation to the available empirical evidence. Much of this suggests that parental care patterns vary within species and may often be adjusted by individuals according to prevailing and projected conditions. Data could not be found to test all aspects of the theory, however, so further field studies would be valuable.