The canalized parental roles of a Eudyptes penguin constrain provisioning and growth of chicks during nutritional stress

Abstract

Behavioral plasticity may allow organisms to respond adaptively to reduced food availability caused by climate change, facilitating population persistence. Conversely, inflexible parental roles may constrain sex-specific parental investment and amplify reduced reproductive fitness during nutritional stress. We examined chick-provisioning rates of transponder-tagged female and male eastern rockhopper penguins (Eudyptes chrysocome filholi) using an automated gateway on Campbell Island, New Zealand in a year of good diet quality and a poor year of nutritional stress. All seven species of Eudyptes penguins are unique in exhibiting canalized parental roles during the first 3–4 weeks of chick-rearing: males fast while guarding chicks provisioned exclusively by females. In the remaining 5–6 weeks before fledging, chicks form creches and are typically fed by both parents. Each species of Eudyptes is also “vulnerable” or “endangered”, generally because of long-term population declines linked to climate-induced nutritional stress. We hypothesized that the unique role division of Eudyptes penguins contributes to their sensitivity to nutritional stress. We found that chick growth was strongly positively correlated with total provisioning rate. Both sexes made longer foraging trips and provisioned less often under nutritional stress, but males decreased their investment in chick-provisioning more than females by making extra-long self-feeding trips early in the creche period. We show that Eudyptes chicks would be fed more often if the sexes shared all chick-provisioning, especially under nutritional stress. We conclude that the canalized division of labor strategy of Eudyptes penguins is maladapted to more frequent years of nutritional stress under climate change.