Sex matters? Association between foraging behaviour, diet, and physiology in Magellanic penguins

Ecological segregation has been documented between males and females in different populations of seabirds. Moreover, foraging behaviour and diet have been associated with markers of oxidative status, and have been suggested to be a driver of sex-biased oxidative costs of reproduction in wild marine vertebrates. Nevertheless, the ecological role of sex driving such associations has been little studied. We, therefore, examined whether foraging habitat (δ13C), trophic level (δ15N), dietary antioxidants (retinol and α-tocopherol) and oxidative status (antioxidant capacity and oxidative damage, ROM) were ecologically segregated by sex in Magellanic penguins (Spheniscus magellanicus) breeding in Peninsula Valdés (Argentina) visualizing the isotopic, dietary antioxidant, and oxidative status Bayesian spaces as proxies for ecological niches. Our results suggest that specific sexual segregation by ecological niche partially drives the relation between foraging, dietary antioxidants, and oxidative status. The dietary antioxidant niche showed females with extremely low α-tocopherol levels relative to males, although retinol values seemed to be similar between sexes. Higher trophic levels preys (high δ15N) were positively associated with α-tocopherol in males suggesting that their greater dependence on the Argentinian hake (a benthopelagic fish rich in α-tocopherol) led to a higher absorption of specific dietary antioxidants than females. In addition, a positive relation between α-tocopherol and ROMs in males suggested that their benthic foraging was associated with greater oxidative damage, and that higher levels of alpha-tocopherol in benthopelagic fish were not sufficient to prevent higher levels of oxidative damage associated with the consumption of such fish. Overall, sex-biased dietary antioxidant niche linked with sex-specific ecological segregation.