Mates but not sexes differ in migratory niche in a monogamous penguin species

International audienceStrong pair bonds generally increase fitness in monogamous organisms, butmay also underlie the risk of hampering it when re-pairing fails after thewinter season. We investigated whether partners would either maintain contactor offset this risk by exploiting sex-specific favourable niches duringwinter in a migratory monogamous seabird, the southern rockhopper penguinEudyptes chrysocome. Using light-based geolocation,we showthat although thespatial distribution of both sexes largely overlapped, pair-wise mates werelocated on average 595+260 km (and up to 2500 km) apart during winter.Stable isotope data also indicated a marked overlap between sex-specific isotopicniches (d13C and d15N values) but a segregation of the feeding habitats(d13C values) within pairs. Importantly, the tracked females remained longer(12 days) at sea than males, but all re-mated with their previous partnersafter winter. Our study provides multiple evidence that migratory speciesmaywell demonstrate pair-wise segregation even in the absence of sex-specificwinter niches (spatial and isotopic).We suggest that dispersive migration patternswith sex-biased timings may be a sufficient proximal cause forgenerating such a situation in migratory animals