Mates but not sexes differ in migratory niche in a monogamous penguin species
Résumé
Strong pair bonds generally increase fitness in monogamous organisms, but
may also underlie the risk of hampering it when re-pairing fails after the
winter season. We investigated whether partners would either maintain contact
or offset this risk by exploiting sex-specific favourable niches during
winter in a migratory monogamous seabird, the southern rockhopper penguin
Eudyptes chrysocome. Using light-based geolocation,we showthat although the
spatial distribution of both sexes largely overlapped, pair-wise mates were
located on average 595+260 km (and up to 2500 km) apart during winter.
Stable isotope data also indicated a marked overlap between sex-specific isotopic
niches (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 partners
after winter. Our study provides multiple evidence that migratory species
maywell demonstrate pair-wise segregation even in the absence of sex-specific
winter niches (spatial and isotopic).We suggest that dispersive migration patterns
with sex-biased timings may be a sufficient proximal cause for
generating such a situation in migratory animals.