title: Mates but not sexes differ in migratory  niche in a monogamous penguin species.
abstract: 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 show that 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 (δ¹³C and δ¹⁵N values) but a segregation of the feeding habitats (δ¹³C 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 may well 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.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Thiebot
authors.forename: Charles-André
authors.initials: CA
authors.lastname: Bost
authors.forename: Nina
authors.initials: N
authors.lastname: Dehnhard
authors.forename: Laurent
authors.initials: L
authors.lastname: Demongin
authors.forename: Marcel
authors.initials: M
authors.lastname: Eens
authors.forename: Gilles
authors.initials: G
authors.lastname: Lepoint
authors.forename: Yves
authors.initials: Y
authors.lastname: Cherel
authors.forename: Maud
authors.initials: M
authors.lastname: Poisbleau
mesh_terms: D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D002247:Carbon Isotopes; D005247:Feeding Behavior / Q000502:physiology; D005260:Female; D008297:Male; D009587:Nitrogen Isotopes; D010152:Pair Bond; D012621:Seasons; D012737:Sex Factors; D046429:Spheniscidae / Q000502:physiology*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes