Future climate-induced distribution shifts in a sexually dimorphic key predator of the Southern Ocean

The response to climate change in highly dimorphic species can be hindered by differences between sexes in habitat preferences and movement patterns. The Antarctic fur seal, Arctocephalus gazella, is the most abundant pinniped in the Southern Hemisphere, and one of the main consumers of Antarctic krill, Euphausia superba, in the Southern Ocean. However, the populations breeding in the Atlantic Southern Ocean are decreasing, partly due to global warming. Male and female Antarctic fur seals differ greatly in body size and foraging ecology, and little is known about their sex-specific responses to climate change. We used satellite tracking data and Earth System Models to predict changes in habitat suitability for male and female Antarctic fur seals from the Western Antarctic Peninsula under different climate change scenarios. Under the most extreme scenario (SSP5-8.5; global average temperature +4.4 degrees C projected by 2100), suitable habitat patches will shift southward during the non-breeding season, leading to a minor overall habitat loss. The impact will be more pronounced for females than for males. The reduction of winter foraging grounds might decrease the survival of post-weaned females, reducing recruitment and jeopardizing population viability. During the breeding season, when males fast on land, suitable foraging grounds for females off the South Shetland Islands will remain largely unmodified, and new ones will emerge in the Bellingshausen Sea. As Antarctic fur seals are income breeders, the foraging grounds of females should be reasonably close to the breeding colony. As a result, the new suitable foraging grounds will be useful for females only if nearby beaches currently covered by sea ice emerge by the end of the century. Furthermore, the colonization of these new, ice-free breeding locations might be limited by strong female philopatry. These results should be considered when managing the fisheries of Antarctic krill in the Southern Ocean. La resposta al canvi climatic en especies amb dimorfisme sexual pot veure's dificultada per les diferencies entre sexes respecte a les seves preferencies d'us de l'habitat i els seus patrons de moviment. L'os mari antartic (Arctocephalus gazella), es el pinnipede mes abundant a l'Hemisferi Sud i un dels principals consumidors de krill antartic, (Euphausia superba), a l'Ocea Antartic. No obstant aixo, les poblacions que es reprodueixen al sector Atlantic de l'Ocea Antartic estan disminuint, en part a causa de l'escalfament global. Els mascles i les femelles de l'os mari antartic difereixen considerablement en la seva mida corporal i ecologia trofica, i es te poc coneixement sobre les seves respostes especifiques al canvi climatic. En aquest estudi hem utilitzat dades de seguiment per satel center dot lit i models del Sistema Terrestre per predir els canvis en la idoneitat de l'habitat per als mascles i les femelles d'os mari antartic de la Peninsula Antartica Occidental sota diferents escenaris de canvi climatic. Sota l'escenari mes extrem (SSP5-8.5; temperatura mitjana mundial +4.4 degrees C prevista per a 2100), les zones d'habitat idoni es desplacaran cap al sud durant l'epoca d'hivernada (no reproduccio), provocant una lleugera perdua d'habitat idoni. Tot i aixo, l'impacte sera mes pronunciat per a les femelles que per als mascles. Aquesta reduccio dels territoris d'alimentacio durant l'hivern podria disminuir la supervivencia de les femelles postdeslletades, reduint-ne el reclutament i posant en perill la viabilitat de la poblacio. Durant l'epoca de cria, quan els mascles es troben majoritariament en deju a terra, els territoris d'alimentacio idonis per a les femelles al voltant de les Illes Shetland del Sud romandran en gran part sense modificar-se, i n'emergiran de nous al mar de Bellingshausen. Com que les femelles d'os mari antartic es continuen alimentant durant la cria, els territoris d'alimentacio de les femelles han d'estar raonablement a prop de la colonia de cria. Com a resultat, aquestes noves zones d'alimentacio seran utils nomes si les platges properes, actualment cobertes de gel mari, emergeixen al llarg del segle. A mes, la colonitzacio d'aquests nous llocs de reproduccio lliures de gel podria veure's limitada per la forta filopatria de les femelles. Aquests resultats haurien de tenir-se en compte en la gestio de les pesqueries de krill a l'Ocea Antartic. Climate change poses challenges for sexually dimorphic species, such as the Antarctic fur seal, where males are larger than females. By tracking individuals from both sexes, we assessed their responses to current environmental conditions and projected their future responses using various climate models. Findings reveal a sex-skewed impact: females face more severe consequences as they may lose vital winter feeding grounds which will shift southward. Breeding season habitats near current colonies will persist, but female philopatry poses adaptation challenges, given the southward shift of their prey, Antarctic krill. Conserving this species requires recognizing sex-specific vulnerabilities in a changing climate, which is crucial for sustaining their populations amidst habitat alterations and prey migrations.image