Reisinger, Ryan RudolfLandman, MarietjieMgibantaka, NonkolisoSmale, Malcolm J.Bester, Marthan NieuwoudtDe Bruyn, P.J. NicoPistorius, Pierre Anton2018-06-122018-06-122018-04-20Ryan R. Reisinger, Marietjie Landman, Nonkoliso Mgibantaka, Malcolm J. Smale, Marthán N. Bester, P.J. Nico De Bruyn & Pierre A. Pistorius (2018) Overlap and temporal variation in the diets of sympatric Antarctic and Subantarctic fur seals (Arctocephalus spp.) at Marion Island, Prince Edward Islands, Polar Research, 37:1, 1451142, DOI: 10.1080/17518369.2018.1451142.0800-0395 (print)1751-8369 (online)10.1080/17518369.2018.1451142http://hdl.handle.net/2263/65133Antarctic (Arctocephalus gazella) and Subantarctic (A. tropicalis) fur seals are important predators in the Southern Ocean. Marion Island (southern Indian Ocean) hosts the largest sympatric breeding populations of these two species. Environmental and population changes here over two decades may have influenced their diet and trophic interactions. To quantify diet, we analysed prey remains in scat samples from Antarctic (661 scats) and Subantarctic (750 scats) fur seals collected at Marion Island (2006–2010). We assessed diet composition over time and calculated dietary overlap. The diet of both species was dominated by fish prey (98.2% and 99.4% of prey items), mainly myctophids. Antarctic fur seals consumed small numbers of penguins, cephalopods and crustaceans. In Subantarctic fur seal scats, crustaceans and cephalopods were rare and penguin remains were absent. The diets of the two species overlapped substantially (Pianka’s index = 0.98), however, small but significant differences in the relative proportions of prey were evident. Seasonal and annual diet changes suggest that their diet is similarly influenced by patterns of local prey availability and abundance. Despite substantial changes in the population size and trajectory of Antarctic and Subantarctic fur seals – which would be expected to influence trophic interactions between them – comparing our data to those from earlier studies (1989–2000) did not reveal significant long-term dietary changes in either species.en© 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/).PreyScatsForagingMarine mammalPinnipedConfidence interval (CI)Permutational multivariate analysis of variance (PERMANOVA)WinterAntarctic fur seal (Arctocephalus gazella)Subantarctic fur seal (A. tropicalis)Pup growthMarion Island, Prince Edward IslandsStable isotopeSeasonal changesForaging behaviorPopulation changesSouthern Ocean predatorArticle