1. Trend changes in sympatric Subantarctic and Antarctic fur seal pup populations at Marion Island, Southern Ocean
- Author
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Marie-Pierre Etienne, P J Nico de Bruyn, Mia Wege, Ryan R. Reisinger, W. Chris Oosthuizen, Marthán N Bester, Mammal Research Institute - Department Zoology and Entomology, University of Pretoria (UPSpace), Mathématiques et Informatique Appliquées (MIA-Paris), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Mammal Research Institut - Department Zoology and Entomology, Department of Zoology, Nelson Mandela Metropolitan University [Port Elizabeth, South Africa], Department of Science and Technology, through the National Research Foundation (NRF) Hanse-Wissenschaftskollege (Institute for Advanced Study), University of Pretoria [South Africa], and AgroParisTech-Institut National de la Recherche Agronomique (INRA)
- Subjects
0106 biological sciences ,Sympatry ,population estimate ,[SDV]Life Sciences [q-bio] ,Aquatic Science ,Biology ,010603 evolutionary biology ,01 natural sciences ,sympatry ,Population estimate ,Marine mammal ,Arctocephalus ,Marion Island ,14. Life underwater ,Ecology, Evolution, Behavior and Systematics ,Subantarctic fur seal ,Antarctic fur seal ,density ,Ecology ,010604 marine biology & hydrobiology ,Foundation (engineering) ,biology.organism_classification ,hierarchical Bayesian model ,count ,Sympatric speciation ,detection probability ,Fur seal - Abstract
Recent pup population estimates of sympatric Subantarctic (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) at Marion Island are presented. Published pup population estimates of A. tropicalis (1995 and 2004) with an unpublished total island count in 2013, and annual counts on subsets of rookeries (2007-2015) were analyzed using a hierarchical Bayesian model. The pup population declined by 46% (95% credible interval CI: 43%-48%) between 2004 (mean = 15,260, CI: 14,447-16,169 pups) and 2013 (mean = 8,312, CI: 7,983-8,697), mirrored by a 58%-60% decline at rookeries counted annually (2007-2015). Population decline was highest at high-density west and north coast rookeries, despite negligible change in female attendance patterns, pup mortality or median pupping date over the previous 25 yr. A better understanding of foraging behavior and its effects on reproductive success and survival in this A. tropicalis population is needed before we can attribute population decline to any external factors. In contrast, total island counts of A. gazella pups in 2007, 2010, and 2013, suggest that this population is still increasing although the annual intrinsic rate of population growth decreased from 17.0% (1995-2004, 744 pups) to 4.0% (2010-2013, 1,553 pups). The slowed growth of A. gazella is likely the result of saturation at the main rookery.
- Published
- 2016