Vagrant Antarctic fur seals at the Tristan da Cunha Islands

Bester, Marthán N; Ryan, Peter G.; Bester, W. A.; Glass, Trevor

doi:10.1007/s00300-014-1549-z

Cited by 8 publications

(12 citation statements)

References 4 publications

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“…Despite the counts not being corrected, there is no doubt that the overall population of fur seals in beaches (Bester 1982a) on the north coast. This would then be similar to what had appeared to Whereas the fur seal population at Gough Island has possibly recovered to pre-exploitation levels (Bester et al 2006) and numbers some 300,000 animals with an estimated 60,000 pups born which is about 80% of the world population (Bester and Ryan 2007), the fur seals were extinct at the northern islands of TdC in the early 20th century. Gough Island probably is the main source area for the current re-colonization of the proximate islands of TdC to the north after the severe population decreases due to commercial sealing in the early 1800s (Bester 1987;Cooper & Headland 1991), which decimated the fur seal populations at the TdC islands (Wace and Holdgate 1976;Bester 1987, Bester andRyan 2007).…”

Section: Discussionsupporting

confidence: 77%

“…Total island counts of fur seals were not done in any year on the TdC islands Bester and Ryan 2007) and no previous estimates of pups present at any of the beaches on Nightingale existed. The only counts at Inaccessible Island (04 -20 November 1999) produced a total of about 503 adult males, adult females and juveniles but no pups (PG Ryan pers comm), as pups are only born between the last week in November and the first week in January (Bester 1987).…”

Section: Discussionmentioning

confidence: 99%

“…The Tristan da Cunha (TdC) islands are home to the majority of the world population of Subantarctic fur seals (Arctocephalus tropicalis), with more than 80% of the global population 2 breeding on Gough Island alone (Bester et al 2006;Bester and Ryan 2007). The islands lie 2,700 km from South Africa and 3,700 km from the nearest coastline of South America.…”

Section: Introductionmentioning

confidence: 99%

“…At Nightingale, fur seal have colonized all the beaches in the more protected eastern sector. At Tristan, only one small breeding colony of Subantarctic fur seals has developed (mentioned inBester et al 2014), pups numbering 70 in January 2017, some six weeks after the median birthdate (presumably similar to the 10-11 December at Gough -Bester 1987), therefore past the conclusion of the pupping season. Anthropogenic disturbance perhaps prevent breeding colony development elsewhere on Tristan, the inhabited island (seeWace and Holdgate 1976).…”

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confidence: 99%

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Increase of sub-Antarctic fur seals at the Tristan da Cunha Islands

Bester

Wege

Glass³

2018

Polar Biol

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Subantarctic fur seal, Arctocephalus tropicalis, pups were counted on some of the beaches on all four Tristan da Cunha (TdC) islands, in January 2017, to determine the status of the population, in the face of climate change that is magnified in polar regions. Compared to counts done 40 years earlier on Gough, the breeding population increased markedly on some beaches, although negligibly on the largely open boulder beaches on the leeward northeastern sector of the island.Similarly, on the northern group of the TdC islands, the breeding population had increased markedly (including the very first pup counts at Inaccessible and Nightingale), despite fur seal females currently selecting only certain beaches for pupping (at Inaccessible and Tristan). At Tristan da Cunha, only one small breeding colony occurs which is remote from the human settlement, probably the result of anthropogenic disturbance.

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Section: Discussionsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Increase of sub-Antarctic fur seals at the Tristan da Cunha Islands

Bester

Wege

Glass³

2018

Polar Biol

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“…Fur seals are able to travel extensive distances ( e.g ., Bester and Reisinger , Bester et al . ) and settle at new rookeries (Wynen et al . ).…”

Section: Resultsmentioning

confidence: 99%

Trend changes in sympatric Subantarctic and Antarctic fur seal pup populations at Marion Island, Southern Ocean

Wege

Étienne

Oosthuizen

et al. 2016

Marine Mammal Science

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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)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(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 beaches counted annually (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(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. However, 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.

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