Median pupping date, pup mortality and sex ratio of fur seals at Marion Island

Hofmeyr, G. J. G.; Bester, Marthán N; Pistorius, Pierre A.; Mulaudzi, T.W.; Bruyn, P. J. Nico de; Ramunasi, Justice A.; Tshithabane, Hendrik N.; McIntyre, Trevor; Radzilani, Phathu M.

doi:10.3957/0379-4369-37.1.1

Cited by 30 publications

(48 citation statements)

References 50 publications

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“…Although median birth dates have not been measured at either site, they are similar at both South Georgia and Marion Island (see Hofmeyr et al 2007), which are much farther apart, indicating that pup body mass data may constitute a valid index of relative prey availability. Daily PMG per foraging trip was also significantly higher at IN, with longer, potentially older, females transferring more mass to pups than smaller females.…”

Section: Provisioning Successmentioning

confidence: 99%

Colony-based foraging segregation by Antarctic fur seals at the Kerguelen Archipelago

Lea¹,

Guinet²,

Cherel³

et al. 2008

Mar. Ecol. Prog. Ser.

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The foraging behaviour of conspecific female Antarctic fur seals (AFS) was compared simultaneously at 2 breeding colonies at Îles Kerguelen (S Indian Ocean). A remnant colony at ÎIes Nuageuses (IN) thought to have escaped sealing is hypothesized to be the source of increasing fur seal numbers at Cap Noir (CN) on the Kerguelen mainland. Inter-annual variability in foraging areas is known to occur in response to local oceanographic changes at CN. Given the distance between the 2 sites (~160 km), we hypothesize that seals from the 2 colonies may show spatial segregation in foraging due to variability in local prey resource availability, although the transfer of foraging knowledge between sites via emigration may override such behaviour. The foraging zones, diving activity, diet and foraging success of seals were compared between sites using satellite telemetry, dive recorders and faecal analysis. No evidence of spatial foraging overlap was observed, with seals from IN conducting longer foraging trips, typified by a longer initial transit phase, than CN seals, which spent less time diving at night and dived more deeply. Pups nevertheless received higher absolute and daily energy delivery rates at IN. Diet was superficially similar at ~98% myctophid consumption; however, IN seals favoured the high-energy Gymnoscopelus nicholsi, indicating that local heterogeneity in marine resources likely influences the foraging zone choice of AFS. Finally, distribution patterns of 54 female AFS tracked during summer months from 1998 to 2006 reveal the importance of both on-shelf (< 500 m) and shelf-break regions as foraging habitat. The core foraging area for CN in all years (10 400 km 2 ) was small (~10% of total foraging space); however, time spent in this region alone totaled 38%. The likelihood of spatial overlap in foraging range is higher on the east coast of Kerguelen. KEY WORDS: Fur seal · Segregation · Myctophid · Diving · Southern OceanResale or republication not permitted without written consent of the publisher

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Section: Provisioning Successmentioning

confidence: 99%

Colony-based foraging segregation by Antarctic fur seals at the Kerguelen Archipelago

Lea¹,

Guinet²,

Cherel³

et al. 2008

Mar. Ecol. Prog. Ser.

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“…The Prince Edward Islands (comprised of Marion Island and the smaller Prince Edward Island) support a large, increasing population of subantarctic fur seals , Hofmeyr et al 2006. Aspects of subantarctic fur seal population growth (Hofmeyr et al 2006(Hofmeyr et al , 2007, attendance behaviour (Bester & Bartlett 1990, Kirkman et al 2002 and species biology (Kerley 1983, Bester & Van Jaarsveld 1994 have been investigated at Marion Island. However, long-range dispersal by subantarctic fur seals based on flippertagged individuals (Bester 1989), and a preliminary technical report on 4 lactating females tracked from the east coast of Marion Island (Osbourne et al 2002) are the only previous movement studies for the area.…”

Section: Introductionmentioning

confidence: 99%

Bathymetry and frontal system interactions influence seasonal foraging movements of lactating subantarctic fur seals from Marion Island

Bruyn

Tosh²,

Oosthuizen³

et al. 2009

Mar. Ecol. Prog. Ser.

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Sixteen lactating subantarctic fur seals Arctocephalus tropicalis were satellite-tracked during the winter of 2006 (n = 6), summer of 2006/07 (n = 6) and autumn/winter (n = 4) of 2007, from Marion Island, Southern Ocean. Despite varied individual movement patterns, a favoured foraging area lay to the northeast of the island. In contrast to findings for populations at similar latitudes, seals from Marion Island did not undertake short overnight foraging trips, but trips consistently went beyond 300 km from the island. This aligns with the at-sea duration of lactating seals' foraging trips from temperate Amsterdam Island, but differs from subantarctic Crozet and Macquarie islands. Time spent at sea, maximum distances travelled and movement variation of tracks from the island varied seasonally. Faecal analysis suggests the diet comprised primarily myctophid fish with limited seasonal variation. Well-defined areas of restricted movement coincided with significant bathymetric features to the west/northwest of the Crozet Plateau, with the Del Caño Rise clearly being important. Positive and negative sea-surface height anomalies (compared to the mean) appeared to be preferred by most seals across seasons. Higher summer sea-surface temperatures correlated with the movements of some seals. Higher chlorophyll a concentrations dictated transit and foraging areas during summer. Bathymetrically influenced oceanographic variables likely explain these preferred long-distance eastward movements. The Îles Crozet and Marion Island subantarctic fur seals differ in their foraging ecology despite being neighbours. Conversely, the subantarctic fur seal populations from the distant Amsterdam and Marion islands appear to be similarly influenced by such environmental factors.

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“…This arising despite twice daily observation sessions (2 hrs per session) for 52 consecutive days after 24 June 2008, and thereafter once every second day at this rookery. However, by 19 September 2008 (mean pup age 270 days; Hofmeyr et al, 2007) the pup weighed 18.5 kg (8 kg heavier than the mean 300 day wean mass and 3 kg heavier than the 210 day mean mass). On 10 October 2008 (mean weaning date; Hofmeyr et al, 2007) the pup weighed 10 kg, which is equal to the Island mean for males at this stage (MNB unpublished data).…”

Section: Sustained Milk-stealing or Fostering Accountmentioning

confidence: 99%

“…However, by 19 September 2008 (mean pup age 270 days; Hofmeyr et al, 2007) the pup weighed 18.5 kg (8 kg heavier than the mean 300 day wean mass and 3 kg heavier than the 210 day mean mass). On 10 October 2008 (mean weaning date; Hofmeyr et al, 2007) the pup weighed 10 kg, which is equal to the Island mean for males at this stage (MNB unpublished data). The sustained good condition of the pup after abandonment by the mother implies that the pup must have received milk from a female(s) other than its mother.…”

Section: Sustained Milk-stealing or Fostering Accountmentioning

confidence: 99%

“…The pups were tagged with uniquely numbered and colour-coded tags (Dalton Jumbo s Rototags, Henley-on-Thames, U.K.) in the trailing edge of each fore-flipper for easier future identification. The pups weighed 8.5 (female) and 15.5 kg (male) respectively, on 21 July 2009 (210 days of age, Hofmeyr et al, 2007). The male pup's mass exceeds the island population mean for male pups at this age by about 2 kg, while the female's mass was considerably lower (5 kg) than the mean for females at this age (MNB unpublished data).…”

Section: Potential Twin or Fostering Accountmentioning

confidence: 99%

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Prevalence of allosuckling behaviour in Subantarctic fur seal pups

et al. 2010

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Non-offspring maternal care should be rare due to the high costs of raising offspring, particularly lactation, but nonetheless occurs in a variety of taxa. Misguided parental care, associated with recognition errors and/or inattentiveness by lactating females, has been hypothesized as an explanation for allolactation in mammals. In an extension of this hypothesis, we suggest that milk-stealing is parasitism instigated by non-filial offspring, and that maternal behaviour is of secondary interest in an evolutionary context if she is unaware of the interaction. We provide evidence for frequent milk-stealing attempts by Subantarctic fur seal (Arctocephalus tropicalis) pups, including an example of sustained non-maternal care (4 three months) for one pup during the confirmed absence of his mother, leading to a weaning mass equal to the population mean. We also present only the second account of fostering/twins in the species at this locality. We suggest that rather than the hitherto suggested rare and anomalous behaviour, milk-stealing behaviour (while not always successful) is common.

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Median pupping date, pup mortality and sex ratio of fur seals at Marion Island

Cited by 30 publications

References 50 publications

Colony-based foraging segregation by Antarctic fur seals at the Kerguelen Archipelago

Colony-based foraging segregation by Antarctic fur seals at the Kerguelen Archipelago

Bathymetry and frontal system interactions influence seasonal foraging movements of lactating subantarctic fur seals from Marion Island

Prevalence of allosuckling behaviour in Subantarctic fur seal pups

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