Pre-natal investment in reproduction by female Antarctic fur seals

Boyd, Ian L.; McCann, Tom

doi:10.1007/bf00293265

Cited by 93 publications

(85 citation statements)

References 24 publications

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“…This includes both Subantarctic (Bester 1987) and Antarctic fur seals (Boyd & McCann 1989;Shaughnessy & Goldsworthy 1990). Although the sample sizes are small, the data presented here indicate that this is also the case at Marion Island.…”

Section: Sex Ratiomentioning

confidence: 59%

“…In fur seals, the sex ratio is at parity, both for foetuses (York & Hartley 1981;Oosthuizen 1991;De Villiers & Roux 1992;Ximinez et al 1984in Wickens & York 1997, and newborn pups (Stirling 1971;Payne 1977;Payne 1979;Trillmich 1986;Bester 1987;Boyd & McCann 1989;Shaughnessy & Goldsworthy 1990;Page et al 2003) of a number of species. This includes both Subantarctic (Bester 1987) and Antarctic fur seals (Boyd & McCann 1989;Shaughnessy & Goldsworthy 1990).…”

Section: Sex Ratiomentioning

confidence: 99%

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

Hofmeyr¹,

Bester²,

Pistorius³

et al. 2007

South African Journal of Wildlife Research

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Modelling fur seal populations requires the accurate assessment of demographic parameters such as age-specific mortality. Owing to the highly variable mortality rates that pups are subject to, mortality of this age class is perhaps the most important factor determining the number of surviving individuals within each cohort. Early pup mortality, sex ratio and median pupping date were determined for sympatric populations of Subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) at Marion Island, Southern Ocean. Mortality for this species was density dependent, varying from 0.8% at low density sites to 10.9% at high density sites. More accurate methods employed at low-density sites showed a substantially higher pup mortality at three weeks of 1.3-3.4% for Subantarctic fur seals. The same method yielded a mortality estimate at four weeks of age of 1.1-5.1% for Antarctic fur seals. Despite the underestimate inherent in island-wide counts for Subantarctic fur seals, these estimates are still useful for observing temporal and spatial patterns. Sex ratios were at parity for newborns of both species. The sex ratio of eightweek-old Subantarctic fur seal pups was also at parity, which is unusual for fur seal populations. The median pupping dates determined for Subantarctic fur seals and Antarctic fur seals did not differ substantially from previous estimates.

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Section: Sex Ratiomentioning

confidence: 59%

Section: Sex Ratiomentioning

confidence: 99%

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

Hofmeyr¹,

Bester²,

Pistorius³

et al. 2007

South African Journal of Wildlife Research

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“…In Antarctic fur seals, Costa et al (1988) found a better correlation between maternal mass and pup mass at birth for female pups than for male pups. However, Boyd and McCann (1989) found no correlation between maternal mass and female pup mass at birth, although mothers in good condition gave birth to heavier male pups than mothers in poor condition. Differences in environmental conditions and maternal state between the two studies are thought to be responsible for these different relationships (Trillmich 1996).…”

Section: Introductionmentioning

confidence: 71%

“…In several studies it was assumed that the energetic cost of gestation was likely to be higher for male offspring than for females because males are heavier than females at birth (Trillmich 1986;Boyd and McCann 1989;Lunn and Boyd 1993a;Ono and Boness 1996). However, body composition should also be taken into account because, despite differences in body mass, the total amounts of energy may be similar (Stamps 1990).…”

Section: Introductionmentioning

confidence: 99%

Prenatal investment in the subantarctic fur seal, Arctocephalus tropicalis

Georges¹,

Guinet²

2001

Can. J. Zool.

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Abstract:We investigated prenatal investment in a large sexually dimorphic mammal, the subantarctic fur seal, Arctocephalus tropicalis, on Amsterdam Island in the Indian Ocean. Pups' sex ratio and body mass, body length, and body condition at birth were studied in relation to timing of birth and maternal characteristics (body length and body condition) during three consecutive breeding seasons. Pups' sex ratio did not differ from unity throughout the pupping period. The sex of the pup was related to neither maternal body length (i.e., maternal age) nor maternal body condition when mating occurred or at parturition (1 year later), which suggests that the sex ratio was not biased toward one sex during gestation. Newborn male pups were heavier and longer than female pups in all years. Longer mothers tended to arrive later in the season regardless of their body condition, and gave birth to heavier pups whatever the sex of the pup. Mothers in good condition gave birth to heavier male pups than mothers in poor condition, but no significant differences were found for female pups, suggesting that the costs of carrying male foetuses is higher than that of carrying female foetuses. Differences in allocation of maternal resources between male and female pups may be due to sexrelated differences in body composition, since male pups were heavier than female pups for a given body length at birth. Thus, male and female foetuses may use maternal resources differently, with males growing in length whereas females appear to grow in body mass. The mothers we monitored over 2 consecutive years gave birth to pups that were similar in quality (in terms of birth mass) over years regardless of the sex of the previous pup and the mother's body length, suggesting that individual reproductive value is independent of maternal age. Furthermore, maternal body condition was not affected by the sex of the foetus, suggesting that there is no differential reproductive cost in carrying a male or a female foetus. Interannual differences in pup body size at birth suggest that environmental conditions such as prey availability during the last stages of gestation, and consequent maternal body condition, are important components of maternal investment in fur seals. 609Résumé : Nous avons étudié l'investissement prénatal chez un grand mammifère à dimorphisme sexuel, l'Otarie à fourrure des l'îles Kerguelen, Arctocephalus tropicalis, se reproduisant sur l'île Amsterdam, dans l'océan Indien. Le rapport mâles : femelles de même que la masse, le longueur et la condition physique des nouveau-nés ont été étudiés en relation avec la date de naissance et avec les caractéristiques de la mère (taille et condition physique) durant trois saisons consécutives de reproduction. Le rapport mâles : femelles à la naissance ne diffère pas de l'unité durant la période de mise bas. Le sexe des petits n'est relié ni à la longueur de la mère (c.à.d. l'âge de la mère), ni à sa condition physique au moment de l'accouplement ou de la mise bas, ce qui indique que le rapport mâle...

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“…For instance, Boyd & McCann (1989) and Boltnev & York (2001) found a positive relationship between maternal size and pup size in some pinniped species. Similarly, a positive relationship between maternal age and pup size has been shown (e.g.…”

Section: Discussionmentioning

confidence: 99%

Latitudinal variation in local productivity influences body condition of South American sea lion pups

Sepúlveda¹,

Olea²,

Carrasco³

et al. 2014

Aquat. Biol.

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Local productivity is essentially important for colonial species, such as seabirds and otariids (fur seals and sea lions). These species are central place foragers and income breeders that combine foraging ABSTRACT: In otariids, the condition and growth of offspring are linked to prey availability be cause females show a strong dependence on local food availability. Thus, it is expected that body condition of sea lion pups will vary spatially and/or temporally as a response to variations in the abundance of prey species on which females feed. The objective of this study was to analyze the geographic and temporal variation in the body condition of South American sea lion Otaria flavescens pups in Chile, and to relate it to spatio-temporal variations in prey availability. We captured 340 live pups in 2 distant colonies, Punta Patache/Punta Negra and Cobquecura, along the Chilean coast during consecutive breeding seasons. A morphometric index of pup body condition was estimated by comparing pups in all years using least-squares linear regression of the log 10 -transformed measurements of standard length vs. body mass. We analyzed the relationship between this index and estimates of fish biomass (as a proxy of prey availability) at each locality. We found that body condition was significantly different between years and between colonies, suggesting that animals of the central-south area were in better condition than those in the north. A positive relationship between body condition and fish biomass was found, suggesting that differences in body condition may be explained by spatial and temporal differences in prey availability.

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Pre-natal investment in reproduction by female Antarctic fur seals

Cited by 93 publications

References 24 publications

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

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

Prenatal investment in the subantarctic fur seal, Arctocephalus tropicalis

Latitudinal variation in local productivity influences body condition of South American sea lion pups

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