Estimating mean age at sexual maturity in the crabeater seal (Lobodon carcinophagus)

1995 ◽  
Vol 52 (11) ◽  
pp. 2347-2352 ◽  
Author(s):  
Karin C. Hårding ◽  
Tero Härkönen
Keyword(s):  
Breeding Season ◽  
Sexual Maturity ◽  
Reproductive Status ◽  
Strong Indication ◽  
Specific Population ◽  
Crabeater Seal ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus

Mean age at sexual maturity (ASM) in crabeater seals (Lobodon carcinophagus) was estimated according to two different methods. Samples were from 1964, 1977, and 1989. Using the first method, the estimated ASM in 1989 was 6.57 ± 0.82 years, which was considerably older than reported earlier. This estimate is the only one existing for crabeater seals that can be used to compare populations and species. The first method was based on the maturity rate at age. Behavioural segregation of mature and immature seals could give skewed maturity rates in samples. Because the 1964 and the 1977 samples were collected during a season when segregated behaviour was expected (breeding season), results from these years were not comparable with the 1989 estimate (collected during moult). The second method does not produce absolute values of ASM, but the estimates could be used as indices of ASM within a specific population. There was a statistically significant increase in the ASM index in 1989 (4.93 ± 0.57), compared with 1964 (3.75 ± 0.31) and 1977 (3.80 ± 0.44). This is a strong indication of a true increase in ASM in crabeater seals. Recommendations are made to improve future procedures for studying reproductive status in seals.

Reproductive aspects of female crabeater seals (Lobodon carcinophagus) along the Antarctic Peninsula

1981 ◽  
Vol 59 (1) ◽  
pp. 92-102 ◽  
Author(s):  
John L. Bengtson ◽  
Donald B. Siniff
Keyword(s):  
Antarctic Peninsula ◽  
Reproductive Performance ◽  
Sexual Maturity ◽  
Marine Ecosystem ◽  
Geographical Differences ◽  
The Past ◽  
Antarctic Marine ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus ◽  
The Antarctic

Examination of a sample of 94 female crabeater seals collected in November, 1977, indicated that, for the past 7 years, the average age at sexual maturity was 3.8 years. Reproductive performance as evidenced by uterine scars and ovarian corpora is discussed. No females inseminated at age 4 or less successfully carried a fetus full term. Timing of ovulation was affected by both age and social category. Younger seals ovulate later in the season than older seals. No females ovulated prior to weaning their pups. Ovulation in experienced females occurred sometimes while still in a mated pair, but mostly at or after dissolution of the pair bond. Comparison of recent age of sexual maturity with earlier reports shows an increase in this age since 1967. This trend may reflect geographical differences or changes in the Antarctic marine ecosystem following a slowdown in Antarctic whaling.

scholarly journals Digestibility of krill (Euphausia superba and Thysanoessa sp.) in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus)

1994 ◽  
Vol 72 (5) ◽  
pp. 713-716 ◽  
Author(s):  
P.-E. Mårtensson ◽  
E. S. Nordøy ◽  
A. S. Blix
Keyword(s):  
Chemical Composition ◽  
Energy Density ◽  
Euphausia Superba ◽  
Balaenoptera Acutorostrata ◽  
Crabeater Seal ◽  
Minke Whales ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus ◽  
Very High

Apparent digestible efficiency (% DE) was studied by use of dietary Mn as an inert marker, in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus) which had been eating krill. Median % DE in minke whales (n 5) eating krill of the genus Thysanoessa sp. (energy density (ED) 23·8 kJ/g) was 93 (range 87–93). Median % DE in crabeater seals (n 6) eating krill of the species Euphausia superba (ED 20·8 kJ/g) was 84 (range 79–85), which is significantly lower than the % DE of krill in minke whales (P = 0·008). Since the chemical composition in E. superba and in Thysanoessa sp. is similar, it is suggested that the complex multi-stomached system of minke whales, which contains both chitinase (EC 3.2.1.14)-producing as well as several other types of bacteria, is superior to the single-stomached system of crabeater seals with regard to krill digestion. It is worth noting, however, that the % DE of krill in the crabeater seal is still very high.

Underwater vocalizations of leopard seals (Hydrurga leptonyx) and crabeater seals (Lobodon carcinophagus) near the South Shetland Islands, Antarctica

1979 ◽  
Vol 57 (6) ◽  
pp. 1244-1248 ◽  
Author(s):  
Ian Stirling ◽  
Donald B. Siniff
Keyword(s):  
Geographic Variation ◽  
Relative Abundance ◽  
Seasonal Variations ◽  
South Shetland Islands ◽  
The South ◽  
Shetland Islands ◽  
Crabeater Seal ◽  
Hydrurga Leptonyx ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus

Four underwater vocalizations of leopard seals (Hydrurga leptonyx) and one from the crabeater seal (Lobodon carcinophagus), representing most of their vocal repertoires, are described quantitatively and illustrated with sound spectrographs. Most of the underwater vocalizations given by these seals can now be identified, which will facilitate future investigation of possible geographic variation. Coupled with further studies of diurnal and seasonal variations in seal vocalizations, underwater recording may be used to study sub-ice distribution and possibly relative abundance.

Breeding season and embryonic diapause in crabeater seals (Lobodon carcinophagus)

Reproduction ◽  
2003 ◽  
pp. 365-370 ◽  
Author(s):  
RM Laws ◽  
A Baird ◽  
MM Bryden
Keyword(s):  
Reproductive Biology ◽  
Breeding Season ◽  
Direct Observation ◽  
Total Duration ◽  
Embryonic Diapause ◽  
Timing Of Births ◽  
The Mean ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus ◽  
Duration Of Pregnancy

Direct observation of 387 embryos in the early stages of development was combined with observations on breeding behaviour and reproductive biology obtained from the published literature, to estimate the timing of births, oestrus, ovulation and implantation, and to derive estimates of the duration of pregnancy, embryonic diapause and active gestation for crabeater seals (Lobodon carcinophagus). The total duration of pregnancy (conception to birth) is estimated to be 11.3 months (344 days). It is estimated that the pupping season extends from late September to early November, with peak births in mid-October. The estimated mean duration of lactation is approximately 17 days; the mean date of weaning is 31 October (14 October to 17 November); and the mean date of conception is 4 November (18 October to 21 November). Oestrus, ovulation and conception occur approximately 4 days after weaning. Estimates of times of weaning and conception were made assuming that the preimplantation period is the same in all individuals. The mean date of implantation of the embryo is 24 January+/-17 days; the duration of embryonic diapause is 2.7 months (81 days); and the duration of active gestation (implantation to parturition) is 8.8 months (264 days).

Reproduction in Dasykaluta-Rosamondae (Marsupialia, Dasyuridae) - Field and Laboratory Observations

1991 ◽  
Vol 39 (5) ◽  
pp. 549 ◽  
Author(s):  
PA Woolley
Keyword(s):  
Breeding Season ◽  
Granulosa Cells ◽  
Sexual Maturity ◽  
Reproductive Development ◽  
Interstitial Cells ◽  
Field Population ◽  
Interstitial Tissue ◽  
Mating Period ◽  
Reproductive Senescence ◽  
Age Class

Observations on reproduction in both wild-caught and laboratory-maintained Dasykaluta rosamondae have led to the conclusion that this species is one of 10 dasyurid marsupials in which males die soon after their first mating period. D. rosamondae have a short annual breeding season. The females are monoestrous, mating in September and bearing the young in November. Laboratory-reared young are weaned at an age of about 3 1/2-4 months, in February and March, and juveniles appear in the field population at this time. Both mates and females reach sexual maturity at an age of about 10 months. In the laboratory, males breed in only one season, after which those that survive become reproductively senile. Mature males disappear from the field population about the time the young are born; those collected shortly before this show signs of reproductive senescence. Males collected in the months after the young are weaned represent a single age-class; their reproductive development parallels that of maturing known-age males. Females are capable of breeding in at least two seasons and litters of up to eight are reared. Development of the pouch young is described. Unusual interstitial tissue masses develop in the ovaries of D. rosamondae; the granulosa cells of some follicles undergo transformation to interstitial cells, and the oocytes in these follicles degenerate, shortly before the females enter oestrus.

Reproduction in the Ningbing Antechinus (Marsupialia, Dasyuridae) - Field and Laboratory Observations

1988 ◽  
Vol 15 (2) ◽  
pp. 149 ◽  
Author(s):  
PA Woolley
Keyword(s):  
Breeding Season ◽  
Western Australia ◽  
Sexual Maturity ◽  
Males And Females

The ningbing antechinus is a species of small dasyurid marsupial found in the Kimberley region of Western Australia. Observations on reproduction have been made on newly captured and laboratory maintained specimens. The breeding season is short and mating occurs in June. The young are born after a long gestation, estimated to be between 45 and 52 days, in late July and early August. They are weaned in November when about 16 weeks old and they reach sexual maturity at 10-11 months, in the first breeding season after birth. Both males and females are potentially capable of breeding in a second season.

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