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

Reproduction ◽  
2003 ◽  
Vol 126 (3) ◽  
pp. 365-370
Author(s):  
R. Laws
Keyword(s):  
Breeding Season ◽  
Embryonic Diapause ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus

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).

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.

Age estimation in crabeater seals (Lobodon carcinophagus)

2002 ◽  
Vol 258 (2) ◽  
pp. 197-203 ◽  
Author(s):  
R. M. Laws ◽  
A. Baird ◽  
M. M. Bryden
Keyword(s):  
Age Estimation ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus

Social and reproductive behavior of crabeater seals (Lobodon carcinophagus) during the austral spring

1979 ◽  
Vol 57 (11) ◽  
pp. 2243-2255 ◽  
Author(s):  
D. B. Siniff ◽  
I. Stirling ◽  
J. L. Bengston ◽  
R. A. Reichle
Keyword(s):  
Predatory Behavior ◽  
Population Parameters ◽  
Austral Spring ◽  
Reproductive Behaviors ◽  
The Social ◽  
Fast Ice ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus ◽  
The Impact ◽  
Family Groups

The social and reproductive behaviors of crabeater seals (Lobodon carcinophagus) were studied from September through November, during 1975, 1976 and 1977. Seals were immobilized, or controlled with a canvas bag over the head, then tagged and measured. Behavioral observations were recorded on all seals encountered.Crabeater seals were classified into three groups: (1) family groups (2) mated pairs, and (3) fast ice concentrations. Family groups consisted of an adult female, her pup, and an adult male. After weaning, the male and female formed a mated pair, and remained together for 1 to 2 weeks or until copulation. Adult females without a pup were joined by a male as they came into estrus, forming the mated pair category. Fast ice concentrations, primarily composed of sexually immature animals ranged from 50 to over 1000 seals and inhabited bays where seasonal ice persisted.Data were obtained on the predatory behavior of leopard seals (Hydrugra leptonyx), which indicated intensive predation on crabeater pups just after weaning; the degree of predation probably declines through the 1st year of life. Crabeater seals older than 1 year are probably seldom attacked by leopard seals. Further studies to determine the impact of this predation on population parameters of the crabeater seal are suggested.

An acoustic technique for determining diurnal activities in leopard (Hydrurga leptonyx) and crabeater (Lobodon carcinophagus) seal

1982 ◽  
Vol 60 (8) ◽  
pp. 2028-2031 ◽  
Author(s):  
J. A. Thomas ◽  
D. P. DeMaster
Keyword(s):  
Correction Factors ◽  
Vocal Behaviour ◽  
Acoustic Technique ◽  
Hydrurga Leptonyx ◽  
Crabeater Seals ◽  
Ice Floes ◽  
Lobodon Carcinophagus

Hourly variations in the rate of underwater vocalizations produced by leopard (Hydrurga leptonyx) and crabeater seals (Lobodon carcinophagus) were compared with counts of these seals on ice floes. For both species maximum "haulout" corresponded with minimum underwater vocalizations. Consequently, sampling the vocal behaviour of pinnipeds may be used to determine their diurnal haulout pattern. This underwater vocalization rate potentially may be used to calculate a series of hourly correction factors that compensate for submerged seals not seen during a census.

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