Growth From Birth to 20 Days in the Elephant Seal, Mirounga-Leonina, at Macquarie-Island

1987 ◽  
Vol 35 (4) ◽  
pp. 307 ◽  
Author(s):  
GJ Little ◽  
MM Bryden ◽  
A Barnes
Keyword(s):  
Birth Weight ◽  
Elephant Seal ◽  
Lactation Period ◽  
Mirounga Leonina ◽  
Average Birth Weight ◽  
Macquarie Island ◽  
Seal Population ◽  
Antarctic Research ◽  
Breeding Seasons ◽  
Pup Growth

Recent investigations by members of Australian National Antarctic Research Expeditions to Macquarie I. have revealed a decrease in the elephant seal population there of approximately 50% over the last 36 years. Lower birth weights and/or slower growth during the lactation period might explain this decrease. To test this hypothesis, growth of pups was studied from birth to 20 days during the 1984 and 1985 breeding seasons; these results were compared as far as possible with similar results for the 1956 and 1965 seasons. Average birth weight has not changed significantly over the last 20 years; it is suggested that if food supply were a major factor in the reduction of the elephant seal population, then birth weights in 1985 would have been lower than those in 1956. At birth, male pups were 7% (3 kg) heavier than female pups in 1985. Results from previous years suggest that this is probably normal in this seal. The weight of pups near weaning (20 or 21 days old) is shown to be significantly less in 1984 and 1985 than 1965, but this may be explained by differences in methodology. It is concluded that, on the evidence available, the pattern of pup growth on Macquarie I. has not altered significantly with time, but more work is needed to reach a clear conclusion.

Branding Elephant Seals for life-history studies

Polar Record ◽  
1967 ◽  
Vol 13 (85) ◽  
pp. 447-449 ◽  
Author(s):  
Susan E. Ingham
Keyword(s):  
Ecological Study ◽  
Individual Recognition ◽  
Elephant Seal ◽  
Southern Elephant Seal ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
Macquarie Island ◽  
Heard Island ◽  
Antarctic Research

In 1949 the Australian National Antarctic Research Expeditions (ANARE) began a long-term ecological study of the Southern Elephant Seal (Mirounga leonina) at HeardIsland. The biologists devised a method of branding seals for individual recognition (Chittleborough and Ealey, 1953) which has been modified only in detail since then (Carrick and Ingham, 1962a). At Heard Island, pups were branded every year until 1953, but the study here came to an end with the closing of the ANARE station in 1955. At Macquarie Island, pups have been branded every year from 1951 to 1965, giving a sample of individuals of known age and known history.

Age in relation to Breeding to Status of the Male Southern Elephant Seal, Mirounga leonina (L.), at Macquarie Island

1981 ◽  
Vol 8 (2) ◽  
pp. 327 ◽  
Author(s):  
E Jones
Keyword(s):  
Elephant Seal ◽  
Progressive Increase ◽  
Southern Elephant Seal ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
Macquarie Island ◽  
Southern Elephant Seals ◽  
Definition Of ◽  
Breeding Seasons ◽  
Breeding Status

Records of the breeding status of known-age male southern elephant seals at Macquarie I. were kept during five breeding seasons between 1969 and 1976. The seven status categories used were: beachmaster, secure assistant, medium harem owner, insecure assistant, small harem owner, attending bachelor, avoiding bachelor. There was a progressive increase in breeding status with age; none younger than 10-y-old bred: 16% of 10-y-olds, 30% of 11-y-olds and 55% of 12-y-olds did so; none younger than 12-y-old attained secure assistant status. At the earliest, beachmaster status may be attained at 14 y old, but no beachmasters of known age were recorded. Due to mortality and competition, most males do not breed and few breed for more than two seasons. Problems associated with the precise definition of status categories are discussed.

Twinning in southern elephant seals: the implications of resource allocation by mothers

2003 ◽  
Vol 30 (1) ◽  
pp. 35 ◽  
Author(s):  
Clive R. McMahon ◽  
Mark A. Hindell
Keyword(s):  
Reproductive Success ◽  
Rare Event ◽  
Elephant Seal ◽  
Lactation Period ◽  
Mirounga Leonina ◽  
Elephant Seals ◽  
Growth And Survival ◽  
Southern Elephant Seals ◽  
Lactation Duration ◽  
Pup Growth

Southern elephant seals (Mirounga leonina) typically give birth to a single pup and raise it over a short 24-day lactation period. Lactation is characterised by: maternal fasting, rapid pup growth and abrupt weaning after which the weaned pups rely on stored fat for growth and survival. Females are not able to transfer all of their stored resources to their pups because they themselves need to use some to return to their remote foraging grounds after the breeding effort. Therefore the amount of energy expended by a female during lactation may affect not only the survival of her pup, but her own survival and future reproductive success. Female southern elephant seals are therefore under strong selective pressure to allocate finite amounts of resources to their pups. In the rare event of producing twins, females that wean both pups are likely to experience reduced reproductive success. Twin births accounted for 0.38% of all the observed elephant seal births at Macquarie Island in 1999. The mean birth masses, weaning lengths and lactation duration for twin and singleton pups did not differ significantly but weaning mass, weaning girths and lactation growth rates did differ significantly. In all cases, singleton pups were larger and grew faster than twin pups. Twin pups suffered greater pre-weaning mortality than singletons (16.7% and 4.6% respectively) and fewer were seen alive after 18 months (20% compared with 47% respectively).

Human disturbance, nursing behaviour, and lactational pup growth in a declining southern elephant seal (Mirounga leonina) population

2002 ◽  
Vol 80 (11) ◽  
pp. 1876-1886 ◽  
Author(s):  
Georg H Engelhard ◽  
Antonie N.J Baarspul ◽  
Martijn Broekman ◽  
Jeroen C.S Creuwels ◽  
Peter J.H Reijnders
Keyword(s):  
Human Disturbance ◽  
Population Decline ◽  
Elephant Seal ◽  
Southern Elephant Seal ◽  
Mirounga Leonina ◽  
Maternal Aggression ◽  
Human Presence ◽  
Macquarie Island ◽  
Southern Elephant Seals ◽  
Pup Growth

We studied lactation behaviour in relation to pup growth in southern elephant seals (Mirounga leonina) at Macquarie Island, and compared harems in areas of high and low human presence to determine if there is an effect attributable to human activities, including scientific research. Pup weaning mass, a known correlate of first–year survival, was positively influenced by suckle bout durations during early and middle lactation and by maternal aggression during late lactation; no other behavioural variables were associated with weaning mass. In the area of high human presence, we observed from a distance the behaviour of mother–pup pairs directly before, during, and after visits to harems by other researchers. Alertness was raised threefold in the presence of people but quickly returned to predisturbance levels after their departure; there were no significant short-term effects on other behavioural variables. In the areas of high and low human presence, we observed the undisturbed behaviour of the seals in the absence of other people. No significant differences in any behavioural variables examined were found, indicating no long-term changes in behaviour resulting from human presence. Human disturbance therefore appears not to have significantly contributed to the population decline observed at Macquarie Island, but the conclusion requires caution given the fairly low power of our analyses.

Population status and seasonal haulout patterns of the southern elephant seal (Mirounga leonina) at Heard Island

1999 ◽  
Vol 11 (1) ◽  
pp. 38-47 ◽  
Author(s):  
David J. Slip ◽  
Harry R. Burton
Keyword(s):  
Total Population ◽  
Elephant Seal ◽  
Southern Elephant Seal ◽  
Mirounga Leonina ◽  
Population Status ◽  
Elephant Seals ◽  
Adult Females ◽  
Seal Population ◽  
Heard Island ◽  
One Year

We surveyed the southern elephant seal population at Heard Island regularly from February 1992 to March 1993, and determined the haulout patterns of the major components of the population. While haulout patterns of moulting and immature seals may give broad indices of population trends, the breeding haulout of adult females was the only reliable haulout that could be used to determine annual pup production. During the breeding season 14 277 adult females were counted. Raw counts were corrected using two models, one purely mathematical and the other based on the haulout behaviour of adult female seals. The two models have slightly different assumptions, but both provided good fits to the observed haulout patterns and estimated total population with a coefficient of variation of less than 5%. Total pup production was estimated at between 17 000 and 18 000 for 1992. Previous counts of elephant seals from 1949–51, 1985 and 1987 were corrected using the same models. The two models gave estimates of the population that were within ± 2.5% for all but one year. The population declined by about 50% between 1949 and 1985 but there appears to have been little change from 1985–92. The previous decline may be related to changes in sea-ice.

scholarly journals Dispersal of southern elephant seals (Mirounga leonina) from Davis Base, Antarctica: Combining population genetics and tracking data

2021 ◽  
Author(s):  
Michelle Chua ◽  
Simon Ho ◽  
Clive McMahon ◽  
Ian Jonsen ◽  
Mark de Bruyn
Keyword(s):  
Genetic Diversity ◽  
Marine Environment ◽  
Elephant Seal ◽  
Southern Elephant Seal ◽  
Tracking Data ◽  
Mirounga Leonina ◽  
Long Distance ◽  
Elephant Seals ◽  
Macquarie Island ◽  
Southern Elephant Seals

Marine animals such as the southern elephant seal (Mirounga leonina) rely on a productive marine environment and are vulnerable to oceanic changes that can affect their reproduction and survival rates. Davis Base, Antarctica, acts as a moulting site for southern elephant seals that forage in Prydz Bay, but the genetic diversity and natal source populations of these seals has not been characterized. Determining the genetic diversity of moulting populations like this one provides essential information on seal dispersal, inter-population mixing, and foraging behaviours. In this study, we combined genetic and animal tracking data on these moulting seals to identify levels of genetic diversity, natal source population, and movement behaviours during foraging and haul-out periods. Using mitochondrial sequence data, we identified two major breeding lineages of seals at Davis Base. We found that the majority of the seals originated from breeding stocks within the South Atlantic Ocean and South Indian Ocean. One seal was grouped with the Macquarie Island breeding stock (South Pacific Ocean). The Macquarie Island population, unlike the other two stocks, is decreasing in size. Tracking data revealed long-distance foraging activity of the Macquarie Island seal around Crozet Islands. We speculate that changes to the Antarctic marine environment have resulted in a shift in foraging and dispersal strategies, which subsequently affects seal population growth rates. These findings have implications for conservation management plans aimed at improving the population status of the southern elephant seal.

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