DEMOGRAPHY AND BREEDING BIOLOGY OF A SMALL, LOCALIZED POPULATION OF SOUTHERN ELEPHANT SEALS (MIROUNGA LEONINA)

Abstract

Southern elephant seals have been studied in depth in most of their breeding range. One notable exception is the Falkland Islands population. We present data on demography and breeding biology of elephant seals of Sea Lion Island, the main breeding site of this species in the Falklands. Sea Lion Island shelters a small, localized population of southern elephant seals (5 16 breeding females in 1995 and 518 in 1996). Comparison with the few available census data collected prior to our study suggests that the population has been stable in the short term (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996). Females produced pups at maximum rate and pup mortality was low (2.13%). Breeding sex ratio was strongly unbalanced, with about 14 females per breeding male and 47 females per harem-holding male at peak haul-out. Survival rate between breeding seasons was 67.4% for females and 50% for males. Timing of the breeding season was very similar to that recorded in other populations and was in accordance with clinal variation with latitude. Sex ratio at birth was balanced, and no significant weight dimorphism at weaning between sexes was detected (males: 135.4 kg; females: 132.0 kg). Weaning weight was correlated with size class of the mother.

Genetic and morphometric differentiation between island and mainland southern elephant seal populations

“…Mark-recapture studies have indicated a high proportion of seals showing philopatry, and these studies have not produced any matches between PV and SG (see Lewis et al 1996). However, subadult males have been resighted between PV and the Falkland islands during both moulting and breeding seasons (C. Campagna, unpublished data;Galimberti & Boitani 1999), and this geographically intermediate island could serve as a conduit for dispersal between PV and SG. This is supported by the observation that males (but not females) tagged in SG have been resighted at the Falkland islands.…”

Advances in New Zealand mammalogy 1990–2000: Pinnipeds

“…Females first bred at between 4 and 7 years of age (mean at Macquarie Island 5.2 ± 1.8 years) and the estimated annual fecundity rate at South Georgia was 0.391 (Hindell 1991). At Peninsula Valdes, 96% of females that came ashore gave birth, and in the Falkland Islands, 100% (Campagna et al 1993;Galimberti & Boitani 1999). The successful pupping by the 23 year old females seen by Hindell & Little (1988) suggest that there may be no reproductive senescence.…”

“…Across their distribution, the day the maximum number of females is hauled out varies from 2 October at Punta Delgada (42° 30'S) through 18 October at Heard Island (53°00'S) to 25 October at South Georgia (54° 19'S) and King George Island (62° 16'S) (Campagna et al 1993;Galimberti & Boitani 1999). The duration of the parturition period is reasonably consistent across their distribution at close to 60 days, and the number of females ashore approximates a Gaussian model (Hindell & Burton 1987;Galimberti & Boitani 1999). Small females tend to arrive earlier than large females, and the departure date is slightly more irregular than arrival.…”

“…(Hindell & Burton 1988;Hindell et al 1994;), Bester and team on Marion Island (Bester & Pansegrouw 1992;Wilkinson & Bester 1990;Wilkinson 1991), Campagna and team at Peninsula Valdes, Argentina (Campagna et al 1992(Campagna et al , 1993Baldi et al 1996) and Galimberti and Boitani in the Falkland Islands (Galimberti & Boitani 1999).…”

Site fidelity and behaviour of killer whales (<i>Orcinus orca</i>) at Sea Lion Island in the Southwest Atlantic

“…One of the tourist attractions is the chance of viewing killer whales close to shore. On the eastern side of the island, sandy beaches on the north and south coasts are the site of the largest elephant seal (Mirounga leonina) breeding colony in the Falklands, which produces around 500 pups per year (Galimberti and Boitani, 1999). Reproduction in elephant seals occurs over a three month period, starting in early September on Sea Lion Island with maximum presence on 20 October.…”