Leptonychotes weddelli
Creators: name: Russell A. Mittermeier
name: Don E. Wilson
Publisher: name: Lynx Edicions
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Carnivora
Phocidae
Leptonychotes
Leptonychotes weddelli

description: 6.
Weddell Seal
Leptonychotes weddelli
French: Phoque de Weddell / German: \Weddell-Robbe / Spanish: Foca de Weddell
Other common names: \ Weddell's Seal
Taxonomy. Otaria weddellii Lesson, 1826,
“sur les cotes des Orcades australes, situées sour 60 degrés 37 minutes de lat” (= South Orkney Island in British Antarctic Trust Territory).
This species is monotypic.
Distribution. Circumpolar in the Southern Ocean.
Descriptive notes. Total length 280-290 cm (males) and 300-330 cm (females); weight ¢.400-600 kg (males and females). Newborns are ¢.120 cm in length and weigh ¢.25-30 kg. Weddell Seals are relatively large-bodied, robust seals with small heads and relatively short front flippers. Pelage of an adult Weddell Seal is short and generally dark bluish black to brown dorsally and lighter gray ventrally, with pale blotches and streaks over the entire body. Neonates have a light brown to gray woolly lanugo (fine, soft hair) that is molted c.2-3 weeks after birth. Weddell Seals have large,slightly forward-pointing canine teeth and incisors that firmly snap at and catch fish and other prey and, at times, also are used to keep breathing holes open.
Habitat. Fast ice (ice fastened to land) and pack ice of Antarctica. Primary breeding colonies of Weddell Seals are in fast-ice habitats abutting Antarctica at scattered locations, but there are also small land-breeding colonies in the South Shetland and South Orkney Islands and farther north at South Georgia Island. Recent studies have found non-reproductive adult and juvenile Weddell Seals in pack-ice habitats in the Ross, Amundsen, and Bellingshausen seas, where they apparently remain for several years before returning to coastal breeding colonies.
Food and Feeding. Weddell Seals eat Antarctic cod (Dissostichus mawsoni) and smaller aggregating nototheniid fish that are endemic to Antarctica; squid and other invertebrates also represent small percentages of diets. They feed in the water column and near the seafloor at depths of ¢.600 m but occasionally as deep as 1000 m.
Breeding. Female Weddell Seals aggregate around breathing holes or tidal cracks and give birth from late September through early November and nurse their offspring for c.4—6 weeks. Adult male Weddell Seals rarely haul-out on ice during the breeding season, but instead, they patrol breathing holes and along tidal cracks throughout the season, attempting to exclude other males from these areas with vocal and visual displays and waiting for estrous females to enter the water for the first time. Females are impregnated in late October-November, and mating appears to occur exclusively in the water. The fertilized egg develops briefly, and then the blastocyst floats freely for about two months before it attaches to the uterine wall and fetal growth resumes. Twin births are occasionally reported. Most females give birth at 6-8 years old.
Activity patterns. During the breeding season, offspring remain on the ice for the first two weeks after birth but then gradually start entering the water for brief periods with their mothers. Adult female Weddell Seals sometimes leave their offspring unattended on ice while they forage, particularly late in lactation. Post-breeding, adult Weddell Seals forage for c.1-2 months to recover body mass that was lost while fasting during the breeding season and then spend more time hauled out while molting. Juveniles and non-reproductive adults return to fast-ice habitats to molt in November-December. In some areas, Weddell Seals move northward from fast-ice habitats into open water or pack ice for autumn and winter and actively forage in preparation for the next breeding season. They dive continually then and haul-out to rest less often. Most dives are to depths of 400-800 m for 15-40 minutes and occasionally as long as 80 minutes.
Movements, Home range and Social organization. Weddell Seals aggregate at fast-ice and sea-ice habitats in late spring and early summer to breed and molt. In fast-ice habitats, they occur in dispersed groups of dozens to hundreds of individuals along tidal cracks but are still relatively dispersed and asocial. Weaned offspring leave fast-ice habitats and may spend 3—4 years in northern pack-ice and open-water habitats before they return to breeding colonies when sexually mature. Adult Weddell Seals disperse northward—in some locations at least—after molting and migrate into open-water and pack-ice habitats to forage until moving south to fast-ice breeding colonies in the next season.
Status and Conservation. Classified as Least Concern on The IUCN Red List. In the late 1800s, Norwegian sealers evidently harvested substantial numbers of Weddell Seals, and Soviet sealers experimentally harvested much smaller numbers in the mid-1980s. Weddell Seals were harvested at some research stations and sites used by Antarctic expeditions in the early and mid-20" century for food for sled dogs and occasionally for humans, until sled dogs were removed from Antarctica by international agreement in the 1980s. Long-term population studies of Weddell Seals have been conducted at some USA and Australian research bases, and estimates of local abundances suggested relatively stable populations. Estimates of circumpolar abundance have more recently been obtained during collaborative international circumpolar surveys and by genetic analyses. The global population of Weddell Seals might number c.1,000,000 individuals.
Bibliography. Cameron & Siniff (2004), Croxall & Hiby (1983), Davis et al. (1999), Gelatt & Southwell (2008), Kooyman (1981b), Lake et al. (2006), Plotz et al. (2001), Siniff et al. (1977), Thomas & Stirling (1983).
description: Published as part of Russell A. Mittermeier & Don E. Wilson, 2014, Phocidae, pp. 120-183 in Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona :Lynx Edicions on pages 173-174, DOI: 10.5281/zenodo.6607185