These seals are named after Sir James Weddell, commander of British sealing expeditions into the sea which is also named after him, the Weddell Sea.
The eyes of Leptonychotes weddellii are well developed for low light visibility. This is an adaptive feature of this creature which assists it in locating breathing holes in the ice (Stirling 1971). Vocalization occurs underwater for communication. Overlapped calls are longer than solitary calls, which constitute the varied repertoire of vocal communication in the Weddell seal (Terhume 1994).
Communication Channels: acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
US Federal List: no special status
IUCN Red List of Threatened Species: least concern
Leptonychotes weddellii are often killed and used as dog food. Their dead bodies are also of benefit to those studying worms and parasite infestation since these occur so often in this species. Study of their vocal abilities has advanced our attempt to communicate with animals, similar to the vocal communication studies performed with dolphins (Terhune 1994).
These seals are heavily infested with worms and often reguritate them as a means of expulsion. The louse, Antarctophthirus ogmorhini, attacks the hind quarters as well as the penile orifice of these seals. Lice also infest subadults.
Commensal/Parasitic Species:
The diet of Leptonychotes weddellii consists of notothenid fishes, squids, and crustaceans, although they have been witnessed attacking Dissostichus mawsoni (Antarctic toothfish) as large as 54 kg in weight (Stirling 1971). These seals can dive up to 600 meters in search of food and are stealthy hunters, able to sneak attack fish from close range. They also use a method of disturbing fish from ice cracks by blowing bubbles into them and preying on the fish that emerge.
Animal Foods: fish; mollusks
Primary Diet: carnivore (Piscivore , Molluscivore )
Weddell seals are found throughout the Antarctic continent as well as on fifteen small neighboring islands (Stirling 1971).
Biogeographic Regions: antarctica (Native ); oceanic islands (Native ); atlantic ocean (Native ); pacific ocean (Native )
Leptonychotes weddellii live in Antarctic regions on fast ice areas and in the sea. They don't migrate and local movements are caused by changes in ice conditions. Underwater swimming occurs under natural ice cracks or under ice areas thin enough so that the seals can chew breathing holes using canine teeth. Ice areas where these seals dwell are usually flat icy plains (Stirling, 1970).
Habitat Regions: polar ; saltwater or marine
Terrestrial Biomes: icecap
Aquatic Biomes: pelagic ; coastal
Adult Weddell seals have a dark gray coat that is marked with black and lighter gray areas. Males are 2.5 to 2.9 meter in length and females reach up to 3.5 meters. They weigh between 400 and 600 kg.
Range mass: 400 to 600 kg.
Range length: 2.5 to 3.5 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger
Weddell's seals can be preyed on by orcas (Orca orcinus) or, occasionally, leopard seals (Hydrurga leptonyx).
Known Predators:
Reproductive behavior occurs underwater. The female is mounted by the male from behind while her sides are held by his foreflippers. Quite often she is bitten on her neck while copulation occurs. Male-male fighting occurs, which suggests that mating systems are polygynous.
Mating System: polygynous
From mid-September to late December active spermatogenesis occurs. In late November to mid-December females are impregnated and about mid-January implantation occurs (Stirling 1971). Gestation last 9 to 10 months. Young pups are born with their permanent dentition. Birth occurs onto the sea ice, which often results in a change of external temperature in newborn pups. Pups are usually born singly, and the time of birth usually varies with latitude from early September at latitude 60 degrees south to late October at latitude 78 degrees south (Stirling 1971). Weddell seal pups weigh about 29 kg at birth. They have a gray lanugo, which after 3 to 4 weeks turns to a dark coat. Weaning takes place at 6 weeks of age and maturity at 3 years. First breeding of females may be denied for 1 or 2 years under some population conditions and males usually don't mate until 6 to 8 years of age because of social pressures (Stirling 1971).
Breeding season: In late November to mid-December females are impregnated and about mid-January implantation occurs.
Average number of offspring: 1.
Range gestation period: 9 to 10 months.
Average weaning age: 6 weeks.
Average time to independence: 6 weeks.
Range age at sexual or reproductive maturity (female): 3 to 5 years.
Range age at sexual or reproductive maturity (male): 6 to 8 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous ; delayed implantation
Average birth mass: 29000 g.
Average number of offspring: 1.
Parental Investment: precocial ; pre-fertilization (Provisioning); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Female)
