Ross Seal

Ross Seal

Big-eyed seal, Singing seal

Kingdom
Phylum
Subphylum
Class
Order
Suborder
Clade
Family
Genus
SPECIES
Ommatophoca rossii
Population size
above 78,000
Life Span
21 yrs
WEIGHT
129-216 kg
LENGTH
1.7-2 m

Ross seals are a semi-aquatic and somewhat elusive species. With their relatively small and narrow bodies, they do not look the same as many of the other seals, having broad heads, bigger eyes, very short coats and tiny mouths. On land these seals are slow and sluggish, crawling on their bellies by grasping the ice with their short, black claws. They cannot manage an upright stance and often assume a posture with their head raised and mouth open, pointing upwards, and are therefore often known as the ‘singing seal’.

Distibution

The Ross seal lives in areas in the Southern Ocean surrounding the Antarctic. From late summer, they may migrate north towards the open ocean, some vagrants venturing as far north as the Falkland Islands, South Georgia, and the South Sandwich Islands. These seals for a good part of the year are found on remote, inaccessible areas of dense ice, where they haul out to molt and breed. They spend more time in the open ocean from late summer to mid-spring, sometimes going as much as 2,000 km from the ice when feeding.

Ross Seal habitat map

Geography

Climate zones

Habits and Lifestyle

Unlike many other species of Antarctic seal, the Ross seal is mostly solitary and does not gather in large colonies for breeding. Instead, females haul out on their own onto the ice to give birth. These seals dive as deep as 100 to 200 meters to hunt for prey, and will stay under water for about six minutes. They use a variety of vocalizations for communication between each other or as warnings to predators. When people approach on land, a seal may make a series of thumping noises and trills with its mouth wide open. While in water the sounds it makes are a range of chirps, which may be for the purpose of defending territories from others of its species, although its solitary nature suggests otherwise. They also make explosive noises, siren calls and pulsed chugs, sometimes during mating and sometimes when a mother and pup are communicating with each other.

Diet and Nutrition

Ross seals are carnivores (molluscivores), they mainly eat squid, fish and krill. Their diet is approximately 64% of cephalopods, 22% of fish, and 14% is other invertebrates.

Mating Habits

REPRODUCTION SEASON
early December, but implantation is delayed until early March
PREGNANCY DURATION
9 months
BABY CARRYING
1 pup
INDEPENDENT AGE
4-6 weeks
FEMALE NAME
cow
MALE NAME
bull
BABY NAME
pup

Little is known about the Ross seal's mating behavior, which takes place early December, with implantation being delayed until early March. Gestation is for 9 months and pups are born in early November. Females give birth to a single pup, which is nursed on its mother’s energy-rich milk until being weaned at about 4-6 weeks. Pups are able to swim very soon after being born. Females reach maturity at the age of 2 to 4 years, and males between the ages of 3 and 4.

Population

Population threats

The primary threat to the Ross seal is probably global climate change. As the sea surface temperature is likely to increase, it is expected that pack ice will decline. The Ross seal will be affected, as it uses pack ice for birthing and avoiding predators. Climate change may also change the abundance and distribution of its prey species. The exact way climate change will impact Antarctic marine mammals is currently not clear.

Population number

According to the IUCN Red List, the total Ross seal population size is over 78,000 individuals, including 40,000 mature individuals. Currently this species is classified as Least Concern (LC) on the IUCN Red List.

Ecological niche

Ross seals are important predators on fish and cephalopods.

Fun Facts for Kids

  • Ross seals are named after James Clark Ross, commander of a British exploration ship, the H.M.S. Erebus, that travelled via the Ross Sea while exploring the Antarctic from 1839 to 1843.
  • Seals can be distinguished from sea lions because seals do not have visible ear flaps.
  • Young Ross seals are called 'pups'. Females are 'cows' and males 'bulls'. A group is a 'pod’, ‘colony’, ‘crash’, ‘harem’, ‘flock’, ‘bob’, ‘herd’, ‘hurd’, ‘rookery’, or ‘team’.
  • The Ross is the only seal species whose range is completely confined to the Antarctic.
  • These seals not only have small mouths compared to other seal species, but the shortest hair.
  • Ross seals ‘warble’ or ‘trill’ when calling to a mate or when they are threatened.
  • A Ross seals has small teeth that face backwards, which enables it to get a firm grip on slippery prey like squid.

References

1. Ross Seal Wikipedia article - https://en.wikipedia.org/wiki/Ross_seal
2. Ross Seal on The IUCN Red List site - http://www.iucnredlist.org/details/15269/0

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