The presence of an animal carcass from Antarctics on the coast of West
Nias regency in the province of North Sumatra is a very interesting natural
phenomenon. The walrus is an Antarctic species which is not found in Indonesia,
but the carcasses of these animals can reach Indonesia.
"From Antarctica
to Nias island is a very, very long distance, but the carcass of this animal
could arrive in Nias island. This carcass should had been consumed by other
fish. My guess, this animal was separated from its group and died. Then, maybe
it was not eaten by other fish because it was deep in the sea and moved through
deep sea water," Rasyid Dongoran, a senior biologist in Medan, North
Sumatra, told Scorpion Foundation on Tuesday (2018-07-10).
According to Rasyid -
who is also the Executive Director of the Sumatra Rainforest Institute (SRI),
the presence of this carcass needs to be studied further, because it is “a very
interesting natural phenomenon.”
The West Nias community
was overwhelmed with the discovery of the body of a large animal with huge
fangs that washed ashore. This animal carcass was seen by local residents of
Sirombu subdistrict, West Nias Regency on Thursday (2018-06-28). The body has a
length of approximately 10 meters and a width of one and half meters.
A zoologist, Erni Jumilawaty, also stated to local press that the animal is a walrus (Odobenus rosmarus) from the Antartic region. "Walrus is a typical animal from the Antarctic South Pole and was carried by the ocean currents from the Indian Ocean to the Nias Island," Erni told Tribunnews.com on Tuesday (2018-7-3).
Rasyid Dongoran, Senior Biologist Walrus carcass on Nias island.
Taxonomic
Notes (IUCN)
The
Walrus, Odobenus rosmarus, was in the past divided into three
subspecies: the Atlantic Walrus (O. r. rosmarus), the Pacific Walrus (O.
r. divergens), and the Laptev Walrus (O. r. laptevi) (Rice 1998).
However, the status of the Laptev Walrus has always been somewhat uncertain,
animals from that region are described as being intermediate in size between
the Pacific and Atlantic forms, with skull morphology most similar to the
Pacific subspecies (Fay 1982). Recent analyses of mitochondrial DNA and
morphometric data suggest that the taxon O. r. laptevi should
be abandoned (Lindqvist et al. 2009). The walruses found in
the Laptev Sea are in all probability the westernmost part of the Pacific Walrus
population.
The
IUCN Pinniped Specialist Group has assessed the status of the Atlantic and
Pacific Walrus subspecies separately. This assessment combines those two
analyses to assess the global status of the Walrus as a species.
Habitat
and Ecology (IUCN)
The Walrus’s most
distinctive feature is the external tusks, which are possessed by both males
and females. The tusks can grow to be a meter long and can weigh 5 kg in large
bulls. They are one of the largest pinnipeds with Pacific Walrus males reaching
3.6 m in length and weighing 880-1,557 kg; adult females are about 3 m and
580-1,039 kg. Atlantic Walrus adults are slightly shorter and lighter. Newborns
are 1-1.4 m long and weigh 33-85 kg (Fay 1981, Kovacs and Lydersen 2006).
Walruses are extremely social animals, and when on land or ice they are
normally found in tight groups ranging in size from a few individual up to
thousands. At sea they usually travel in groups as well (Fay 1981, Kovacs and
Lydersen 2006). There is significant sexual segregation outside the breeding
season, with males often being found in areas away from females and their
calves. Walruses have a narrow ecological niche. They depend on: 1) the
availability of large areas of shallow water with suitable bottom substrate to
support a productive bivalve community, 2) the presence of reliable open water
over rich feeding areas, particularly in winter when access to feeding areas is
limited by ice cover, and 3) the presence of haul out areas in reasonably close
proximity to feeding areas. The preferred haul out platform is sea ice,
although both subspecies routinely use terrestrial haul out sites in the summer
and autumn (Fay 1981, Hamilton et al. 2015).
Because they feed in shallow, coastal areas Walruses usually perform only
relatively shallow, short dives (Fay and Burns 1988, Born 2005). The Walrus’s
main prey is bivalve mollusks that they search for using their sensitive
whiskers on or in soft-bottom substrates. In addition to Clams, their diet can
include Worms, Snails, soft shell Crabs, Amphipods, Shrimp, Sea Cucumbers,
Tunicates, and even slow-moving Fishes (Born 2005, Sheffield and Grebmeier
2009). Some Walruses prey on birds and other marine mammals, eating a variety
of Seal species (Lowry and Fay 1984, Fox et al. 2010,
Seymour et al. 2014). Walrus make foraging trips that last
from a few hours to several days; in the Pacific, trips are shorter in duration
and distance when they originate from sea ice versus land (Udevitz et
al. 2009).
Courtship and mating occur in the winter. Walruses are polygynous and the males
establish small aquatic territories where they vigorously vocalize and display
adjacent to females hauled-out on ice floes (Sjare and Stirling 1996,
Sjare et al. 2003). Most births occur in May of the following
year. Most female Walrus give birth at 7-10 years old and usually they only
produce one calf every three years. Males become sexually mature between 7-10
years old, but are not physically and socially mature enough to successfully
compete for breeding opportunities until they are approximately 15 years old.
Longevity is approximately 40 years (Fay 1981).
The primary predators of Walrus are Polar Bears and Killer Whales (Killian and
Stirling 1978, Fay 1981).
