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Individual differences |
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| Eurasian otter (Lutra lutra)|
Eurasian otter (Lutra lutra)
Otters are semi-aquatic (or in one case aquatic) fish-eating mammals. The otter subfamily Lutrinae forms part of the family Mustelidae, which also includes weasels, polecats, badgers, as well as others. With twelve species in seven genera, otters have an almost worldwide distribution. They mainly eat aquatic animals, predominantly fish and shellfish, but also other invertebrates, amphibians, birds and small mammals.
An otter's den is called a holt or couch. A male otter is a dog (otter), a female a bitch (otter), and a baby a whelp or pup. The collective nouns for otters are bevy, family, lodge or romp, being descriptive of their often playful nature, or when in water raft.[How to reference and link to summary or text]
The time of pregnancy in otters is about 60 to 86 days. The newborn baby is taken care of by the mother, the father, and all the other offspring. Female otters reach sexual maturity at approximately 2 years of age, while males can produce offspring at approximately 3 years of age. After one month, the young otter can come out of the cave, and after 2 months it is able to swim. It lives with its family for about one year so that it can learn and be kept safe until maturity. Otters live up to ten years.
Otters have long, slim bodies and relatively short limbs, with webbed paws. Most have sharp claws on their feet, and all except the sea otter have long muscular tails. The twelve species range in adult size from 0.7 to 1.8 metres (2 to 6 feet) in length and 5 to 45 kilograms (10 to 100 pounds) in weight.
They have a very soft, insulated underfur which is protected by their outer layer of long guard hair. This traps a layer of air, and keeps them dry and warm under water.
Many otters live in cold waters and have very high metabolic rates to help keep them warm. Eurasian otters must eat 15% of their body-weight a day, and sea otters 20 to 25%, depending on the temperature. In water as warm as 10°C (50°F) an otter needs to catch 100 grams (3 oz) of fish per hour to survive. Most species hunt for 3 to 5 hours a day, and nursing mothers up to 8 hours a day.
For most otters, fish is the primary staple of their diet. This is often supplemented by frogs, crayfish and crabs. Some otters are expert at opening shellfish, and others will feed on available small mammals or birds. Prey-dependence leaves otters very vulnerable to prey depletion.
Otters are very active, chasing prey in the water or searching the beds of rivers, lakes or the seas. Most species live beside water, entering it mainly to hunt or travel, otherwise spending much of their time on land to avoid their fur becoming waterlogged. The sea otter does live in the sea for most of its life.
Otters are playful animals and appear to engage in various behaviors for sheer enjoyment. Different species vary in their social structure, with some being largely solitary, while others live in groups – in a few species these groups may be fairly large.
- Spotted-necked otter (Hydrictis maculicollis)
- Smooth-coated otter (Lutrogale perspicillata)
- Northern river otter (Lontra canadensis)
- Southern river otter (Lontra provocax)
- Neotropical river otter (Lontra longicaudis)
- Marine otter (Lontra felina)
- Giant otter (Pteronura brasiliensis)
- Sea otter (Enhydra lutris)
Northern river otter Edit
- Main article: Northern river otter
The northern river otter (Lontra canadensis) became one of the major animals hunted and trapped for fur in North America after European contact. River otters eat a variety of fish and shellfish, as well as small land mammals and birds. They grow to one metre (3 to 4 ft) in length and weigh from five to fifteen kilograms (10 to 30 lb).
In some areas this is a protected species, and some places have otter sanctuaries, which help sick and injured otters to recover.
- Main article: Sea otter
Sea otters (Enhydra lutris) live along the Pacific coast of North America. Their historic range included shallow waters of the Bering Strait and Kamchatka, and as far south as Japan. Sea otters have about 26,000 to 165,000 strands of hair per square centimetre of skin, a rich fur for which humans hunted them almost to extinction. By the time the 1911 Fur Seal Treaty gave them protection, so few sea otters remained that the fur trade had become unprofitable. Sea otters eat shellfish and other invertebrates (especially clams, abalone, and sea urchins), frequently using rocks as crude tools to smash open shells. They grow to 1.0 to 1.5 metres (2.5 to 5 ft) in length and weigh 30 kilograms (65 lb). Although once near extinction, they have begun to spread again, from remnant populations in California and Alaska.
Unlike most marine mammals (such as seals or whales), sea otters do not have a layer of insulating blubber. As with other species of otter, they rely on a layer of air trapped in their fur, which they keep topped up by blowing into the fur from their mouths. They spend most of their time in the water, whereas other otters spend much of their time on land.
Eurasian otter Edit
- Main article: Eurasian otter
This species (Lutra lutra) inhabits Europe, and its range also extends across most of Asia and parts of North Africa. In the British Isles they occurred commonly as recently as the 1950s, but became rare in many areas due to the use of chlorinated hydrocarbon pesticides and as a result of habitat-loss and water pollution (they remained relatively common in parts of Scotland and Ireland). Population levels attained a low point in the 1980s, but are now recovering strongly. The UK Biodiversity Action Plan envisages the re-establishment of otters by 2010 in all the UK rivers and coastal areas that they inhabited in 1960. Roadkill deaths have become one of the significant threats to the success of their re-establishment.
Giant otter Edit
- Main article: Giant Otter
The giant otter (Pteronura brasiliensis) inhabits South America, especially the Amazon river basin, but is becoming increasingly rare due to poaching, habitat loss, and the use of mercury and other toxins in illegal alluvial gold mining. This gregarious animal grows to a length of up to 1.8 metres (6 ft), and is more aquatic than most other otters.
In popular cultureEdit
For countless generations, fishermen in southern Bangladesh have bred otters and used them to chase fish into their nets. Once a widespread practice passed down from father to son throughout many communities in Asia, this traditional use of domesticated wild animals is still in practice in the district of Narail, Bangladesh.
Religion and mythology Edit
In some Native American cultures, otters are considered totem animals.
See also Edit
- Pantolestidae, an extinct otter-like mammal (60-40 mya)
References and further readingEdit
- ↑ otter. Merriam Webster's online dictionary. URL accessed on 16 Sep 2009.
- ↑ Kruuk H (2007). Otters: ecology, behaviour and conservation, 99–116, Oxford Biology.
- ↑ Koepfli KP, Deere KA, Slater GJ, et al (2008). Multigene phylogeny of the Mustelidae: resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation. BMC Biol. 6 (1): 4–5.
- ↑ Bininda-Emonds OR, Gittleman JL, Purvis A (1999). Building large trees by combining phylogenetic information: a complete phylogeny of the extant Carnivora (Mammalia). Biol Rev Camb Philos Soc 74 (2): 143–75.
- ↑ OTTERS - Physical Characteristics. URL accessed on 17 November 2009.
- ↑ 6.0 6.1 Sea Otter - Enhydra lutris - facts, video, and sound - Defenders of Wildlife. URL accessed on 17 November 2009.
- ↑ The Otter's Ransom. URL accessed on 2007-07-05.
- ↑ Cooper, JC (1992). Symbolic and Mythological Animals, 171–72, London: Aquarian Press.
- Gallant, D., L. Vasseur, & C.H. Bérubé (2007). Unveiling the limitations of scat surveys to monitor social species: a case study on river otters. Journal of Wildlife Management 71:258–265.
- ARKive Photographs and Videos of Eurasian Otter. On the same site are photos and videos of Marine otter (Lontra felina), Sea otter (Enhydra lutris), Marine otter (Lontra felina) , Sea otter (Enhydra lutris), Smooth-coated otter (Lutrogale perspicillata) and the Giant otter (Pteronura brasiliensis).
- Otters in Trouble in Hungary
- International Otter Survival Fund
- otter stories and pictures
- Blog: Saving Otters
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