水獭种

分布及栖息地

欧亚水獭(Common otter)是分布区域最广的水獭，分布地横跨亚洲、非洲及欧洲。不过，它们已在列支敦士登、荷兰、瑞士、以及台湾本岛灭绝，但在金门群岛上仍有小群聚落。它们在拉脱维亚、挪威沿岸及英国北部很是普遍。在意大利，它们聚居于卡洛雷卢卡诺河（Calore lucano）地区。

欧亚水獭主要吃鱼类，但也会吃鸟类、昆虫、青蛙、甲壳类及细小的哺乳动物。它们栖息在淡水的环境，包括湖泊、河流、溪涧及池塘等。它们也会栖息在沿海地区，但需要定时回到淡水区清洁。

行为及繁殖

欧亚水獭是强势地盘性的，主要都是独居的。它们的领地约1-40公里长，一般长18公里。领地的长短视乎食物供应及适合猎食的河流阔度。它们的领地只抗拒同性，故雄獭及雌獭的领地是重叠的。雄獭及雌獭全年任何时间都可以繁殖，会在水中交配。妊娠期约63日，每胎会产1-4只幼獭，头一年会依赖母獭。雄獭不会照顾幼獭，雌獭与幼獭的领地，很多时都完全包含在雄獭的领地中。它们会于夜间觅食，日间则会留在巢穴中。它们的巢穴很多是河床附近的洞穴或树孔，很多时要在水中进入。

保育状况

欧亚水獭于20世纪下半叶数量开始下降，原因是有机氯杀虫剂及多氯联苯。其他威胁包括失去栖息地及用作毛皮、药用以及视为渔业害兽而被猎杀。它们在欧洲很多地区都正在恢复，于1994年至2002年就已经上升55%，原因是禁止使用大部分有害杀虫剂及受到保护。世界自然保护联盟将它们列为近危。

The Eurasian otter (Lutra lutra), also known as the European otter, Eurasian river otter, European river otter, common otter, and Old World otter, is a semiaquatic mammal native to Eurasia and the Maghreb. It is the most widely distributed member of the otter subfamily (Lutrinae) of the weasel family (Mustelidae) and is found in the waterways and on the coasts of Europe, much of Asia, and parts of North Africa. The Eurasian otter eats mainly fish, and is strongly territorial. It is endangered in some parts of its range, but is recovering in others.

Description

The Eurasian otter is a typical member of the otter subfamily. With brown fur on their backs and cream-coloured fur on their bellies, these long, slender creatures are well-equipped for their aquatic lifestyle. Their bones show osteosclerosis, which increases their density and reduces buoyancy. This otter differs from the North American river otter by its shorter neck, broader visage, the greater space between the ears and its longer tail. However, the Eurasian otter is the only otter in much of its range, so it is rarely confused for any other animal. Normally, this species is 57 to 95 cm (22.5 to 37.5 in) long, not counting a tail of 35–45 cm (14–17.5 in). The female is shorter than the male. The otter's average body weight is 7 to 12 kg (15 to 26 lb), although occasionally a large old male may reach up to 17 kg (37 lb).

Distribution and habitat

The Eurasian otter is the most widely distributed otter species. Its range includes Europe, North Africa and parts of Asia as far as the Palestine region. Though currently thought to be extinct in Liechtenstein and Switzerland, it is now common in Latvia, along the coast of Norway, in the western regions of Spain and Portugal and across Great Britain and Ireland. In Italy, it lives in the southern part of the peninsula.

It inhabits unpolluted bodies of fresh water such as lakes, streams, rivers, canals and ponds, as long as the food supply is adequate. In Andalusia, it uses artificial lakes on golf courses. It prefers the open areas of streams and also lives along the coast in salt water, but requires regular access to fresh water to clean its fur.

In Syria, the Eurasian otter was recorded in montane creeks in Latakia and Raqqa Governorates and in the lower Euphrates valley in Deir ez-Zor Governorate.

Behaviour and ecology

Diet

The Eurasian otter's diet consists primarily of fish, particularly in Mediterranean and temperate freshwater habitats where fish is most abundant.

During winter and in cooler climates, the Eurasian otter's diet includes worms, caterpillars, clams, crustaceans, insects, eggs, birds, and small mammals, including young European beavers, and amphibians.

The Eurasian otter is capable of overpowering prey that is significantly larger than itself, and it occasionally hunts large waterbirds such as adult greylag geese.

Breeding

The Eurasian otter is strongly territorial and typically lives alone. The length of an individual's territory may vary in the range of 1 and 40 km (0.62–24.85 mi), with about 18 km (11 mi) being usual. The size of the territory depends on the availability of food and the width of suitable hunting grounds. It is shorter on coasts, where the available width is much greater, and longer on narrower rivers.

Taxonomy

The extinct Japanese otter is sometimes considered a subspecies. However, recent studies have found that it falls outside the subspecific clades comprising L. lutra, so it has been reclassified as a distinct species. Nevertheless, uncertainty remains.

Conservation

The Eurasian otter declined across its range in the second half of the 20th century primarily due to pollution from polychlorinated biphenyls and pesticides such as organochlorine. Other threats included habitat loss and hunting, both legal and illegal. Eurasian otter populations are now recovering in many parts of Europe. In the United Kingdom, for example, the number of sites with an otter presence increased by 55% between 1994 and 2002. In August, 2011, the Environment Agency announced that otters had returned to every county in England, having previously disappeared from all but the West Country and parts of Northern England.