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Volume 17 Pages 1 - 58 (April 2000) Citation: Conroy, J & Calder, D. (2000) Otters Lutra lutra killing Mountain Hares Lepus timidus IUCN Otter Spec. Group Bull. 17 (1): 52 - 54 Otters Lutra lutra killing Mountain Hares Lepus timidus 1Institute
of Terrestrial Ecology, Banchory Research Station, Banchory,
Aberdeenshire, AB31 4BY, Scotland,
During the 1989-90 winter, dead mountain hares Lepus timidus were regularly found along the banks of the Water of Nochty, Ernan Water, Spearach Burn and Folly Loch in Aberdeenshire, north-east Scotland. These burns are fast flowing mountain streams which mostly flow through open heather moorland, with grass and rush/sedge along their banks before entering the River Don near the village of Strathdon (Grid Reference NJ 346124). The Burn of Nochty also has extensive areas of mature coniferous woodland along its bankside. The Folly Loch is near the headwaters of the Spearach Burn. All the carcasses were found between 300 and 500 metres above sea level. On one visit, nine of 11 dead hares, were found within two metres of the water's edge or on islets/rocks in the burns, near places where otters Lutra lutra regularly defaecated (spraint sites). In January and February 1990, 14 carcasses were examined along a 2.5km length of the Spearach Burn and the Burn of Nochty. Extensive areas of fresh blood in the snow near most of the bodies, suggested that at least 12 of the hares had been killed, rather than having died there, and been eaten as carrion. Of 25 faeces (spraints) examined from the area, 21 (84%) included hare remains (hair), while of 15 spraints from the larger River Don nearby, 10 (67%) contained mammal remains, including hare. Fish remains were found in all the spraints analysed from the River Don, but in only 17 from the study area, the remaining eight had only hare remains. Carcasses were found along a section of riverbank over a period of two to three weeks, then on other parts of the burns, either upstream or downstream, suggesting that the predator was systematically using the watercourses. No bodies were found between March and October. During this period, the riverbanks were covered with snow, making the examination of animal tracks in the area relatively easy to follow and identify. Otters were considered being responsible for the deaths because:
How did the otters manage to kill the hares - the latter being a relatively alert and swift animal, the former more cumbersome and slower on land? In fact, CHANIN (1985) wrote Otter are not sufficiently agile to catch many species of mammals, which do not, therefore, feature prominently in the diet. We would argue that it would not be too difficult for otters to catch hares. Although swift, and at times timid animals, they can also be naive, relying on keeping perfectly still rather than taking flight at the approach of a predator. DC has watched foxes prey on hares. On the appearance of the predator, most hares run, however, a few sit tight and the kills, with one exception, were achieved by the fox pouncing from a few feet away. If the hares were resting and sheltering in the vegetation at the water's edge, and were up wind, otters could thus catch them by emerging quietly from the burn. We have no idea of how many otters are involved, but footprints in the snow in January 1990 suggested at least two individuals. The upper reaches of the two burns where most of the carcasses were found are separated by only a few hundred metres of relatively flat ground, so it is possible that the same animals used both burns. An examination of literature shows that in most studies of otter diet, mammal remains are found at low frequencies, to about 10%, more usually around 5% (see MASON and MACDONALD, 1986 for details). The most common species recorded is rabbit Oryctolagus cuniculus - nearly 50% of the mammalian prey caught in Scotland, and about 75% in Devon - and most are caught near the water edge (KEY et al.,1979; WISE et al., 1981; MASON and MACDONALD 1986). There are a few references to otters eating hares, but none list them as an important component of diet. STEPHENS (1957) reported the remains of brown hare L. capensis in spraints, and that in November. BATTEN (1953) refers to leverets being eaten, while ST. JOHN (1893) reported that in severe frosts, etc., the otter..... catches and eats rabbits, hares and any animals it can surprise... Our observations suggest that during the winter months, when fish prey might be difficult to find, mountain hares can form an important part of the diet of otters, and catching them is not necessarily restricted to period of cold weather. This is further supported by results from a more detailed survey of otter in north-east Scotland. On three rivers, including the River Don, which flow through the upper parts of the Grampian mountains, there is an increase in the number of mammal remains recorded in spraints collected during the winter months (JC pers. obs.) REFERENCES Batten, H.M. (1953). Habits and
characters of British wild animals. Chambers, London. Resumen: Nutrias Lutra lutra
matando liebres de montaña Lepus timidus |
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