Eurasian Otter
Lutra lutra L., 1758
Lutra vulgaris Erxl., 1777: Kovachev, 1925: 15.
Order Carnivora
Family Mustelidae
Conservation status: in Bulgaria: Vulnerable VU [A4 c,d,e + D1], BDA-II, III; International: IUCN-NT, BeC-II, CITES-I, HD-II, IV.
General distribution. The largest part of Eurasia, Atlas.
Distribution and abundance in Bulgaria. Until the 1930s it was present almost throughout the country, numbering 4 000 – 5 000 individuals [1], however, in the 1950s it declined significantly and become a threatened species [2]. In the 1970-1990 period its numbers increased again: 800 – 1 400 individuals [3; 4]. It is found in the valleys, along the sea coast and in the mountains at altitudes of up to 600 m in 54% of the water catchments; 600 – 1 100 m in 27%; 1100-1500 m – in 19% (in the Western Rhodopes). Calculated numbers as per 2007 (without the cubs): about 1 300 – 1 500 individuals, at an average length of the individual river territory 5-15 km and 2-5 km of the coastal sections of closed water basins and the Black Sea; 800 – 1 000 breeding individuals. The higher population density is in Southeastern Bulgaria [3; 4; 5; 6; Questionnaire, G. Spiridonov, L. Mileva 1989; N. Spassov, V. Ivanov, unpubl. information].
Habitats. Natural river currents and closed water basins with a length of at least 15-20 km: with overgrown shores – dense tree and shrub vegetation, alder-groves and reed (low shores), various fish fauna with a minimum mass of 40 kg/ha, abundance of crayfish, frogs, vertebrates, mollusks [5; 7; 8; N. Spassov, V. Ivanov, unpubl. information].
Biology. The individual territory of the male may overlap that of 1 or more females [4; 7; 9; 10]. The dens are in the roots of shore trees. The cubs (2-4) are born in March – August [Questionnaire, 1989] and follow their mother for 1 year. In Southeastern Bulgaria fish is up to 93% of the prey (an average of 62% spring-summer and 74% autumn-winter); accessory food: crustaceans (14, respectively 7,5%, in an abundance up to 51%), frogs (11, 6%, and up to 23%), mammals, birds, reptiles [10; N. Spassov, V. Ivanov, unpublished information]. It catches its prey at a depth of up to 4 m [7].
Negative factors. Dikes and correction of riverbeds; pollution of the waters; reduction of the quantity of fish; drying up marshes; clearing the tree and shrub shore vegetation; water construction; ballast quarries; human poaching (53% of the losses, mainly near microdams and fisheries) [11]; accidents with road vehicles; catching in fishing nets; victims of wandering dogs; disturbance; winter-autumn drying of rivers (up to 105 days; ice phenomena in Northern Bulgaria and in the mountains over 1 500 m.
Conservation measures taken. Included in the Bulgarian Red Data Book, 1985. Legal protection (1962, 1986) and discontinuation of the trade with otter furs. Declaration of protected territories inhabited by 10% of the population.
Conservation measures needed. Declaration of river networks in the valleys and in the Rhodopes protected territories and zones [4]. Restoration of the shore vegetation. Ensuring passage routes through the roads. Monitoring of the species. Artificial fish breeding. Enclosing fisheries. Popularization of the role of the species in the ecosystems. Compensation of damages made by the otter.
References. 1. Drenski, 1926; 2. Atanassov, 1954; 3. Spassov & Spiridonov, 1985; 4. Spiridonov & Spassov, 1989; 5. Spiridonov & Dimitrov, 2006; 6. Georgiev, 2005; 7. Erlinge, 1967; 8. Muller et al., 1976; 9. Erlinge, 1968; 10. Georgiev, 2006a; 11. Georgiev, 2006b.
Authors: Geko Spiridonov, Nikolai Spassov
