Ograniczanie wyników

Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 32

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  American mink
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
In Poland, feral population of the American mink Mustela vison Schreber, 1777, originating from the immigrants from Belarus and Lithuania, as well as from Polish fur farm escapees, started to develop in the beginning of 1980s in the north-east and north-west of the country. According to questionnaires sent to hunters, up to the end of 1980s mink colonized 9 out of 16 Polish provinces. Within next decade mink were observed in next 6 provinces. In Warmińsko-Mazurskie and Podlaskie provinces (north­-eastern Poland) mink presence has been confirmed by over 90% of hunting units, whereas in the north-west of the country by over 50% of respondents. In southern provinces mink are still uncommon but they successfully enlarge geographical range. During the 20-year period, mink have colonized over half of the Polish territory. Colonization of particular regions was correlated in time with a decline of muskrat and waterfowl populations. From the beginning of 1980s to the half of 1990s, in north­eastern provinces hunting bag of muskrat decreased 10-fold, whereas in other parts of Poland the number of hunted muskrats was more or less stable. Despite the lack of complex ecological studies on the mink impact on their prey, it is highly probable that this introduced carnivore negatively affects populations of semi-aquatic birds and mammals.
Stomach and intestine contents of 211 American mink Mustela vison Schreber, 1777 from two areas (Thy and Bornholm) in Denmark and stomach contents of 47 polecats M. putorius Linnaeus, 1758 from Thy were analysed. Sympatric mink (from Thy) preyed mostly on mammals (55% occurrence), followed by amphibians (36%), birds (33%) and fish (30%), whereas polecat preyed mostly on amphibians (87%) and mammals (34%), and only occasionally on birds (9%) and fish (6%). Allopatric mink (from Bornholm) preyed mostly on birds (50%), followed by mammals (42%), fish (25%) and amphibians (4%). With the possible exception of some amphibians, no endangered species were found in their diet. No differences were found in food composition between wild and escaped farm mink. The concern that mink in general might have a detrimental effect on its prey species and other mustelids in terms of food competition in Denmark may be unjustified. It cannot be ruled out, however, that mink may locally have a seriously negative effect on some specific prey species, and clearly, more data is needed on eg prey abundance and spring and summer mink diet, to make stronger conclusions.
Reproduction of the American mink Mustela vison Schreber, 1777 population intro­duced to Belarus was studied in 1983 — 1992. Material consisted of 52 male genitalia, carcasses of 45 pregnant females, and observations of 19 litters with blind cubs and 31 litters with larger cubs, The study was conducted in two areas in northern Belarus: Rossony, where the decrease of mink numbers due to excessive trapping was recorded, and Gorodok, where the expansion of American mink in the presence of the native European mink Mustela lutreola was observed. Mating period of American mink lasted from mid February to mid April. Young were born from April till mid June. Litter size was on average 4.2 (blind cubs) and 3.3 in older cubs (> 2 months old). Repro­duction intensity on Drissa river and its tributaries was related to density. On average, 3.3 embryos per pregnanat female were found in 1-yr females and 4.3 in > 2-yr old females at the density of 13.3 mink/10 km of watercourse. In the low density population (2.8 mink/10 km due to overexploitation by hunters) reproduction intensity increased to an average of 4.2 embryos in 1-yr females and 6.0 in £ 2-yr females. During population decrease, percentage of young increased and the sex ratio became biased towards females. In an expanding population of American mink that had newly colonised Lovat river, the reproduction was very intense (7.3 - 7.6 embryos/female). The results show a great reproductive plasticity of American mink that obviously helped this species to successfully colonise new ranges after introduction.
The European mink (M. lutreola) and the American mink (M. vison) are riparian mustelids inhabiting Spain. During the last few decades, M. lutreola populations have declined almost everywhere, but, since being introduced in Europe, the American mink has become wide spread there. The present study presents the first comprehensive helminthological data of both mink species in Western Europe and analyses the possible cross-transmission of some pathogenic helminths between neighbouring Spanish populations of both mustelids. One hundred and forty specimens (28 M. lutreola and 112 M. vison) from several Spanish zones were analysed. A total of thirteen helminth species were found: Metorchis bilis, Parametorchis sp., Pseudamphistomum truncatum, Euryhelmis squamula and Apophallus donicus (Trematoda), Taenia martis and T. tenuicollis (Cestoda), Aonchotheca putorii, Strongyloides mustelorum, Molineus patens, Crenosoma melesi and Aelurostrongylus pridhami (Nematoda), and Centrorhynchus ninnii (Acanthocephala). The helminth fauna of M. lutreola was qualitatively and quantitatively richer than that of M. vison. This fact was particularly evident amongst digeneans with four species (M. bilis, Parametorchis sp., P. truncatum and A. donicus) exclusively present in M. lutreola. Twenty-five M. lutreola individuals were infected with parasitic worms (89.3%). In contrast, less than half (41.1%) of the American minks analysed were infected by helminths. The helminth fauna of both European and American minks in Spain are compared with those of both mustelids in Belarus, where another important population of M. lutreola is present. Also considered are some epidemiological and pathogenic aspects of the helminth fauna of both mink species that might act as regulatory factors over the Spanish population of M. lutreola.
The diet of American mink Mustela vison Schreber, 1777 and otter Lutra lutra (Linnaeus, 1758) and their occupation of the various stretches over approximately 70 km of two Mediterranean rivers in the centre of Spain were studied during January 1995. No spatial segregation is thought to exist between the two species. The otter diet, mainly fish (93% of excrement) and American red crayfish Procambarus clarkii (30%), is no different from that found in other studies. The mink fed mainly on mammals (present in 52% of the excrements) and arthropods (27%), while fish are much less common (19%). The diet is statistically different from that found in a river without otters. The latter eats larger fish and rejects small (< 5 cm) examples, in contrast to mink. The coexistence of the two species is discussed. Despite the con­siderable overlap in diet the two mustelids can coexist due to the otter's superior ability to capture aquatic prey and the American mink's great degree of ecological adaptability.
Feeding experiment on nine feral mink Mustela vison Schreber, 1777 was carried out to find differences in digestibility of particular prey types. The values of correction factors (CF), which show the ratio between consumed prey biomass and undigested remains, were calculated for seven food types. The experiment revealed that results obtained by commonly used percentage of occurrence methods differed from the real intake of food. Food types which were intensively digested were underestimated by percentage of occurrence methods and prey which had hardly digestive elements of their body were overestimated. The calculated values of CF are as follows: crayfish - 14.8, fish - 30.8, frog - 61.3, small passerine bird - 17.2, chicken - 41.3, rodent - 17.3, egg - 687.5. The variability in CF values did not depend on mink individuals but could be explained by the mean weight of prey items eaten by mink. The positive correlation between the prey size and its digestibility was recorded for crayfish, fish and chicken. The biomass of frog, passerine and rodent remains was not related to the body mass of eaten prey. The use of evaluated correction factors enables more accurate estimates of the food composition of wild living mustelids.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.