The aim of this study was to investigate the effects of changes in various environmental parameters on the underwater foraging behaviour of the American mink, Mustela vison. The study was conducted in an indoor pool. The effects of changes in the following parameters were investigated: (i) Water Depth. This was altered from 0.3 m to 1.65 m. (ii) Current Flow. Presence of either a deep or a surface current was compared to no current flowing. (iii) Prey Density. Four prey densities were used, 25%, 50%, 75% and 100%. (iv) Habitat Complexity. Hides were arranged in a regular, random or clumped pattern. The effects of habitat complexity were investigated in conjunction with prey density. Results are presented for gross changes in foraging behaviour, i.e. dive rate (number of dives per min), successful dive rate, hide visit dive rate, proportion of dives visiting a hide, proportion of successful dives and proportion of successful hide visits, and for finer changes within each dive, i.e. dive duration, time on bottom, number of hides visited per dive, mean time in hide, proportion of time on bottom spent hide searching, distance travelled underwater, proportion of direct to indirect dives, mean number of turns per dive, directionality of dives and revisiting of hides. The results showed that as depth increased, animals made fewer dives, but the dives were of longer duration. The extra time on bottom appeared to be used for locating hideswhich could no longer be located aerially before diving. Deep current was found to be not strong enough to seriously affect foraging behaviour. However, the surface disruption caused by the surface current, led to an increased dive rate, possibly in an attempt to locate hides that could no longer be located aerially, although other parameters such as proportion of dives visiting hides, dive duration etc., were generally unaffected by current flow. The conclusion was that mink were well able to continue foraging with current speeds of up to 0.86 m s(^-1). It was found that as prey density increased, animals, generally, made fewer dives of shorter duration, more of which were successful, although there was considerable individual variation. For habitat complexity, animals, generally, behaved similarly if hides were arranged randomly or in clumps, but when hides were regularly distributed, fewer hide visit dives were performed. However, mean time on bottom tended to be longer, resulting in little difference in foraging efficiency between the three conditions. A brief review of individual strategies revealed that there were considerable individual differences in foraging strategy. These were not related to sex, thus, some individuals consistently used a strategy of many short duration dives, generally visiting only one hide per dive. Others opted for fewer, longer duration, dives, generally involving more than one hide visit. Further, mean dive duration was not related to body weight. An investigation into the maximum underwater swimming speed achieved by mink showed that animals could reach speeds of over 1 m s(^-1). However, comparison with swimming speeds of fish species preyed on by mink, revealed that the fish swam faster. A review of the habits of the fish eaten, however, revealed that most were sedentary, bottom dwellers. The implications from this are that commercially important fish, e.g. salmon and trout, may well be taken mainly as diseased or spent individuals. The overall conclusion reached was that mink are highly versatile mustelids, and have 'specialised' in the ability to utilize both terrestrial and aquatic habitats.

Nutritional aspects of size-related sex differences in the diets of free-living mink were investigated in laboratory-based feeding trials with adult farm-bred mink maintained on 'natural' diets. As preliminary studies had shown that carcase utility was virtually complete, the rations presented comprised the minced whole carcasses of wild rabbit Oryctolagus cunniculus, eel Anquilla anguilla, laboratory rats and mice, and domestic fowl. Determinations of gross composition revealed significant differences between these diets; the smaller prey types, including rodents, birds and fish, were found to have a higher ratio of Apparent Digestible Energy to Nitrogen than larger items such as rabbits, although comparisons with data presented by other workers demonstrated that the variations between species within these prey groups are as great as, or greater than, those between the diets themselves. From the results of the feeding trials, it was also apparent that such diets do not differ significantly, either in digestibility or biological value and attempts to classify particular prey items in terms of their nutritional value are, therefore, of limited application in analyses of the feeding ecology of a generalist predator. Nutrient intake was related to diet composition and varied widely between trials, although the mass-specific requirements of females were higher than those of males. Comparisons of gut morphology indicated that, in females, hypertrophy of the alimentary tract may develop in response to increased energy demands. A similar adaptation was evident in both males and females from wild populations, suggesting that the natural diets of free-living mink are generally of a lower quality than the rations fed to commercially raised animals. Feeding trials were also carried out on growing kits from 56 to 105 days post partum. Sex differences in nutrient metabolism were not significant but the growth rates of males were higher than those of females. In both sexes the growth rates of kits feeding on 'natural' diets were lower than those of animals raised on commercial rations. This effect was most pronounced in males, a finding which supports the hypothesis that the degree of sexual dimorphism in this species is dependent on the extent to which the growth potential of males is constrained by dietary regime during the early phases of development.

No description available.

The Mink Creek region is centered 14 miles northeast of Preston in Franklin County, Idaho (see Index Map, Figure 1). The area of this report comprises approximately 70 square miles. It is bounded on the north and south by parallels 42°17' and 42°11' North Latitude and on the east and west by meridians 111°37' and 111°49'. The easternmost part of the area is located in the Bear River Range and is part of the Cache National Forest. The region is readily accessible. A paved Idaho State Highway goes through the center of the area and State Highway 34 skirts the nothwest corner. Numerous dirt roads, jeep roads, and cattle trails traverse the area.

The detrimental impact of invasive, non-native species on biodiversity conservation and ecosystem function is widely recognised. The invasion of predatory species can have particularly deleterious consequences on native species in the invaded range and there is an increasing awareness of, and necessity for, management action to minimise these impacts. There is a growing body of literature identifying the impacts of invasive species and priorities for conservation action. However, there is a noticeable gap between the rising scientific output regarding invasive species control and conservation measures, and the management action required to implement recommendations. The American mink (Neovison vison, hereafter mink) has been a recent focus of invasive species research and management. Mink are semi-aquatic mustelids and generalist predators and were introduced to countries around the world for fur farming. Feral populations have established across the introduced range with devastating consequences for native species, particularly birds and mammals. In the UK, mink are held partly responsible for the decline in water voles (Arvicola amphibius) and in Scotland in particular, breeding seabirds are significantly impacted by mink predation. Control of mink in North East Scotland has proven successful using an adaptive management, community-based approach but there is currently no equivalent project in the complex, coastal landscape of west Scotland. This study aimed to provide information that could refine and further develop management plans for mink in north and west Scotland by acquiring a better understanding of the ecology of mink in Scotland to inform the implementation of control. Mink were distributed across all but the far north of Scotland. There was spatial and temporal variation in the pattern and rate of their expansion which was attributed to landscape heterogeneity. In northwest Scotland, availability of suitable habitat was restricted to the coastline and consequently, the availability of prey was hypothesised to be limited to coastal areas. Indeed, the diet of mink in northwest Scotland had a greater input from marine resources than those in southwest Scotland, where habitat availability and, therefore, terrestrial food resources, extended inland. Landscape features were shown to affect the direction of colonisation, with mountains restricting and valleys facilitating dispersal. Population genetic studies confirmed that mink dispersal in northwest and northeast Scotland was limited by mountain barriers. Additionally, populations in northwest Scotland were likely to have originated from southwest Scotland. These results suggest that mink control should be primarily focussed in coastal habitats in west Scotland and that the risk of reinvasion from relatively close populations in northeast Scotland is minimal. Volunteer involvement in conservation projects is being accepted increasingly as a cost-effective way to gather ecological information and implement conservation over large spatial scales. The landscape of west Scotland, particularly in northern areas, is complex, remote and sparsely populated by humans which consequently creates challenges for executing mink control. Ecotourism boat operators were concerned about the presence of mink and their effect on local wildlife in coastal areas and were willing to volunteer in mink management. Consequently ecotourism boat operators could provide a key link between management recommendations and implementation. This study combined methodologies from ecological modelling, population genetics, chemical analyses and social science to address questions regarding invasive species management. This holistic approach has resulted in a thorough overview of the distribution and ecology of an invasive species as well as recommendations for management action and implementation that will be applicable to a range of invasive species.

Captive animals are sometimes very inactive, which can elicit concern for their welfare. However, inactivity is difficult to interpret in terms of welfare, since while some forms reflect chronic fear (hiding), apathy, or depression-like states, others reflect positive states (e.g. relaxation). This thesis aimed to determine whether high levels or particular sub-types of inactivity indicate poor welfare in fur-farmed mink (Neovison vison), and to identify the specific psychological states involved. These questions were addressed by studying individual differences within populations on three commercial farms, and comparing mink in standard, non-enriched cages to those in enriched cages. Two hypotheses were tested on farms: that the most inactive mink experience chronic stress, and that this would impair reproduction. Inactive females did have smaller litters, a difference that was not attributable simply to their greater body fat. However, there was no evidence of endocrine stress nor increased fear in “glove tests”, and their kits also grew more quickly. This suggests that inactive females do not experience more chronic stress than active females do. Tests of responsiveness to stimuli (measured in terms of contact and orientation) showed that, compared to mink in enriched cages, non-enriched mink were more responsive to all types of stimuli, especially neutral ones. This finding is inconsistent with the hypothesis that inactive individuals in these conditions are apathetic or depressed; instead, it supports the alternative hypothesis that non-enriched cages induce boredom. However, this boredom-like hyper-responsiveness did not co-vary with inactivity levels. Finally, non-enriched cages did not consistently elevate total inactivity. However, they did induce specific types: inactivity in the nest box, lying alert (vs. sleeping), and lying belly down rather than curled up were all more common than in enriched cages. Inactivity in the nest box may reflect hiding; it seemed linked to fearfulness in glove tests and to endocrine stress responses. In sum, while non-enriched conditions induce poor welfare, they do not increase overall inactivity; furthermore, within populations, the welfare of highly inactive individuals is no more compromised than that of their more active counterparts. However, subtypes of inactivity provide more information about welfare than total inactivity. / NSERC (PGS)

Thesis (Ph. D.)--Columbia University, 1956. / eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [133]-144).

Thesis (Ph. D.)--Columbia University, 1956.

No description available.