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Waterbird hunting is a widespread activity in wetlands throughout Europe and constitutes one of the most significant sources of disturbance during autumn and winter. The biological evidence for effects of hunting disturbance on the behaviour and distribution of migratory and wintering waterbirds and its possible impacts on population dynamics is reviewed. Most of the literature has been concerned with local effects of disturbance, focussing on quarry geese and dabbling ducks. Comparatively little is known about effects on diving ducks and waders, while there is no direct evidence for impacts at the population level for any waterbird species. Hunting disturbance can cause temporary disruption of normal activities of waterbirds, alter their diurnal rhythms and increase escape flight distances. It can displace waterbirds from preferred feeding and roosting habitats at local or regional level and increase turnover, so that the carrying capacity of a site is not reached. Quarry waterbirds, and those occurring in large inshore concentrations, such as many dabbling ducks, geese and waders, are potentially most sensitive to disturbance. Hunting disturbance can disrupt pair-bonds and family structures which may affect reproductive output. Evidence is provided that many waterbird populations are limited by winter conditions and that the majority of studied waterbird species lose body reserves during winter. Because hunting disturbance causes under-exploitation of potential feeding grounds where population limitation is considered to occur, such disturbance will, by definition, have an impact at the population level. However, the magnitude of this impact has not been quantified and requires a modelling approach.
A total of 111 papers and reports, coming from 79 major studies and 19 other studies, on neonatal (first summer) mortality of 10 species of northern, temperate ungulates were reviewed. To avoid biases from indirect techniques only studies on radio-collared neonates and/or their dams were included, apart from a few notable exceptions. Neonatal mortality rates observed for different studies averaged 47% (68 studies) in environments where predators occurred, with predation accounting for an average of 67% (53 studies) of this mortality. No other single cause of mortality exceeded that of predation, which accounted for 0–100% of the mortality recorded in various studies. In contrast, mortality averaged 19% for studies in environments lacking predators. Other prominent causes of mortality were hypothermia/starvation and accidents. Disease was found to play a small role only. The predator species involved varied greatly between study areas, with both medium sized (bobcat Lynx rufus, Canada lynx Lynx canadensis, coyote Canis latrans and red fox Vulpes vulpes) and large (wolf Canis lupus, mountain lion Felis concolor, black bear Ursus americana and brown bear Ursus arctos) terrestrial predators preying upon the neonates. Despite the prominent role of predation, little is known about its long-term compensatory or additive nature, and therefore its impact on population dynamics is unclear. Factors influencing predation rates are poorly understood, although a few studies found significant sex-biased predation, and effects of weather or juvenile/maternal body condition. Timing of mortality within the first summer varied with the predators involved and the neonatal security strategy of the species, but was not confined to the immediate post-partum period.
The relationship between reproduction, age-structure, inbreeding and population density was analysed in an enclosed moose Alces alces population in Sweden. There was a strong negative relationship between the yearly average number of calves produced per cow and population density. Other variables, such as the average age of the cows and inbreeding also covaried with density. Taking these variables into account, a relationship remained between density and reproductive rate. An inbreeding index of three-year-old cows was negatively related to their calf production. Inbred, old (≥ 4 years) cows had a significantly lower calf production than old, outbred cows. Taking density into account, the effect of inbreeding remained. Even though inbreeding had a measurable effect at the individual level, the impact at population level was small and insignificant. During the early growth phase of the founder population, inbreeding remained low and had no negative effect on early population dynamics. The reason for this is that the first inbred individuals did not appear until the third generation. Therefore, a founder population can grow for a fairly long time and reach high population numbers before the effect of inbreeding appears. This means that the negative effects of inbreeding may increase in importance beyond our 12 years of study.
The ecology of a feral cat population in an intensively cultivated region of northern Italy was studied. The study area is a land accretion territory, reclaimed in the early 1970s, characterised by the absence of any food source of human origin (e.g. garbage dumps, farms, houses) and surrounded by a continuous irrigation channel that is likely to limit immigration/emigration of cats. The cat population was censused for two successive years using the sighting-resighting method; spacing patterns were studied by means of radio-telemetry; hunting behaviour was assessed by observation. Feral cats avoided any direct contact with humans, and reproduced in the wild. The density of the population remained stable throughout the study period. Turnover appeared very high, and was remarkably higher than that of cats regularly fed by humans. Very low densities, large home range sizes, solitary habits, territorial patterns similar to those of the wildcat, seasonal parturition, and prevalence of hunting activity were found. We speculate that these patterns are related to the peculiar conditions of resource availability and dispersion in the study area. Our results indicate that feral cats, even in agricultural areas and in the absence of any food provided by humans, have solitary habits and low densities, thus confirming a key role of resource availability and dispersion on the ecology of carnivores.
The brown bear Ursus arctos L. has long been believed to skin its prey and to leave behind a large hide and an unmolested skeleton. Camera monitoring in nature and observations in zoos revealed that carcasses were skinned and the skeletons cleaned by scavenging birds, mainly ravens Corvus corax and golden eagles Aquila chrysaetos. These results have implications for the estimates of brown bear densities, supposed damage and compensation.
The diet of red foxes Vulpes vulpes from the province of Pisa, Central Italy, was compared on the basis of analysis of the contents of 320 guts (stomachs and intestines), and of 211 faecal samples. The faeces and guts were collected in the same area during the same period. Mammal remains (in particular of small mammals) were more abundant in faeces than in stomachs and intestines, whereas invertebrates and grass were more abundant in guts. This may be due to different sampling methods which included hunting (guts) which may lead to an overweight of young, inexperienced foxes, eating less preferred food items, being represented in the sample, and collection of faeces which might primarily come from resident, dominant individuals. Bird frequency, but not volume, decreased significantly from stomachs to intestines, and from intestines to faeces. Studies based on stomach contents report a higher percentage of bird remains than studies based on faeces (frequency of occurrence: 19.4 ± 10.3% vs. 9.1 ± 6.9%; P = 0.014). The bias presented may be related to the mechanics of digestion and suggestions to limit such biases are put forward.
The extent of roe deer Capreolus capreolus feeding on the highly toxic yew Taxus baccata during winter was quantified from 1989–1994 in areas with varying density of bilberry Vaccinium myrtillus. Yew was most heavily harvested by roe deer in areas with low densities of bilberry. In areas with high densities of bilberry shrub, roe deer started browsing on yew when snow depth increased and reduced access to the field layer. However, in areas with low densities of bilberry, roe deer browsed heavily on yew also when snow was absent. Our observations suggest that roe deer may be the main factor affecting yew survival in areas where other preferred feeding plants are not available.
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