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A general warming of climate in the future may profoundly affect wildlife populations in terms of numbers, distribution and characteristics of the individuals, therefore leading to new challenges in terms of management and conservation. The effects of global warming can already be detected through the analysis of long-term databases, but insights into these processes can also be acquired by studying changes in wildlife populations during periods with clear trends in climatic changes. We analysed ringing data from more than 38,000 teal Anas crecca caught at the Station Biologique de la Tour du Valat in the Camargue, Southern France, between September 1954 and April 1971. Temperature in the Camargue clearly decreased over the ringing period. There was no correlation between average annual body mass and temperature in any age or sex class, nor a significant effect of temperature on the age ratio of the population. In adults, there were more males when average daily maximum winter temperature increased, while the opposite trend was found for juveniles. The clearest pattern we observed was a positive relationship between temperature and wing length of the individuals: in all sex and age classes, birds tended to get smaller as temperature decreased. It is unlikely that this pattern was related to harsh climate affecting teal feather growth. Rather, we hypothesise that climate affected the distribution of the individuals in Europe: as temperature got colder, small birds found it still more difficult to remain in northern areas and increasingly used the Camargue as a refuge. Reversing the observed pattern suggests that a global warming of climate in the future may have profound consequences for the distribution of wintering teal in Europe, as more and more birds will become able to remain in northern areas closer to their breeding grounds.
Based on data compiled from the official Danish Bag Record and from the annual wing surveys of waterfowl, analyses of long-term trends in the bag of common eiders Somateria mollissima were performed for the period 1958–2000, while more detailed analyses of factors affecting bag size were made for the period 1980–1999. The bag size increased from ca 100,000 in the late 1950s to ca 140,000 in the 1970s and 1980s. During the 1990s, the bag size decreased to ca 83,000 in parallel with a decrease in the number of eiders wintering in Danish waters and in parallel with a significant decrease in the number of eider hunters. Assessed from both national and regional developments in bag size, hunter numbers and numbers of eiders bagged per hunter during 1980–1999, there were no indications that bag size was related to the number of wintering eiders. Stepwise multiple regression on data from 1983–1999 showed that the number of eider hunters significantly explained 71.3% of the variation in bag size, and the annual juvenile:adult female ratio in October significantly explained 10.6% of the variation. Marked decreases in the number of eider hunters during the mid-1980s and between the hunting seasons of 1992/93 and 1993/94 coincide with public debates and introductions of legislative restrictions on waterfowl hunting in Denmark. My results stress the importance of detailed analyses of factors contributing to variation in the bag size of waterfowl before accepting an apparent correlation between bag size and population size.
During late winter 1991 and 1992, we investigated the influence of raven Corvus corax scavenging on the predation rate by different-sized wolf Canis lupus packs on moose Alces alces in the Yukon Territory, Canada. To assess the magnitude of scavenging, we presented 10 ungulate carcasses, pre-warmed to simulate the flesh temperature of freshly-killed prey, to scavengers and measured their daily consumption. Ravens were by far the main scavengers and on average, we counted 18.5 ± 12.7 (SD) ravens and documented removal of 14.1 ± 1.3 (SE) kg biomass each day (N = 53 observation days). However, assuming a daily scavenging rate of 14 kg by ravens fails to explain the almost equally short handling times for moose carcasses of small, medium and large packs. Only when raven consumption rate varies with pack size can we match the observed pattern. Assuming complete consumption, daily raven scavenging has to be 43 kg for ravens feeding on the kills of small wolf packs, 21 kg for ravens feeding on the kills of medium packs and close to zero for ravens feeding on the kills of large packs. Thus raven-wolf competition is highest for small packs, where ravens manage to remove up to 75% of the edible biomass and very low for large packs where ravens hardly manage to remove any edible biomass. Large packs seem to leave less opportunity for ravens to feed on carcasses, possibly because some wolves are always present at the kill and either actively chase away ravens or inhibit access to the carcass.
This study examines how the distribution and abundance of prey species influenced arctic fox Alopex lagopus diet on Svalbard during the summers of 1997, 1998 and 1999. The arctic fox together with the glaucous gull Larus hyperboreus are the only predators of this terrestrial ecosystem, and during summer the potential prey are confined to a few prey species such as various colonial seabirds, geese and Svalbard reindeer Rangifer tarandus platyrhynchus. There is great variation in distribution of prey over short distances, resulting in highly contrasting patterns in terms of both prey abundance and availability. Arctic fox diet was investigated by collecting scats (N = 818) at dens used for breeding. A cluster analysis based on similarities in the contents of scats revealed that arctic fox habitat could be divided into three distinct prey resource landscapes: two inland areas dominated by the prey species 'reindeer' and 'reindeer and geese', respectively, and one coastal resource area dominated by 'seabirds'. The occurrence of reindeer, geese and seabirds in the scats varied significantly among these resource landscapes. Svalbard reindeer, seabirds belonging to Alcidae and Procellariidae and geese belonging to Anseridae were the dominant prey species; volume percentages in the scats were 33, 33 and 15%, respectively. Svalbard rock ptarmigan Lagopus mutus hyperboreus, eggs, waders, snow buntings Plectrophenax nivalis and vegetation also occurred in minor proportions of the scats. The arctic fox showed a functional response to changes in prey availability. There was a positive correlation between the availability of these main prey species and their occurrence in the scats. Whenever available, arctic foxes preferred geese to seabirds and reindeer, and seabirds to reindeer. The arctic foxes in our study were opportunistic feeders, varying their food habits with prey availability.
During 1986–2001, denning behaviour of brown bears Ursus arctos was documented for 55 dennings of 33 radio-marked males in central Sweden, and 12 and 29 dennings of nine males and 19 females, respectively, in northern Sweden. Male brown bears spent on average 161 days (27 October–4 April) in dens in the southern area. The duration of their denning decreased with increasing age and body mass. Comparing these data with those obtained for females in the same study area by Friebe et al. (2001), males emerged from dens earlier than females, spending significantly less time in their dens. The denning period of females was influenced by their reproductive status; pregnant females spent the longest time in their dens. Denning dates correlated clearly with timing of autumn snowfall. Males in the north denned earlier, emerged later and spent on average 45 days more in their dens than males in central Sweden. Similarly, females in the north spent on average 37 days more in their dens than females in the south. Daily movements of males tracked to their dens in 2001 showed a general trend towards lower rates of movement in the last two weeks before denning, as found in females. Mean distance between dens used in successive years varied with age and sex; it was significantly greater for subadult males than for females and adult males as a result of dispersal behaviour. Adult bears showed a high degree of fidelity to a general denning area within their annual ranges.
We determined the seasonal food habits of brown bears Ursus arctos in three regions of Hokkaido, Japan, over eight years (1991–1998) by analysing the stomach contents of 556 bears killed for nuisance control or sport hunting. Seasonally dominant food items changed from herbaceous plants (61–80% in volume) in spring, to herbaceous plants (53–97% in volume) and ants (0–18% in volume) in early summer, crops (32–46% in volume) and herbaceous plants (26–31% in volume) in late summer, and berries (25–39% in volume), acorns and nuts (8-16% in volume) in autumn. These diet shifts were consistent among the three investigated regions. Crop depredation by brown bears in late summer occurred extensively in Hokkaido and was probably driven by a shortage of alternative food sources during this season. The proportion of sika deer Cervus nippon yesoensis in the diet increased during the 1990s in eastern Hokkaido (25.2% in frequency), where bears consumed deer throughout the year. Bears probably acquired deer meat from carcasses left in the fields after the deer were shot for nuisance control and sport hunting. In the Oshima Peninsula of southern Hokkaido, bears consumed large amounts of anthropogenic waste (16% in frequency).
Space use and activity of radio-collared leopards Panthera pardus (two adult males and one adult female) were monitored during 3–25 months in a prey-rich part of the Royal Bardia National Park, Nepal. Annual home ranges of the two males were 47 and 48 km2 and had an overlap of only 7%, whereas the overlap between the female's home range (17 km2) and that of one of the males was 56%. The range sizes were larger than reported from other studies in southeast Asia, but much smaller than some ranges in Africa. When comparing different studies, the sexual difference in range size increased significantly with increasing average range size. Thus, the cost by males of traversing large home ranges is probably not a determinant factor in shaping leopard communities. The female's seasonal home ranges (5.2 and 6.6 km2) were smallest during the seasons when her cubs were less than six months of age. She moved her home range closer to agricultural fields during the season when the abundant and important prey axis deer Axis axis visits these areas most frequently. No such pattern was detected among the two males. Instead they frequented human settlements throughout the year, probably in order to hunt easily accessible domestic animals. Home ranges in similar seasons in consecutive years overlapped more (female = 64%, male = 75%) than ranges in different seasons in the same year (female = 38%, male = 64%). Intensive tracking sessions of 24 hours revealed that the diel activity levels of the two sexes were similar (female: 62.3%, males: 62.6%). However, their patterns of activity were different as the males moved mainly at night (day: 1,582 m, night: 5,244 m) and the female moved similar distances day and night (day: 2,381 m, night: 2,698 m). The female may have restricted her movement at the time when conspecific males were likely to be active in order to protect her cubs from infanticide. The males moved in a more linear manner than the female, and the linear distances between radio locations from consecutive days differed significantly between the sexes (male: 3,324 m, female: 881 m), but the actual distances moved during the 24-hour cycles were fairly similar (male: 6,826 m, female: 5,079 m).
During 1995–1997, 52 male and 52 female roe deer Capreolus capreolus, captured in the Forest of Trois-Fontaines in northeastern France, were introduced into the Petit Luberon state forest in southern France; of these 49 females (21 young that were < 1 year old and 28 adults that were > 1 year old) were monitored by radio-tracking. The overall mortality rate among the females monitored was 47% within one year of release. The first month following the release (February) was critical for the success of the operation as 35% of introduced animals died within this time span. It appears that stress was a major cause of mortality at this time, but traumatic deaths caused by drowning, collision with cars, and falling off cliffs were also frequent. The survival rate increased to 0.9 in spring, summer and early fall and decreased again during late fall and early winter. The high mortality rate occurring during this period may be explained by an increased mobility resulting from disturbance from wild boar Sus scrofa hunting. After the reintroduction, the animals stayed close to the release site (50% within 2.4 km, and 75% within 4 km), though the adults established themselves at longer distances than the young. The dispersion pattern of the females was not uniform throughout the study area: they preferentially settled down northwest of the release site, which may be explained by the topography of our study area and by the absence of human structures (roads, canals) in this area.
Effective management of ungulates requires regular estimates of population abundance, but these are often expensive and hard to obtain. We therefore examined if change-in-ratio (CIR) estimation methods, in combination with age- and sex-specific data on moose Alces alces observed and killed, could be a cheap alternative for estimating moose abundance in Norway. We used the large number of moose observations reported by moose hunters and estimated pre-harvest adult population size based on annual changes in adult sex ratio. Similarly, we estimated 1) annual recruitment rate based on the proportion of calves observed during the hunting season, 2) the harvest rate, and 3) the natural mortality rate based on variation in recruitment rate and harvest rate. During 1991–2000, annual variation in abundance was correlated with two of three independent indices of moose density, indicating that the CIR methods provide relatively precise estimates of abundance. Similarly, the estimated average natural mortality rate was similar to natural mortality rates of radio-collared moose in Scandinavia, and the estimated abundance was close to what we expected based on the annual harvest. However, large annual variation in estimated rates of natural mortality indicated that over- and underestimation of population abundance occurred for some years. This was likely due to the fact that harvesting occurred during periods of moose observations. Because we had no independent estimates of abundance, we were unable to estimate the bias. Hence, we concluded that variation in CIR abundance is a sensitive index of moose density, but that more studies are needed to determine the accuracy of CIR estimates as measurements of abundance. Future studies should focus on smaller populations with independent estimates on abundance, and base CIR estimation on changes in sex ratio within the hunting season to reduce the number of possible confounding effects.