Factors affecting habitat occupancy by wolves in northern Apennines (northern Italy): a model of habitat suitability

The expansion of the wolf population all over Europe has posed problems on wolf-man coexistence in those areas where the wolf was not present for a long time. Breeding activities are now threatened by high predation on livestock. We investigated the relationship between wolf and its habitat, in order to evaluate wolf habitat suitability and to predict its presence. The study areas covered 3289 km². A 23 km² grid was used to identify 143 sample squares. For each sample square 58 habitat variables were measured from land-use (1:25 000), and from topographical maps. Wolf presence (4 classes) was assessed by scat collection, direct observations, snow tracking, wolf-howling, and predation records. Univariate and multivariate statistical analyses were carried out to investigate the influence of habitat features on wolf presence. The habitat suitability model was based on two different equations: a dichotomous logistic regression model, and a polytomous one. The first one discriminated between suitable and unsuitable habitats, and its predictions were confirmed in 93% of grouped cases; the second provided predicted values of wolf presence that were concordant with the observed response levels in 82.5% of contrasts. Both models underlined the importance of three factors in determining wolf habitat suitability: wild prey abundance, human presence and forest cover.     

Summer kill rates and predation pattern in a wolf–moose system: can we rely on winter estimates?

So far the vast majority of studies on large carnivore predation, including kill rates and consumption, have been based on winter studies. Because large carnivores relying on ungulates as prey often show a preference for juveniles, kill rates may be both higher and more variable during the summer season than during the rest of the year leading to serious underestimates of the total annual predation rate. This study is the first to present detailed empirical data on kill rates and prey selection in a wolf–moose system during summer (June–September) as obtained by applying modern Global Positioning System-collar techniques on individual wolves (Canis lupus) in Scandinavia. Moose (Alces alces) was the dominant prey species both by number (74.4%) and biomass (95.6%); 89.9% of all moose killed were juveniles, representing 76.0% of the biomass consumed by wolves. Kill rate in terms of the kilogram biomass/kilogram wolf per day averaged 0.20 (range: 0.07–0.32) among wolf territories and was above, or well above, the daily minimum food requirements in most territories. The average number of days between moose kills across wolf territories and study periods was 1.71 days, but increased with time and size of growing moose calves during summer. Over the entire summer (June–September, 122 days), a group (from two to nine) of wolves killed a total of 66 (confidence interval 95%; 56–81) moose. Incorporation of body growth functions of moose calves and yearlings and wolf pups over the summer period showed that wolves adjusted their kill rate on moose, so the amount of biomass/kilogram wolf was relatively constant or increased. The kill rate was much higher (94–116%) than estimated from the winter period. As a consequence, projecting winter kill rates to obtain annual estimates of predation in similar predator–prey systems may result in a significant underestimation of the total number of prey killed. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Testing the risk of predation hypothesis: the influence of recolonizing wolves on habitat use by moose

Considered as absent throughout Scandinavia for >100 years, wolves (Canis lupus) have recently naturally recolonized south-central Sweden. This recolonization has provided an opportunity to study behavioral responses of moose (Alces alces) to wolves. We used satellite telemetry locations from collared moose and wolves to determine whether moose habitat use was affected by predation risk based on wolf use distributions. Moose habitat use was influenced by reproductive status and time of day and showed a different selection pattern between winter and summer, but there was weak evidence that moose habitat use depended on predation risk. The seemingly weak response may have several underlying explanations that are not mutually exclusive from the long term absence of non-human predation pressure: intensive harvest by humans during the last century is more important than wolf predation as an influence on moose behavior; moose have not adapted to recolonizing wolves; and responses may include other behavioral adaptations or occur at finer temporal and spatial levels than investigated.     

Site fidelity and the demographic implications of winter movements by a migratory bird, the harlequin duck Histrionicus histrionicus

Understanding the degree of demographic connectivity among population segments is increasingly recognized as central to the fields of population ecology and conservation biology. However, delineating discrete population units has proven challenging, particularly for migratory birds as they move through their annual cycle. In this study, radio telemetry was used to assess movement rates among habitats by harlequin ducks Histrionicus histrionicus during the non-breeding season in Prince William Sound, Alaska. A total of 434 females were outfitted with radio transmitters over six years of data collection, and their signals tracked by aircraft. Using a spatially nested design, it was determined that 75% of radioed females remained in the bay or coastline area where they were originally trapped, 94% remained on the same island or mainland region of Prince William Sound where they began the winter period, and 98% remained within the 4500 km² study area as a whole. Home range analyses corroborated these findings, indicating that the scale of individual movements was small, with 95% kernel home range estimates averaging only 11.5±2.2 km². A simple demographic model, which incorporated estimates for population size, survival, and movement rates, was used to infer the degree of independence among population segments. Immigrant females were found to contribute little to population numbers in most areas, accounting for only 4% of the adult female population at a scale of approximately 100 km². These results have important implications for the scale of conservation action for the species and demonstrate that winter movements can have a strong influence local population dynamics.     

Wintering site fidelity and movement patterns of Western Sandpipers Calidris mauri in the San Francisco Bay estuary

Western Sandpipers Calidris mauri are the most numerous shorebird species in the San Francisco Bay estuary during winter. A sample of 106 Western Sandpipers was captured in mist nets and radio-marked with 1-g transmitters to examine their wintering site fidelity and movements. Differences in distances moved, home range extent and core area size were examined by age, sex, season, site, time of day and tide. All birds remained in the south San Francisco Bay region during winter and exhibited strong site fidelity, with a mean home range of 22.0 km² or only 8% of the study area. First-year birds had larger home ranges (26.6 ± 3.6 km²) than adults (17.2 ± 2.5 km²) in winter, but home range sizes of males and females were not significantly different in any period. Home range sizes were similar between seasons, but core areas were smaller in spring (6.3 ± 1.2 km²) than in early (9.6 ± 4.0 km²) or late (11.6 ± 1.6 km²) winter. Movements and home range size were similar for radio-marked birds located during day and night. The high degree of regional and local site fidelity demonstrated that the mixture of natural mud fiats and artificial salt ponds in southern San Francisco Bay provided sufficient resources for large wintering populations of Western Sandpipers.     

Spatial organization in the Ethiopian wolf Canis simensis: large packs and small stable home ranges

The spatial organization of the rare Ethiopian wolf ( Canis simensis ) was studied in the Afroalpine heathlands of Bale Mountains National Park, southern Ethiopia, between 1988 and 1992. Nineteen animals were radio-tracked, 48 ear-tagged and 64 others recognized by coat patterns and observed directly. Dry season (October—March) home ranges of resident wolves covered between 2 and 15 km². The ranges of adult males were slightly larger than those of females, and subadults' home ranges were slightly smaller than those of adults. The population density of the wolves was correlated with prey biomass. In optimal habitat, wolves lived in packs of 3—13 adults (mean 5.9 wolves > 1year old) containing several close-kin males; adult sex ratio favoured males 1.88: 1 and combined pack home ranges averaged 6.0km². In an area of lower prey productivity, wolves lived in pairs or small groups (mean 2.7), adult sex ratio was 1:1 and home ranges averaged 13.4 km².
Home ranges overlapped extensively (mean 85%) between members of the same pack. Four to seven percent of the population was additionally composed of non-resident females, inhabiting larger ranges (mean 11.1 km²). Home ranges of neighbouring packs were largely discrete, forming a tessellating mosaic of packs occupying all available habitat. Pack home ranges were stable in time, drifting only during major pack readjustment after the disappearance of a pack or significant demographic changes. Ethiopian wolf home ranges were smaller than would be expected for a carnivore of its size and sociality, presumably as a result of the high rodent productivity of the Afroalpine ecosystem.     

White rhinoceros range size in the south-western Kruger National Park

White rhinoceros range size was ascertained telemetrically in the south-western Kruger National Park. The mean annual range size of territorial males was 9.86 km² compared to 22.83 km² for adult females. White rhinoceros females' summer wet season range was larger (21.44 km²) than the winter dry season range (11.64 km²). It is argued that abundant field-water during the wet season enables animals to range further from permanent water supplies and to utilize larger foraging areas. White rhinoceros have core areas in their individual ranges that usually are situated along riverbanks in the preferred grazing regions. These core areas also include some favourite resting spots on high-lying areas. White rhinoceros range sizes in the south-western Kruger National Park were similar to those of other reserves with comparable white rhinoceros densities. In the Umfolozi Game Reserve, which has a higher white rhinoceros density than the Kruger National Park, the individual ranges are much smaller.     

Carrying Capacity and Potential Production of Ungulates for Human Use in a Mexican Tropical Dry Forest

Data are provided on the carrying capacity and potential production for sustainable human use of white-tailed deer ( Odocoileus virginianus ) and collared peccary ( Pecari tajacu ) in a protected tropical dry forest at Chamela on the Pacific coast of Mexico. In this paper, the carrying capacity was defined as the equilibrium density plus the number of animals removed by predators. The equilibrium point was estimated from the density dependent relationship between the finite population growth rate and the current density according to a logistic model. Annual density was estimated using the line transect method. Carrying capacity estimates were 16.5 to 17.2 deer/km² and 9.3–9.5 peccaries/km², representing a combined biomass of 841–874 kg/km². A potential production for human use of 2.1 deer/km² and 4.4 peccaries/km² was estimated employing the model of Robinson and Redford (1991) . The data suggest that, in the protected tropical dry forest of Chamela, the density and biomass of wild ungulates can maintain a similar or greater density and biomass than other Neotropical forests. To obtain an accurate estimation of the maximum sustainable yield ( MSY ), it is necessary to consider predation. From a management point of view, it is important to consider that carrying capacity varies as a function of the rainfall pattern.     

Livestock damage and wolf presence

Depredation on livestock and wolf pack Canis lupus distribution was investigated in the province of Arezzo, Tuscany, from 1998 to 2001. Although livestock was uniformly distributed, damage level and distribution were focused in the mountainous area inhabited by wolf packs hence there were huge differences between areas with and without wolves. In the whole province a few farms were persistently affected by predation (6%), and they reported 38% of the total attacks and 37% of the total losses. Surplus killing phenomena involved only sheep and goat farms, affecting 18% of the total. Thirty-five attacks (14% of the total attacks) reported 536 kills (44% of the total livestock killed in the whole province of Arezzo). During the period 1998–2001, compensation costs in the province averaged 86 863 Euros (range: 68 805–99 318 Euros). In the same period, no farmer requested prevention funding from the Tuscan region. During the study period wolf population was stable: wolf packs were distributed on 47% of the whole province (1504 km²), with a density estimated at 2.9±0.7 wolves 100 km⁻².     

Factors affecting the abundance of introduced hedgehogs (Erinaceus europaeus) to the Hebridean island of South Uist in the absence of natural predators and implications for nesting birds

Introduced hedgehogs Erinaceus europaeus are a known threat to ground-nesting birds on many islands. Spring hedgehog density and sex ratio were measured over a 5-year period at four plots on the 315 km² Hebridean island of South Uist. The mean instantaneous density on the sandy-soiled machair plots (31.8 hedgehogs km⁻², se 2.95) was over twice that on the peaty-soiled blackland plots (15.4 hedgehogs km⁻², se 3.46), a difference reflecting the amount of preferred foraging habitat (mainly pasture). Plot population densities fluctuated approximately in unison. Year-to-year density changes were strongly correlated with temperature in the preceding winter and previous year's spring/summer, indicating that warmer conditions promote both survival and breeding success. The mean spring sex ratio of sub-adults (animals born in the previous calendar year) was not significantly different from 1M:1F. However, the 1.8M:1F ratio observed for adults was significantly male biased, probably a result of female mortality associated with rearing young. The study estimates that in an average year the South Uist hedgehog population numbers c . 2750 (95% confidence limit±800) adults and sub-adults and these produce around 3000 young. Compared with the native range, hedgehog densities on South Uist are shown to be unusually high, probably because their natural predators are absent. High hedgehog densities have led directly to high rates of egg predation of ground-nesting shorebirds and subsequent declines in bird populations. The results suggest that over the past 20 years egg losses have become more severe and control of hedgehogs more difficult because climate warming has resulted in generally more favourable conditions for hedgehogs on the islands.     

Effects of predator treatments,individual traits,and environment on moose survival in Alaska

We studied moose (Alces alces) survival, physical condition, and abundance in a 3-predator system in western Interior Alaska, USA, during 2001–2007. Our objective was to quantify the effects of predator treatments on moose population dynamics by investigating changes in survival while evaluating the contribution of potentially confounding covariates. In May 2003 and 2004, we reduced black bear (Ursus americanus) and brown bear (U. arctos) numbers by translocating bears ≥240 km from the study area. Aircraft-assisted take reduced wolf (Canis lupus) numbers markedly in the study area during 2004–2007. We estimated black bears were reduced by approximately 96% by June 2004 and recovered to within 27% of untreated numbers by May 2007. Brown bears were reduced approximately 50% by June 2004. Late-winter wolf numbers were reduced by 75% by 2005 and likely remained at these levels through 2007. In addition to predator treatments, moose hunting closures during 2004–2007 reduced harvests of male moose by 60% in the study area. Predator treatments resulted in increased calf survival rates during summer (primarily from reduced black bear predation) and autumn (primarily from reduced wolf predation). Predator treatments had little influence on survival of moose calves during winter; instead, calf survival was influenced by snow depth and possibly temperature. Increased survival of moose calves during summer and autumn combined with relatively constant winter survival in most years led to a corresponding increase in annual survival of calves following predator treatments. Nonpredation mortalities of calves increased following predator treatments; however, this increase provided little compensation to the decrease in predation mortalities resulting from treatments. Thus, predator-induced calf mortality was primarily additive. Summer survival of moose calves was positively related to calf mass (β > 0.07, SE = 0.073) during treated years and lower (β = −0.82, SE = 0.247) for twins than singletons during all years. Following predator treatments, survival of yearling moose increased 8.7% for females and 21.4% for males during summer and 2.2% for females and 15.6% for males during autumn. Annual survival of adult (≥2 yr old) female moose also increased in treated years and was negatively (β = −0.21, SE = 0.078) related to age. Moose density increased 45%, from 0.38 moose/km² in 2001 to 0.55 moose/km² in 2007, which resulted from annual increases in overall survival of moose, not increases in reproductive rates. Indices of nutritional status remained constant throughout our study despite increased moose density. This information can be used by wildlife managers and policymakers to better understand the outcomes of predator treatments in Alaska and similar environments. © 2011 The Wildlife Society.     

Distribution, status and conservation of Indian gray wolf (Canis lupus pallipes) in Karnataka, India

The Indian gray wolf Canis lupus pallipes is the major large carnivore in the plains of Karnataka, India. We carried out a study on its distribution and status from November 2001 to July 2004. We estimated 555 wolves occupying about 123 330 km² of the state. In the past 40 years, wolves have disappeared from the southern plateau from an area of about 31 801 km². Their distribution is now largely restricted to the north-eastern dry plains. The wolf has also disappeared in recent years from some 'protected areas' such as Melkote Temple Wildlife Sanctuary, and their present population is largely found in 'non-protected' areas. Blackbucks are the only natural prey of wolves in Karnataka, but their density in most parts of the state is extremely low. The major prey species is domestic livestock, especially sheep. The available 'remote area' (forests or rocky terrains) in the wolf-occupied regions determined the status of the wolf. Killing of adult wolves and pups was common throughout the range of the wolf. However, such killings were made largely by local sheepherders with small sheep holdings and not by nomadic shepherds who maintained large sheep herds. The forests in the north-eastern parts of the state exist in small patches every few kilometers. Because each wolf pack ranges over large distances and is by and large a commensal species, we propose that the management of these small forest patches, considering them as components of a larger landscape, is the only effective conservation practice for the wolf. Although existing locally in low densities, because of a large ranging area of a single pack, the seemingly isolated wolf packs can become parts of a large metapopulation, providing a sustainable population.     

Spatial organization of leopards Panthera pardus in Taï National Park, Ivory Coast: is rainforest habitat a 'tropical haven'?

Between June 1992 and July 1994, two female leopards and one male were radio-tracked. Regular locations of the leopards, the use of a phototrap, and spoor data, provided the first detailed ecological data about this elusive felid in tropical rainforest habitat. The home range of the male was 86 km², those of the two females were 29 km² and 22 km², respectively. One female's home range was fully included within that of the male. Home ranges of neighbouring residents were not exclusive. Population density is estimated at one leopard per 9-14 km². Intraspecific interactions were rare and predominantly involved mating. The large size of the home ranges and a relatively high population density imply large overlap between adjacent resident leopards' ranges. Differences in the leopard's land tenure system between the rainforest and the savanna are discussed. Doubt is cast on the validity of the often-quoted estimate of one leopard per 1 km² in tropical rainforest habitat.     

Predation on rodents in Białowieza primeval forest, Poland

Autumn and winter predation on bank vole Clethrtonomys glareolus and yellow-necked mouse Apodemus flavicollis was studied in 1985/86-88/89 in an 11 2 km² area of the Bialowieza National Park Rodents regularly increased in numbers from spring to autumn and decreased throughout winter Out of 23 species of predators, the most common were tawny owl Strix aluco (43-57 adult ind 10 km⁻²) weasel Mustela ntvahs (17-27 ind), buzzard Buteo buteo (12-16) and pine marten Martes martes (5-8) Voles and mice were the staple food for two specialists the stoat Mustela erminea and the weasel, and two generahsts the tawny owl and the pine marten The generalists exploited different alternative prey when rodents were scarce tawny owl -amphibians, marten - small mammals, and the red fox Vulpes vulpes - ungulate carcasses and hares The depth of snow and abundance of voles were two major factors shaping the contribution of voles to tawny owl and marten diets No such relationships were found for mice and generalist predators The predation by 8 species (tawny owl, buzzard, marten, weasel, stoat, polecat Mustela putortus fox, and raccoon dog Nyctereutes procyonoides) from 1 October to 15 April in 1986/87, 87/88, and 88/89 was estimated to be on average 28-35 voles and 14-17 mice ha Estimates suggested that three species were responsible for 86-95% of the total predation impact tawny owl (56-71%), weasel (11-21%) and marten (10-15%) The predation impact was similar to the annual decrease in rodent numbers from autumn till spring voles 35 (SD 111) lnds ha^-1in autumn and 8 (SD 2 6) lnds ha^-1in spring, and mice 24 (SD 16 3) mds ha⁻¹ in autumn and 3 (SD 2 5) in spring Predation, therefore, was regarded as the main agent of rodent mortality throughout autumn and winter     

Preliminary estimates of the population density of the Sokoke scops owl Otus ireneae Ripley in the East Usambara lowlands, Tanzania

Preliminary population density estimates are presented for a recently discovered population of the Sokoke scops owl Otus ireneae in the lowlands of the East Usambara mountains, Tanzania. Calling birds were mapped at two sites totalling 6·3 km². Approximate densities were 3–4 territories/km² in Kwamgumi Forest Reserve and <1·5 territories/km² in Manga Forest Reserve, a much more heavily logged site. Densities in prime habitat in Arabuko‐Sokoke forest, Kenya, the only other locality for the species, exceed seven territories/km². The total population in the East Usambaras cannot be calculated, but it is probably markedly smaller than in Arabuko‐Sokoke. Suggestions for more precise surveys are made.     

Seasonal changes in the numerical responses of predators to cyclic vole populations

Theoretical models predict that a delayed density-dependent mortality factor with a time lag of ca 9 months is able to drive 3–5-yr population cycles of northern voles. We studied numerical responses of predators in western Finland during 1986–92, in an area with 3-yr population cycles of voles. Abundances of small mammals were monitored in several farmland areas (each 3 km²) by snap-trapping in April, June, August, and October (only in 1986–90), and the abundances of avian, mammalian, and reptilian predators by visual censuses during trapping occasions. The 3-yr cycle studied was a cycle of Microtus voles (field vole M. agrestis and sibling vole M. rossiaemeridionalis ) and their small-sized predators (small mustelids and vole-eating birds of prey). The numerical responses of both migratory avian predators and small mustelids to changes in vole densities were more alike than different. In late summer (August), the time lag in the numerical response of all main predators was short (0–4 months), whereas longer time lags prevailed from spring to early summer. The length of the time lag in spring appeared to be related to the length of the winter, which indicates that strong seasonality may create longer time lags to the numerical response of predators at northern latitudes than at more southern latitudes. Our results suggest that, from spring to early summer, predation by migratory avian predators may act in concordance with mustelid predation to produce the long time lag necessary to drive the 3-yr cycle of voles, whereas almost direct density-dependent predation by all major predators in late summer may dampen spatial variation in prey densities.     

Moose-wolf dynamics and the natural regulation of moose populations

Summary In southwestern Québec, non-harvested moose populations stabilize at a density of 0.40 animal·km^-2. In an attempt to test whether or not moose were regulated by predators, we investigated wolf predation near this equilibrium density (0.37) and at 2 lower densities (0.23, 0.17). Scat analysis in summer and feeding observations in winter indicated a greater use of alternative food resources by wolves at lower moose densities. Each wolf pack killed on average 5.3, 1.8, 1.1 moose·100 days in the area of 0.37, 0.23, and 0.17 moose·km^-2, respectively. Consumption of moose per wolf was 2.8, 1.7, and 1.6 kg/day, respectively. January wolf densities were estimated at 1.38, 0.82, and 0.36 animals·100 km^-2, respectively. Year-long predation rates proved to be density-dependent, increasing with moose density from 6.1 to 19.3% of the postnatal populations. We conclude that moose populations in southwestern Québec are regulated largely by predators (wolves and maybe black bears) at a density where competition for forage produces no detrimental effect. We support the concept that wolf predation can have an important regulatory effect at low moose densities but also a depensatory (inversely density-dependent) effect at higher densities.     

Abundance and distribution of endangered Franciscana dolphins in Argentine waters and conservation implications

This is the first study in Argentine waters on the abundance of the threatened Franciscana dolphin, Pontoporia blainvillei . During 2003–2004 we carried out 17 aerial surveys using line transect sampling methodology. We observed 101 Franciscanas in 71 sightings. In northern areas density was estimated at 0.106 individual/km². Density was lower in southern areas (0.055/km²) and declined with depth beyond 30-m isobaths (0.05/km²). A correction factor for submerged dolphins was applied to density and then extrapolated to the strip between the coastline and the 30-m isobath. Abundance in the northern area was estimated at 8,279 (4,904–13,960) individuals, while in the southern area it was estimated at 5,896 (1,928–17,999) individuals. Considering an annual mortality of about 500–800 individuals, about 3.5%–5.6% of the stock may be removed each year by the fishery and over the 2% recommended by the International Whaling Commission (IWC) and may not be sustainable by the population. Higher densities in coastal areas make Franciscanas more vulnerable to coastal fishing camps, which increased mortality in recent years. A remarkable finding was that while density decreases to the south, values of catch per unit effort (CPUE) increases, indicating different catchability of dolphins between areas.     

Breeding biology and breeding success of the Lesser Grey Shrike Lanius minor in a stable and dense population

The Lesser Grey Shrike Lanius minor is highly endangered throughout Europe, having declined markedly in abundance and range. Long-term changes in climate and agricultural practices have been identified as the main reasons for its decline. To determine which factors influence short-term changes in breeding success, we examined several aspects of its breeding biology. Our investigation revealed that our study area bears a large and stable population of this species. In 1996 and 1997, we recorded 84 and 77 breeding pairs in an area of 20 km², with an average of 4.20 and 3.85 pairs/km² respectively. Data on breeding density, clutch size and fledging success from 1989 to 1997 (excluding 1992) indicate a stable breeding population with a constant high breeding success. Reproductive success declined through the season, mainly through seasonal variation in clutch size rather than chick mortality. However, breeding success was generally high (69% and 79% of the nests produced chicks], with low hatching failure and few nest losses. The main cause of breeding failure was nest predation (at least 50% of nest losses), mainly by magpies (at least 66% of depredated nests). Although in this population the Lesser Grey Shrike tends to aggregate in clusters, breeding density had no obvious effect on breeding success and nest predation.     

Home range and habitat use of wolverines Gulo gulo in Yukon, Canada

Home ranges and habitat use are described for three adult female, one adult male, and one subadult male wolverines in the Kluane Game Sanctuary, Yukon. When long distance excursions are not included, home ranges of wolverines in the Kluane Game Sanctuary were between 76 and 269 km² for females and 209 and 269 km² for males. Habitat use of females was similar to habitat availability. Males used subalpine coniferous habitats more frequently than other habitat types during winter. Although individual variation in the use of forest cover types, aspects, slopes and elevations was apparent, seasonal use did not differ from availability for each sex. Within the 1590 km² study area, three adult males and six adult females were present, corresponding to a density of one resident wolverine 177 km^-2.