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Hunters' estimates of pair densities of the grey partridge Perdix perdix as derived from an annual questionnaire survey (‘Game Survey Lower Saxony’, WTE) were evaluated by comparison with detailed ground-truthing censuses in 123 randomly chosen hunting districts representing 63,847 ha potential grey partridge habitat. Estimates and evaluation-census-densities were highly significantly correlated. The median of the hunters' estimate errors, disregarding the direction of the relative discrepancy, was 24.2%. Hunters underestimated the density per 100 ha potential habitat by 0.16 breeding pairs on average. The discrepancy increased with higher grey partridge densities and increasing size of the hunting district. The satisfactory agreement between the estimates of the hunters, in most cases local farmers, and the evaluation survey is explained by their comprehensive year-round presence through their hunting, farming but also their leisure activities and their special interest in this charismatic bird combined with its site fidelity. We recommend the consultation of WTE data as a valuable source of basic information on distribution and abundance of grey partridges to identify spatial conservation priorities, to justify conservation initiatives and to adapt management practices.
Over the last 50 years, the modernisation and mechanisation of agricultural techniques caused important habitat alterations in agricultural ecosystems that lead to the decline of farmland wildlife populations throughout Europe. During 2008 and 2009, we investigated the effects of Habitat Improvement Actions (HIAs) and reforestations on populations of common pheasant Phasianus colchicus in order to evaluate the influence of both habitat management strategies on pheasant male density and distribution. We estimated the density of territorial males in four study areas located in the western Po Plain (northern Italy) through the method of crowing cock counts during the breeding season. We analysed the spatial distribution of territorial males in relation to the HIA and reforestation patches comparing points with crowing cocks with random ones. Moreover, we analysed the effects of habitat characteristics including HIAs and reforestations on male pheasant density by multiple regression analyses with theoretic information approach and multimodel inference. Our results showed that both HIAs and reforestations had an important role in determining male distribution. Moreover, HIAs and reforestations were good predictor variables of male pheasant density. We concluded that HIAs and reforestations provide common pheasant with suitable habitats and can represent proper solutions for enhancing habitat diversity and quality in intensive agro-ecosystems.
The globally endangered snow leopard Panthera uncia is sparsely distributed throughout the rugged mountains in Asia. Its habit of preying on livestock poses a main challenge to management. In the remote Phu valley in northern Nepal, we obtained reliable information on livestock losses and estimated predator abundance and diet composition from DNA analysis and prey remains in scats. The annual diet consisted of 42% livestock. Among the wild prey, bharal (blue sheep/naur) Pseudois nayaur was by far the most common species (92%). Two independent abundance estimates suggested that there were six snow leopards in the valley during the course of our study. On average, each snow leopard killed about one livestock individual and two bharal per month. Predation loss of livestock estimated from prey remains in scats was 3.9%, which was in concordance with village records (4.0%). From a total count of bharal, the only large natural prey in the area and occurring at a density of 8.4 animals/km2 or about half the density of livestock, snow leopards were estimated to harvest 15.1% of the population annually. This predation rate approaches the natural, inherent recruitment rate of this species; in Phu the proportion of kids was estimated at 18.4%. High livestock losses have created a hostile attitude against the snow leopard and mitigation measures are needed. Among innovative management schemes now being implemented throughout the species' range, compensation and insurance programmes coupled with other incentive measures are encouraged, rather than measures to reduce the snow leopard's access to livestock. In areas like the Phu valley, where the natural prey base consists mainly of one ungulate species that is already heavily preyed upon, the latter approach, if implemented, will lead to increased predation on this prey, which over time may suppress numbers of both prey and predator.
Increasing populations of wild boar and feral domestic pigs Sus scrofa have evoked growing concern due to their potential as disease reservoir and as an origin of agricultural damages. Reliable population estimates are needed for effective management measures of this species. As an alternative to traditional methods, non-invasive genetic population estimation approaches based on hair or faeces sampling have yielded promising results for several species in terms of feasibility and precision. We developed and applied a non-invasive population estimation approach based on wild boar faeces in a study area situated in the Palatinate Forest, southwestern Germany. We collected 515 faeces samples along transects in January 2008. We carried out genotyping using six microsatellite markers to discriminate between individuals. During the trial, we identified 149 individual wild boar. Using multimodel inference and model averaging, we obtained relatively consistent estimates. Population densities calculated using the estimated population sizes ranged from 4.5 (2.9-7.8) to 5.0 (4.0-7.0) wild boar/km2. In the future, to further improve the precision of population estimates based on wild boar faeces, the detection probability should be increased. However, even when comparing a conservative population estimate to the hunting bag, our results show that the present hunting regime in our study area is not effective in regulating the wild boar population. The method which we present here offers a tool to calibrate hunting or other management measures for wild boar.
Populations of mule deer Odocoileus hemionus have declined throughout most of their historic range in recent decades, and habitat alteration has been hypothesized as one potential cause of those declines. Consequently, understanding how patterns of behaviour change as landscapes are altered through time may provide important insights into mechanisms underlying observed demographic trends in populations of mule deer. We examined resource selection in relation to habitat change by mule deer on the Tex Creek winter range in southeastern Idaho, USA. We created a GIS-based map of habitats available to mule deer during two time periods, past (1985-1986) and current (2007-2009), to document changes in habitat over time. We then modeled past and current patterns of resource selection by mule deer based on locations obtained from visual observation, radio-telemetry and GPS collars. Abundance and distribution of juniper Juniperus spp., aspen Populus tremuloides, sagebrush steppe Artemisia spp. and riparian habitat did not change significantly between past and current time periods. In contrast, we documented an increase in grassland from 3.5 to 30.7% of our study area, and a corresponding decrease in agricultural land, which provides high-quality forage for mule deer, from 37.8 to 12.5% of our study area. Patterns of resource selection largely were similar between the two time periods. Nevertheless, mule deer significantly increased selection of agricultural fields and areas far from roads between the 1980s and 2007-2009. In addition, juniper stands were strongly selected in all years, and importance values (use × availability rescaled to 100%) for grassland and sagebrush steppe increased between past and current time periods. Our results indicated that mule deer responded behaviourally to declining availability of high-quality forage (i.e. agricultural land) by increasing selection of agricultural fields. Such functional responses in habitat selection may have important consequences for dynamics of mule deer populations, but additional research is necessary to link those responses to demography and population performance. Although juniper encroachment often is thought to have affected mule deer negatively on many summer ranges, strong selection for juniper in our study highlights the potential importance of that species on winter range, likely because it provides both thermal and hiding cover.
Wildlife species may respond to industrial development with changes in distribution. However, discerning a response to development from differences in habitat selection is challenging. Since the early 1990s, migratory tundra Bathurst caribou Rangifer tarandus groenlandicus in the Canadian Arctic have been exposed to the construction and operation of two adjacent open-pit mines within the herd's summer range. We developed a statistical approach to directly estimate the zone of influence (area of reduced caribou occupancy) of the mines during mid-July-mid-October. We used caribou presence recorded during aerial surveys and locations of satellite-collared cow caribou as inputs to a model to account for patterns in habitat selection as well as mine activities. We then constrained the zone of influence curve to asymptote, such that the average distance from the mine complex where caribou habitat selection was not affected by the mine could be estimated. During the operation period for the two open-pit mines, we detected a 14-km zone of influence from the aerial survey data, and a weaker 11-km zone from the satellite-collar locations. Caribou were about four times more likely to select habitat at distances greater than the zone of influence compared to the two-mine complex, with a gradation of increasing selection up to the estimated zone of influence. Caribou are responding to industrial developments at greater distances than shown in other areas, possibly related to fine dust deposition from mine activities in open, tundra habitats. The methodology we developed provides a standardized approach to estimate the spatial impact of stressors on caribou or other wildlife species.
Most ungulates in East African savannahs experience some form of human disturbance, such as direct pursuit (e.g. hunting and poaching), habitat degradation and competition with livestock. In many studies, the impact of human activities on wildlife is assessed through census counts, i.e. by estimating population sizes or densities, but also the social organisation of gregarious species can be affected. Using seven species of ungulates occurring in the Akagera Ecosystem, we compared grouping patterns (i.e. group sizes and compositions) of different group types (e.g. bachelor, all-female and mixed-sex groups) between sites situated inside a protected area, i.e. Lake Mburo National Park in Uganda and the adjacent Ankole Ranching Scheme (ARS), an unprotected area with intense human pursuit. Differences in group sizes were detectible in only a few cases, e.g. bachelor group size in common eland Tragelaphus oryx pattersonianus increased in the ARS, which may be advantageous due to increased vigilance. However, we found pronounced differences in group compositions in numerous species and for different group types, for example, in eland and waterbuck Kobus ellipsiprymnus defassa (i.e. in all group types), and topi Damaliscus lunatus jimela, oribi Ourebia ourebi and warthog Phacochoerus aetiopicus (all-female and mixed-sex groups). We discuss that continuous monitoring of grouping patterns of these (and other) species may be a valuable approach to detect ‘subtle’ effects of human nuisance even before an overall population decline can be observed.
Different environmental features may serve as cues of the risk of predation. Therefore, when foraging in heterogeneous landscapes, the costs of predation for optimal foragers should vary along with the environmental features. In our study, we describe how foraging costs of predation vary spatially for Nubian ibex Capra nubiana with respect to characteristics of their natural environment, i.e. we quantified their ‘landscape of fear’. To do so, we established a five by five array of feeding trays within the natural environment of free-ranging Nubian ibex and measured the variation of giving-up densities (GUD, i.e. the amount of food remaining in a resource patch following exploitation) in relation to the landscape variables. The ibex' perceptions of risk of predation increased with distance from cliff and slope edges, and decreased with vegetation cover. Although several environmental variables are probably involved in the determination of an animal's foraging behaviour, with our study we revealed the most prominent features influencing the landscape of fear of Nubian ibex. Since Nubian ibex are endangered, this information is relevant for planning their conservation and management.
Ranging behaviour is one of the most important aspects of the life history of many species. Spatial distributions of individuals in the wild is linked to factors such as foraging, mating, population density, availability of resources and competition. Accurate data on the spatial location of individuals over time is often difficult to collect. Here, we propose a new simple, non-invasive and economic method for collecting accurate spatial data usable for many different species of free-ranging animals. Our instrument for collecting animal locations consists of three elements: a laser range finder, a laser tilt sensor and a protractor. This instrument can obtain three-dimensional parameters of the space from a fixed point allowing the user to collect geographical locations of the animals and, in general, of any point of interest. The device we tested showed a very low average error among (1.76 ± 0.643 m) and within (1.79 ± 0.058 m) observers, and the locations we obtained were all within the 95% probability of the tolerance intervals for the 20 positions which we measured repeatedly with a Global Position System for each of 10 different test locations. We tested a range of different distances to the target points (from 20 to 222 m), and we propose formulas to calculate precision of the instrument inside this interval. Precision of estimated locations was between 0.32 to 3.55 m from the real location and it was slightly related to distance of the target point (r = 0.38, P = 0.054). As an example of its practical application, we present data on the use of the instrument within the framework of a study on a population of free-ranging individually tagged alpine marmots Marmota marmota.
We used snow-tracking surveys to determine the probability of detecting Canada lynx Lynx canadensis in known areas of lynx presence in the northern Rocky Mountains, Montana, USA during the winters of 2006 and 2007. We used this information to determine the minimum number of survey replicates necessary to infer the presence and absence of lynx in areas of similar lynx density (approximately 2.8 lynx/100 km2) with confidence. The probability of detecting lynx in mountainous habitats that support resident populations was 0.80-0.99 when surveys were conducted on an 8 × 8 km2 grid with 10 km of search effort per cell. Snow-track surveys were highly successful at detecting the presence of Canada lynx over large landscapes. Two survey replicates established absence of Canada lynx with 95% certainty. The high probability of detection associated with snow-track surveys makes this method useful for documenting populations of Canada lynx in areas where their status is uncertain.
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