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Leisure activities in fragmented western European forests are thought to threaten local populations of capercaillie Tetrao urogallus. We studied impacts of human disturbance on capercaillie in three Scottish woods by documenting the distribution of their droppings in relation to woodland tracks and entrances, surrogates for human activity. Droppings were sparser within 300–800 m of entrances and 70–235 m of tracks, depending on track use and habitat. Some 75% of each wood lay within 130 m of a track. In the most disturbed wood, droppings were most abundant in the centres of larger patches of trackless boggy ground, which acted as refuges. The reproductive rate (chicks reared per hen) at our three study areas was no less than in other, less disturbed parts of the same valley. The ratio of full-grown hens to cocks, however, was unusually low in the two most disturbed woods. Disturbance reduces the birds' living space, possibly affecting hens more than cocks. It might therefore impact metapopulation dynamics and contribute to genetic impoverishment in small populations. Ensuring that people and dogs keep to tracks, closing tracks and creating refuges should mitigate such effects.
Density estimates are critical to proper population management and conservation, yet difficult to obtain for many wide-ranging or cryptic species. One proven method used to quantify carnivore density, especially species difficult to individually identify from photos taken by camera traps, utilizes overlapping home ranges of individual animals in the study area. This method, however, may be particularly prone to residency and extrapolation biases. Residency bias occurs when the reference area for the density estimate is incorrect, and extrapolation bias occurs when scaling a density to a different spatial extent than that of the study area upon which the estimate was based. We used a simulation approach based on GPS locations to diagnose potential biases in published densities of pumas Puma concolor from Patagonia, where Franklin et al. 1999 (Biol. Conserv. 90: 33–40) reported ‘minimum’ densities of 6 and 30 pumas per 100 km2, and Elbroch and Wittmer 2012a (Mammal. Biol. 77: 377–384) reported densities of 3.4 pumas per 100 km2. Using GPS data from the latter study we tested methods described in Franklin et al. (1999) and compared their outcomes. Our results showed that density estimates that do not account for residency bias resulted in severely inflated density estimates. Our findings also indicated that actual densities from Franklin et al. (1999) might have been an order of magnitude lower than reported, and therefore consistent with puma densities reported across the range of the species. Both studies introduced extrapolation bias by translating linearly their estimates to new spatial extents, although the magnitude of this bias was much less than that of residency bias. Our results underscore the need for rigorous accounting of residential space in estimating population density, and highlight the scale-dependency of density estimates.
Insight into the spatial ecology of predators might help biologists to design wildlife reserves that maximize conservation success. We investigated the spatial ecology of endangered black-footed ferrets Mustela nigripes during the post-breeding seasons (June–October) of 2007 and 2008 on a 452-ha colony of black-tailed prairie dogs Cynomys ludovicianus in South Dakota, USA. Ferrets of both sexes frequently used areas with an abundance of active openings to prairie dog burrows, suggesting a positive response to refuge and prey. Densities of active burrow openings were similar in areas of same-sex overlap and areas of exclusive space use, which might suggest limited defense of resources by ferrets. However, this result could be expected in our study because much of the study colony contained high densities of active burrow openings. Same-sex home ranges overlapped in area, but the intensity of space use overlap was low. For male ferrets with overlapping home ranges, both males tended to spend low amounts of time in areas of overlap. In contrast, for pairs of overlapping female home ranges, one female frequently used areas of overlap while the second apparently avoided them, suggesting a dominance hierarchy of some sort. Core areas were essentially exclusive. Our data are consistent with the hypothesis of intrasexual territoriality by ferrets in habitats of high quality, which would limit the number of ferrets a habitat supports. Where wildlife managers aim to maximize densities of free-ranging ferrets, it might be beneficial to create reserves that 1) provide each ferret with sufficient prey and refuge, 2) reduce social conflict and competition for space, and 3) facilitate dispersal.
Relationships between foraging habitat and reproductive success provide compelling evidence of the contribution of specific vegetative features to foraging habitat quality, a potentially limiting factor for many animal populations. For example, foraging habitat quality likely will gain importance in the recovery of the threatened red-cockaded woodpecker Picoides borealis (RCW) in the USA as immediate nesting constraints are mitigated. Several researchers have characterized resource selection by foraging RCWs, but emerging research linking reproductive success (e.g. clutch size, nestling and fledgling production, and group size) and foraging habitat features has yet to be synthesized. Therefore, we reviewed peer-refereed scientific literature and technical resources (e.g. books, symposia proceedings, and technical reports) that examined RCW foraging ecology, foraging habitat, or demography to evaluate evidence for effects of the key foraging habitat features described in the species' recovery plan on group reproductive success. Fitness-based habitat models suggest foraging habitat with low to intermediate pine Pinus spp. densities, presence of large and old pines, minimal midstory development, and herbaceous groundcover support more productive RCW groups. However, the relationships between some foraging habitat features and RCW reproductive success are not well supported by empirical data. In addition, few regression models account for > 30% of variation in reproductive success, and unstandardized multiple and simple linear regression coefficient estimates typically range from -0.100 to 0.100, suggesting ancillary variables and perhaps indirect mechanisms influence reproductive success. These findings suggest additional research is needed to address uncertainty in relationships between foraging habitat features and RCW reproductive success and in the mechanisms underlying those relationships.
Thermal cover may influence habitat selection by white-tailed deer Odocoileus virginianus in subtropical climates with hot summers. We 1) tested the hypothesis that thermal environment is more important in habitat selection at midday during summer than forage quality or quantity and concealment cover and 2) determined whether operative temperature, vegetation height, or woody plant canopy cover (or some combination of these) explain habitat selection at midday. We predicted that during crepuscular periods and at night habitat use increases with increasing forage quality and quantity and concealment cover and is unrelated to thermal environment. Male white-tailed deer were fitted with GPS collars to determine resources selected within habitats during June and July 2008 and 2009. A generalized linear mixed model using logistic regression was used to estimate resource selection functions. We used the first principal component in a principal components analysis (PCA) of forage standing crop, crude protein, and acid detergent fiber (ADF) to create a ‘forage index’. This index and vegetation height, operative temperature and concealment cover, together with their interactions with activity period, were used to develop a priori candidate models. Akaike weights were used to compare candidate models. A model that included the forage index, vegetation height, operative temperature, concealment cover and their interactions with activity period was the best model out of 97 candidate models for explaining habitat selection by adult male white-tailed deer. Male white-tailed deer selected areas with taller vegetation in morning and midday activity periods but selected shorter vegetation during evening and nighttime. Forage quality was important in habitat selection in all activity periods. Male white-tailed deer did not select areas with greater concealment cover during any activity period. A combination of operative temperature, vegetation height, and woody plant canopy cover predicted midday habitat use better than any of these three variables alone. Thermoregulatory behavior in male white-tailed appears to include a combination of seeking cooler environments during midday but at the same time using areas with greater forage quality.
Demographic rates are critical pieces of information for understanding ungulate population dynamics and effectively managing populations. In harvested elk Cervus elaphus canadensis populations, human harvest is often the greatest source of adult male mortality. In the Cypress Hills of southeast Alberta and southwest Saskatchewan, Canada, hunting is a tool to mitigate conflicts between elk and agricultural producers in the area. We estimated survival (S) and animal recovery (f) rates based on individually marked male elk (n = 47) using hunter-returned ear tags from 1998–2001. Recovery rate differed between jurisdictions and was substantially lower in Saskatchewan (f = 0.16, SE = 0.05) compared to Alberta (f = 0.31, SE = 0.08). A constant survival rate (S = 0.61, SE = 0.15) was most supported. The average longevity for male elk in the Cypress Hills was 2.02 (SE = 0.51) years after surviving their first year of life. This research highlights the importance of considering regulatory regimes and requirements when investigating and interpreting demographic and population dynamics of populations managed across jurisdictions.
Susceptibility to antimicrobial agents among Enterobacteriaceae recovered from feces of the Okinawa least horseshoe bat Rhinolophus pumilus (OLHB) in Japan was investigated in 78 isolates. Of these, one isolate was resistant to chlortetracycline and streptomycin, and nine were resistant to sulfadimethoxine (SDMX). Half of these (n = 5) resistant isolates had the transmissible R plasmid for antimicrobials suggesting that OLHB is a species that hardly harbors antimicrobial-resistant Enterobacteriaceae. One possible reason for this low prevalence of antimicrobial resistance is that the bat lives in a clean environment with no or only very low artificial drug contaminations due to low contact with such as livestock that frequently carries antibiotic-resistant bacteria. This study suggests that it's important to monitor antimicrobial resistance of Enterobacteriaceae in OLHB as a model for natural R plasmid transfer in a natural environment without specific pathological bacteria and artificial drugs.