Abundance Of Medium-sized Mammals Research Articles

Snow track counts for density estimation of mammalian predators in the boreal forest

Context Methods for estimating density of meso-carnivores in northern ecosystems are labour intensive and expensive to implement if mark–recapture and radio collaring are used. One alternative is to count tracks in the snow along transects as an index of density, but this method has been criticised as imprecise and lacking validation. Aims We aimed to examine the utility of track counts along snowmobile trails in the snow for measuring changes in populations of Canada lynx and coyotes in the boreal forest of north-western Canada. Methods We compared winter track counts of Canada lynx at three study sites and of coyotes at one site with concurrent estimates of density based on locations of radio-collared animals and estimates of numbers of uncollared animals from three 7–9-year studies in the Yukon and Northwest Territories, during a period of cyclical population fluctuations. Key results Snow track counts were positively correlated (r2 = 0.83) with density of Canada lynx, estimated by live trapping and radio collaring in the three survey areas. Coyotes also showed a clear relationship (r2 = 0.80) between known density and snow track counts, but track counts were strongly affected by season, with much higher counts in the early winter when snow was shallower. This indicates the need to control for season or snow depth when using track counts as indices of coyote abundance. We recommend sample sizes of at least 10 track counts per winter along a 25-km transect to maximise precision. Conclusions Snow track counts are a relatively simple, inexpensive method of concurrently tracking abundance of multiple species of meso-carnivores. These data indicate that track counts may be reliably used to monitor trends in numbers, but we suggest site-specific validation of the regressions reported here between tracks and animal abundance are required to translate these indices into estimates of density. Implications Track counts have the potential to be an affordable alternative to more intensive methods of monitoring trends in abundance of medium-sized mammals, for purposes such as management of harvest or to measure the success of programs to increase or reduce population abundance.

Providing Habitat for Native Mammals through Understory Enhancement in Forestry Plantations

The Convention on Biological Diversity (CBD) expects forestry plantations to contribute to biodiversity conservation. A well-developed understory in forestry plantations might serve as a surrogate habitat for native species and mitigate the negative effect of plantations on species richness. We experimentally tested this hypothesis by removing the understory in Monterey pine (Pinus radiata) plantations in central Chile and assessing changes in species richness and abundance of medium-sized mammals. Frequency of occurrence of mammals, including kodkods (Leopardus guigna), culpeo foxes (Pseudalopex culpaeus), lesser grisons (Conepatus chinga), and Southern pudu deer (Pudu puda), was low in forest stands with little to no understory relative to stands with well-developed undergrowth vegetation. After removing the understory, their frequency of occurrence decreased significantly, whereas in control stands, where understory was not removed, their frequency did not change. This result strongly supports the idea that facilitating the development of undergrowth vegetation may turn forestry stands into secondary habitats as opposed to their containing no habitat for native mammals. This forestry practice could contribute to conservation of biological diversity as it pertains to CBD targets.

Abundance of Conepatus chinga (Carnivora, Mephitidae) and other medium-sized mammals in grasslands of southern Brazil

Between January 2007 and December 2010, the abundance of medium-sized mammals was studied, with special focus on the Molina's hog-nosed skunk, Conepatus chinga (Molina, 1782), at four locations in southern Brazil. In this study, transect line methodology was used to obtain data for Distance Analyses. Transects were traveled by car at night, searching with spotlights along the edges of secondary roads in agricultural landscapes. Along 1,811 km, we obtained 620 observations of 20 mammal species. The most common species was the exotic European hare, Lepus europaeus (Pallas, 1778); the highest abundance estimated for South America was observed in one of the study areas, where its density was estimated as 32 individuals/km². Carnivores were the most commonly recorded mammals, represented by 10 species and comprising 51% of all observations. Molina's hog-nosed skunk occurred in all study areas, but occurred in sufficient numbers to obtain density estimates in only two of the areas. We estimated 1.4 to 3.8 individuals/km², in the first density estimate made by the transect method for a member of Conepatus in the Neotropics. These values are similar to those estimated for North American species of Mephitidae. In Brazil, C. chinga is apparently more abundant in the Pampa biome than in the grasslands of the Atlantic Forest. For two other carnivores, Lycalopex gymnocercus (Fisher, 1814) and Cerdocyon thous (Linnaeus, 1766), we estimated preliminary densities that were similar to those previously cited for different regions.

Assessment of the Diet of the Fox, Vulpes vulpes, in Habitats of the Eastern Otway Ranges, Victoria.

The Eastern Otway Ranges, Victoria have highly diverse native mammal communities. Although the Red Fox (Vulpes vulpes) has been recorded in the area the extent of its distribution and effects on native mammals are unclear. The aims of this study were to analyse the diet of the Red Fox in the study area, to compare the diet between seasons and habitats (woodland, forest, heathland) and to assess the diet in the habitat of the New Holland Mouse (Pseudomys novaehollandiae) which is endangered in Victoria. Fox scats collected monthly in each habitat were analysed to determine the composition of the diet and small mammal trapping was carried out in each habitat to determine potential small mammal prey species. Overall, mammals (42%) constituted the highest proportion in the fox scats and sixteen species, including nine native species were recorded. Large-sized native mammals including Swamp Wallaby (Wallabia bicolor) and the Eastern Grey Kangaroo (Macropus giganteus) constituted 60% of the mammal diet category. The occurrence of plant material was significantly different between seasons, being more abundant in winter. There was a significant difference in the frequency of large introduced mammals in the diet between seasons, with consumption being higher in winter. The occurrence of large, native mammalian prey increased from 15% in winter to 47% in autumn. The frequency of occurrence of the major dietary categories (plant material, invertebrates, reptiles, birds, mammals) was similar across habitats. Large introduced mammals occurred in higher proportions in the diet from woodland habitat. Small mammals were more numerous in scats of heathland and scats from the forest contained the highest abundance of medium-sized mammals. There was no evidence of the endangered New Holland Mouse in scats collected from habitat where a population of the species was present.