Cats, canines, and coexistence: dietary differentiation between the sympatric Snow Leopard and Grey Wolf in the western landscape of Nepal Himalaya

Understanding the dietary habits of sympatric apex carnivores advances our knowledge of ecological processes and aids their conservation. We compared the diets of the sympatric Snow Leopard Panthera uncia and Grey Wolf Canis lupus using standard micro-histological analyses of scats collected from the western complex of Nepal Himalaya. Our study revealed one of the highest recorded contributions of livestock to the diet of top predators (55% for Grey Wolf and 39% for Snow Leopard) and high dietary overlap (0.82) indicating potential exploitative or interference competition. Their diet composition, however, varied significantly based on their consumption of wild and domestic prey. Limitation in data precludes predicting direction and outcome of inter-specific interactions between these predators. Our findings suggest a high rate of negative interaction with humans in the region and plausibly retaliatory killings of these imperilled predators. To ensure the sustained survival of these two apex carnivores, conservation measures should enhance populations of their wild prey species while reducing livestock losses of the local community through preventive and mitigative interventions.

Density effects and snake predation: prey limitation and reduced growth rate of adders at high density of conspecifics

To test the hypothesis that snakes limit the population growth of their prey, we measured the density of adders (Vipera berus) and field voles (Microtus agrestis) over several years on six small islands (1–12 ha) in the Baltic Sea. In both 1989 and 1990 we found a negative relationship (significant in one year) between the density of adders and voles across islands, indicating that on islands with high densities the adders exert such a high predation pressure that the voles become predator limited. In 1991 and 1993 we experimentally manipulated adder densities to rule out potential island effects. A comparison between transferred and resident snakes revealed no negative effects of being transferred to an unfamiliar environment. Furthermore, vole density decreased more on islands where we had experimentally increased adder density compared with islands with reduced densities and unmanipulated controls, but the difference was not significant. To test the hypothesis that adders at high densities of conspecifics decrease the vole population so much as to become resource limited, we calculated mean annual relative growth rate (a size-independent measure of growth rate) of adders on all islands during 1989 through 1993. In all 5 years we found a negative relationship across islands between adder density and growth rate of adders. Combining all years there was a significant negative effect of adder density, suggesting that on islands with high densities the adders suffer a reduction in growth rates that was due to intense exploitative competition.

INSECT COMMUNITIES OF NEWFOUNDLAND BOG POOLS WITH EMPHASIS ON THE ODONATA

The arthropod and annelid fauna of a series of small, acidic pools in a domed, ombrotrophic bog on the Avalon Peninsula, Newfoundland, was studied over the ice-free season of 1986. Pools were assigned to four classes on the basis of their surface area (<1; 1.1–10; 10.1–100; >100 m2) and at least two 1-m2 (entire pool if area <1 m2) substrate samples, plankton samples, and moss samples were taken from pools of each size class biweekly. One hundred and thirty-one taxa, most identified to the species level, were collected. Taxa varied in abundance between pools of various size classes and, using Cluster Analysis and TWINSPAN, two principal communities were identified. Oligochaetes, beetles, and mosquitoes dominated small, astatic pools and odonates, chironomids, and several other taxa predominated in large, stable, vegetated pools. Water level stability is postulated to be the principal factor determining this community structure. Within large pools, odonate larvae were the dominant predators and comprised the majority of the standing crop. Odonate larvae have life cycles of 2 or more years; their slow growth is probably due to prey limitation. Odonate larvae potentially exert a powerful predation pressure within the large pool community, and may be the principal biotic factor determining abundance and distribution of prey taxa within the bog pool system.