Twenty-five years ago, the snow leopard Uncia uncia, an endangered large cat, was eliminated from what is now Sagarmatha National Park (SNP). Heavy hunting pressure depleted that area of most medium–large mammals, before it became a park. After three decades of protection, the cessation of hunting and the recovery of wild ungulate populations, snow leopards have recently returned (four individuals). We have documented the effects of the return of the snow leopard on the population of its main wild prey, the Himalayan tahr Hemitragus jemlahicus, a ‘near-threatened’ caprin. Signs of snow leopard presence were recorded and scats were collected along a fixed trail (130 km) to assess the presence and food habits of the snow leopard in the Park, from 2004 to 2006. Himalayan tahr, the staple of the diet, had a relative occurrence of 48% in summer and 37% in autumn, compared with the next most frequent prey, musk deer Moschus chrysogaster (summer: 20%; autumn: 15%) and cattle (summer: 15%; autumn: 27%). In early summer, the birth rate of tahr (young-to-female ratio: 0.8–0.9) was high. The decrease of this ratio to 0.1–0.2 in autumn implied that summer predation concentrated on young tahr, eventually altering the population by removing the kid cohort. Small populations of wild Caprinae, for example the Himalayan tahr population in SNP, are sensitive to stochastic predation events and may be led to almost local extinction. If predation on livestock keeps growing, together with the decrease of Himalayan tahr, retaliatory killing of snow leopards by local people may be expected, and the snow leopard could again be at risk of local extinction. Restoration of biodiversity through the return of a large predator has to be monitored carefully, especially in areas affected by humans, where the lack of important environmental components, for example key prey species, may make the return of a predator a challenging event
Cuckoo bees and velvet ants use different resources of their shared host bees, the former laying eggs on the host pollen stores and the latter on immature stages. We studied the activity patterns of the cuckoo bee Sphecodes monilicornis and the velvet ant Myrmilla capitata at two nesting sites of their host, the social digger bee Lasioglossum malachurum, over a 3 year period. Due to the difference in host exploitation, we expected different temporal patterns of the two natural enemies as well as a positive spatial association with host nest density for both species. At a daily level, S. monilicornis was more abundant between 10.00 and 15.00 h, while M. capitata was most active in the early morning and late afternoon; both species activities were independent from host provisioning activity. The activity of cuckoo bees was in general positively correlated with the density of open host nests (but not with the total number of nests), while that of velvet ants was rarely correlated with this factor. Sphecodes monilicornis was seen both attacking the guard bees and directly entering into the host nests or digging close to nest entrances, while M. capitata only gained access to host nests through digging. We conclude that the temporal and spatial segregation between the two species may be, at least partially, explained both by the different resources exploited and by the different dynamics of host interactions.
Abstract. At a nest site in Northern Italy of females of the weevil-hunting digger wasp Cerceris arenaria L. (Hymenoptera: Crabronidae) the provisioning activity and predator-prey relationship were investigated, in particular their specialization in choice of prey. Females were active from middle of June to end of July, and from 8.00 to 19.00. The wasps made provisioning flights throughout the day, mostly in late morning and early afternoon. Individual wasps generally only hunted for 1 or 2 prey species of all those available, maybe because of their higher abundance. The size of prey, which is positively correlated with that of the female wasps, seems to be the main factor determining choice of prey. The nature of the provisioning flights seems to be related to the size of the prey, being more frequent and shorter for smaller weevils. The correlation between prey and wasp biomass is discussed in relation to the size range of the wasps.
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