Madan K. Oli

Snow leopard Panthera uncia predation of livestock: An assessment of local perceptions in the Annapurna Conservation Area, Nepal

Abstract Public attitudes towards snow leopard Panthera uncia predation of domestic livestock were investigated by a questionnaire survey of four villages in snow leopard habitat within the Annapurna Conservation Area, Nepal. Most local inhabitants were subsistence farmers, many dependent upon yaks, oxen, horses and goats, with an average livestock holding of 26.6 animals per household. Reported losses to snow leopards averaged 0.6 and 0.7 animals per household in two years of study, constituting 2.6% of total stockholding but representing in monetary terms almost a quarter of the average annual Nepali national per capita income. Local people held strongly negative attitudes towards snow leopards and most suggested that total extermination of leopards was the only acceptable solution to the predation problem. Snow leopards were reported to be killed by herdsmen in defence of their livestock. The long-term success of snow leopard conservation programmes may depend upon the satisfactory resolution of the predation conflict. Some possible ways of reducing predation losses are also discussed.

Population cycles in small mammals : the role of age at sexual maturity

Several hypotheses have been proposed to explain cyclic fluctuations in abundance of some small mammal populations. These hypotheses have been controversial, however, and there is no consensus among biologists as to why population cycles occur In a demographically based model, we tested the potential influence of phase-specific changes in life history traits (age at maturity, fertility, juvenile survival and adult survival) on population cycles. Our demographic model considers, and is logically consistent with, the empirical pattern of population characteristics during a cycle The essence of the model is that phase-specific changes in age at maturity, abetted secondarily by changes in juvenile survival, result in cyclic fluctuations in population size. Changes in adult survival and fertility may play a minor role, but they are neither necessary nor sufficient by themselves to generate population cycles. Phase-specific changes in age at maturity might be related to primary changes in the quality of the ecological and social environment that permit particularly high densities.

Snow leopards and blue sheep in Nepal: densities and predator: prey ratio

I studied snow leopards ( Panthera uncid ) and blue sheep ( Pseudois nayaur ) in Manang District, Annapurna Conservation Area, Nepal, to estimate numbers and analyze predator-prey interactions. Five to seven adult leopards used the 105-km2 study area, a density of 4.8 to 6.7 leopards/100 km2. Density of blue sheep was 6.6–10.2 sheep/km2, and biomass density was 304 kg/km2. Estimated relative biomass consumed by snow leopards suggested that blue sheep were the most important prey; marmots ( Marmota himalayana ) also contributed significantly to the diet of snow leopards. Snow leopards in Manang were estimated to harvest 9–20% of total biomass and 11–24% of total number of blue sheep annually. Snow leopard:blue sheep ratio was 1:114–1:159 on a weight basis, which was considered sustainable given the importance of small mammals in the leopards diet and the absence of other competing predators.

Population cycles in small mammals : The α-hypothesis

Abstract Causes of cyclic fluctuations in abundance (population cycles) of some small-mammal populations remain poorly understood despite 6 decades of research and >20 hypotheses. Population cycles are demographic processes and cannot be fully explained without considering demographic mechanisms that underlie cyclic fluctuations in abundance. From simulation studies, we have recently shown that phase-related, density-dependent changes in age at maturity, abetted secondarily by changes in juvenile survival, are likely the main demographic causes of cyclic fluctuations in population size. The suggested mechanism of population cycles is based primarily on changes in age at maturity (α); we refer to this idea as the α-hypothesis. Here, we fully develop the α-hypothesis and present a testable, demographically based, mechanistic explanation of population cycles. The α-hypothesis identifies the demographic basis of population cycles and provides a mechanistic explanation of how changes in key demographic variables (age at maturity and juvenile survival) might cause cyclic fluctuations in abundance and biologic attributes of the cycles. The α-hypothesis is supported by, and logically consistent with, empirical patterns of life history and dynamics of cyclic populations of small mammals. Future research should focus on empirically determining causes of phase-related changes in age at maturity and juvenile survival.

Effect of density reduction on uinta ground squirrels: analysis of life table response experiments.

The effects of natural or experimental environmental perturbations on pop- ulations can be diverse, simultaneously affecting several life history variables. Population- level responses to such influences frequently are measured as changes in projected popu- lation growth rate (l). Sensitivity and elasticity analyses can be used to quantify the potential influence of small changes in different life history variables on l. When a population is subjected to an experimental treatment, life table response experiment (LTRE) analysis allows decomposition of changes in l into contributions due to observed changes in in- dividual life history variables. We investigated the potential and actual influence of de- mographic characteristics (age at maturity, juvenile and adult survival, fertility, and age at last reproduction) on l of Uinta ground squirrels (Spermophilus armatus) in the Wasatch Mountains of Utah, USA. Ground squirrels were studied in three different habitats, before and after an experimental reduction of population size. Survival and reproduction of squir- rels increased in response to a reduction in population density. Consequently, l increased by at least 21% in two of the three habitats. Population growth rate was potentially most sensitive to changes in age at maturity (a) and fertility. LTRE analysis revealed that a did not change and contributed nothing to changes in l, but changes in fertility were large and contributed most to observed changes in l. Age at last reproduction (v) increased after density reduction but contributed little to observed changes in l because of low sensitivity of l to changes in v. Thus, there was little correspondence between potential influence and actual contributions to observed changes in l. We concluded that some demographic var- iables, notably a, had little environmental or phylogenetic scope for reduction, whereas fertility and to some degree survival rates were considerably more plastic under the ex- perimental treatment. Because LTRE analysis incorporates observed changes in life history variables and also sensitivity of l to these changes, it worked well for quantifying the response of Uinta ground squirrel populations to density manipulation and holds promise for evaluating alternative management strategies in conservation biology.

Viability analysis of endangered Gulf Coast beach mice (Peromyscus polionotus) populations

Beach mice, endangered subspecies of oldfield mice (Peromyscus polionotus), occur in a few, isolated populations along the Gulf Coast of Alabama and Florida, USA. To provide information needed for the management of these species, we conducted population viability analyses (PVA) using a stochastic differential equation (Wiener-drift) model applied to long-term demographic data for four populations of beach mice. In the absence of catastrophic events, the probability that the mouse populations would decline to one mouse ranged from 0.002 for the population of Alabama beach mice (P. p. ammobates) at the Perdue unit of Bon Secour National Wildlife Refuge (BSPU) to 1.00 for the Perdido Key beach mouse (P. p. trissyllepsis) population at Gulf Island National Seashore (GINS). Modal time to extinction for those sample paths reaching extinction ranged from 5 years for the Fort Morgan population of Alabama beach mice to 21 years for the GINS population of Perdido Key beach mice. When the BSPU data set was extended to include data collected following Hurricane Opal, the probability of extinction increased to 0.479. If catastrophic events, which are frequent in the Gulf Coast habitats, are considered, virtually all populations of beach mice appear in substantial danger of extinction unless current levels of habitat fragmentation are reversed. In addition, ongoing development continues to reduce or fragment the habitat exacerbating the already precarious existence of these mice. It is our conclusion that the results obtained from the PVA analyses provide independent evidence that further loss of beach mouse habitat (including the scrub dune component) should be avoided, and that populations should be re-established within their historic range wherever feasible.

PARTIAL LIFE-CYCLE ANALYSIS: A MODEL FOR BIRTH-PULSE POPULATIONS

Matrix population models have become standard tools for the demographic analysis of age- or stage-structured populations. Although age-classified (Leslie) matrix models make maximum use of age-specific demographic data, age at first reproduction, which has been suggested to be an important life-history variable, does not appear as an explicit parameter in these models. Consequently, the sensitivity of population growth rate to changes in age at first reproduction cannot be calculated using standard techniques. Age-specific demographic data to parameterize age-structured models are difficult to collect, and models that can be parameterized with partial demographic data (“partial life-cycle models”) have been developed. Partial life-cycle models are based on life-history stages, and these models can also be used to calculate sensitivity of population growth rate to changes in various life-history variables, including ages at first and last reproduction. Here, we present a partial life-cycle model appropriate for situations where demographic data are collected immediately after the birth pulse (post-breeding census). We present methods of parameterizing the partial life-cycle model, and derive formulas for calculating the sensitivity of the population growth rate to changes in model parameters, including ages at first and last reproduction. We analyzed life-table data for several species of mammals using the partial life-cycle model and found that results of our partial life-cycle model compare favorably with those obtained from the corresponding age-classified models.