Hunting and the Likelihood of Extinction of Amazonian Mammals

Species inhabiting tropical forests are thought to be on the verge of mass extinction. Much work has focused on extinction rates caused by deforestation; however, many of the recorded extinctions that have occurred since 1600 were a result of overhunting. We collected data on the relative abundance of large-bodied mammals in the northeastern Peruvian Amazon in areas with persistent hunting pressure and in areas with infrequent hunting pressure. We quantified the effects of hunting by calculating the change in abundance of species between the infrequently and persistently hunted sites. We report that in Amazonian mammals weighing more than 1 kg the degree of population declines caused by hunting is correlated with the species' intrinsic rate of natural increase (r_max  ), longevity, and generation time. Our results show that species with long-lived individuals, low rates of increase, and long generation times are more vulnerable to extinction than species with short-lived individuals, high rates of increase, and shorter generations.     

Infectious Diseases and Extinction Risk in Wild Mammals

Abstract:  Parasite-driven declines in wildlife have become increasingly common and can pose significant risks to natural populations. We used the IUCN Red List of Threatened and Endangered Species and compiled data on hosts threatened by infectious disease and their parasites to better understand the role of infectious disease in contemporary host extinctions. The majority of mammal species considered threatened by parasites were either carnivores or artiodactyls, two clades that include the majority of domesticated animals. Parasites affecting host threat status were predominantly viruses and bacteria that infect a wide range of host species, including domesticated animals. Counter to our predictions, parasites transmitted by close contact were more likely to cause extinction risk than those transmitted by other routes. Mammal species threatened by parasites were not better studied for infectious diseases than other threatened mammals and did not have more parasites or differ in four key traits demonstrated to affect parasite species richness in other comparative studies. Our findings underscore the need for better information concerning the distribution and impacts of infectious diseases in populations of endangered mammals. In addition, our results suggest that evolutionary similarity to domesticated animals may be a key factor associated with parasite-mediated declines; thus, efforts to limit contact between domesticated hosts and wildlife could reduce extinction risk.     

Body Size and Risk of Extinction in Australian Mammals

Abstract: The link between body size and risk of extinction has been the focus of much recent attention. For Australian terrestrial mammals this link is of particular interest because it is widely believed that species in the intermediate size range of 35–5500 g (the "critical weight range") have been the most prone to recent extinction. But the relationship between body size and extinction risk in Australian mammals has never been subject to a robust statistical analysis. Using a combination of randomization tests and phylogenetic comparative analyses, we found that Australian mammal extinctions and declines have been nonrandom with respect to body size, but we reject the hypothesis of a critical weight range at intermediate sizes. Small species appear to be the least prone to extinction, but extinctions have not been significantly clustered around intermediate sizes. Our results suggest that hypotheses linking intermediate body size with high risk of extinction in Australian mammals are misguided and that the focus of future research should shift to explaining why the smallest species are the most resistant to extinction.     

Ecological Correlates of Extinction Proneness in Australian Tropical Rain Forest Mammals

Abstract. There is a dire need to predict the vulnerability of tropical forest biotas to habitat fragmentation I tested the efficacy of seven ecological traits (body size Iongeuity, fecundity, trophic level, dietary specialization, natural abundance in rain forest and abundance in the surrounding habitat matrix) for predicting responses of 16 nonflying mammal species to rain forest fragmentation in tropical QueenslaM Australia An ordination analysis revealed that most (84%) of the variation in traits was described by two axes, the first separating rand K-selected species, and the second discriminating rare species with specialized diets from common species with generalized diets.
Using multiple regression analysis, the two ordination axes explained 51.7% of variation in mammal extinction proneness (F = 9.96 P = 0.009). Howem, univariate tests revealed tbat a single trait abundance in the mawas a betterpredictor of vulnerability (r²= 63.8%, F = 24.69, P < 0.001). Partial correlations demonstrated that once the effects of matrix abundance tuete remove4 no other traits or ordination axes were significant predictors of extinction proneness.
These results highlight the importance of tolerance of modijied habitats in determining survival of nonpying mammals in tropical forest fragments. Species tbat traverse or exploit modaxied habitats tend to remain stable or inmase in fragments whereas those tbat avoid these habitats often disappem The implications of these findings for hopical forest conservation are discussed.     

Extinction of Mammal Populations in Western North American National Parks

Patterns of local extinction of mammal populations in western North American parks were examined in relation to current biogeographic and population lifetime models. The analysis was based on species sighting records as of 1989. While western North American parks are obviously not true isolates, patterns of mammal extinction in them are nonetheless consistent with two predictions of the land-bridge island hypothesis. First, the number of extinctions has exceeded the number of colonizations since park establishment, and, second, the rate of extinction is inversely related to park area. Factors influencing the lifetime of mammal populations were evaluated using a stepwise multivariate survival analysis procedure for censored data. Survival time for mammal populations was positively related to estimated initial population size. After accounting for population size, species within the order Lagomorpha were particularly prone to extinction. Finally, after controlling for population size and taxon variation, survival time was positively related to age of maturity, indicating that species with longer generation times—age of maturity and generation time are highly correlated in mammals—persist longer in absolute time.     

Evaluating the Predicted Local Extinction of a Once-Common Mouse

Abstract:  In an earlier paper ( Pergams & Nyberg 2001 ) we found that the proportion of the prairie deer mouse ( Peromyscus maniculatus bairdii ), among all local Peromyscus museum specimens collected in the Chicago region, had significantly declined over time. This proportion changed from about 50% before 1900 to <10% in the last 25 years. Based on this proportion a regression model predicted the local extinction of the prairie deer mouse in 2009. To evaluate that prediction, we estimated current deer mouse abundance by live trapping small mammals at 15 preserves in Cook and Lake counties, Illinois (USA) at which prairie deer mice had previously been caught or that still contained their preferred open habitat. In 1900 trap nights, 477 mammals were caught, including 251 white-footed mice ( P. leucopus ), but only one prairie deer mouse. The observed proportion of Peromyscus that were prairie deer mice, 0.4%, was even lower than the 4.5% predicted for 2000. Here we also introduce a simple, new community proportions model, which for any given geographic region compares the proportions of species recently caught with the proportions of species in museums. We compared proportions of seven species collected in Cook and Lake counties and examined by Hoffmeister (1989) with proportions of these species that we caught. Ten percent of the museum community was prairie deer mice, but only 0.2% of our catch was. The current local scarcity of the prairie deer mouse is consistent with the regression-based prediction of its eminent local extinction. More conservation attention should be paid to changes in relative abundance of once-common species.     

Collaborating to Conserve Large Mammals in Southeast Asia

Abstract:  Depressed mammal densities characterize the interior of many Southeast Asian protected areas, and are the result of commercial and subsistence hunting. Local people are part of this problem but can participate in solutions through improved partnerships that incorporate local knowledge into problem diagnosis. The process of involving local people helps build a constituency that is more aware of its role (positive and negative) in a protected area and generates site-specific conservation assessments for management planning. We illustrate the practical details of initiating such a partnership through our work in a Thai wildlife sanctuary. Many protected areas in Southeast Asia present similar opportunities. In local workshops, village woodsmen were led through ranking exercises to develop a spatially explicit picture of 20-year trends in the abundance of 31 mammal species and to compare species-specific causes for declines. Within five taxonomic groups, leaf monkeys (primates), porcupines (rodents), tigers (large carnivores), civets (small carnivores), and elephants (ungulates) had declined most severely (37–74%). Commercial hunting contributed heavily to extensive population declines for most species, and subsistence hunting was locally significant for some small carnivores, leaf monkeys, and deer. Workshops thus clarified which species were at highest risk of local extinction, where the most threatened populations were, and causes for these patterns. Most important, they advanced a shared problem definition, thereby unlocking opportunities for collaboration. As a result, local people and sanctuary managers have increased communication, initiated joint monitoring and patrolling, and established wildlife recovery zones. Using local knowledge has limitations, but the process of engaging local people promotes collaborative action that large mammals in Southeast Asia need.     

A Test of the Vegetation Mosaic Hypothesis: A Hypothesis to Explain the Decline and Extinction of Australian Mammals

The vegetation mosaic hypothesis suggests that medium-sized mammals occupying arid and semi-arid areas of Australia require a habitat that is a fine-grained mosaic of different vegetation types or seral stages. This mosaic is believed to have been created in the spinifex deserts of central Australia by Aboriginal burning practices. Its loss in the period 1940–1960 is postulated to be a primary reason for both major reductions in range and mainland extinctions of many species of medium-sized mammals at this time. This study measured the responses of three species of medium-sized mammals to vegetation patterns within spinifex grasslands that ranged from comparatively uniform to highly diverse. The abundance, condition, and reproductive status of golden bandicoots (Isoodon auratus) , northern brush-tailed possums (Trichosurus vulpecula arnhemensis) , and burrowing bettongs (Bettongia lesueur) were assessed within vegetation mosaics of various scales on Barrow Island, off the northwest coast of Australia. Scale of mosaic proved to have no significant effect on the numbers, condition, or reproductive status of any of the three species. Similarly, the creation of fine-grained mosaics of early seral-stage vegetation mixed within climax vegetation by extensive oil-field operations over nearly half the island had no significant effect on the number or condition of animals. Hence, scale of mosaic seems unlikely to be related to the mainland decline or extinction of these species. The pattern of decline and extinction on the mainland but continued survival on offshore islands is more consistent with the presence (mainland) or absence (islands) of introduced predators (foxes and cats) and herbivores (rabbits and stock).     

Natural Die-Offs of Large Mammals: Implications for Conservation

The viability of populations is a central concern of biological conservation. The occurrence of catastrophic die-offs may greatly reduce the long-term viability of populations. Theoretical extinction models and viability analyses require information on the frequency of die-offs and on the distribution of die-off severities. A review of literature identified 96 natural die-offs in large mammal populations, with a die-off being defined as a peak-to-trough decline in estimated population numbers of at least 25%. If such die-offs are common, population viability analyses that ignore them may be overly optimistic. The severities of the natural die-offs of large mammals presented here are not uniformly distributed. There is a relative overabundance of die-offs in the 70–90% range, and an underabundance of die-offs greater than 90%. This may indicate the presence of buffers against population extinction. The reported causes of large mammal die-offs were significantly related to trophic level: herbivore die-offs were more often attributed to starvation, while carnivore die-offs were more often attributed to disease. Populations subject to large-scale phenomena such as drought and severe winters may not be protected from die-offs by population subdivision. On the other hand, populations subject to catastrophic disease epidemics may be protected by subdivision, and threatened by corridors between conservation areas and by translocation efforts.     

Globalization of the Cashmere Market and the Decline of Large Mammals in Central Asia

As drivers of terrestrial ecosystems, humans have replaced large carnivores in most areas, and human influence not only exerts striking ecological pressures on biodiversity at local scales but also has indirect effects in distant corners of the world. We suggest that the multibillion dollar cashmere industry creates economic motivations that link western fashion preferences for cashmere to land use in Central Asia. This penchant for stylish clothing, in turn, encourages herders to increase livestock production which affects persistence of over 6 endangered large mammals in these remote, arid ecosystems. We hypothesized that global trade in cashmere has strong negative effects on native large mammals of deserts and grassland where cashmere‐producing goats are raised. We used time series data, ecological snapshots of the biomass of native and domestic ungulates, and ecologically and behaviorally based fieldwork to test our hypothesis. In Mongolia increases in domestic goat production were associated with a 3‐fold increase in local profits for herders coexisting with endangered saiga (Saiga tatarica).That increasing domestic grazing pressure carries fitness consequences was inferred on the basis of an approximately 4‐fold difference in juvenile recruitment among blue sheep (Pseudois nayaur)in trans‐Himalayan India. Across 7 study areas in Mongolia, India, and China's Tibetan Plateau, native ungulate biomass is now <5% that of domestic species. Such trends suggest ecosystem degradation and decreased capacity for the persistence of native species, including at least 8 Asian endemic species: saiga, chiru (Pantholops hodgsoni), Bactrian camel (Camelus bactrianus), snow leopard(Panthera uncia), khulan(Equus hemionus), kiang (E. kiang), takhi (E. przewalski), and wild yak (Bos mutus). Our results suggest striking yet indirect and unintended actions that link trophic‐level effects to markets induced by the trade for cashmere. Globalización del Mercado de Cachemira y la Declinación de Mamíferos Mayores en Asia Central     

Risk of Local Extinction of Odonata Freshwater Habitat Generalists and Specialists

Understanding the risk of a local extinction in a single population relative to the habitat requirements of a species is important in both theoretical and applied ecology. Local extinction risk depends on several factors, such as habitat requirements, range size of species, and habitat quality. We studied the local extinctions among 31 dragonfly and damselfly species from 1930 to 1975 and from 1995 to 2003 in Central Finland. We tested whether habitat specialists had a higher local extinction rate than generalist species. Approximately 30% of the local dragonfly and damselfly populations were extirpated during the 2 study periods. The size of the geographical range of the species was negatively related to extinction rate of the local populations. In contrast to our prediction, the specialist species had lower local extinction rates than the generalist species, probably because generalist species occurred in both low‐ and high‐quality habitat. Our results are consistent with source–sink theory. Riesgo de Extinción Local de Odonatos de Agua Dulce Generalistas y Especialistas de Hábitat     

Human Population Density and Prediction of Local Plant Extinction in Britain

Throughout the world, and particularly in densely populated countries like Britain, human activities exert a dominant influence on the abundance of both plants and animals. The commonness and rarity of plants in Britain has been plausibly linked to human land use. In Western Europe the identity of increasing and decreasing plants appears to depend on human population density, which is itself a crude measure of human impact on the landscape. The publication of new data on the changing distributions of scarce British plants allowed us to investigate the relationship between loss of scarce plants and human population density in Britain. Our results confirm that a direct effect of human population density on local plant extinctions can be detected at the regional scale in Britain. Although intensive agriculture is conventionally regarded as the greatest threat to British wildlife, our analysis suggests that urbanization may be at least as significant a danger.     

Genetically Effective Population Size of Large Mammals: An Assessment of Estimators

Calculamos tamuños de poblaciones genéticamente efectivas (N_e) para poblaciones simuladas del oso gris (Ursus arctos) trazando la péridida de heterozigasidad a tráves del tiempo, luego las comparamos con estimaciones de N_e Producidas aplicando fórmulas publicadas a los resultados demográficos de la simulación. Los valores de N_e calculados usando diferentes fórmula.s con datos idénticos, variaron mucho. Las ecuaciones publicadas por Hill (1972), y modificaciones de las usuadas por Ryman, et aL (1981) y Reed et al. (1986), proporcionaron los cálculos más precsios Fluctuaciones menores en las poblacionales tuvieron poco efecto sobre N_e pero la variación en el éxito repductivo por vida entre los machos V_km redujo tremendamente el N_e comparado con el valor esperado bajo exito reproductivo al azar. Todos los métodos para calcular N_e para poblaciones con demografias complejas requieren datos extensos, pero estimaciones para V_km en especies poligamas son especialmente dificiles de obtener. Sugerimos que modelos de simulación pueden proveer métodos alternutivos para calcular V_km y N_e.     

Tropical Forest Fragmentation and the Local Extinction of Understory Birds in the Eastern Usambara Mountains, Tanzania

Abstract. Small tropical forest fragments in the Eastern Usambara Mountains have lost understory bird species following forest fragmentation. The local extinction of these species is documented through a comparison of species number on nine smaller fores t fragments with species number on a tenth larger control forest site. The number of species captured in the control forest site is significantly larger than the number captured in eight of the nine smaller forest fragments under an equivalent capture effort. Forest-dependent understory species vary greatly in their vulnerability to forest fragmentation. Relatively rare species and forest interior species are the avifauna most adversely affected by forest fragmentation. A concerted effort should be made to protect the existing corridors of native forest that link established forest reserves in the Eastern Usambara Mountains.