Research Article
Can parks protect migratory ungulates? The case of the Serengeti wildebeest
- Simon Thirgood, Anna Mosser, Sebastian Tham, Grant Hopcraft, Ephraim Mwangomo, Titus Mlengeya, Morris Kilewo, John Fryxell, A. R. E. Sinclair, Markus Borner
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- Published online by Cambridge University Press:
- 11 May 2004, pp. 113-120
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The conservation of migratory species can be problematic because of their requirements for large protected areas. We investigated this issue by examining the annual movements of the migratory wildebeest, Connochaetes taurinus, in the 25000 km2 Serengeti-Mara Ecosystem of Tanzania and Kenya. We used Global Positioning System telemetry to track eight wildebeest during 1999–2000 in relation to protected area status in different parts of the ecosystem. The collared wildebeest spent 90% of their time within well-protected core areas. However, two sections of the wildebeest migration route – the Ikoma Open Area and the Mara Group Ranches – currently receive limited protection and are threatened by poaching or agriculture. Comparison of current wildebeest migration routes to those recorded during 1971–73 indicates that the western buffer zones appear to be used more extensively than in the past. This tentative conclusion has important repercussions for management and needs further study. The current development of community-run Wildlife Management Areas as additional buffer zones around the Serengeti represents an important step in the conservation of this UNESCO World Heritage Site. This study demonstrates that detailed knowledge of movement of migratory species is required to plan effective conservation action.
Conflicts between traditional pastoralism and conservation of Himalayan ibex (Capra sibirica) in the Trans-Himalayan mountains
- Sumanta Bagchi, Charudutt Mishra, Y. V. Bhatnagar
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- Published online by Cambridge University Press:
- 11 May 2004, pp. 121-128
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There is recent evidence to suggest that domestic livestock deplete the density and diversity of wild herbivores in the cold deserts of the Trans-Himalaya by imposing resource limitations. To ascertain the degree and nature of threats faced by Himalayan ibex (Capra sibirica) from seven livestock species, we studied their resource use patterns over space, habitat and food dimensions in the pastures of Pin Valley National Park in the Spiti region of the Indian Himalaya. Species diet profiles were obtained by direct observations. We assessed the similarity in habitat use and diets of ibex and livestock using Non-Metric Multidimensional Scaling. We estimated the influence of the spatial distribution of livestock on habitat and diet choice of ibex by examining their co-occurrence patterns in cells overlaid on the pastures. The observed co-occurrence of ibex and livestock in cells was compared with null-models generated through Monte Carlo simulations. The results suggest that goats and sheep impose resource limitations on ibex and exclude them from certain pastures. In the remaining suitable habitat, ibex share forage with horses. Ibex remained relatively unaffected by other livestock such as yaks, donkeys and cattle. However, most livestock removed large amounts of forage from the pastures (nearly 250 kg of dry matter/day by certain species), thereby reducing forage availability for ibex. Pertinent conservation issues are discussed in the light of multiple-use of parks and current socio-economic transitions in the region, which call for integrating social and ecological feedback into management planning.
A preliminary evaluation of the sustainability of cassowary (Aves: Casuariidae) capture and trade in Papua New Guinea
- Arlyne Johnson, Robert Bino, Paul Igag
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- 11 May 2004, pp. 129-137
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Wildlife capture and trade for traditional use in Papua New Guinea has led to the extirpation of cassowary in some areas and increasing pressure for trade from areas where they remain. We tested a village-based monitoring programme to evaluate sustainability of wildlife capture and trade by households in the Crater Mountain Wildlife Management Area. We monitored the type and number of wildlife species captured and traded. For the most heavily traded species, dwarf cassowary, we compared estimated annual offtake of live cassowary to maximum sustainable offtake and also compared change in hunter effort over time. We found that live offtake rates of 0.06–0.07/km2 were unsustainable in one village catchment and on the threshold of unsustainable use in another. Extirpation of cassowary will probably occur in the management area unless the location or quantity of the harvest can be restricted and the husbandry of captive birds improved. Results indicate that village monitoring of cassowary offtake is feasible when done in collaboration with outside, trained observers. Such monitoring should be encouraged as a means for landowners and management agencies to collectively evaluate the sustainability of the cassowary harvest in Papua New Guinea. This study provides an example of how scientists working with local communities in tropical forests can contribute to systematic monitoring and evaluation of wildlife offtake for sustainable use.
The effects of inbreeding on mortality during a morbillivirus outbreak in the Mediterranean striped dolphin (Stenella coeruleoalba)
- Elena Valsecchi, William Amos, Juan Antonio Raga, Michela Podestà, William Sherwin
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- 11 May 2004, pp. 139-146
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Between 1990 and 1992, Mediterranean striped dolphins (Stenella coeruleoalba) suffered high mortality due to a morbillivirus epidemic. Ten highly variable microsatellite markers were used to assess the population structure of a sample of these stranded animals and to assess the genetic consequences of the epizootic on present stocks. We found little evidence of population structure within the Mediterranean, but distinct separation between this and the North Sea (Atlantic) population, the latter also showing greater genetic diversity. Using a genetic measure of inbreeding, we found that dolphins dying early in the outbreak were significantly more inbred than those dying later. Within 10 years of the end of the epidemic, the level of inbreeding among stranded dolphins had returned to its pre-outbreak levels. However, on average all stranded animals showed elevated levels of inbreeding, suggesting that animals dying from disease may venture towards the shore more than those dying of old age. Our results imply an important role for inbreeding in the dynamics of disease spread and that, in marine mammal research, caution should be exercised when inferring demographic parameters from stranded specimens.
Detecting the vanishing populations of the highly endangered Darwin's fox, Pseudalopex fulvipes
- Carles Vilà, Jennifer A. Leonard, Agustín Iriarte, Stephen J. O'Brien, Warren E. Johnson, Robert K. Wayne
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- 11 May 2004, pp. 147-153
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Darwin's fox (Pseudalopex fulvipes) is known to survive only on Chiloé Island off the coast of southern Chile and in Nahuelbuta National Park, 600 km to the north in mainland Chile. The Valdivian coastal forest, in which the Darwin's fox lives, historically spanned from Nahuelbuta National Park southward past Chiloé Island on the mainland. Furthermore, the forest on Chiloé Island was connected to the mainland forest by a land bridge for much of the Pleistocene. Thus, the distribution of Valdivian forest suggests that the historic range of Darwin's fox may have been much larger. We searched the remnant pockets of coastal forest on mainland Chile using live traps, non-invasive techniques and interviews to look for new populations of the critically endangered Darwin's fox. Although no Darwin's fox was captured, evidence of a new population near Punta Chanchán was found.
Is anti-predator behaviour in Tasmanian eastern quolls (Dasyurus viverrinus) effective against introduced predators?
- Menna E. Jones, Georgina C. Smith, Susan M. Jones
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- 11 May 2004, pp. 155-160
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Exotic predators, particularly red foxes (Vulpes vulpes) and feral cats (Felis catus), have been implicated in the declines and extinctions of many Australian mammals and a recent incursion of foxes into Tasmania has therefore caused great concern. We tested the behavioural responses of eastern quolls (Dasyurus viverrinus) to acoustic cues of native (masked owl (Tyto novaehollandiae castanops) and Tasmanian devil (Sarcophilus laniarius)) and non-native (fox and cat) predators and to non-predators (cow (Bos taurus) and control noise). Juvenile quolls treated fox vocalisations like those of cows (as measured by an increase in movement), in contrast to their responses (a decrease in movement) to sympatric predators. Cats are probably a lesser threat to eastern quolls than native predators or foxes, their impact probably being greatest on the juveniles. Juvenile quolls, but not adults, showed similar responses to cat vocalisations as they did to owls and devils. Adult quolls responded differently from juveniles to owls and devils, by increasing vigilance. This is consistent with the smaller body size, inexperience and the presumed greater vulnerability of juveniles to predation. The lack of appropriate anti-predator responses to foxes suggests that eastern quolls would be vulnerable to predation by foxes in Tasmania.
Ecological correlates of the threat of extinction in Neotropical bird species
- G. S. Gage, M. de L. Brooke, M. R. E. Symonds, D. Wege
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- 11 May 2004, pp. 161-168
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Predicting the threat of extinction aids efficient distribution of conservation resources. This paper utilises a comparative macroecological approach to investigate the threat of extinction in Neotropical birds. Data on ecological variables for 1708 species are analysed using stepwise regression to produce minimum adequate models, first using raw species values and then using independent contrasts (to control for phylogenetic effects). The models differ, suggesting phylogeny has significant effects. The raw species analysis reveals that number of zoogeographical regions occupied, elevational range and utilisation of specialised microhabitats were negatively associated with threat, while minimum elevation and body mass were positively associated, whereas the independent contrasts analysis only identifies zoogeographical regions as important. Confining the analysis to the 582 species restricted to a single zoogeographical region reveals elevational range and number of habitats occupied to be negatively correlated with threat whether the analysis is based on the raw data or on independent contrasts. Analysis of four contrasting zoogeographical regions highlights regional variation in the models. In two Andean regions the threat of extinction declines as the elevation range across which the species occurs increases. In the presence of substantial human populations on high Andean plateaus, a species with a greater elevational range may be more likely to persist at some (relatively) unsettled altitudes. In Central South America, the strongest predictor of threat is minimum elevation of occurrence: species with a lower minimum are less threatened. The minimum elevation result suggests that lowland species experiencing an ecological limit to their minimum elevation (min. elevation >0 m) may be more at risk than those not experiencing such a limit (min. elevation = 0 m). Finally, in southern Amazonia, where there is little altitudinal variation, the only weak predictors of threat are body size, larger species being more threatened, and number of habitats, species occupying more habitats being less threatened. These contrasting results emphasise the importance of undertaking extinction risk analyses at an appropriate geographical scale. Since the models explained only a low percentage of total variance in the data, the effects of human-mediated habitat disturbance across a wide range of habitats may be important.
Bird responses to shade coffee production
- César Tejeda-Cruz, William J. Sutherland
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- 11 May 2004, pp. 169-179
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It has been documented that certain types of shade coffee plantations have both biodiversity levels similar to natural forest and high concentrations of wintering migratory bird species. These findings have triggered a campaign to promote shade coffee as a means of protecting Neotropical migratory birds. Bird censuses conducted in the El Triunfo Biosphere reserve in southern Mexico have confirmed that shade coffee plantations may have bird diversity levels similar to, or higher than, natural forest. However, coffee and forest differed in species composition. Species with a high sensitivity to disturbance were significantly more diverse and abundant in primary ecosystems. Neotropical migratory birds, granivorous and omnivorous species were more abundant in disturbed habitats. Insectivorous bird species were less abundant only in shaded monoculture. Foraging generalists and species that prefer the upper foraging stratum were more abundant in disturbed habitats, while a decline in low and middle strata foragers was found there. Findings suggests that shade coffee may be beneficial for generalist species (including several migratory species), but poor for forest specialists. Although shade coffee plantations may play an important role in maintaining local biodiversity, and as buffer areas for forest patches, promotion of shade coffee may lead to the transformation of forest into shade coffee, with the consequent loss of forest species.
Extinction risk in fragmented habitats
- David H. Reed
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- Published online by Cambridge University Press:
- 11 May 2004, pp. 181-191
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Population models incorporating demographic, environmental and genetic stochasticity were created from long-term data on natural populations of 30 species of vertebrates. The probability of extinction for a single population in a continuous habitat was compared to that of multiple isolated, or semi-isolated, populations occupying a fragmented landscape with an equivalent total carrying capacity. Populations occupying a fragmented landscape were modelled for a range of dispersal rates and levels of asynchrony in the effects of environmental disturbances. Dispersal among subpopulations in the fragmented landscape partially alleviates the effect of fragmentation on extinction rates, despite the models explicitly incorporating disease epidemics which spread between subpopulations through dispersal. Even moderate environmental correlations among subpopulations greatly reduces the viability of the metapopulation relative to the case where the populations are totally independent. Whether a population performed better as a single population or as a metapopulation was strongly affected by the carrying capacity assumed, the time frame examined and the initial fitness of the population. A single population always fared better when the total habitat available was capable of supporting ≤1000 adults. Thus, continued habitat fragmentation can be expected to fuel the ongoing global extinction crisis and conservation efforts should be aimed at interconnecting isolated habitat patches.
A second outbreak of rabies in African wild dogs (Lycaon pictus) in Madikwe Game Reserve, South Africa, demonstrating the efficacy of vaccination against natural rabies challenge
- Markus Hofmeyr, Declan Hofmeyr, Louis Nel, John Bingham
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- 11 May 2004, pp. 193-198
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An outbreak of rabies in a pack of endangered wild dogs (Lycaon pictus) in the Madikwe Game Reserve, South Africa, is described. The outbreak, which occurred in early 2000, was the second outbreak of rabies in wild dogs followed their re-introduction to the Reserve in 1995. The outbreak resulted in the death or disappearance of 10 out of 12 eight-month-old pups. Gene sequence analysis indicates that the virus is distinct from that of the previous, 1997, outbreak, although it falls within the same group as other canid isolates from northern South Africa. Since jackals (Canis mesomelas) are the principal host species of rabies in the area and domestic dogs do not occur in the Reserve, it is assumed that the jackal cycle was the source of the infection. Whereas the pups had not been vaccinated, the five adults, all of which survived, had each been vaccinated by the parenteral route at least twice and each had significant rabies serum neutralising antibodies. This indicates that multiple vaccination against rabies is effective in protecting wild dogs against challenge. Our findings extend previous observations that indicated failure of protection against rabies with single parenteral vaccinations in African wild dogs.
Non-invasive genotyping of the endangered Apennine brown bear: a case study not to let one's hair down
- Rita Lorenzini, Mario Posillico, Sandro Lovari, Annino Petrella
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- 11 May 2004, pp. 199-209
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Individual identification was assessed for 30 brown bears (Ursus arctos) from the endangered Apennine population in central Italy, mostly through non-invasive sampling. Shed hairs were used as a source of DNA to obtain single genotype profiling at 12 microsatellite loci. Average expected heterozygosity (0.438) and mean number of alleles per locus (2.2) showed that the level of genetic diversity was one of the lowest recorded for brown bear populations across their European and North American ranges. A large portion of the original genetic variation may have been lost through random genetic drift during the recent period of isolation. The level of genetic variability proved sufficient to identify the bears individually by using nine microsatellite loci. The probability that two animals shared by chance the same multilocus genotype was estimated to be 1 in 100. Despite the recent history of small population size, the average relatedness indicated that the majority of individuals are not first-order relatives. Simulated paternity tests showed that a 12-loci genotype may be necessary to assign paternity with an 80–95% confidence level. Lack of genetic diversity, as well as the maintenance of an adequately effective number, may seriously jeopardise the long-term survival of this population. Furthermore, high mortality rates, poaching and encroachment by human activities represent immediate, urgent concerns. A population increase through enforced protection and habitat restoration is recommended. Presently, restocking with bears from other source populations should be discouraged to avoid genetic extinction. Non-invasive sampling provided reliable population and individual genetic data. Microsatellite genotyping proved a valuable genetic tagging method and a feasible alternative to conventional field counts for the brown bear in central Italy.
Genetic variability and population structure among wild Baird's tapirs
- James E. Norton, Marry V. Ashley
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- Published online by Cambridge University Press:
- 11 May 2004, pp. 211-220
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Baird's tapir, Tapirus bairdii, is an endangered, large, Central American mammal whose shy behaviour, solitary social structure and preference for deep tropical forests make it difficult to study using traditional field biology techniques. Despite great concern regarding its conservation status, very little is known about its population structure, mating system or dispersal patterns, information needed for designing appropriate management plans. Molecular genetic approaches can be of use in obtaining such information. In this study, we developed six polymorphic microsatellite genetic markers from genomic libraries of T. bairdii and T. terrestris. Using these markers, we completed the first assessment of genetic variability and population genetic structure in Baird's tapirs. Populations from southern Costa Rica and southern Panama were found to have low levels of genetic variability (allelic content, heterozygosity) but no indication of a recent population bottleneck. Bayesian and standard (F-statistic) analyses of genotype data indicate that the southern Costa Rican and southern Panamanian populations of Baird's tapirs were connected by some (at least one migrant per generation) gene flow prior to the destruction of intermittent habitat. These results indicate that the connection of these two populations by a MesoAmerican Biological Corridor (MBC) would be appropriate.