Nearshore oceanic archipelagos are natural laboratories that could provide valuable insight into the role of evolutionary processes such as founder effects and incipient speciation in biotic conservation. The Alexander Archipelago of Southeast Alaska is an example of such a complex, yet few biological investigations have been conducted. For the past 50 years, the region has experienced intense anthropogenic disturbances (particularly timber harvesting), causing habitat fragmentation and potential disruption of biotic communities. As part of a series of studies of mammals endemic to Southeast Alaska, we examined mitochondrial DNA sequences from 118 flying squirrels to investigate genetic diversity across Southeast Alaska. Mitochondrial sequence divergence corroborates the subspecific designation of the endemic Prince of Wales flying squirrel (Glaucomys sabrinus griseifrons). This island lineage exhibits severely reduced genetic variation and may be the result of an early Holocene founder event. Nearly all of the animals we examined on Prince of Wales Island and ten islands to the west had identical cytochrome b (52 of 53) and control region (21 of 21) sequences. In contrast, substantial polymorphism and little genetic structuring were found in comparable populations on the mainland of Southeast and Interior Alaska. Because flying squirrels in the Pacific Northwest are associated with old-growth forest, forest-use plans should aim to conserve this unique lineage of island squirrels.

Modern concrete dams have devastated fish populations world-wide. However, dams vary greatly in how they are engineered and operated, and thus pose a range of threats to riverine fauna. Understanding the differences in the impacts of dams is critical for setting conservation priorities. We used a modified BACI (before-after-control-impact) sampling design as a means to quantify the effects of dams on spring/summer chinook salmon in two watersheds (Snake and Upper Columbia Rivers) of the Columbia River Basin, USA. The construction of four dams in the Columbia River Basin from 1966 to 1975 allowed us to test the hypothesis that the presence of these dams does not affect the abundance, survival and population growth of chinook salmon. In both the Snake and Upper Columbia Rivers, there was a significant decline from the period before dams were constructed (1959-65) to the period after dams were constructed (1980-90). In the Upper Columbia River, declines in productivity or population performance (measured as recruits per spawner or Ricker function residuals) were greater than in the control region. On the other hand, patterns of fish productivity in the Snake River were similar to those seen in the control region. The disparity between fates of Upper Columbia and Snake River populations points to the differences between regions in current efforts to reduce fish mortality associated with dams. Our analysis suggests that dams in the Upper Columbia River, but not Snake River, are a potential force preventing recovery of endangered salmon populations.

The New Zealand fairy tern (Sterna nereis davisae) is considered an endangered subspecies. The aims of this study were to quantify fairy tern responses to decoys and sound recordings and determine the viability of decoys as a technique for re-establishment of this species in protected habitat. Sixteen decoy trials were conducted in an area suitable for nesting from 9 September to 2 October 1999 at Papakanui Spit, New Zealand (36°26′S, 174°13′E). The decoy models were effective in attracting fairy terns to a specific area. There was a significant effect due to decoys with >80% of landing episodes occurring in the decoy plots. There was no effect due to individual plots. A planned contrast between decoys with and without recordings showed no significant difference. The behaviour of the fairy terns towards the decoys paralleled live tern interactions, e.g., erect postures, one aggressive response and a possible courtship feeding. Fairy terns appear to be less social than other members of the Laridae family (although their population numbers make the level of gregariousness difficult to determine). Despite low numbers, the response to the decoys was highly significant. We suggest that decoy techniques could be used as a simple and effective management tool for a wide range of group-living species. Such techniques will become particularly important as the availability of suitable habitat declines owing to anthropogenic effects. Finally, regardless of whether the attraction of fairy terns towards these decoys encourages residence and nesting in this area, the effectiveness of attracting terns to a specific location results in a safe and efficient means of trapping adults away from the nest and/or outside the breeding season.

Introduced species can compete with, prey upon or transmit disease to native forms, resulting in devastation of indigenous communities. A more subtle but equally severe effect of exotic species is as a supplemental food source for predators that allows them to increase in abundance and then overexploit native prey species. Here we show that the introduction of feral pigs (Sus scrofa) to the California Channel Islands has sustained an unnaturally large breeding population of golden eagles (Aquila chrysaetos), a native predator. The resulting increase in predation on the island fox (Urocyon littoralis) has caused the near extirpation of three subspecies of this endemic carnivore. Foxes evolved on the islands over the past 20,000 years, pigs were introduced in the 1850s and golden eagles, historically, were only transient visitors. Although these three species have been sympatric for the past 150 years, this predator-prey interaction is a recent phenomenon, occurring within the last decade. We hypothesize that this interaction ultimately stems from human-induced perturbations to the island, mainland and surrounding marine environments.

We estimated the extent of inbreeding depression for juvenile survival in 589 captive-born bighorn sheep, and, unlike an earlier report, found no evidence of significant inbreeding depression. There did not appear to be any overall effect of year of birth, place of birth, subspecies, sex or ancestral inbreeding upon the viability of inbred animals as compared to non-inbred animals. However, for the first few years of data, there was lower survival for inbred than non-inbred offspring. After this period, there was an increase in the viability of inbred offspring, probably reflecting a general improvement in husbandry conditions in the zoos. It should be emphasized that the lack of significant inbreeding depression does not necessarily imply that there may not be inbreeding depression for other traits or in a less benign or more natural environment for juvenile viability.

Allozyme electrophoresis and mitochondrial DNA sequences were used to assess genetic variation in a small macropod marsupial, the quokka (Setonix brachyurus). Setonix brachyurus is restricted to the southwest corner of Western Australia. Its habitat has been fragmented at least since the late Pleistocene by rising sea levels, creating two island populations, and more recently through anthropomorphic modification of the mainland habitat. Genetic analyses showed low levels of variation for allozymes (two polymorphic loci), although there was significant heterogeneity among populations (overall FST=0.362). Nucleotide sequence diversity was low (π=0.028) while haplotype diversity was high (H=1.0). Overall, the patterns of genetic variation reflect a shallow history, but with restricted gene flow across the species' range.

Conventional census techniques are inappropriate for estimating numbers of nocturnal animals such as the spotted hyaena (Crocuta crocuta). A technique based on attracting animals by taped sounds to calling stations is described. A simple independent experiment to estimate the probability of response to the sounds, as well as a probability model for estimating the population size in a given habitat based on the response counts, is proposed. The model allows for the possibility that some animals may not respond to sounds. The estimate of the population size has a simple form and the sensitivity of the estimate to changes in the response probability can be assessed. The model allows statistical comparisons to be made between different habitats or different times. Likelihood-based confidence intervals can be found for all estimates. The results of surveys in the Kruger National Park illustrate the technique which can be applied in different areas and possibly to other species.

In a recent analysis Woodroffe (2000) found a positive relationship between historical patterns of large carnivore extinction probability and human population density. However, much of the data in this analysis came from a period when carnivore extermination was a management objective. In order to explore the hypothesis that large carnivores can persist at high human densities when the management regime is more favourable we have repeated the analysis using up-to-date data from North America and Europe. In North America we found that large carnivore populations have increased after favourable legislation was introduced, despite further increases in human population density. In Europe we found no clear relationship between present carnivore distribution and human population density. We therefore believe that the existence of effective wildlife management structures is more important than human density per se.

Risks of population decline are studied extensively in conservation biology, but are difficult to estimate because they change abruptly over a relatively narrow range of parameters. We propose that risks of decline may be usefully summarized by the expected minimum population size. This is the smallest population size that is expected to occur within a particular time period. Analytical solutions for the expected minimum population size are obtained for a stochastic population model of exponential growth. In more complex models that are analyzed by Monte Carlo simulation, the expected minimum population size may be determined by recording the smallest population size obtained in each iteration and taking the average of these values. Whereas risks of decline change abruptly with changes in parameter values, the expected minimum population size changes more gradually. The results demonstrate that the expected minimum population size provides a better indication of the propensity for decline than the risk of extinction (or risk of decline to some other small population size), especially when the risk of extinction is small.

Over the past 16 years, 13 new species of geoemydid turtles have been described from China. Ten of these new species are based on specimens purchased through the Hong Kong animal trade. Unfortunately, attempts by scientists to discover wild populations of some these newly described species have failed, raising questions about the legitimacy of the type localities and concerns over the validity of the species. Here the phylogenetic and taxonomic validity of two of these species is tested. Mitochondrial DNA haplotypes and allozyme genotypes of specimens matching the descriptions of Mauremys iversoni and Cuora serrata are compared to specimens of established species collected from known localities. The available evidence is consistent with the hypothesis that the specimens represent polyphyletic, intergeneric hybrids. The systematic status of all the new forms of turtles described from pet trade specimens are critical data for conservation efforts, particularly captive breeding.