Species with ecological (habitat, dietary) specialization and low reproductive output may be at particular risk from anthropogenic habitat disturbance. We studied growth, reproduction and diet of the threatened broad-headed snake (Hoplocephalus bungaroides), a small nocturnal elapid from sandstone habitats in south-eastern Australia. Our data suggest that the life-history traits and diets of broad-headed snakes contribute to their vulnerability. Rather than searching actively for prey (like most sympatric elapids), broad-headed snakes wait under rocks to ambush prey. In consequence, these snakes feed infrequently, grow slowly, mature late and reproduce infrequently (compared with other sympatric snake species). Because of an ontogenetic shift in food habits, populations of broad-headed snakes require access to high densities of velvet geckos (in rock outcrops) as well as small mammals (in adjacent woodland). The specialized diet, reliance upon two distinctive habitats, low rate of growth, delayed maturation and low reproductive output may have exacerbated the vulnerability of broad-headed snakes to habitat destruction. All of these traits may be due to the species' reliance upon ambush predation rather than active foraging. A broader analysis supports the hypothesis that foraging mode may contribute to endangerment: a disproportionate number of ‘threatened’ species of Australian elapid snakes rely on ambush predation.

The Florida panther, Puma concolor coryi, is a subspecies on the verge of extinction. Recent field studies have shown the dwindling population to be suffering from numerous physical problems manifest in their soft tissues. Here we explore the skulls and skeletons of more than 50 P. concolor coryi for corroborative evidence of poor condition such as tooth fracture, arthritis, infection, trauma, and lines of arrested growth (Harris lines). Results are compared with those for an osteological collection of presumed healthy pumas from outside Florida. Although the two samples did not differ significantly in the relative prevalence of most of the pathologies, the Florida cats fractured their teeth more often and exhibited significantly more lines of arrested growth in their long bones. The greater number of teeth broken in life is associated with heavier tooth wear among Florida panthers and a diet depauperate in large prey. The elevated incidence of Harris lines is probably a result of more regular episodes of poor nutrition in the Florida population. Our results demonstrate that the study of osteopathologies is a new tool for the conservation biologist and highlight the value of preserving entire skeletons, as has been done for P. concolor coryi.

Mammalian record collection densities and bias attributable to observer survey preferences are assessed for the former Transvaal region of South Africa using a geographic information system (GIS). A method is presented which may be used to distinguish between highly biased and relatively unbiased sampling densities. Small mammal survey records within the region appear to have been collected relatively independently of the road and urban area infrastructure and are not biased towards nature reserves. Large mammal data on the other hand has mostly been collected within existing conservation areas. Although this latter data set would appear to be highly biased, it does accurately reflect the current distributions of larger mammalian taxa, which are presently almost entirely restricted to conservation areas.

With increasing awareness of disease as an endangering process, an assessment of which pathogens might pose a problem and their patterns of infection in natural hosts is necessary. This paper examines the exposure of sympatric Ethiopian wolves (Canis simensis) and domestic dogs to canine distemper virus (CDV), canine adenovirus (CAV) and canine parvovirus (CPV) in the Bale region, Ethiopia and then relates these data to population trends of wolves. Wolves (n = 30) sampled between 1989 and 1992 had been exposed to CDV, CAV and CPV, but only CAV might be able to persist in this wolf population. Anecdotal and serological evidence suggested that an epidemic of CDV occurred in the dog population of the Bale Mountains National Park (BMNP) in 1992–93. All park dogs born since this time were seronegative to CDV, although some young dogs in the nearby urban population were seropositive. Despite evidence of CAV infection in wolves, none of the dogs sampled in the park were CAV seropositive, although this virus appeared highly seroprevalent and endemic in urban dogs. All dogs tested for CPV antibodies were seropositive. The BMNP wolf population declined in the late 1980s and early 1990s, with rabies responsible for a dramatic population reduction between 1990 and 1992. Although the population declined further up until 1995, it is not possible to assess whether the concurrent canine distemper epidemic in park dogs also affected wolves. Nevertheless, with evidence of rabies, CDV, CAV and CPV infections in sympatric domestic dogs and Ethiopian wolves, canid diseases clearly pose a significant threat to the future persistence of this Ethiopian wolf population.

The abundance of foraging bats (Pipistrellus pipistrellus and Myotis daubentonii) and flying insects over two rivers in north-east Scotland (Dee and Ythan), differing eightfold in nitrate levels, were compared by paired samples over three periods in summer 1995, during each of which 10 nights' sampling was undertaken using ultrasonic detectors and insect suction traps. Thirteen out of the 18 pairwise comparisons of bat passes, insect numbers, biomass and diversity were not significantly different. The oligotrophic Dee supported higher numbers of bats than the eutrophic Ythan in June, but this was attributed to an effect of adverse weather conditions affecting the Ythan. In July and August–September, neither bat abundances nor the abundance of Chironomidae and Trichoptera, the main food of the bats, differed significantly between the two rivers, although the Ythan showed higher total insect biomass than the Dee. The Ythan also showed a much higher abundance of small Diptera, mainly Psychodidae and Cecidomyiidae, associated with elevated nitrogen levels in the intensively farmed river valley. Thus a small eutrophic river can support as many bats and as high an insect density as a large oligotrophic one.

A common ‘rule of thumb' in conservation biology is that populations of more than 100 individuals are not threatened by demographic stochasticity alone. However, the effect of demographic stochasticity on population survival may be strengthened if the population has a non-homogeneous demography. A recently developed measure, the demographic effective population size ND, scales population size by taking the differential contribution of individuals into account. We exemplify the estimation of ND with the current population of the Saimaa ringed seal, comprising about 200 individuals. The estimate of ND is shown to be dependent on how independently individuals can be assumed to reproduce. Completely independent reproduction leads to ND ≈ 250, suggesting a safe future for the population. However, when acknowledging the potential of breeding failure due to habitat limitation and difficulties of dispersal among the different subareas of Lake Saimaa, ND lies in an alarming range from six to 30 individuals. The effective means to increase the ND value are limited. Although subdivision itself decreases the value of ND, improving dispersal of individuals is shown to be of limited aid. Instead, the most effective way to enhance future prospects of the Saimaa seal population is to improve pup survival to maturity.

Ivory poaching has been a serious problem in Asian elephant (Elephas maximus) populations. Reliable records of elephants killed and ivory harvested are generally unavailable. We have used a simulation modelling approach to estimate the numbers of male elephants killed and the quantities of ivory harvested over a 20 year period (1974–94) in the Periyar Reserve of southern India. The age-structured Leslie matrix projection model was modified for this purpose by considering three segments (female, tusked male and tuskless male), relating fecundity to adult sex ratio and iteratively simulating tusked male mortality rates so as to match the observed elephant population structure at Periyar. Four different scenarios of poaching all gave very similar results. We estimate conservatively that 336–388 tuskers have been poached and 3256–3334 kg of ivory harvested by poachers over the 20 year period. The maximum harvest came from the 10–20 year age class. Trends in various demographic parameters such as population numbers, tusked male to tuskless male ratios and female fecundity are described. The implications of ivory poaching and the extremely skewed sex ratios for the conservation and management of the elephant population at Periyar are discussed.

One hundred and sixty-one river sites throughout the Thames catchment area were surveyed during the summer of 1995 and a number of habitat features were recorded in order to identify relevant habitat variables for the water vole (Arvicola terrestris; Arvicolidae). In addition, the role of the American mink (Mustela vision; Mustelidae) in determining the present distribution of water voles in the Thames region was investigated. The data were analysed by using generalized linear models (GLM).

Water voles were found in places characterised by low banks, unmodified channels, vegetated bars, submerged vegetation and were tolerant of moderate levels of bank reinforcement. The presence of mink was the most important variable. The results suggest that the American mink is the main factor determining the current distribution of water voles in this area. Restoration and recreation of habitat for water voles are likely to be a powerful tool in the recovery of water vole populations. It is hypothesised that mink control will be necessary only while the water vole population is small; once the population starts to increase both species could co-exist provided that the habitat is suitable.

Previous studies have revealed considerable genetic variation, geographic localization, and genealogical depth for mitochondrial DNA (mtDNA) haplotypes within each of several species of freshwater turtles in the south-eastern United States of America. Here we report a notable exception to such phylogeographic patterns. In control-region sequences of 66 snapping turtles (Chelydra serpentina) collected from 10 south-eastern states, a single mtDNA haplotype predominated and the two rare variants detected were nearly identical to the common genotype. This pattern of low mtDNA variation and a lack of appreciable geographic population structure is extremely unusual for a widely distributed animal species. For purposes of taxonomy and conservation, these findings suggest the presence of only one ‘evolutionarily significant unit' for C. serpentina in this otherwise phylogeographically rich region of the country. Possible explanations for this phylogeographic pattern in the snapping turtle are considered.

Sequences from complete mitochondrial cytochrome b genes of 34 tigers support the hypothesis that Sumatran tigers are diagnostically distinct from mainland populations. None of the latter, including Bengals, Siberians, or Indochinese tigers, were found to have fixed diagnostic characters. Phylogenetic analysis of these sequences confirms these results. Within the framework of a phylogenetic species concept, current evidence thus supports the recognition of two distinct taxa, and within the context of this definition they could be ranked at the species level. This paper also documents a previously unrecognized nuclear insert of mitochondrial DNA that includes, minimally, mitochondrial homologues of a control region that lacks the feline mitochondrial repeat sequences, a complete cytochrome b gene, and complete tRNAThr and tRNAsurPro genes. In a phylogenetic analysis of the nuclear cytochrome b-like sequences and various feline mitochondrial sequences, the nuclear insert clusters with lion mitochondrial cytochrome b sequences, which suggests the insert is at least as old as the split between lions and tigers. The results of this study emphasize the importance of doing more to conserve Sumatran tigers. Because they are underrepresented in zoos relative to Bengals and Siberians, an effort should be made to increase captive breeding stocks of Sumatrans. That Sumatrans are a distinct taxonomic entity relative to mainland populations can be used in educational programs to increase conservation efforts within Indonesia.

The detection of reductions in effective population size (Ne) or census size (Nc) is essential for conservation. Recent developments allow wildlife researchers to obtain genetic material via non-invasive sampling techniques that may provide the large sample sizes necessary for precise estimates of Ne and Nc. Population genetic theory provides several methods to estimate Ne from allele frequency data: including temporal change in allele frequencies, gametic disequilibrium and heterozygote excess methods. Modification of capture–mark–recapture methods for use with multi-locus genotype data provides new means for estimating Nc. The combination of new DNA sampling techniques, polymerase chain reaction-based DNA markers and analytical methods may provide unprecedented power to detect reductions in Ne and Nc of endangered populations. However, these genetic methods are largely untested in the field. We review some relatively unexplored, but promising ways that multi-locus genetic data can be used to provide important genetic and demographic information and suggest avenues for further research in this area.

Between 1959 and 1968 the entire world population of Seychelles warblers (Acrocephalus sechellensis) comprised only 26–29 individuals entirely confined to Cousin Island (26 ha). Through conservation actions the island population has reached a carrying capacity of ca 320 birds since 1982. The warbler population has significantly lower levels of genetic variation, as determined by multilocus DNA fingerprinting, compared with its mainland relative, the Australian warbler (Acrocephalus australis) and other outbred natural bird populations (mean band sharing coefficients are 0.50, 0.22 and 0.21, respectively), and has a very low annual reproductive rate of 0.28 yearlings per breeding pair. Therefore some degree of inbreeding may have occurred in this population.

The relatively low level of genetic variation is not directly responsible for this low reproductive output since breeding pairs that were transferred to the islands of Aride (68 ha) and Cousine (29 ha) with similar vegetation and climate, but with higher year-round insect food abundance, had significantly higher fecundity and survival. In contrast, no difference in reproductive success was observed between incestuous breeding pairs and non-incestuous breeding pairs.

In addition, annual production of yearlings by pairs on Aride was on average 44 times higher than that by the same pairs on Cousin before the transfer. Annual production of yearlings by pairs on Cousine, that were as inbred as those on Aride, was on average five times higher than that by the same pairs on Cousin before the transfer. Eight years after translocation, the Aride population had grown to over 1000 birds, and six years after translocation, the Cousine population had grown to 186 birds.

The experiments, controlled for group size, breeding partner, breeder age and experience, showed that the differences in reproductive success by warblers on the three islands cannot be due to genetic differences because of similar band-sharing similarities, but seem entirely accounted for by differences in food supply. Although the amount of genetic variation in the Seychelles warblers is relatively low, the demographic parameters do not indicate apparent signs of inbreeding depression in these populations.

A small blackish muntjac has been discovered in the west Quang Nam province of Vietnam. DNA sequencing of six individuals showed that this is a distinct species. A description is given. The new find is the third new ungulate species to be discovered in Vietnam in five years. The paper predicts that more species remain to be found in the Annamite mountain range and includes DNA analysis from two more undescribed species. The DNA analysis indicates that there has been a radiation of several related muntjac species in the Annamite mountains, also that the new truongson muntjac shows high intraspecific genetic diversity indicative of a large effective population size. The paper discusses the significance of these finds from an evolutionary and conservation viewpoint. The authors urge conservation authorities in the IndoChinese countries to devote special measures to protect this site of dynamic evolution which retains a combination of relict endemics (e.g. Pseudoryx) as well as on-going speciation.

White Sands pupfish (Cyprinodon tularosa) are endemic to southern New Mexico and occur in only four localities: Malpais Spring, Salt Creek, Mound Spring and Lost River. Recently reported historical accounts indicate that the latter two populations were derived from translocations. Their limited distribution and complicated history suggest that knowledge of population genetic structure would be useful for the development of a sound conservation strategy. Mitochondrial DNA (mtDNA) sequences for a segment of the control region showed little variation. Variation was observed for microsatellite and allozyme loci with 37% attributable to divergence among populations. The mean genetic distance between Malpais Spring and the other three populations was high (allozymes: Darc = 0.541; microsatellites: Rst = 0.684) compared with the mean distance among the other three populations (Darc= 0.161, Rst = −0.016). There were fixed or nearly fixed differences in allele frequency between the Malpais Spring population and the other three populations at one allozyme locus (hexokinase) and two microsatellite loci (WSP-02 and WSP-11). We suggest the recognition of two evolutionarily significant units (ESUs) for the White Sands pupfish: Malpais Spring and Salt Creek. Our data indicate that the Lost River and Mound Spring populations descended from translocations from the Salt Creek population. Therefore, conservation efforts should focus on the Malpais Spring population.

Maintaining genetic variation for future evolutionary change is an important issue for conservation biology. However, there is controversy over the effective population size (Ne) required for endangered species to retain their evolutionary potential, with proposed sizes ranging from 500 to 5000. The highest estimate is based on the assumption that 90% of mutations are deleterious. We review the arguments for an effective size of 5000 and conclude that it assumes effective mutation rates that are too low, and heritabilities that are, in general, very high. We conclude that an Ne of 500–1000 is appropriate at this time.

For practical reasons, managers and policy-makers have to make rapid decisions with limited information on the status of endangered species. Because of its relative ease of acquisition, the most common surrogate used to derive inferences about the risk of extinction is population size. This is not to say that population size is the best indicator of risk; other considerations, such as the recent rate of population decline, are of clear importance (Mace & Lande, 1991). A popular rule of thumb for the critical population size necessary for the maintenance of adequate genetic variance for adaptive evolution in quantitative traits, originally espoused by Franklin (1980) and Soulé (1980), has been an effective population size (Ne) of 500 individuals. More recent assessments, based on both empirical and theoretical developments, suggest that this number should be revised upwards to Ne≃1000–5000 (Lande, 1995a; Lynch, 1995; National Research Council, 1995; Bürger & Lynch, 1997). Here we address the arguments of Franklin & Frankham (1998) that a critical Ne≃500–1000 is adequate for conservation purposes.

Lynch & Lande's (1998) comments on our paper (Franklin & Frankham, 1998) misrepresent our purpose, deal largely with a different issue and do not refute our original criticism. Our paper is a commentary on Lande's (1995) suggestion that an effective size of 5000 is required to maintain evolutionary potential, not whether this size ‘is adequate for conservation purposes'.