Many species modify their behaviour in response to the scents of their predators, but species or populations living without predators may lose such abilities. This loss has been suggested to be irreversible, and to constitute a significant hurdle in restoring historical ecosystems. Olfactory predator recognition was studied in two macropodid marsupials - the tammar wallaby (Macropus eugenii) and the red-necked pademelon (Thylogale thetis). Both species are in the ‘critical weight range’ of Australian native mammals that have been negatively affected by the introduction of novel predators since European settlement. Predator-naïve animals were tested by exposing subjects simultaneously to two feeders with either a predator or a herbivore faecal or urine sample beneath the food tray. The presence of predator olfactory cues beneath the feeder did not affect foraging behaviour or feeder use when compared to control stimuli (herbivore faeces or urine). Previous studies have found that predator-experienced herbivorous marsupials modify their behaviour in the presence of predator scents. In contrast, our studies of predator-naïve individuals found no evidence of such selectivity, suggesting that marsupial herbivores may have to learn to modify their behaviour in response to olfactory cues from predators. This implies that the loss of olfactory predator recognition may not be irreversible. Animals translocated from predator-free areas could potentially be trained to recognise the smells of their predators.

The extant genetic variation of a population is the legacy of both long-term and recent population dynamics. Most practical methods for estimating effective population size are only able to detect recent effects on genetic variation and do not account for long-term fluctuations in species abundance. The utility of a maximum likelihood estimator of long-term effective population size based upon the coalescent theory of gene genealogies is examined for three endangered Colorado River fishes: humpback chub (Gila cypha), bonytail chub (Gila elegans) and razorback sucker (Xyrauchen texanus). Extant mitochondrial DNA (mtDNA) variation in humpback chub suggests this species has retained its historical equilibrium genetic variation despite recent declines in abundance. The mtDNA variation in razorback suckers indicates the population was quite large and expanding prior to recent declines and that rare alleles still survive in the remnant populations. The remaining mtDNA variation in bonytail chub indicates that dramatic, recent declines may have already obliterated a substantial portion of any historical variation. The results from long-term effective population size analyses are consistent with known natural history and illustrate the utility of the analysis for endangered species management.

Vocal individuality is widely suggested as a method for identifying individuals within a population. But few studies have explored its performance in real or simulated conservation situations. Here we simulated the use of vocal individuality to monitor the calling corncrake (Crex crex), a secretive and endangered land rail. Our data set contained 600 calls from 30 individuals and was used to simulate a population of corncrakes being counted and monitored. We tested three different neural network models for their ability to discriminate between and to identify individuals. Neural networks are non-linear classification tools widely applied to both biological and non-biological identification tasks. Backpropagation and probabilistic neural networks were used to simulate the reidentification of members of a known population (monitoring) and a Kohonen network was used to simulate the counting of a population of unknown size (census). We found that both backpropagation and probabilistic networks identified all individuals correctly all the time, irrespective of sample size. Kohonen networks were more variable in performance but estimated population size to within one individual of the actual size. Our results indicate that neural networks can be used effectively together with recordings of vocalizations in census and monitoring tasks.

In the UK, hen harriers (Circus cyaneus) are illegally killed on moorland that is managed for red grouse (Lagopus lagopus scoticus), and they produce fewer young per female on grouse moorland than on either unmanaged moorland or forestry. However, those breeding attempts on grouse moorland that escape nest destruction produce more young than in other land-use classes. One explanation for this difference is that food is more available to harriers on managed moorland than elsewhere. To examine this hypothesis, we compared the capture rates of hunting male harriers on sites across Scotland. Four of these sites were managed for grouse whilst the remaining three consisted of either unmanaged moorland or a mixture of unmanaged moorland and young forestry plantations. We found a significant difference in capture rates, with harriers on managed grouse moorland capturing prey at a greater rate than elsewhere, supporting the idea that prey were more available on grouse moorland. However, there was no difference in strike rates between the land-use classes, suggesting that prey were not necessarily more abundant on grouse moors. Males on unmanaged moorland tended to catch larger prey, though this was insufficient to compensate fully for the reduced capture rates. The improved hunting success on grouse moorland means that this habitat is likely to be more attractive to breeding harriers, thereby increasing the conflict between those interested in maximizing grouse numbers and those interested in conserving rare raptors.

The search for easy-to-use indices that substitute for direct estimation of animal density is a common theme in wildlife and conservation science, but one fraught with well-known perils (Nichols & Conroy, 1996; Yoccoz, Nichols & Boulinier, 2001; Pollock et al., 2002). To establish the utility of an index as a substitute for an estimate of density, one must: (1) demonstrate a functional relationship between the index and density that is invariant over the desired scope of inference; (2) calibrate the functional relationship by obtaining independent measures of the index and the animal density; (3) evaluate the precision of the calibration (Diefenbach et al., 1994). Carbone et al. (2001) argue that the number of camera-days per photograph is a useful index of density for large, cryptic, forest-dwelling animals, and proceed to calibrate this index for tigers (Panthera tigris). We agree that a properly calibrated index may be useful for rapid assessments in conservation planning. However, Carbone et al. (2001), who desire to use their index as a substitute for density, do not adequately address the three elements noted above. Thus, we are concerned that others may view their methods as justification for not attempting directly to estimate animal densities, without due regard for the shortcomings of their approach.

Most species-specific conservation efforts require estimates of population size to establish priorities and to monitor management activities. Yet obtaining reliable estimates of animal populations is often difficult, especially given time and funding limitations experienced by many research programmes. Consequently, there is a great need for practical methods to provide indices of animal density. Ideally, accurate estimates of populations would be obtained through mark-recapture data collected from recognizable individuals over multiple censuses that cover the entire population range. Such data are rarely available, so conservation biologists have no alternative but to resort to analyses of less perfect data, ranging from permanent-point censuses from cameras through to transect data on sightings and spoor encounters. The importance of census and monitoring data makes the development, and validation, of new techniques a priority. Because we do not live in a perfect world, there is a need to develop methods that can give an estimate of population sizes. It would be naïve to assume that these will give hugely accurate estimates of population size, but these techniques can prove useful in identifying areas that are likely to benefit from conservation action.

Maximum likelihood mixed stock analysis was used to identify the natal origin of immature loggerhead turtles (Caretta caretta) in a tropical developmental habitat in Caribbean Panamá. Approximately 65-70% of the loggerhead turtles in Chiriquí Lagoon originate from South Florida nesting beaches, and the other 30-35% originate from Mexico. Haplotype frequencies of the Chiriquí Lagoon loggerhead population are significantly different from those observed in the pelagic environment in the eastern Atlantic, and estimated nesting beach contributions to Chiriquí Lagoon are significantly different from values expected if recruitment were based solely on the size of nesting populations. These observations suggest that dispersal of loggerheads into benthic developmental habitats from the pelagic environment is not random. The occurrence of US and Mexican loggerheads in tropical developmental habitats has not been previously recognized. Exploitation and other mortality factors operating in the Caribbean area must be taken into account in demographic models and management plans for these two populations. This exploitation could be particularly important for the small, demographically vulnerable Mexican population and for other small populations for which no genetic data are currently available.

Recent studies have suggested that contemporary losses of species are unevenly distributed over phylogenies. Here, we show that species of Australian marsupials are at higher risk if they belong to genera that are species-poor, old or phylogenetically distinct. Extinction risk in this group is also related to habitat and body size, being higher for species from non-forested habitats and of intermediate body size. We tested the extent to which the phylogenetic selectivity of extinction was explained by this ecological pattern. We found that while genus size and distinctiveness explain no variation in extinction risk that is not accounted for by habitat and body size, there is a significant residual association of genus age with extinction risk. This suggests that while species in small and distinctive genera are at high risk because they are overrepresented in non-forested habitats and intermediate body size classes, species in old genera are at higher risk over the range of body sizes and habitats and may be intrinsically vulnerable to extinction.

Products from the protected East Sea/Sea of Japan (‘J’ stock) minke whales (Balaenoptera acuturostrata) are sold widely on the commercial markets of Japan and Korea despite the protection of this stock since 1986. To determine the minimum number of individual whales for sale, genotypes from six microsatellite loci were used to profile North Pacific (NP) minke whale products purchased on these markets between December 1997 and October 1999. Genotype differences showed that 99 NP minke whale products from the Japanese market represented 86 unique individuals. Of these, 33.7% were of likely J-stock origin based on mitochondrial (mt) DNA haplotypes. In Korea, genotyping showed that 23 NP minke products from March 1999 represented 18 individuals, and 19 products from October 1999 represented 16 individuals. No matches were found between the two sampling periods, giving a total of 34 unique individuals. A frequency-of-capture model suggests that 98 minke whales were present on the Korean market over the two brief sampling periods. No genotype matches were confirmed between the two countries, indicating that undocumented exploitation of this depleted stock must be additive, and greater than previously assumed.

We develop a stochastic model of population viability which explicitly links demography and genetics in order to examine the consequences for extinction dynamics of different levels of heritable fitness variance within a population. We particularly focus on situations in which a local small population is artificially built with individuals that were taken from several large source populations. Our results suggest that different levels of fitness variability within a population (due to partially recessive deleterious alleles rather than local adaptation) have a large influence on its viability. Moreover, the optimal level of fitness variance for maximizing population persistence is a function of the species life-cycle. Two mechanisms with opposite effects are mainly responsible for the different patterns of extinction obtained depending on the life-cycle, (1) purging of deleterious alleles, (2) demographic stochasticity. For high growth rate or long-lived species, a high fitness variance decreases short-term viability and increases long-term viability. In contrast, for other cases, a high fitness variance increases both short- and long-term viability.

Identification of reliable surrogate indicator taxa and effective shortcuts for the preservation of overall biodiversity is a major challenge. Encouragingly, complementarity-derived priority sets of focal taxa were found highly effective in representing non-target taxa in a study from Ugandan forests. It has been proposed cross-taxon congruence in complementarity is less distinct in temperate regions than in the tropics, because temperate regions have fewer species, and hence focal taxa may be less effective as they are less diverse. To test this, we used all available atlas data (10 × 10 km scale) in Denmark (butterflies, birds, amphibians, reptiles, large moths, bats and click beetles, n = 434 species), and looked at whether conservation priority areas based on one taxonomic group represent species richness of other groups in a highly fragmented landscape. We apply a new approach (based on G-statistics) that enables statistical evaluation of cross-taxon congruence in complementarity-derived priority sets. We found indications that the same taxa represented other groups effectively and exhibited cross-taxon congruence in complementarity-derived priority sets. Birds performed significantly, but relatively poorly, butterflies somewhat better and bats relatively well in representing species richness of other groups. Large moths performed best and may be an overlooked predictor of diversity in other animal taxa.