Explore the vast range of titles available.

It is generally assumed that an individual of a prey species can benefit from an increase in the number of its group's members by reducing its own investment in vigilance. But what behaviour should group members adopt in relation to both the risk of being preyed upon and the individual investment in vigilance? Most models assume that individuals scan independently of one another. It is generally argued that it is more profitable for each group member owing to the cost that coordination of individual scans in non-overlapping bouts of vigilance would require. We studied the relationships between both individual and collective vigilance and group size in Defassa waterbuck, Kobus ellipsiprymnus defassa, in a population living under a predation risk. Our results confirmed that the proportion of time an individual spent in vigilance decreased with group size. However, the time during which at least one individual in the group scanned the environment (collective vigilance) increased. Analyses showed that individuals neither coordinated their scanning in an asynchronous way nor scanned independently of one another. On the contrary, scanning and non-scanning bouts were synchronized between group members, producing waves of collective vigilance. We claim that these waves are triggered by allelomimetic effects i.e. they are a phenomenon produced by an individual copying its neighbour's behaviour.

Urban development is thought to negatively affect most native mammals. Here we assess whether adjacent suburbia, fire regime and vegetation influence the activity of mammal species in a reserve in Hobart, Tasmania, Australia. We used multiple regression to analyse the relationship between distance from houses, fire history, vegetation structure and floristics, and mammal activity, derived from camera visits and signs. Animal diggings and visits by long-nosed potoroos, southern brown bandicoots and cats were greater close to houses, while visits by red-necked wallabies, rufous-bellied pademelons, brushtail possums and short-beaked echidnas were not. The structure of the vegetation, particularly related to shelter, was important in many models. Many models also included floristic ordination axes that reflected drainage, fire regime and distance from high-density housing. Positive relationships between the introduced predatory cat and some of its potential native prey animals may reflect the influences of close proximity to suburbia, such as elevated domestic mesopredator populations, and elevated resource availability in domestic gardens. Our results suggest that urban areas can have a valuable role in nature conservation, despite, or because of, their effects on remnant native ecosystems.

An emerging infectious facial cancer threatens Tasmanian devils with extinction. The disease is likely to occur across the range of the devil within 5 years. This urgent time frame requires management options that can be implemented immediately: the establishment of insurance populations, in captivity, wild-living on islands, and aiming for eradication in areas that can be isolated. The long-term options of the spontaneous or assisted evolution of resistance or development of a field-deliverable vaccine are unlikely to be available in time. The disease's characteristic allograft transmission through intimate contact simplifies isolation of insurance populations and breaking transmission in suppression trials. Better knowledge of contact matrices in wild devils will help focus timing and demographic targets of removals. A metapopulation approach is needed that integrates captive and wild-living island and peninsula (disease suppression) populations to minimize the loss of genetic diversity over 50 years until either extinction and reintroduction can occur, resistance evolves or a field-deliverable vaccine is developed. Given the importance of the insurance populations and the low genetic diversity of devils, a conservative target for retention of 95% genetic diversity is recommended. Encouraging preliminary results of the first disease-suppression trial on a large peninsula show fewer late stage tumors and no apparent population decline. Limiting geographic spread or suppressing the disease on a broadscale are both unlikely to be feasible. Since the synergy of devil decline and impending fox establishment could have devastating consequences for Tasmanian wildlife, it is crucial to manage the dynamics of new and old predator species together.[PUBLICATION ABSTRACT]

In several vertebrate taxa, males and females differ in the proportions of time they individually devote to vigilance, commonly attributed to sex differences in intra-specific competition or in absolute energy requirements. However, an effect of sex on collective vigilance is less often studied (and therefore rarely predicted), despite being relevant to any consideration of the adaptiveness of mixed- vs single-sex grouping. Controlling for group size, we studied the effect of sex on vigilance in the sexually dimorphic eastern grey kangaroo Macropus giganteus, analysing vigilance at two structural levels: individual vigilance and the group's collective vigilance. Knowing that group members in this species tend to synchronise their bouts of vigilance, we tested (for the first time) whether sex affects the degree of synchrony between group members. We found that females were individually more vigilant than males and that their vigilance rate was unaffected by the presence of males. Collective vigilance did not differ between female-only and mixed-sex groups of the same size. Vigilance in mixed-sex groups was neither more nor less synchronous than in single-sex groups of females, and the presence of males seemed not to affect the degree of synchrony between females. Sixty-six percent of vigilant acts were unique (performed when no other kangaroo was alert), and only about one unique vigilant act in every three induced a collective wave of vigilance. The proportions of vigilant acts that were unique were 60% for females but only 46% for males. However, the sexes differed little in the rates at which their unique vigilant acts were copied. This limited study shows that the differences in vigilance between male and female kangaroos had no discernible effect upon collective vigilance.

In group-forming prey species, theory assumes that individuals within groups should scan independently of one another, with vigilance sequences being relatively unpredictable, making interscan durations highly variable. We attempted to detect any divergence from randomness in the scanning process in three mammalian prey species phylogenetically and geographically separated and exposed to different levels of predation: waterbuck, Kobus ellipsiprymnus defassa, under a high observed predation risk, eastern grey kangaroo, Macropus giganteus, still experiencing occasional predation and European roe deer, Capreolus capreolus, under a very low natural predation risk. Our results revealed that the focal interscan duration increased when the duration of the preceding interscan increased, whatever the studied species and the predation risk that its individuals experienced, and decreased with the preceding scan duration in two species under, respectively, occasional and low predation risks. The exponential distribution was the tested model that fitted the observed distributions of interscan durations least well. We discuss what can trigger non-randomness in scanning, through a non-homogenous Poisson process, at both intra-individual and inter-individual levels, particularly with regard to previous studies that have demonstrated synchronisation of vigilance in such mammals. Our results suggest the need to reconsider any assumption of randomness in scanning in the basic model predicting form and frequency of scanning behaviour by prey species.

The relevance of vigilance activity to predator detection has been demonstrated in numerous studies. However, few studies have investigated the effect of one group member being vigilant on the probability of others being vigilant in group-forming prey species. Thus, we studied vigilance activity of eastern gray kangaroos Macropus giganteus that still experience occasional predation. We video recorded the behavior of all group members simultaneously and investigated the probability of a focal group member being vigilant (or nonvigilant) in relation to other individuals' vigilant and nonvigilant behaviors. Our results show that the decision of an individual to exhibit a vigilant posture depended on what it and other group members had been doing (scanning or foraging) at the preceding second and on group size. The probability of an individual being vigilant was positively affected by the proportion of companions that were vigilant at the previous second, confirming the existence in this species of a tendency for synchronization of individual vigilance. Group size affected individuals' vigilance in 3 ways. First, individuals were more likely to be vigilant if the proportion of their group mates that was vigilant was high, and this was strengthened with increasing group size. Second, the effect of the individual's own vigilance state (vigilant or not) at the previous second also increased with group size. Third, the probability of an individual being vigilant decreased with group size. These findings increase our understanding of the much-studied relationship between vigilance and group size. Key words: allelomimesis, group size, kangaroos, neighbor effect, probability of being vigilant, social facilitation, vigilance.

The local-resource-competition hypothesis predicts that where philopatric offspring compete for resources with their mothers, offspring sex ratios will be biased in favour of the dispersing sex. This should produce variation in sex ratios between populations in relation to differences in the availability of resources for philopatric offspring. However, previous tests of local resource competition in mammals have used indirect measures of resource availability and have focused on sex-ratio variation between species or individuals rather than between local populations. Here, we show that the availability of den sites predicts the offspring sex ratio in populations of the common brushtail possum. Female possums defend access to dens, and daughters, but not sons, occupy dens within their mother's range. However, the abundances of possums in our study areas were determined principally by food availability. Consequently, in food-rich areas with a high population density, the per-capita availability of dens was low, and the cost of having a daughter should have been high. This cost was positively correlated with male bias in the sex ratio at birth. Low per capita availability of dens was correlated with male bias in the sex ratio at birth.

We studied microhabitat use by black-faced impala in different herd types during the rut in the cold dry seasons of 2001 and 2002 in the Etosha National Park, Namibia. We investigated whether black-faced impala select feeding sites consistently for their microhabitat characteristics in 2 vegetation types, Karstveld and Tamboti Woodland. We also investigated intra-population differences in microhabitat use between herds of different types. In both habitats, sites used by impala for feeding were more likely to be in the shade, within 2 m of the edges of wooded areas and grassy clearings, with high visibility at 1 m height, and with lower grass swords than nearby nonfeeding sites. In Karstveld, feeding sites of impala were also located closer to the nearest shrub than were nonfeeding sites. A degree of fine-scale sexual segregation in microhabitat use was demonstrated, but it was not consistent across habitats. Incorporating these trends in the microhabitat use of black-faced impala into management decisions should maximize the success of small populations released at selected off-park sites.

1. An evaluation of the potentially adverse effects of measurement must be made before concluding that one is dealing with a 'dispersal sink'. 2. We conducted a spatially and temporally replicated removal experiment on common brushtail possums (Trichosurus vulpecula) in uniformly suitable old-growth eucalypt forest in south-eastern Australia, that was designed to address the question: does immigration 'rescue' populations from extinction? 3. Despite taking precautions to minimize potential harm, analyses indicated some evidence of an adverse effect of handling on the survival of pouch-young and strong evidence of effects on adult survival. In addition, symptoms of stress associated with handling observed at our site, corresponded to symptoms reported in connection with the long-term (15 + years) trapping study on possums conducted by Efford et al. in the Orongorongo Valley (OV) of New Zealand. 4. Initial projections from a demographic model indicated that the resident population at our site was not replacing itself (births < deaths), suggesting that the site was a dispersal sink. This was inconsistent with the fact that the site was in prime habitat. Moreover, the measured rate of true immigration in response to experimental removals was not sufficient to maintain the population density. Using data from Efford (1998), our model confirmed his suggestion that the OV site also appears to be a dispersal sink for possums, despite being in prime habitat. 5. When otherwise undiagnosable deaths among adults were assumed to be due to handling and 'right-censored' (excluded), the projection was that the resident population at our site was stable (r ≅ 0), and therefore not in need of 'rescue' by immigration. Similarly, when survival estimates for the OV site were corrected by the same amounts, the projection was that the population at that site was also stable. 6. Most vacancies created by our experimental removals were filled by neighbouring residents that expanded their ranges into the removal areas. We suggest that the artificial 'removal' of residents as a consequence of deaths due to handling, may often induce an influx of such apparent immigrants, thereby giving the impression that immigration is 'rescuing' populations from extinction.

Raising endangered species in captivity for reintroduction necessarily results in animals that lack appropriate skills for coping with problems to be faced in the wild, such as predators. Using classical conditioning techniques involving linking fear of a live dog with the image of a fox, we demonstrate an adjusted fear response for two wallaby species (rufous bettongs Aepyprymnus rufescens, quokkas Setonix brachyurus). No differences in response to the fox were found for wild-caught and captive-born bettongs, even though wild-caught subjects were likely to have encountered canids prior to capture. Attempts to condition a fear response by quokkas to an odour were unsuccessful. An attempt to induce fear of the stuffed fox by linking to fear of humans in quokkas was unsuccessful, but quokkas generalised from fear of the dog to fear of the fox, despite a delay of several weeks. Trained dogs offer a valuable and ethically acceptable mechanism for improving the ability of captive-reared (or sequestered) animals to recognise and cope with predators.