Decline and likely extinction of a northern Australian native rodent, the Brush-tailed Rabbit-rat Conilurus penicillatus

Contemporary fire patterns are considered the most likely cause for regional population decline amongst small to medium mammals in northern tropical Australia. Here we assess the extinction risk faced by a vulnerable north Australian native rodent, the Brush-tailed Rabbit-rat Conilurus penicillatus in relation to fire frequency. This species has recently suffered a significant contraction in range. We provide the first quantitative evidence to demonstrate the immediate threat destructive wildfires and regular annual fire pose to the long-term population persistence of C. penicillatus. We show that late-dry season fires cause a reduction in both juvenile and adult survival probabilities. However, abundance declined at the unburnt as well as a frequently burnt site, suggesting that fire exclusion alone does not guarantee the species’ long-term persistence. Our model projections indicate that the remaining populations of C. penicillatus on the Northern Territory mainland risk extirpation within the next ten years. Conservation requires decisive management action to ameliorate extensive and destructive fires. A multi-faceted management plan needs to focus on restoring a fire management regime which generates a fine-scale mosaic of burnt and unburnt habitat, and the release of captive bred animals into fenced reserves free of exotic predators.     

Large-scale noninvasive genetic monitoring of wolverines using scats reveals density dependent adult survival

Noninvasive genetic monitoring has the potential to estimate vital rates essential for conservation and management of many species. In a long-term genetic capture-mark-recapture study using scats we evaluated temporal variation in adult survival in a wolverine (Gulo gulo) population in southern Norway. In contrast to most previous studies of large mammals we found evidence for negative density dependence in adult survival in this large carnivore. Both sexes showed the same pattern of density dependence, with higher annual survival rates in adult females than males. In addition, we also found an additive mortality effect of harvesting in the population, resulting in the lowest adult survival rates at a combination of high population density and high harvest rate. The additive effects of density and harvest on adult survival of wolverines have relevance to the conservation and management of solitary carnivores with strong intrasexual territoriality, especially for species where combats among conspecifics can cause serious injury or even mortality.     

Increase of a Caribbean leatherback turtle Dermochelys coriacea nesting population linked to long-term nest protection

The leatherback turtle Dermochelys coriacea is considered to be at serious risk of global extinction, despite ongoing conservation efforts. Intensive long-term monitoring of a leatherback nesting population on Sandy Point (St. Croix, US Virgin Islands) offers a unique opportunity to quantify basic population parameters and evaluate effectiveness of nesting beach conservation practices. We report a significant increase in the number of females nesting annually from ca. 18-30 in the 1980s to 186 in 2001, with a corresponding increase in annual hatchling production from ca. 2000 to over 49,000. We then analyzed resighting data from 1991 to 2001 with an open robust-design capture-mark-recapture model to estimate annual nester survival and adult abundance for this population. The expected annual survival probability was estimated at ca. 0.893 (95% CI: 0.87-0.92) and the population was estimated to be increasing ca. 13% pa since the early 1990s. Taken together with DNA fingerprinting that identify mother-daughter relations, our findings suggest that the increase in the size of the nesting population since 1991 was probably due to an aggressive program of beach protection and egg relocation initiated more than 20 years ago. Beach protection and egg relocation provide a simple and effective conservation strategy for this Northern Caribbean nesting population as long as adult survival at sea remains relatively high.     

Long-term survival of de-oiled Cape gannets Morus capensis after the Castillo de Bellver oil spill of 1983

After oil spills, oiled wildlife are regularly cleaned at considerable cost. Yet the conservation value of this intervention has been questioned, mostly because cleaned animals appear to have poor post-release survival. However, reliable long-term data are needed to judge the success of such programs. We used 16 ring recoveries to estimate survival of 932 Cape gannets (Morus capensis) that were oiled, cleaned and released in 1983. For the period 1989-2006, we further compared survival of 162 surviving cleaned gannets to that of 10,558 non-oiled gannets using capture-recapture data. We used modern statistical tools that account for recapture probabilities, recovery rates, transience, and temporary absence from the breeding colonies. Mean annual survival rates of de-oiled gannets ranged from 0.84 (se = 0.05) to 0.88 (se = 0.02), depending on analysis and colony. Between 1989 and 2006, rehabilitated gannets survived slightly less well than unoiled birds, but the difference was similar to the difference in survival between the two colonies where the birds were studied. Our results show subtle long-term effects of oiling and subsequent treatment. However, they also show that cleaned gannets can survive at almost the same rate as unoiled birds, at least if they survived the initial years after release. Rehabilitation of these birds may thus be a valuable conservation intervention for this localised species where a single spill can threaten a large proportion of the world population.     

Reintroducing endangered Vancouver Island marmots: Survival and cause-specific mortality rates of captive-born versus wild-born individuals

Recovery of the endangered Vancouver Island marmot (Marmota vancouverensis) is contingent upon releases of captive-born marmots into natural habitats. Success of such re-introduction programs largely depends on the ability of released animals to survive in the wild. However, whether and to what extent survival and cause-specific mortality rates of captive-born marmots differ from those of their wild-born counterparts remains unknown. We used radio-telemetry (1992–2007) and mark-resighting (1987–2007) data to estimate seasonal and annual survival rates of the Vancouver Island marmot, to compare survival and cause-specific mortality rates of captive-born marmots that have been released into the natural habitat with those of wild-born marmots, and to test for the effect of age-at-release on survival of the released marmots. Analysis of radio-telemetry data suggested no difference in survival of males versus females. However, annual survival of captive-born marmots released into the wild was low (S = 0.605; 95% CI = 0.507–0.696) compared to wild-born marmots (S = 0.854; 95% CI = 0.760–0.915). Marmots released as 2-year-old or older survived more successfully than those released as yearlings. Additional forensic evidence reinforced the idea that predation was the most important cause of mortality. Causes of death differed significantly between captive-born and wild-born marmots. Predation by golden eagles (Aquila chrysaetus) was the most important cause of mortality for captive-born marmots, whereas predation by wolves (Canis lupus) and cougars (Felis concolor) was more important for wild-born marmots. Age-specific apparent annual survival rate, estimated using the combined mark-resighting and radio-telemetry data, was lowest for pups (S = 0.500; 95% CI = 0.375–0.616) and highest for yearlings and adults (S = 0.656; 95% CI = 0.604–0.705); and apparent survival of 2-year-old was similar to that of yearlings and adults (S = 0.649; 95% CI = 0.527–0.754). Our results, based on the analysis of radio-telemetry data, suggest that delaying release of captive-born marmots until 2 years of age may enhance their probability of survival in the wild, and will likely improve the success of the release program.     

Metapopulation dynamics and conservation of the marsh fritillary butterfly: Population viability analysis and management options for a critically endangered species in Western Europe

This study investigates the dynamics and viability of a marsh fritillary butterfly Euphydryas aurinia metapopulation in a Belgian successional landscape. Based on capture-mark-recapture and winter nest census data, we first estimated demography (survival and recruitment rates, population size, density dependence) and dispersal parameters (emigration rate, effect of patch connectivity on dispersal, mortality during dispersal). Then using RAMAS/GIS platform, we parameterised a population viability analysis (PVA) model with these parameters to simulate the future of this metapopulation under different scenarios.The metapopulation does not seem viable even if natural reforestation is controlled by adequate management. In its present state, the patch system is not able to sustain enough individuals: due to the large temporal fluctuations in demographic parameters, a carrying capacity far higher than currently would be necessary to limit extinction risk to 1%, suggesting the existence of an extinction debt for the species in Belgium. The situation of E. aurinia appears much worse compared to two other fritillary species threatened in Belgium, for which similar PVA are available. It is therefore urgent to increase the carrying capacity of the patch system. How and where it is achieved are of secondary importance for the gain in viability: improvement of habitat quality through restoration, or increase of habitat quantity via enlargement of existing patches and/or creation of new habitat in the matrix. A regime of management based on regular re-opening and maintenance of habitat patches may be the only guarantee of long-term persistence for this critically endangered species in Belgium.