Hunting for answers: rabbit (Oryctolagus cuniculus) population trends in northeastern Spain

Effect of Myxoma Virus Species Jump on Iberian Hare Populations

The myxoma virus species jump from European rabbits (Oryctolagus cuniculus) to Iberian hares (Lepus granatensis) has raised concerns. We assess the decline suffered by Iberian hare populations on the Iberian Peninsula and discuss the association between the effect of myxomatosis and the average abundance index, which we estimated by using hunting bags.

Models of spatiotemporal variation in rabbit abundance reveal management hot spots for an invasive species

The European rabbit (Oryctolagus cuniculus) is a notorious economic and environmental pest species in its invasive range. To better understand the population and range dynamics of this species, 41 yr of abundance data have been collected from 116 unique sites across a broad range of climatic and environmental conditions in Australia. We analyzed this time series of abundance data to determine whether interannual variation in climatic conditions can be used to map historic, contemporary, and potential future fluctuations in rabbit abundance from regional to continental scales. We constructed a hierarchical Bayesian regression model of relative abundance that corrected for observation error and seasonal biases. The corrected abundances were regressed against environmental and disease variables in order to project high spatiotemporal resolution, continent-wide rabbit abundances. We show that rabbit abundance in Australia is highly variable in space and time, being driven primarily by internnual variation in temperature and precipitation in concert with the prevalence of a non-pathogenic virus. Moreover, we show that internnual variation in local spatial abundances can be mapped effectively at a continental scale using highly resolved spatiotemporal predictors, allowing "hot spots" of persistently high rabbit abundance to be identified. Importantly, cross-validated model performance was fair to excellent within and across distinct climate zones. Long-term monitoring data for invasive species can be used to map fine-scale spatiotemporal fluctuations in abundance patterns when accurately accounting for inherent sampling biases. Our analysis provides ecologists and pest managers with a clearer understanding of the determinants of rabbit abundance in Australia, offering an important new approach for predicting spatial abundance patterns of invasive species at the near-term temporal scales that are directly relevant to resource management.

Harvest of Red-Legged Partridge in Central Spain

A basic rule to attain sustainable use of harvested resources is to adjust take to availability. Populations of red-legged partridges in Spain have decreased in recent decades, and releases of farm-bred partridges to improve short-term availability are increasingly common. We used questionnaires and bird surveys to assess whether harvest was related to availability of wild partridges or intensity of farm-bred partridge releases. We studied 50 hunting estates, including 6 administratively labeled as intensive (with few numerical and temporal restrictions to releases). In addition, we considered hunting pressure (number of hunters × hunting days/km²) and habitat as explanatory variables in the analyses. In intensive estates, annual harvest was exclusively related to release intensity, indicating that in these estates hunting is detached from natural resources and approaches an industrial activity based on external inputs. In non-intensive estates, harvest was affected by wild stock availability, walked-up shooting pressure, and habitat (greater harvest in estates with more Mediterranean shrubland). In these estates, releases did not increase annual harvest, and can be considered an inefficient practice. Additionally, the relationship between abundance estimates and harvest disappeared in estates with low partridge abundance estimates, suggesting possibilities for overharvesting in a large proportion of estates. Increasing the abundance of wild red-legged partridge through techniques like habitat management, and improving the adjustment of harvest to availability, may be a good strategy to increase long-term harvest in non-intensive estates. Additionally, Government and managers must create ways to segregate and label the estates where only wild red-legged partridges are managed from those where releases are used, to reduce ecological costs of management decisions. © 2012 The Wildlife Society.

The role of ponds as feeding habitat for an umbrella species: best management practices for the black stork Ciconia nigra in Spain

To establish recommendations for wetland management that promote wildlife diversity in Mediterranean habitats we examined the factors that determine feeding habitat selection by the black stork Ciconia nigra in ponds. The black stork is considered an umbrella species because it is threatened, requires large foraging ranges in priority areas, is selective in its choice of diet and nesting sites, and inhabits a characteristic biological community with endemic and threatened taxa. Eighty-five ponds were monitored in central and western Spain to detect the stork feeding. At the same time, pond variables that could affect black stork feeding preferences were periodically evaluated. Generalized linear mixed models were used to analyse principal components obtained from groups of factors related to structural, location and ecological conditions. The black stork selects ponds distant from roads, with a large surface area, high water level, shallow shores, low turbidity, few traces of wild ungulates on the shores, a high diversity of fish and amphibian species, and a vegetated perimeter, in flat and open areas. Potential factors affecting feeding behaviour are discussed. We suggest measures for pond construction and management that could favour this species in particular and biodiversity in general in the Mediterranean environment.

The usefulness of field data and hunting statistics in the assessment of wild rabbit (Oryctolagus cuniculus) conservation status in Portugal

Context. The wild rabbit (Oryctolagus cuniculus) is a keystone species from the Iberian Peninsula that has suffered a strong decline in Spain during the past decades. Data on historical and current population trends in Portugal are virtually non-existent. Aims. To investigate changes in rabbit abundance at the national level so as to inform conservation status assessments, and to evaluate the usefulness of hunting bags as a rabbit abundance index. Methods. Field surveys based on latrine counts in linear transects were performed in two periods (1995 and 2002) to assess variation in population abundance. Hunting bags were also analysed for the same period to verify whether these data showed the same trends. General trends of rabbit abundance were estimated using TRIM software. Key results. Field data revealed that most of the sampling units across Portugal have low abundances, despite the observation of local high-density spots. A population reduction of 27% was estimated. Although some fluctuations were observed in hunting bags, global results obtained from these data suggest a slightly increasing trend in rabbit abundance. Conclusions. A discrepancy between field data and hunting statistics was observed. Because hunting bags may be influenced by sporadic management operations undertaken by hunters and the lack of systematic procedures in data collection, we believe that hunting statistics are not representative of real changes in rabbit populations. Thus, observed reduction in rabbit abundance estimated by field data, combined with the high initial morbidity due to rabbit haemorrhagic disease (RHD) after 1988 and the potential for continuing decline in population trends because of other factors, led to an inference of a reduction of >30% in rabbit abundance in Portugal during the past decade. Implications. Taking into account the estimated reduction, the species’ biology and socioeconomic implications, wild rabbit in Portugal was listed in 2005 in the Near Threatened category under IUCN criteria. Because of its ecological and economic importance, this classification prompted the definition of several conservation actions aimed at the recovery of the species in Portugal.

Disease-related conflicts in mammal conservation

Diseases pose a major direct or indirect threat to the conservation of endangered species, and can be a source of conflict among the stakeholders in conservation efforts. We aim to provide examples of disease-related conflicts in conservation, and information that can be used to identify means to reduce existing conflicts and avoid potential new ones. After introducing how diseases can affect conservation efforts, we have provided examples of different types of disease-related conflicts, including (1) those related to the movements of hosts, vectors and pathogens, (2) those linked to cats and dogs living in contact with wild carnivores, (3) those related to ungulate overabundance and (4) those related to carrion and hunting remains. We then discuss the management options available to mitigate these situations and resolve the conflicts surrounding them. Disease-related conflicts can affect conservation in several different ways. Whereas it is clear that diseases must be considered in any recovery plan for endangered species, as well as for sympatric and related abundant species such as relevant prey, it is also important to foresee and mitigate any eventual disease-related conflicts. Where conflicts have arisen, identifying the cultural carrying capacity for a disease or disease host species will help identify management strategies. It is important to quantify the risks for stakeholders and educate them about possible solutions. Multidisciplinary research teams that communicate their work to stakeholders should help resolve conflicts. Management options will not only depend on the status of the endangered host species and the epidemiology of the diseases considered, but also on the levels of existing conflict. Conservation strategies affected by diseases should explicitly include efforts to educate and inform all stakeholders as required throughout the process, and tackle any conflicts that arise.

Trypanosoma spp. infection in wild rabbits (Oryctolagus cuniculus) during a restocking program in Southern Spain

The effect of parasites on managed rabbit populations may prove crucial to develop sanitary strategies during restocking programs of such key prey species. We investigated natural infection of European wild rabbits (Oryctolagus cuniculus) with Trypanosoma spp. in Spain. By fencing part of the warrens during a rabbit restocking program, we induced host variation in rabbit density across these socio-spatial units. We aimed (i) to compare Trypanosoma spp. infection spread between fenced and open warrens and (ii) to assess the relationship between body condition and infection. Trypanosoma spp. parasitaemia peaked in juveniles and decreased onwards. Adult females showed statistically higher infection rates than males. Rabbits from fenced warrens presented statistically higher infection rates than those from open ones, but did not differ in body condition. Parasite abundance negatively correlated with body condition in adults. Sex differences could resemble increased susceptibility to infection in females as a cost of reproduction and/or a higher exposition inside the warrens. Future studies should clarify whether aggregation caused enhanced exposition to intermediate hosts (fleas) and subsequent transmission of the parasite, and we stress that the study of non-lethal parasites during restocking programs provides valuable information on host contact rates and on factors affecting disease susceptibility.

Rabbit conservation: models to evaluate the effects of timing of restocking on recipient and donor populations

In recent decades, the translocation of European wild rabbits (Oryctolagus cuniculus) has been a common strategy used by gamekeepers and conservationists to improve populations with low rabbit abundance. Using a non-spatial, mixed stochastic–deterministic model, we assessed the effects of the timing of restocking of rabbits on the persistence of wild rabbit populations, as well as the effects of extraction on donor populations. Different age-structured restocking strategies and extraction rates were tested. We also assessed the number of restocking batches that a donor population can supply while remaining stable. Our results indicate that the best months to introduce individuals are October–March, with the highest success in January. In contrast, the best timing for extraction is during summer, when the number of individuals is high. Authorities should therefore include the timing and number of rabbits released or captured in their management strategies, especially where these factors have been previously overlooked.