An experimental study of translocation success and habitat improvement in wild rabbits

The translocation of wild animals is a strategy frequently used in the conservation and management of natural populations. The aim of this study was to evaluate the impact of translocation (population supplementation) and habitat improvement on the abundance of European wild rabbit Oryctolagus cuniculus . We used eight open plots with different habitat treatments: two with increased shelter, two with increased food, two with increased shelter and food and two without habitat treatment (control plots). We translocated wild rabbits during 3 consecutive years, each year in four of the eight plots, with the remaining plots serving as control for the translocation treatment. Rabbit abundance (translocated plus native rabbits) was calculated by means of pellet counts, and the results were evaluated mainly by generalized linear mixed models. We found that rabbit abundance was determined primarily by habitat improvement. Rabbits were more abundant in treated than in control plots, and most abundant in the plots where food availability was increased. This effect persisted throughout the year. Translocation also increased abundance, but this effect was the strongest where shelter and food had also been improved and declined and disappeared after breeding. These findings suggest that the habitat is an important factor for rabbit abundance, with food availability being the prime factor regulating densities. Moreover, translocations on their own are only effective in the short term in situations in which factors limiting population growth (e.g. disease and predation) have not been corrected. Translocations should be carried out in conjunction with improvements in release habitat as rabbit densities will depend on the maximum carrying capacity of the habitat.     

High levels of nucleotide diversity in the European rabbit (Oryctolagus cuniculus) SRY gene

We have sequenced 2,388 bp of the European rabbit sex determining region Y (SRY) gene. These data provide a 10-fold increase in the coverage of the Y chromosome in this species, including the entire open reading frame of the SRY, the polyadenylation signal, and two repetitive sequences in the 5' -region. A survey of 2021 bp of this gene in eight domestic breeds and four wild individuals revealed a total of nine single nucleotide polymorphisms and one indel, defining two deeply divergent lineages. The resulting estimation of nucleotide diversity (pi=1.34 x10(-3)) is very high when compared with other species, but no variability was detected among the domestic breeds. This study represents a first step in the characterization of the European rabbit Y chromosome and its variability. These sequences can be used in additional phylogeographical analyses of the European rabbit and other Leporid species, as well as in evolutionary studies of sex determination and the Y chromosome in wild species.     

Absence of a genetic bottleneck in a wild rabbit (Oryctolagus cuniculus) population exposed to a severe viral epizootic

Infectious diseases and their demographic consequences are thought to influence the genetic diversity of populations. In Europe, during the last 50 years, the European rabbit (Oryctolagus cuniculus) has suffered two important viral epizootics: myxomatosis and rabbit viral haemorraghic disease (RVHD). Although mortality rates were very high, the impact of these diseases on genetic diversity has never been assessed directly. The subject of this paper is a wild rabbit population in France, which has been studied since the beginning of the 1980s. The first outbreak of RVHD occurred in 1995 and provoked a demographic crash. The population, sampled for the first time in 1982 and 1994, was sampled again at the end of 1996 to examine the impact of the epizootic on genetic diversity. In spite of the observed high mortality rate ( approximately 90%), analysis of 14 polymorphic loci (allozymes and microsatellites) showed no loss in genetic diversity after the epizootic. Determination of temporal changes in allele frequencies indicated that the population evolved under genetic drift. The temporal method of Waples demonstrated a significant decrease in the effective population size (Ne) correlated with the demographic crash due to the epizootic. However, the population had only been studied for two generations after the epizootic and the remnant population size probably stayed high enough ( approximately 50 individuals) to keep its genetic diversity at the precrash level. These results suggest that, contrary to what is usually thought and in spite of the subsequent high mortality rates, past epizootics (especially myxomatosis) may have had little effect on the genetic diversity of wild rabbit populations in Europe.     

Reduced introgression of the Y chromosome between subspecies of the European rabbit (Oryctolagus cuniculus) in the Iberian Peninsula

The role of the Y chromosome in speciation is unclear. Hybrid zones provide natural arenas for studying speciation, as differential introgression of markers may reveal selection acting against incompatibilities. Two subspecies of the European rabbit (Oryctolagus cuniculus) form a hybrid zone in the Iberian Peninsula. Previous work on mitochondrial DNA (mtDNA), Y- and X-linked loci revealed the existence of two divergent lineages in the rabbit genome and that these lineages are largely subspecies-specific for mtDNA and two X-linked loci. Here we investigated the geographic distribution of the two Y chromosome lineages by genotyping two diagnostic single nucleotide polymorphisms in a sample of 353 male rabbits representing both subspecies, and found that Y chromosome lineages are also largely subspecies-specific. We then sequenced three autosomal loci and discovered considerable variation in levels of differentiation at these loci. Finally, we compared estimates of population differentiation between rabbit subspecies at 26 markers and found a surprising bimodal distribution of F(ST)values. The vast majority of loci showed little or no differentiation between rabbit subspecies while a few loci, including the SRY gene, showed little or no introgression across the hybrid zone. Estimates of population differentiation for the Y chromosome were surprisingly high given that there is male-biased dispersal in rabbits. Taken together, these data indicate that there is a clear dichotomy in the rabbit genome and that some loci remain highly differentiated despite extensive gene flow following secondary contact.     

Is polecat (Mustela putorius) diet affected by “mediterraneity”?

Carnivores in Mediterranean ecosystems respond to the inherent heterogeneity of these systems by tracking the spatial and temporal availability of food resources. This feeding strategy, however, has been associated primarily with generalist carnivores and little is known for specialist species such as the European polecat. We collected polecat scat to determine the diet of this species, how it matches the seasonal availability of food resources, and how it is affected by population spatial structure and anthropogenic disturbance. Polecats were present in only 34% of the surveyed area and were clumped into three main population nuclei. Despite the spatial segregation of the populations, they had no significant differences in food items consumed. Polecats mostly fed on mammals (percentage of occurrence (P.O.)=43%) and arthropods (P.O.=49%). Biomass intake was also mostly from mammals (percentage of biomass (P.B.)=96%), followed by birds (P.B.=3%), with arthropods contributing less than 1%. Lagomorphs were the most consumed prey (P.O.=25% and P.B.=87%), which is consistent with the marked spatial overlap between scat with high content in lagomorphs and the areas with high wild rabbit availability. These results indicate that polecats are specialists in the consumption of wild rabbits, spatially track the availability of this prey, and may be affected by the decrease in abundance of the prey populations. Future conservation of polecats in Mediterranean regions of southern Portugal may be achieved through the restoration of hunted and diseased wild rabbit populations.     

Mortality patterns over 3 years in a sparse population of wild rabbits (Oryctolagus cuniculus) in New Zealand, with an emphasis on rabbit haemorrhagic disease (RHD)

A sparse rabbit population in New Zealand was monitored over 3 years to assess the temporal dynamics of rabbit mortality, in particular to understand the mortality patterns due to rabbit haemorrhagic disease (RHD). A total of 107 deaths were recorded, of which 93 could be classified by cause. The predominant cause of mortality was predation (47% of deaths), followed by RHD (20%). Deaths due to RHD were clustered in time (within 3 weeks), predation occurred most actively from late autumn to spring, while other causes of death did not show pronounced seasonal peaks. No differences in cause-specific death risk were observed between sexes. Predation was the main cause of death in younger animals, while RHD mortality occurred mainly in older rabbits. This study has shown that the impact of RHD can vary considerably between years, indicating that a variety of risk factors are required to initiate a RHD epidemic with a high mortality rate among rabbits.     

Grain sowing aimed at wild rabbit Oryctolagus cuniculus L. enhancement in Mediterranean environments

Although habitat management practices focussed on the enhancement of hunting and protection of threatened species are common, the scientific validation of such practices is scarce. The wild European rabbit Oryctolagus cuniculus L., a hunted and threatened species in its native range, is at the same time a key species for the preservation of threatened Mediterranean predators. Cereal sowing is one of the most common practices to augment the food supply of rabbits, and it is used not only by hunters but also by conservationists. At present, limited scientific information is available regarding the effectiveness of cereal sowing. To evaluate its effectiveness, we analysed data on sowing trials conducted in 125 plots, located in 14 private estates throughout central Spain, most of them with low density populations. Brush was cleared from 44 of these plots prior to sowing. Our results indicated that rabbits preferentially selected sown areas over control (unsown) areas. This selection increased in plots that represented suitable habitats for rabbits, such as pasturelands, as well as when thicket islands and natural or artificial shelters were available within the sown plots. Local enhancement of rabbit populations was also observed. These positive results were also obtained regardless of the initial habitat conditions, not only in the treatment plots but also in the surrounding area. Our recommendations can be broadly applied for managing rabbit-dependent threatened species.     

Hunting for answers: rabbit (<Emphasis Type="Italic">Oryctolagus cuniculus</Emphasis>) population trends in northeastern Spain

Some populations of European wild rabbit (Oryctolagus cuniculus) in Spain have recovered after rabbit hemorrhagic disease, but others (the majority) have not recovered. The European wild rabbit is a keystone species in Spain’s Mediterranean ecosystems, and several factors have been studied to determine what will stabilize populations and possibly propagate recovery. Many of the previous efforts to determine these pivotal factors have been short-term studies focused on few localities. Most management efforts and studies focused on the well-preserved habitats of southwestern Spain. Our objective was to examine spotlight counts from 60 localities over the past 13 years following the arrival of rabbit hemorrhagic disease in Aragón, northeastern Spain, to estimate rabbit population trends using linear regressions. The number of rabbits seen was transformed into a rough kilometric abundance index. With this data, we calculated a population trend index only for those localities with 6 or more years of data (n=42). No clear population trends were observed for the study period at a regional scale [±SE, range]; (0.065±0.081 from −0.860 to 0.915). We also examined factors that potentially influence regional rabbit population trends, including vegetation, topography, soil softness, climate, predator population trends, and hunting pressure. Our results indicate that rabbit trends have their strongest positive correlation with low hunting pressure and are negatively affected in areas of hard soils. In Aragón, the best populations of endangered raptors are concentrated in the Central Valley, which is the same area where rabbit populations are currently increasing.     

Copy number polymorphism in the α-globin gene cluster of European rabbit (Oryctolagus cuniculus)

Comparative genomic studies have revealed that mammals typically possess two or more tandemly duplicated copies of the α-globin (HBA) gene. The domestic rabbit represents an exception to this general rule, as this species was found to possess a single HBA gene. Previous electrophoretic surveys of HBA polymorphism in natural populations of the European rabbit (Oryctolagus cuniculus) revealed extensive geographic variation in the frequencies of three main electromorphs. The variation in frequency of two electromorphs is mainly partitioned between two distinct subspecies of European rabbit, and a third is restricted to the hybrid zone between the two rabbit subspecies in Iberia. Here we report the results of a survey of nucleotide polymorphism, which revealed HBA copy number polymorphism in Iberian populations of the European rabbit. By characterizing patterns of HBA polymorphism in populations from the native range of the European rabbit, we were able to identify the specific amino-acid substitutions that distinguish the previously characterized electromorphs. Within the hybrid zone, we observed the existence of a second HBA gene duplicate, named HBA2, that mostly represents a novel sequence haplotype, which occurs in higher frequency within the hybrid zone, and thus appears to have arisen in hybrids of the two distinct subspecies. Although this novel gene is also present in other wild Iberian populations, it is almost absent from French populations, which suggest a recent ancestry, associated with the establishment of the post-Pleistocene contact zone between the two European rabbit subspecies.     

Polymorphic microsatellite loci in the European rabbit (Oryctolagus cuniculus) are also amplified in other lagomorph species

Six polymorphic microsatellite markers developed for the European wild rabbit ( Oryctolagus cuniculus ) were amplified with 20 other species of lagomorphs, representing both commercially important species and species important from a conservation perspective. Successful amplification of a number of these loci has provided an important set of new molecular markers for this mammalian order.     

A rapid population expansion retains genetic diversity within European rabbits in Australia

The well documented historical translocations of the European rabbit (Oryctolagus cuniculus) offer an excellent framework to test the genetic effects of reductions in effective population size. It has been proposed that rabbits went through an initial bottleneck at the time of their establishment in Australia, as well as multiple founder events during the rabbit's colonization process. To test these hypotheses, genetic variation at seven microsatellite loci was measured in 252 wild rabbits from five populations across Australia. These populations were compared to each other and to data from Europe. No evidence of a genetic bottleneck was observed with the movement of 13 rabbits from Europe to Australia when compared to French data. Within Australia the distribution of genetic diversity did not reflect the suggested pattern of sequential founder effects. In fact, the current pattern of genetic variation in Australia is most likely a result of multiple factors including mutation, genetic drift and geographical differentiation. The absence of reduced genetic diversity is almost certainly a result of the rabbit's rapid population expansion at the time of establishment in Australia. These results highlight the importance of population growth following a demographic bottleneck, which largely determines the severity of genetic loss.     

Arid Recovery – A comparison of reptile and small mammal populations inside and outside a large rabbit,cat and fox‐proof exclosure in arid South Australia

Australian arid zone mammal species within the Critical Weight Range (CWR) of 35 g–5.5 kg have suffered disproportionately in the global epidemic of contemporary faunal extinctions. CWR extinctions have been attributed largely to the effects of introduced or invasive mammals; however, the impact of these threatening processes on smaller mammals and reptiles is less clear. The change in small mammal and reptile assemblages after the removal of rabbits, cats and foxes was studied over a 6‐year period in a landscape‐scale exclosure in the Australian arid zone. Rodents, particularly Notomys alexis and Pseudomys bolami, increased to 15 times higher inside the feral‐proof Arid Recovery Reserve compared with outside sites, where rabbits, cats and foxes were still present. Predation by cats was thought to exert the greatest influence on rodent numbers owing to the maintenance of the disparity in rodent responses through dry years and the differences in dietary preferences between rabbits and P. bolami. The presence of introduced Mus domesticus or medium‐sized re‐introduced mammal species did not significantly affect resident small mammal or reptile abundance. Abundance of most dasyurids and small lizards did not change significantly after the removal of feral animals although reductions in gecko populations inside the reserve may be attributable to second order trophic interactions or subtle changes in vegetation structure and cover. This study suggests that populations of rodent species in northern South Australia below the CWR may also be significantly affected by introduced cats, foxes and/or rabbits and that a taxa specific model of Australian mammal decline may be more accurate than one based on body weight.     

Relationship Between Small-game Hunting and Carnivore Diversity in Central Spain

Small-game hunting plays an important economic role in central Spain and some game species are key food resources for threatened predators. Small carnivores may reduce numbers of important game species. To alleviate predation pressure on game populations, management is often focused on predator control. Control methods can be non-selective, and so could potentially have a negative impact on non-target carnivore species, affecting carnivore guild composition and diversity. Using data on carnivore diversity in 70 quadrants (5 × 5 km) in a large area of central Spain with two main land uses (small-game hunting and a mixture of big-game hunting and forestry), we assessed how game management was related to carnivore diversity. Carnivore species richness was significantly lower in those areas managed for small-game hunting than in areas where other land uses predominated. The apparently least affected species by predator control was the red fox (Vulpes vulpes), the main target species of predator control. Results suggested that low carnivore species richness was linked to small-game hunting activities, which was probably associated with non-selective predator control practices. Therefore, in order to reconcile carnivore conservation and economic goals it is imperative to develop and to evaluate selective predator control techniques.     

Molecular epidemiology of Rabbit Haemorrhagic Disease Virus in Australia: when one became many

Rabbit Haemorrhagic Disease Virus (RHDV) was introduced into Australia in 1995 as a biological control agent against the wild European rabbit (Oryctolagus cuniculus). We evaluated its evolution over a 16‐year period (1995–2011) by examining 50 isolates collected throughout Australia, as well as the original inoculum strains. Phylogenetic analysis of capsid protein VP60 sequences of the Australian isolates, compared with those sampled globally, revealed that they form a monophyletic group with the inoculum strains (CAPM V‐351 and RHDV351INOC). Strikingly, despite more than 3000 rereleases of RHDV351INOC since 1995, only a single viral lineage has sustained its transmission in the long‐term, indicative of a major competitive advantage. In addition, we find evidence for widespread viral gene flow, in which multiple lineages entered individual geographic locations, resulting in a marked turnover of viral lineages with time, as well as a continual increase in viral genetic diversity. The rate of RHDV evolution recorded in Australia ?4.0 (3.3–4.7) × 10^?3 nucleotide substitutions per site per year – was higher than previously observed in RHDV, and evidence for adaptive evolution was obtained at two VP60 residues. Finally, more intensive study of a single rabbit population (Turretfield) in South Australia provided no evidence for viral persistence between outbreaks, with genetic diversity instead generated by continual strain importation.     

Fine-scale genetic structuring in a natural population of European wild rabbits (Oryctolagus cuniculus)

The genetic structure of a free-living tagged population of European wild rabbits (Oryctolagus cuniculus) was investigated for two consecutive years (1990 and 1991) using 10 polymorphic microsatellite loci. A specific social behaviour, the formation of stable breeding groups, influenced the genetic structure of the population. These breeding groups were shown to constitute genetically differentiated units with low levels of gene flow between them. The average relatedness among members of a social group was higher than within the population as a whole. As a result of female philopatry coupled with male-biased natal dispersal, the relatedness of females was higher than that of males, both within social groups and in the whole population. Furthermore, the average relatedness of females within groups was twice the relatedness of females between groups. This study reveals marked fine-scale, intrapopulation genetic structure, which is attributable to the social behaviour of the European wild rabbit.     

Comparative population dynamics of the bug Mepraia spinolai, a sylvatic vector of Chagas' disease, in different hosts

Abstract.  The aim of this work was to determine the impact of specific hosts on a population of Mepraia spinolai (Porter) (Hemiptera, Reduviidae), a sylvatic vector of Chagas' disease in Chile. We assessed whether a recently introduced host could be an important epidemiological factor in maintaining Chagas' disease in Chile. The study stressed the variations in survival, individual weight and fecundity in the insect population when the vector was raised with a species-specific food supply. The study compared the European rabbit Oryctolagus cuniculus , introduced in Chile ≤ 150 years ago, with a wild endemic rodent, Octodon degus . Hosts were placed separately in experimental glass chambers. Groups of insects maintained with rabbits had greater fecundity than those raised with rodents, but both groups had similar survival times and average weights. Both O. degu s and the European rabbit appear to be suitable hosts for M. spinolai , but the rabbit is better than the rodent. Additional research is needed to determine which factors of O. cuniculus produce the observed results.     

Climate changes influence free‐living stages of soil‐transmitted parasites of European rabbits

Climate warming has been suggested to augment the risk of infectious disease outbreaks by extending the seasonal window for parasite growth and by increasing the rate of transmission. Understanding how this occurs in parasite‐host systems is important for appreciating long‐term and seasonal changes in host exposure to infection and to reduce species extinction caused by diseases. We investigated how free‐living stages of two soil‐transmitted helminths of the European rabbit (Oryctolagus cuniculus) responded to experimental changes in temperature by performing laboratory experiments with environmental chambers and field manipulations using open‐top‐chambers. This study was motivated by our previous observations that air temperature has increased over the last 30 years in our field site and that during this period intensity of infection of Graphidium strigosum but not Trichostrongylus retortaeformis was positively associated with this temperature increase. Laboratory and field experiments showed that both parasites accelerated egg development and increased hatching rate and larval survival in response to accumulating thermal energy. Both parasites behaved similarly when exposed to diverse temperature regimes, decadal trends, and monthly fluctuations, however, T. retortaeformis was more successful than G. strigosum by showing higher rates of egg hatching and larval survival. Across the months, the first day of hatching occurred earlier in warmer conditions suggesting that climate warming can lengthen the period of parasite growth and host exposure to infective stages. Also, T. retortaeformis hatched earlier than G. strigosum. These findings showed that seasonal changes in intensity, frequency, and duration of daily temperature are important causes of variability in egg hatching and larva survival. Overall, this study emphasizes the important role of climate warming and seasonality on the dynamics of free‐living stages in soil‐transmitted helminths and their contribution to enhance host exposure to parasitic infections. Yet, the ability to infect might ultimately depend on how hosts interact with parasites.     

Eradication of rabbits from landscape scale exclosures: pipedream or possibility?

Summary High densities of the European Rabbit (Oryctolagus cuniculus) were eradicated from 60 km² of the Arid Recovery Reserve between 1996 and 2001. Eradication was possible due to an initial knockdown caused by rabbit haemorrhagic disease, followed by effective exclusion fencing, broadscale poison baiting, targeted shooting, warren destruction and trapping on rabbit burrows and buckheaps. The efficacy of different broadscale control and intensive rabbit eradication techniques was subsequently estimated in a 26 km² expansion to the Reserve from 2002 to 2006. Non‐target implications of these control techniques were also assessed where possible. An estimated 8000 rabbits were removed in total from both areas and results suggest that rabbit eradication is possible at a landscape scale. Strategies for eliminating rabbits from confined areas are suggested.     

What is going on at the Molí del Salt site? A zooarchaeological approach to the last hunter-gatherers from South Catalonia

Abstract

Small game seems to have increased during the Upper Palaeolithic to the detriment of large game on the Iberian Peninsula. The economical and socio-cultural factors associated with this ecological shift represent a widely discussed topic. The present work attempts to elucidate the subsistence strategies occurring through the Late Pleistocene in Iberia using the example of the Molí del Salt (Tarragona, Spain), an archaeological site located in the NE of the Iberian Peninsula. The taphonomical analysis of faunal remains shows a high incidence of human activity on different taxonomical groups, although the European rabbit (Oryctolagus cuniculus) stands out. This taxon presents cut-marks related to various processing activities (e.g. skinning and defleshing) and intentional bone breakage to access marrow. The abundance of specimens with human-induced damage enables us to make inferences regarding the procurement strategies and the occupational patterns at the site, where long and stable occupations seem to have occurred.