Sacramento Moreno

Traditional management of scrubland for the conservation of rabbits Oryctolagus cuniculus and their predators in Doñana National Park, Spain

Several endangered carnivores and raptors in Mediterranean Spain are very dependent on rabbits Oryctolagus cuniculus, which have shown a progressive decline in abundance for several decades. Land use neglect, and the consequent abandonment of traditional land use methods such as burning, is considered one of the factors responsible for this decrease. To examine this hypothesis we have compared rabbit use of experimentally burned and unburned scrubland areas. Rabbit activity was found to be significantly higher in burned areas, with the greatest use in less productive habitats in close proximity to scrub cover. The promotion of traditional land practices for nature conservation in the natural ecosystems of the Mediterranean Basin is discussed.

First epizootic of rabbit hemorrhagic disease in free living populations of Oryctolagus cuniculus at Doñana National Park, Spain

The first known epizootic of rabbit hemorrhagic disease (RHD) occurred in two free-living wild rabbit (Oryctolagus cuniculus) populations at Doñana National Park, Spain. Rabbit population density was not correlated to RHD mortality. Only adult animals were affected; males and females had similar mortality rates.

Physiological stress levels predict survival probabilities in wild rabbits

Among vertebrates, short-term elevations of glucocorticoid hormones (corticosterone or cortisol) facilitate a suite of physiological and behavioral changes aimed at overcoming environmental perturbations or other stressful events. However, chronically elevated glucocorticoids can have deleterious physiological consequences, and it is still unclear as to what constitutes an adaptive physiological response to long-term stress. In this study, we experimentally exposed European wild rabbits Oryctolagus cuniculus to a source of long-term stress (simulated through a 2- to 4-week period of captivity) and tested whether glucocorticoid physiology predicted two major components of rabbit fitness: body condition and survival probability. Following exposure to long-term stress, moderately elevated serum corticosterone and fecal glucocorticoid metabolites levels in the wild rabbits were negatively associated with body condition, but positively associated with subsequent survival upon release. Our results suggest that the cost of maintaining elevated corticosterone levels in terms of decreased body condition is balanced by the increased chance of survival upon release.

HABITAT-RELATED DIFFERENCES IN RABBIT (ORYCTOLAGUS CUNICULUS) ABUNDANCE, DISTRIBUTION, AND ACTIVITY

Abstract The European rabbit (Oryctolagus cuniculus) is a key prey species in Mediterranean ecosystems and is ecologically plastic. However, ecological responses of rabbits to different habitats are poorly understood. We present data on abundance, distribution, activity, and survival in 3 neighboring habitats in southwestern Spain differing in refuge and forage availability. Scrubland presents dense cover but low forage abundance; grassland offers little protective vegetation but high food availability; the ecotone provides intermediate levels of both resources. Rabbits reached the highest abundance in ecotone, whereas low food and refuge availability seemed to limit their abundance in scrubland and grassland, respectively. In scrubland, rabbits were dispersed among the cover. In grassland, rabbits were linked to aggregated burrows. In ecotone, rabbits dug burrows in the bordering bushes that abutted grassy feeding pasture. Predation by raptors was low in scrubland, and mortality due to mammalian carnivores was higher in spite of more diurnal rabbit activity. Carnivore predation also caused higher mortality in grassland, where rabbits were more nocturnal. In ecotone, the effect of both mammalian carnivores and raptors on rabbits was similar. Mortality by disease seemed to be linked to level of rabbit aggregation.

QUARANTINE LENGTH AND SURVIVAL OF TRANSLOCATED EUROPEAN WILD RABBITS

Abstract European wild rabbits (Oryctolagus cuniculus) are frequently translocated for hunting and conservation purposes. Quarantining these animals prior to release reduces the risk of releasing rabbits incubating field infections of myxomatosis or viral haemorrhagic disease (RHD), and it provides a way to vaccinate these animals against both diseases. However the optimal quarantine period needed to achieve these goals is not known. We therefore assessed the effects of quarantine lengths (2, 4, 6, 8 weeks) on rabbit biochemical parameters, immunity induced by vaccination against myxomatosis and RHD, and survival of translocated rabbits. We found that levels of total bilirubin, urea nitrogen, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) enzymatic activities were significantly (P < 0.05) decreased during quarantine, independent of quarantine length, whereas hematocrit levels increased significantly. All pregnant female rabbits aborted or lost litters during quarantine. Seroconversion against myxomatosis and RHD following vaccination was not related to any biochemical parameter at vaccination time, but the proportion of seronegative rabbits that seroconverted was moderate. The heterophil/lymphocyte ratio, conjugated to unconjugated bilirubin ratio, and the serum AST and creatinine levels we measured after capture and transport were directly related to mortality through the quarantine period, whereas we found total serum protein level was negatively related to mortality. Mortality after release was positively related to urea nitrogen concentration and negatively related to hematocrit and the albumin/globulin ratio, but it was independent of quarantine length. Based on our findings, rabbit translocation programs that include a quarantine period could be improved by decreasing the acute stress induced by capture and handling prior to quarantine; facilitating a more rapid access to high quality feed during quarantine; and improving the vaccination protocol. In addition, the release from quarantine of rabbits should be determined by their physical condition, not merely by elapsed time in quarantine.

Responses of a top and a meso predator and their prey to moon phases

We compared movement patterns and rhythms of activity of a top predator, the Iberian lynx Lynx pardinus, a mesopredator, the red fox Vulpes vulpes, and their shared principal prey, the rabbit Oryctolagus cuniculus, in relation to moon phases. Because the three species are mostly nocturnal and crepuscular, we hypothesized that the shared prey would reduce its activity at most risky moon phases (i.e. during the brightest nights), but that fox, an intraguild prey of lynx, would avoid lynx activity peaks at the same time. Rabbits generally moved further from their core areas on darkest nights (i.e. new moon), using direct movements which minimize predation risk. Though rabbits responded to the increased predation risk by reducing their activity during the full moon, this response may require several days, and the moon effect we observed on the rabbits had, therefore, a temporal gap. Lynx activity patterns may be at least partially mirroring rabbit activity: around new moons, when rabbits moved furthest and were more active, lynxes reduced their travelling distances and their movements were concentrated in the core areas of their home ranges, which generally correspond to areas of high density of rabbits. Red foxes were more active during the darkest nights, when both the conditions for rabbit hunting were the best and lynxes moved less. On the one hand, foxes increased their activity when rabbits were further from their core areas and moved with more discrete displacements; on the other hand, fox activity in relation to the moon seemed to reduce dangerous encounters with its intraguild predator.

Vaccination Success and Body Condition in the European Wild Rabbit: Applications for Conservation Strategies

Abstract The European wild rabbit (Oryctolagus cuniculus) is the main prey for several endangered species and an important game species in the Iberian Peninsula. However, over the last several decades 2 diseases, myxomatosis and rabbit hemorrhagic disease (RHD), have contributed to a decline in rabbit populations. In Spain, vaccination campaigns against both diseases and the translocation of vaccinated rabbits are frequently used in projects aimed at stimulating the recovery of wild populations. We estimated which factors related to body condition were associated with successful immunization by vaccination. In 191 adult wild rabbits, we calculated a body-mass index and analyzed a number of biochemical parameters and antibody concentrations before and after vaccination. Results showed that, respectively, 81 and 84% of initially seronegative rabbits seroconverted after vaccination against myxomatosis and RHD. We also found that RHD antibody concentrations after vaccination were positively associated with total protein concentrations at the moment of vaccination in all rabbits, whereas RHD antibody concentrations were negatively related to the creatinine concentration at the end of our study for initially seronegative rabbits. Our results suggested that in wild rabbits vaccination was an effective way of increasing antibody concentrations and, thus, of fighting myxomatosis and RHD, although the intensity of the immune response was conditioned by the body condition of individual rabbits. Consequently, rabbit translocations could be improved by avoiding the translocation of individuals with poor body condition and by improving vaccination protocols. In addition, success rates in mass vaccination programs carried out in free-living wild populations may be increased if the body condition of individuals is evaluated before vaccination campaigns are carried out.

Proposal for a unified classification system and nomenclature of lagoviruses

Lagoviruses belong to the Caliciviridae family. They were first recognized as highly pathogenic viruses of the European rabbit (Oryctolagus cuniculus) and European brown hare (Lepus europaeus) that emerged in the 1970-1980s, namely, rabbit haemorrhagic disease virus (RHDV) and European brown hare syndrome virus (EBHSV), according to the host species from which they had been first detected. However, the diversity of lagoviruses has recently expanded to include new related viruses with varying pathogenicity, geographic distribution and host ranges. Together with the frequent recombination observed amongst circulating viruses, there is a clear need to establish precise guidelines for classifying and naming lagovirus strains. Therefore, here we propose a new nomenclature based on phylogenetic relationships. In this new nomenclature, a single species of lagovirus would be recognized and called Lagovirus europaeus. The species would be divided into two genogroups that correspond to RHDV- and EBHSV-related viruses, respectively. Genogroups could be subdivided into genotypes, which could themselves be subdivided into phylogenetically well-supported variants. Based on available sequences, pairwise distance cutoffs have been defined, but with the accumulation of new sequences these cutoffs may need to be revised. We propose that an international working group could coordinate the nomenclature of lagoviruses and any proposals for revision.

COCCIDIAN AND NEMATODE INFECTIONS INFLUENCE PREVALENCE OF ANTIBODY TO MYXOMA AND RABBIT HEMORRHAGIC DISEASE VIRUSES IN EUROPEAN RABBITS

The interaction among several parasites in European rabbits (Oryctolagus cuniculus) is crucial to host fitness and to the epidemiology of myxomatosis and rabbit hemorrhagic disease. These diseases have caused significant reductions in rabbit populations on the Iberian Peninsula. Most studies have focused on the epidemiology and pathogenesis of these viruses individually, and little is known about interactions between these viruses and other parasites. Taking advantage of an experimental restocking program in Spain, the effects of coccidian and nematode infections on the probability of having detectable antibody to myxoma and rabbit hemorrhagic disease viruses were tested in European wild rabbits. For 14 mo, we monitored rabbit abundance and parasite loads (coccidia and nematodes) in three reintroduced rabbit populations. While coccidian and nematode loads explained seasonal antibody prevalences to myxoma virus, the pattern was less clear for rabbit hemorrhagic disease. Contrary to expectations, prevalence of antibody to myxoma virus was inversely proportional to coccidian load, while nematode load seemed to play a minor role. These results have implications for viral disease epidemiology and for disease management intended to increase rabbit populations in areas where they are important for ecosystem conservation.

Multi-event capture–recapture modeling of host–pathogen dynamics among European rabbit populations exposed to myxoma and Rabbit Hemorrhagic Disease Viruses: common and heterogeneous patterns

Host–pathogen epidemiological processes are often unclear due both to their complexity and over-simplistic approaches used to quantify them. We applied a multi-event capture–recapture procedure on two years of data from three rabbit populations to test hypotheses about the effects on survival of, and the dynamics of host immunity to, both myxoma virus and Rabbit Hemorrhagic Disease Virus (MV and RHDV). Although the populations shared the same climatic and management conditions, MV and RHDV dynamics varied greatly among them; MV and RHDV seroprevalences were positively related to density in one population, but RHDV seroprevalence was negatively related to density in another. In addition, (i) juvenile survival was most often negatively related to seropositivity, (ii) RHDV seropositives never had considerably higher survival, and (iii) seroconversion to seropositivity was more likely than the reverse. We suggest seropositivity affects survival depending on trade-offs among antibody protection, immunosuppression and virus lethality. Negative effects of seropositivity might be greater on juveniles due to their immature immune system. Also, while RHDV directly affects survival through the hemorrhagic syndrome, MV lack of direct lethal effects means that interactions influencing survival are likely to be more complex. Multi-event modeling allowed us to quantify patterns of host–pathogen dynamics otherwise difficult to discern. Such an approach offers a promising tool to shed light on causative mechanisms.