When more is less: the negative effect of European rabbit release upon local warren occupancy

The European wild rabbit (Oryctolagus cuniculus) is an introduced pest species in Australia and New Zealand. Rabbits have a devastating negative impact on agricultural production and biodiversity in these countries, and Rabbit Haemorrhagic Disease (RHD) is currently included in control strategies for rabbit populations. On the other hand, the European wild rabbit is a key native prey species in the Iberian Peninsula. Since the arrival of RHD, however, rabbit populations have undergone dramatic decreases and several predator species at risk of extinction are currently dependent on the rabbit population density. Therefore, from the point of view of biodiversity conservation, evaluating habitat correlates and trends of rabbit populations after the first RHD epizootic is of great interest to improve the long-term control or promotion of wild rabbit populations. We estimated the relationship between habitat factors and long-term population trends as well as the relationships between habitat factors and rabbit abundance 2 and 14 years after the arrival of RHD in several Iberian rabbit populations. We observed that only 26% of surveyed populations seemed to experience an increase in rabbit abundance over the last 12 years and that this increase was higher in the low-rabbit-abundance areas of l992, leading to high rabbit abundance in 2004. Our results suggested that short- and long-term impacts of RHD were related to habitat quality. The initial impact of RHD was higher in more suitable habitats, but increasing long-term population trends were positively related to good habitat quality.

Recent negative trends of wild rabbit populations in southern Spain after the arrival of the new variant of the rabbit hemorrhagic disease virus RHDV2

The European rabbit Oryctolagus cuniculus, a keystone species of Mediterranean ecosystems, is the target of several recovery and management plans throughout the Iberian Peninsula. The majority of these plans are limited in time by budget constraints and lack postintervention monitoring of population trends. This study was conducted in south‐west Portugal and aimed to understand the effect of habitat management and its early cessation on rabbit populations. We assessed rabbit presence and relative abundance before management (2007), during the implementation of measures (2008), immediately after (2009) and 3 years after measures ended (2012). We applied a model selection approach, using generalized linear models to determine the relative importance of MANAGED and UNMANAGED habitat features on rabbit presence in each year. We used spatial eigenvector mapping to describe the spatial autocorrelation in rabbit presence and a variation partitioning approach to quantify the relative effects of management‐related variables, unmanaged environmental descriptors and spatial characteristics on rabbit presence. Rabbit presence and abundance increased shortly after the management intervention but decreased 3 years after. Rabbit presence was positively related to the proximity of installed crops and the existence of favorable soils for digging. Habitat management‐related variables explained most of the variation in all models. Habitat improvement actions, particularly the sowing of pastures, contributed to increased rabbit presence. We propose a continued long‐term intervention and the cultivation of crops with auto‐regeneration properties (e.g., subterranean clover—Trifolium subterraneum) with the aim of continuing to increase rabbit presence and abundance in areas where rabbit populations are scarce.

Demographic changes were monitored in free-ranging European rabbit (Oryctolagus cuniculus) populations in Australia following the surgical imposition of four levels of female sterility (0%, 40%, 60%, 80%). Rabbit productivity decreased with increasing sterility level, but a greater proportion of offspring were recruited into populations with high levels of sterility. Adult rabbits, particularly sterile females, also survived better in the high sterility populations. Thus we were able to experimentally demonstrate that two density-dependent processes were operating on our rabbit populations: one was acting on juvenile survival, the other on the survival of infertile adult rabbits. However, these compensatory mechanisms were insufficient to overcome the effects of sterility in the high sterility populations and the seasonal abundance of rabbits decreased. Female sterility levels of 60%-80% would benefit rabbit control programs by reducing the peaks of rabbit abundance. This effect is likely to be enhanced if fertility control could be integrated with other pest control strategies.

The wild rabbit (Oryctolagus cuniculus L.) is a significant pest in arid and semi‐arid Australia, where erratic rainfall and irregular pasture growth cause population sizes to oscillate, increasing virtually without limit and then crashing during drought conditions. Vacant habitat patches can be rapidly recolonized from nearby patches in high rainfall years. Using two adjoining rabbit population systems in arid and semi‐arid south‐west Queensland, this study evaluates patterns of population differentiation and proposes a mechanism that may lead to the formation of multiple rabbit population systems in the same locality. Using the combined haplotype frequency data from both a local and regional study, estimates of genetic exchange among local populations are considered in conjunction with ecological data to evaluate the significance of habitat attributes (and their spatial distribution) on the local distribution of rabbit populations, both within and between two adjacent population systems. A tentative model is proposed to explain the observed differences in population structure between the two adjoining systems. Under this model, population structure at specific locations is determined primarily by the availability of areas suitable for prolonged colonization and the quality of the intervening habitat that dictates the degree of isolation between locations and therefore the probability of recolonization following local extinctions. It is also suggested that the current rabbit distribution may be a function of the flexibility of behavioural responses in rabbits to the level of spatial heterogeneity of favourable habitats within the two regions.

The consumption of nontoxic, sliced carrot baits by 10 free-living European rabbit (Oryctolagus cuniculus) populations was investigated using Rhodamine B dye and fluorescent acetate floss fibers as bait markers. Total bait consumption was highest after 5-8 days of exposure. Increases in consumption between the 3rd and 8th days resulted from bait consumption by greater numbers of rabbits rather than increases in the amounts eaten by individuals. The data suggest that the more widely ranging individuals began consuming bait earlier than others. The average daily bait consumption/individual after 8 days of exposure varied between 216 and 346 g/kg body weight. The proportion of individuals eating bait was inversely related to the distance of their burrows from bait. There were no significant differences (P > 0.05) between sexes or among age classes in the proportions of animals consuming bait. Males ate significantly more (P < 0.001) bait than females. Adults ate significantly less (P < 0.05) bait than animals <9 months of age. It is concluded that sliced carrot bait could be used effectively as a vehicle for toxicants to control rabbit populations in Britain, provided that its presence does not substantially reduce bait consumption. A toxicant concentration considerably lower than that employed in Australia and New Zealand could be used because of the large amounts eaten by individual rabbits, thereby substantially reducing the risk to nontarget wildlife. J. WILDL. MANAGE. 51(2):386-392 The European rabbit is a major pest of agriculture in Great Britain. This problem is likely to increase as the effects of myxomatosis on rabbit numbers wane and improved methods of rabbit management become necessary (Ross and Sanders 1984). Toxicants have been successfully used to control rabbits in both Australia and New Zealand (Oliver et al. 1982 a,b). However, distributing toxic baits for rabbits is currently illegal in Britain. The study reported here forms part of an investigation into a baiting method that would be acceptable in Britain if a suitable toxicant (humane, low risk to nontarget species, and efficaceous) was available. The rabbit is a grazing animal and consumes large quantities of food relative to its body size. This suggests that low concentrations of toxin could be used effectively (if its presence does not constrain bait acceptance), hence reducing the risk to many nontarget species that would be unable to consume sufficient bait to receive a lethal dose. In these circumstances an effective baiting technique must involve consumption of large amounts of bait by a high proportion of a given rabbit population. Changes in these parameters with increasing length of exposure to nontoxic, sliced carrot bait, equivalent to a period of prebaiting prior to the use of toxin, have been investigated using 2 bait markers, Rhodamine B dye and fluorescent acetate floss fibers (Cowan et al. 1984). In addition, variations in patterns of bait consumption have been considered in relation to age, sex, and the distance of rabbit warrens (interconnected burrow systems with multiple entrances) from bait points. We thank landowners, C. A. Swan, T. Steele, L. M. Lelliott, G. Lambourne; and other Minist. Agric., Fish., and Food staff for access to the study sites and assistance in the field and laboratory; J. Bell for valuable discussion on the use of bait markers; A. Hart for statistical advice; and W. A. Rees and J. Ross for constructive criticism of earlier drafts of this paper.

The European rabbit (Oryctolagus cuniculus) is a key species in many Mediterranean ecosystems, especially as prey for numerous Iberian predators. Due to its population decline and spatially heterogeneous recovery following different diseases, there is a need to understand the factors driving local abundance, and a potential refuge effect of anthropized sites has been speculated. In this study, 18 peri-urban areas in Central Spain were selected and a rabbit abundance index was measured in those areas and in parallel controls. Urban occupation and vegetation cover around sampling points were measured, as well as distance to roads, forest patches, and rivers, as factors which can drive rabbit abundance. Linear models were built to unravel general trends in data, from the perspectives of vegetation vs. human occupation and larger landscape-scale effects on rabbit abundance. Negative effects of urban development, distance to roads and proportion of pastures on rabbit abundance were identified, in addition to a positive effect of distance to large forest patches. Regarding urbanization, differences were found among urban types, with a significant negative effect of single-family residential occupation in comparison with multi-family and commercial/industrial occupation. In short, urbanization affects rabbit density, but it does not produce a generalized refuge area surrounding human settlements.

The European rabbit (Oryctolagus cuniculus L.) is a key prey species in Mediterranean ecosystems that has declined in its natural ranges as a result of diseases and loss of habitat. This situation has led to the production of wild rabbits in enclosures in which they can acclimate and breed. The efficiency of these enclosures as extensive breeding systems is defined by their population growth rate (PGR). The aim of this study is to analyse the effect of rabbit abundance on the PGR. This has been done by creating general linear models to explain autumn and spring PGR with the use of rabbit abundance estimates, enclosure size, aerial predation and previous PGR as possible explanatory variables. Rabbit abundance and enclosure size negatively affected the autumn PGR, while only rabbit abundance affected the spring PGR in the best-fit models. It is suggested that maintaining rabbit densities at fewer than 30 rabbits per hectare might help to optimise the efficiency inside enclosures.

The European rabbit (Oryctolagus cuniculus) is a key prey species in Mediterranean ecosystems. However, it is also considered a pest on many oceanic islands, even though its true abundance and ecological effects on different island habitats are poorly understood. We present data on rabbit abundance for the best-preserved habitats of the Canary Islands, Spain (National Parks), including ecosystems differing in climate, topography, plant species richness and composition. Three methods of assessing rabbit abundance from faecal pellet density are compared to ascertain the best method to compare highly distinct habitats. The Cleaning method was used during spring, summer, autumn and winter to check whether there were differences in pellet degradation among habitats that could prevent comparisons between them. Rabbit abundance is determined by complex interactions among abiotic and biotic factor. Despite differences in climate conditions, the results obtained for rabbit density with fast methods correlated well with the slow Cleaning method. The Circular method was the most useful to work with for extensive sampling in different habitats. The best models for explaining rabbit density for all habitat types combined included tree cover, abiotic and topographic and climatic variables. Thus, factors influencing rabbit density vary depending on habitat type with Macaronesian laurel forests being the ecosystem least likely to be invaded by rabbits. The present study highlights that rabbits reach damaging densities for plant conservation in most areas on the Canary Islands.

In this study, the pattern of movement of young male and female rabbits and the genetic structures present in adult male and female populations in four habitats was examined. The level of philopatry in young animals was found to vary between 18–90% for males and 32–95% for females in different populations. It was skewed, with more males dispersing than females in some but not all populations. Analysis of allozyme data using spatial autocorrelation showed that adult females from the same social group, unlike males, were significantly related in four of the five populations studied. Changes in genetic structure and rate of dispersal were measured before and during the recovery of a population that was artificially reduced in size. There were changes in the rate and distance of dispersal with density and sex. Subadults of both sexes moved further in the first year post crash (low density) than in the following years. While the level of dispersal for females was lower than that of the males for the first 3 years, thereafter (high density) both sexes showed similar, low levels of dispersal (20%). The density at which young animals switch behaviour between dispersal and philopatry differed for males and females. The level of genetic structuring in adult females was high in the precrash population, reduced in the first year post crash and undetectable in the second year. Dispersal behaviour of rabbits both affects the genetic structure of the population and changes with conditions. Over a wide range of levels of philopatry, genetic structuring is present in the adult female , but not the male population. Consequently, though genetic structuring is present, it does not lead to inbreeding. More long-distance movements are found in low-density populations, even though vacant warrens are available near birth warrens. The distances moved decreased as density increased. Calculation of the effective population size (Ne) shows that changes in dispersal distance offset changes in density, so that Ne remains constant.

[EN] The activity of 2 populations of wild rabbits (Oryctolagus cuniculus, L. 1758), consisting of 14 adults (&gt;9 mo of age) each (4 males and 10 females), was analysed over 2 consecutive years. Rabbits were captured in the wild and kept in 2 separate enclosures of 0.5 ha, with each enclosure divided into 2 zones: a smaller area where warrens were located (breeding area) and a larger area where food and water were provided (feeding area). Seven rabbits in each enclosure were individually tagged with a microchip (2 males and 5 females) and, after installing 2 detection devices, it was possible to identify which of the 2 areas they were located in and record the length of time spent in each. To regulate the size of the breeding population, young rabbits produced in the enclosures were captured and removed regularly. Considering the number of movements between areas and the time spent in the feeding area, a circadian activity pattern was found, reporting 2 maximum activity peaks coinciding with twilight (18.35% of the total movements, 6-8 a.m.) and daybreak (22.95%, 7-10 p.m.) while activity was dramatically decreased during the midday hours (1.86%, 10 a.m.-4 p.m.). Rabbits displayed a seasonal pattern throughout the year, with maximum activity levels during winter (45.76% of the total movements, January-March) and spring (42.91%, April-June), which could be related to higher reproductive activity at this time of the year as a higher breeding output was reported in June and September. The levels of activity exhibited by males (13.44% daily activity rate) were significantly higher than those displayed by females (9.80%). No significant differences were found regarding time spent on the feeding area in relation to season or gender. The average duration of each foray to the feeding area was higher during the summer, higher for females than males and higher during the middle of the night than the rest of the day.

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.

Coexistence of ecologically similar species is sustained by niche partitioning, a fundamental element of which is diet. Overlapping of resource requirements between sympatric species can create interspecific competitive or facilitative effects on the foraging behaviour of herbivores. Brown hares (Lepus europaeus) and European rabbits (Oryctolagus cuniculus) are similar in size, morphology, feeding type and occupy the same habitats, but direct evidence of competition for resources between them is lacking. Both species are widespread and simultaneously pests and species of conservation concern in different parts of their range. We investigated dietary overlap of brown hares and European rabbits in pastures in relation to pasture management and hare and rabbit abundance. Grasses were the predominant component in both hare and rabbit diets with high overlap of plant species. Both rabbits and hares showed some selectivity for particular plants with evidence of consistent selection for Phleum spp. and relative avoidance of Poa spp. However, differences in the smaller components of hare and rabbit diet resulted in significant differences in diet overall. There was no evidence that higher relative density of one species led to dietary shifts but pasture management affected the diet of both species. Nutritional composition of diets of both species also differed between cattle and sheep pastures with higher fibre, ash and fat in the former. Our data provide no evidence of competitive exclusion between rabbits and hares on the basis of diet, but suggest that the effects of livestock on their respective diets may influence indirect competition in favour of rabbits over hares.

High mortality (88-100%) was observed during two outbreaks of myxomatosis between 1973 and 1974 in a population of Oryctolagus cuniculus at Canberra. The presence of immune adult rabbits predisposed the disease to be confined either to the young kittens or to susceptible immature rabbits surviving from the period between the outbreaks. A virulent Lausanne strain myxoma virus was deliberately introduced by means of infective fleas (Spilopsyllus cuniculi). Field strains were present. Reactivation and transmission of virus in natural populations is discussed. The possibility of contact rather than vector (flea) transmission is examined in respect of failure to maintaining the outbreaks. Some observations were made on rabbits that recovered from myxomatosis and on the occurrence in some individuals of persistent sublethal signs of myxomatosis. Frequency of raptor predation is compared between periods with and without myxomatous rabbits. The duration of survival of infected rabbits is not significantly reduced by predation, but some raptors, such as brown hawk and little eagle, may concentrate more on the youngest available rabbits during an outbreak. ADDITIONAL ABSTRACT: High case mortalities (88-100%) were observed during two outbreaks of myxomatosis between 1973 and 1974 in a population of rabbits (Oryctolagus cuniculus), at Canberra, Australia. The presence of immune adult rabbits predisposed the disease to be confined either to the young kittens or to susceptible immature rabbits surviving from the period between the epizootics. A virulent Lausanne strain myxoma virus was deliberately introduced by means of infective Spilopsyllus cuniculi (Dale). Field strains were present. Reactivation and transmission of virus in natural populations is discussed. The possibility of contact rather than vector (flea) transmission is examined in respect of failure to maintaining the epizootics. Some observations were made on rabbits that recovered from myxomatosis and on the occurrence in some individuals of persistent sublethal signs of myxomatosis. The duration of survival of infected rabbits was not significantly reduced by predation, but some raptors sometimes concentrated more on the youngest available rabbits during an epizootic.

Predator-prey studies in semi-arid eastern Australia demonstrated that populations of rabbits (Oryctolagus cuniculus) could be regulated by predators. The functional, numerical and total responses of foxes (Vulpes vulpes) to rabbits and the numerical response of feral cats (Felis catus) to rabbits, are described. Measurement of the rabbit component of foxes' stomach contents indicates a Type III functional response. The size of the fox population in summer was dependent on the availability of rabbits over the immediately preceding rabbit breeding season but there appeared to be no density-dependent aggregation of young foxes in areas of surplus food. The total response of foxes, estimated using the short-term numerical response of dispersing foxes, was directly density-dependent for low rabbit densities and inversely density-dependent for high rabbit densities. Two states are possible with this form of total response: a state with low rabbit densities regulated by predators and a state with high rabbit densities which occurs when rabbits escape predator regulation. The boundary between regulation and non-regulation by predators was demonstrated by a predator-removal experiment. In the treated areas, predators were initially culled and rabbits increased to higher densities than in an untreated area where predators were always present. When predators were allowed back into the treated areas, rabbit populations continued to increase and did not decline to the density in the untreated area. This is the critical evidence for a two-state system. When predators were present, rabbits could be maintained at low densities which were in the density-dependent part of the total response curve for foxes. Exceptionally high rabbit recruitment, or artificially reduced predation, could result in rabbits escaping predator-regulation. Under these circumstances, rabbits could move into the inversely density-dependent region of the total response curve for foxes.