Rabbits killing hares: an invasive mammal modifies native predator-prey dynamics

An assessment of the environmental and socio-economic impacts of alien rabbits and hares

Directly comparable data on the environmental and socio-economic impacts of alien species informs the effective prioritisation of their management. We used two frameworks, the Environmental Impact Classification for Alien Taxa (EICAT) and Socio-Economic Impact Classification for Alien Taxa (SEICAT), to create a unified dataset on the severity and type of impacts caused by alien leporids (rabbits and hares). Literature was reviewed to collate impact data, which was categorised following EICAT and SEICAT guidelines. We aimed to use these data to identify: (1) alien leporid species with severe impacts, (2) their impact mechanisms, (3) the native species and local communities vulnerable to impacts and (4) knowledge gaps. Native species from a range of taxonomic groups were affected by environmental impacts which tended to be more damaging than socio-economic impacts. Indirect environmental impacts were particularly damaging and underreported. No impact data were found for several alien leporid species.

Feral rabbit populations in a peri-urban area: insights about invasion dynamics and potential management strategies

Where introduced, the European rabbit Oryctolagus cuniculus is considered among the most destructive and invasive species. To date, research focused mostly on populations of wild rabbit, whereas little is known on feral domestic rabbit populations. In this work, we reported the establishment of two self-sustaining populations of feral rabbits in Italy. Direct observations were conducted to assess rabbit range expansion and population increase over time. We also evaluated prey-predator interactions between rabbits and native red foxes Vulpes vulpes, by means of camera trapping and the analysis of fox scats. Moreover, we also assessed the social perception towards feral rabbits and the acceptability of various management options through the administration of a structured questionnaire to park visitors. Rabbit populations increased between 2018 and 2019, as well as the size of the invaded range. Rabbits are predated by foxes, but they seem to have adapted their activity rhythms to minimize the risk of predation, becoming diurnal. Park visitors loved rabbits and deemed them to be a positive presence in the park, which deserve to live there. Surgical sterilization of rabbits was the only management option which was partially supported. Feral domestic rabbits, albeit a neglected species in invasion biology, can become extremely successful invaders of urban green areas: in < 5 years, rabbits were able to colonize our study area and become a food resource for native predators and also an iconic species. These three points raise concerns about the potential impacts of invasive feral rabbits in European urban green areas and call for further research in this direction.

A Mathematical Model Supporting a Hyperpredation Effect in the Apparent Competition Between Invasive Eastern Cottontail and Native European Hare

In this work a mathematical model is built in order to validate on theoretical grounds field study results on a three-species system made of two prey, of which one is native and another one invasive, together with a native predator. Specifically, our results mathematically describe the negative effect on the native European hare after the introduction of the invasive Eastern cottontail, mediated by an increased predation rate by foxes. Two nonexclusive assumptions can be made: an increase in cottontail abundance would lead to a larger fox population, magnifying their predatory impact ("hyperpredation") on hares; alternatively, cottontails attract foxes in patches where they live, which are also important resting sites for hares and consequently the increased presence of foxes results in a higher predation rates on hares. The model results support hyperpredation of increasing fox populations on native hares.

Does the Introduction of Alien Species Represent a Sanitary Threat for Native Species? The Case of the Eastern Cottontail Sylvilagus floridanus in Italy

Introduction of alien species is a well-known threat to biodiversity. Where newly introduced, alien species may pose a risk for the local ecological community by competing for resources or by introducing pathogens. Sylvilagus floridanus is an American lagomorph introduced into Europe in the second half of 20th century, for hunting. This study evaluated the structure and epidemiological characteristics of the gastrointestinal parasite community in an introduced population of S. floridanus in the Province of Alessandria (Piedmont Region-Italy). Three alien parasites were reported out of 271 animals: Obeliscoides cuniculi in the stomach, Trichostrongylus calcaratus in the small intestine, and Passarulus nonnanulatus in the large intestine. All these nematodes are commonly reported in S. floridanus in its natural range, but they represent alien species in Europe. The report of these alien parasites is an example of the unexpected consequences caused by the introduction of non-native vertebrates. The documented introduction of new pathogens may alter the parasite community of the native lagomorphs, with possible long-term effects on local ecological dynamics.

“An American near Rome” … and not only! Presence of the eastern cottontail in Central Italy and potential impacts on the endemic and vulnerable Apennine hare

The eastern cottontail Sylvilagus floridanus has been introduced to Italy for hunting purposes since the 1960s. This species is currently present in northern Italy, with some small populations in Central Italy. Data for Central Italy are scanty, but they deserve research attention because this lagomorph is responsible for the spread of disease to an endemic vulnerable species, the Apennine hare Lepus corsicanus. In this work, we summarized the distribution of alien cottontails, over 50 years after their first releases, with special regard to areas where the endemic species is present. Eradication should be recommended where the alien species coexists with the endemic one.

First assessment of the potential introduction by hunters of eastern cottontail rabbits (Sylvilagus floridanus) in Spain

Context Humans have introduced lagomorph species in areas outside their native ranges for their meat, fur or value as game species. Assessing the rate of success of lagomorph introductions is vital to address the ecological damage they may cause. Cases of failed lagomorph introductions in apparently suitable areas may also shed light on mechanisms that may deter invasion, which are useful in developing strategies for population control. In Spain, it has been suggested that hunters introduced the non-native eastern cottontail (Sylvilagus floridanus) to compensate for the recent drastic declines of the native European rabbit (Oryctolagus cuniculus). Aims Our main goals were to investigate (1) whether Sylvilagus rabbits have indeed been introduced by hunters across Spain, and (2) whether the species has become established in Spanish ecosystems. Methods We interviewed 311 hunters or naturalists across Spain. The questionnaires inquired about the characteristics of game management in each locality, including the frequency of rabbit restocking, and particularly whether Sylvilagus rabbits had been released in the surveyed localities. In addition, we sampled 192 rabbit populations (n=3974 individuals) across Spain by using molecular analysis to determine whether Sylvilagus rabbits were present in these areas. Key results Our interview results suggest that Sylvilagus rabbits may have been released in 6% of the 311 localities surveyed. However, molecular analyses failed to confirm their persistence, because all samples belonged to O. cuniculus. Conclusions We infer that Sylvilagus rabbits failed to establish themselves in Spain, although interviewees reported their introduction. Several reasons may explain the unsuccessful establishment of this species, such as a low propagule pressure, competition with native species, predation, inability to cope with local pathogens and unsuitable climatic conditions. Implications The risk of future introductions of non-native game species can be reduced through the implementation of stricter regulations of animal releases into the wild. Long-term monitoring networks should be developed to help identify non-native game species before they become established and spread to neighbouring areas, thereby preventing any ecological or economic impacts these species may cause.