Range expansion and comparative habitat use of insular, congeneric lagomorphs: invasive European hares Lepus europaeus and endemic Irish hares Lepus timidus hibernicus

Abstract

The European hare (Lepus europaeus) has declined throughout its native range but invaded numerous regions where it has negatively impacted native wildlife. In southern Sweden, it replaces the native mountain hare (L. timidus) through competition and hybridisation. We investigated temporal change in the invasive range of the European hare in Ireland, and compared its habitat use with the endemic Irish hare (L. timidus hibernicus). The range of the European hare was three times larger and its core range twice as large in 2012-2013 than in 2005. Its rate of radial range expansion was 0.73 km year -1 with its introduction estimated to have occurred ca. 1970. Both species utilised improved and rough grasslands and exhibited markedly similar regression coefficients with almost every land cover variable examined. Irish hares were associated with low fibre and high sugar content grass (good quality grazing) whilst the invader had a greater tolerance for low quality forage. European hares were associated with habitat patch edge density, suggesting it may be more suited to using hedgerows as diurnal resting sites than the Irish hare. Consequently, the invader had a wider niche breadth than the native but their niche overlap was virtually complete. Given the impact of the European hare on native species elsewhere, and its apparent preadaption for improved grasslands interspersed with arable land (a habitat that covers 70 % of Ireland), its establishment and range expansion poses a significant threat to the ecological security of the endemic Irish hare, particularly given their ecological similarities.

Niche overlap of mountain hare subspecies and the vulnerability of their ranges to invasion by the European hare; the (bad) luck of the Irish

“…Certainly, the Irish hare shares much in common with the European hare, though the latter has a greater association with arable land, typical of its more easterly and central European distribution (Smith et al 2005). Indeed, previous studies have demonstrated that both species exhibit comparable niche breadths and almost complete niche overlap in Ireland Caravaggi et al 2015). Niche overlap metrics in the present study are, on the face of it, contradictory.…”

“…Our ENMs predict that most of Ireland is (and presumably was) unsuitable for the European hare, providing a potential explanation as to why most introductions failed. At present, there is a relatively range-restricted population of introduced European hares in Northern Ireland (Caravaggi et al 2015), the only region of Ireland currently predicted by our ENMs as being suitable for the species. Their range expanded three-fold between 2005 and 2012/2013 (Caravaggi et al 2015) with a core range populated solely by the invader being established recently (Caravaggi et al 2016).…”

“…At present, there is a relatively range-restricted population of introduced European hares in Northern Ireland (Caravaggi et al 2015), the only region of Ireland currently predicted by our ENMs as being suitable for the species. Their range expanded three-fold between 2005 and 2012/2013 (Caravaggi et al 2015) with a core range populated solely by the invader being established recently (Caravaggi et al 2016). Moreover, there is a high degree of multi-generational, bidirectional hybridisation in areas of sympatry (Hughes et al 2009;Prodöhl et al 2013).…”

“…The heath hare was isolated at the most southerly tip of the Scandinavian Peninsula, far from Russian European hares, and buffered by an expansive northern hare population to the north, while the Irish hare was isolated on an island. Thus, in contrast to other mountain hare subspecies, the niches of the heath and Irish hares were, and indeed, are particularly vulnerable to invasion by the ecologically similar European hare, with their populations susceptible to collapse upon contact with the latter after anthropogenic introductions (Thulin 2003;Caravaggi et al 2015). After the introduction of the European hare into southern Sweden, it expanded northwards, rapidly outcompeting and hybridising with the heath hare (Suchentrunk et al 1999;Thulin et al 2003;Winiger 2014) which is now said to be virtually extinct (Carl-Gustaf Thulin pers.…”

“…Other, more recently established contact zones are highly unstable with the larger European hare outcompeting and displacing the smaller mountain hare. Indeed, European hares have displaced mountain hares over much of southern Sweden (Jansson and Pehrson 2007) and part of southern Finland (Levänen et al 2015) during the twentith century, and part of Ireland in the last few decades Reid 2011;Caravaggi et al 2015Caravaggi et al , 2016. Thus, post-introduction sympatry is a typically transient phenomenon (Thulin 2003).…”