Academic journal article The American Midland Naturalist

The Conservation Value of Hedgerows for Small Mammals in Prince Edward Island, Canada

Academic journal article The American Midland Naturalist

The Conservation Value of Hedgerows for Small Mammals in Prince Edward Island, Canada

Article excerpt

ABSTRACT.-

The aim of this study was to investigate the use of hedgerows by small mammals in four agricultural landscapes in Prince Edward Island, Canada. The Island has one of the highest percentages of land (about 48%) devoted to crop production and pasture in all of Canada. Therefore, identifying the landscape elements that can mitigate the effects of habitat fragmentation resulting from agricultural practices is essential to preserve the biodiversity of Prince Edward Island. We quantified species richness, abundance and diversity of small mammals in 13 hedgerows and 13 attached forest patches. Although all the species detected in forest patches were also found in hedgerows, significant differences in species diversity and abundance suggest that not all species benefit equally from hedgerows. The abundance of small mammals other than the eastern chipmunk (Tamias striatus) increased in hedgerows longer than about 225-250 m, but was independent of hedgerow's length in hedgerows smaller than 225-250 m. Predators (Mustela erminea) were captured in hedgerows, but not in forest patches. Relationships between small mammal variables and hedgerow features (microhabitat, macrohabitat and landscape) suggested that most small mammal species would benefit from hedgerows having high shrub diversity, ground cover with vines and leaf litter, and few non-vegetated gaps. Removal of hedgerows, especially large ones, may affect long-term survival of some small mammal species inhabiting agricultural landscapes of Prince Edward Island.

INTRODUCTION

The economy of the province of Prince Edward Island (PBI, Canada) is greatly driven by the agricultural industry with approximately 48% of the island being devoted to agriculture (RTRLUS, 1997). During the last century, agricultural practices developed for large-scale crops production have led to the expansion of cultivated areas and have increased pressure on forest habitats. Forest habitats are small and fragmented in discrete patches, with approximately 32% of them being smaller than 0.5 ha (State of the Forest Report, 2003). In most of these agricultural landscapes, hedgerows are frequently used to alleviate the effects of habitat fragmentation. In PEI, most hedgerows were originally planted to reduce wind velocity (RTRLUS, 1997), thus they tend to be elongated patches of vegetation containing natural and planted species.

Although edge effects are likely extreme in hedgerows, several studies have found that hedgerows provide habitat and refuge sites for many small mammal species (Yahner, 1982, 1983; Wauters et al., 1994; Kotzageorgis and Mason, 1997; Henein et al., 1998; Laurance and Laurance, 1999; Tattersall et al., 2002). Hedgerows facilitate access to resources or habitat that might otherwise be too risky or remote for use or colonization (Henderson et al., 1985; Dmowski and Kozakiewicz, 1990; Clergeau and Burel, 1997). They can also provide winter cover for non-hibernator small mammals (e.g., Kotzageorgis and Mason, 1997) and can act as a movement corridor between forest patches (e.g., Wegner and Merriam, 1979; Bennett et al., 1994; Downes et al., 1997). However, linear habitats can increase predation and/or act as ecological traps and population sinks for some animal species (e.g., Clergeau and Burel, 1997).

The effectiveness of hedgerows as habitat or a movement corridor depends on their ability to retain a significant proportion of the local species pool of small mammals (Butet el al., 2006a). Several studies have shown that this effectiveness depends on structural features of hedgerows, including length, width, connectivity and internal habitat conditions. For example, Laurance and Laurance (1999) found that linear habitats of moderate width (20-80 m) were used by five of the six mammalian species that inhabited adjacent forest patches. However, it has also been shown that the conservation of entire small mammal communities in agricultural landscapes depends on hedgerow length per se (Butet et al. …

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