Action for Riparian Mammal Conservation in the Erewash Valley
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A Report for the People’s Trust for Endangered Species Action for Riparian Mammal Conservation in the Erewash Valley by Esther F. Kettel October 2014 Action for Riparian Mammal Conservation in the Erewash Valley Abstract Riparian mammals have suffered declines in recent decades in the UK due to water pollution, loss of habitat, persecution and the introduction of non-native species. This project aims to determine the distribution of otters, water voles, American mink and water shrews in the Erewash Valley with the aim of updating information which is now very out-dated or non-existent. 58 sites were surveyed, which included river, canal (working and disused), brooks and any other water bodies in the Valley; 60 percent showed signs of water voles and findings suggest that signs are more likely to be found in areas with a high water quality score, and in the river and disused canal. Only two signs of otter were found and five signs of mink, four of which also showed signs of water voles. Of the 42 sites which had bait tubes, 33 contained water shrew scat and the likelihood of finding water shrew scat in a bait tube was not affected by the habitat quality or other habitat characteristics. Acknowledgments First of all I would like to thank the People’s Trust for Endangered Species for kindly funding this project. I would also like to thank Nottinghamshire Wildlife Trust, in particular to Michael Walker and Janice Bradley for providing me with the opportunity to carry out the work, and to Ruth Testa and Claire Sambridge for help with fieldwork. Finally, to Matthew Edwards, Philip Bych and Katie Freeman for all their hard work and help with surveys. 1 Action for Riparian Mammal Conservation in the Erewash Valley Contents Introduction ................................................................................................................................ 3 Otters (Lutra lutra) .............................................................................................................................. 3 Water Voles (Arvicola amphibious) .................................................................................................... 5 Water Shrews (Neomys fodiens) ......................................................................................................... 7 Project Aims ........................................................................................................................................ 9 Study Area and Methodology ....................................................................................................... 9 Study Area ........................................................................................................................................... 9 Survey Methodology ........................................................................................................................... 9 Statistical Analysis ............................................................................................................................. 10 Results ....................................................................................................................................... 11 Habitat Quality Score ........................................................................................................................ 11 General .............................................................................................................................................. 11 Discussion .................................................................................................................................. 16 References ................................................................................................................................. 18 Appendix ................................................................................................................................... 19 2 Action for Riparian Mammal Conservation in the Erewash Valley Introduction Rivers in the UK support a variety of life including aquatic plants and invertebrates, fish, birds, bats and other mammals, including three which are particularly iconic: otters (Lutra lutra), water voles (Arvicola amphibious) and water shrews (Neomys fodiens). However, past engineering works, pollution, and invasive species have all had a harmful impact on the habitat and the life which it supports. Some taxonomic groups of invertebrates (Boon, 1988), including white-clawed crayfish (Austropotamobius pallipes) (Holdich and Reeve, 1991) and bats (Vaughan, Jones and Harris, 1996), for example, have all been adversely affected. More recently, however, effort has been put in to the restoration and improvement of Britain’s rivers and their tributaries by non-governmental organisations and through the Water Framework Directive. Despite our efforts, the success in restoring communities has shown varying results; white-clawed crayfish are still declining and are in danger of extinction (Buglife, 2013), whilst macro- invertebrate communities have shown to recover after restoration (Frieberg et al., 1998). For others, their recovery and distribution is less clear in some parts of the UK, emphasising the need for surveys in order to improve our understanding and thus our conservation efforts. Otters (Lutra lutra) One of Britain’s largest carnivores, the Eurasian otter is a semi-aquatic mammal with dark brown fur, a pale throat and underparts with short legs, a long, sinuous body and webbed feet, adept for an aquatic lifestyle (Woodroffe, 2007). With the exception of coastal populations in Scotland the otter is largely nocturnal, feeding primarily on fish (Woodroffe, 2007); as opportunistic hunters, they will also feed on a small number of frogs, birds, mammals and invertebrates (Copp and Roche, 2003). The species has a rather large distribution worldwide and can be found throughout Europe, parts of Asia and Africa (Corbet and Southern, 1977). In the UK, it suffered substantial declines during the 1950s onwards due to the use of pesticides and habitat loss (Ward, Holmes and José, 1994); the most recent national otter survey, however, has indicated that it is recovering throughout much of the country as a result of legal protection, an improvement in water quality and the ban on certain pesticides (Crawford, 2010). Since 2000, the majority of otter reports in Nottinghamshire have been to the south of the county, including in and around Attenborough Nature Reserve and around the River Trent (Figure 1.1). 3 Action for Riparian Mammal Conservation in the Erewash Valley Otter 0 Key = recorded since 2000 = pre 2000 record 9 8 7 6 5 4 3 5 6 7 8 9 Figure 1.1 Records of otters in Nottinghamshire pre and post 2000. 4 Action for Riparian Mammal Conservation in the Erewash Valley Water Voles (Arvicola amphibious) Water voles are rat-sized semi-aquatic rodents with a rounded muzzle, small, non-protruding ears and chestnut brown (or occasionally black) fur (Corbet and Southern, 1977). Active day and night, water voles create runways and burrows close to the water’s edge and are predominantly vegetarian, consuming roots and rhizomes and coarse vegetation such as grasses, rushes, reeds and sedges (Strachan and Jefferies, 1990). Found throughout the slow-flowing rivers, ditches, ponds and streams of Europe, except for parts of France, Italy and Greece, extending in to Asia, the water vole is rather widely distributed (Corbet and Southern, 1977). They are widespread throughout the lowland regions of the UK, but are absent from Ireland, north-west Scotland and many islands (Ward, Holmes and José, 1994). However, water voles have recently suffered substantial declines across much of their range due to pollution and loss of habitat and predation from the non-native American mink (Neovison vison) (Strachan and Jefferies, 1990). In Nottinghamshire, water voles are rather widespread and signs of them have been recorded across the county, including along the River Erewash, Nottingham Canal and around Attenborough Nature Reserve (Figure 1.2). 5 Action for Riparian Mammal Conservation in the Erewash Valley Water Vole 0 Key = recorded since 2000 = pre 2000 record 9 8 7 6 5 4 3 5 6 7 8 9 Figure 1.2 Records of water voles in Nottinghamshire pre and post 2000. 6 Action for Riparian Mammal Conservation in the Erewash Valley Water Shrews (Neomys fodiens) One of the least known British mammals, the water shrew is the only aquatic species of the country’s shrews, occupying similar habitat to the water vole. They have high metabolic demands and need to feed at regular intervals, thus are active day and night but activity is mostly at dawn and dusk (Carter and Churchfield, 2006a). Water shrews feed on terrestrial invertebrates, but unlike other species of shrew in the UK, also consume aquatic invertebrates, making up 50 percent of their diet (Carter and Churchfield, 2006a). They can be distinguished from other shrew species by their black upper fur and larger size (Corbet and Southern, 1977). Not unlike water voles, water shrews can be found in most of Europe except for the Mediterranean region, stretching to some western parts of Asia; in the UK, they are widely spread but absent from Ireland and some northern parts of Scotland (Corbet and Southern, 1977). There has been no evidence of an overall population decline (due to the paucity of data), but local declines have been noted, with pollution and habitat loss the likely cause (Carter and Churchfield, 2006b). Signs for water shrew are less obvious than for otters and water voles, thus reports