COSEWIC Assessment and Update Status Report on the Pacific Water Shrew Sorex bendirii in Canada ENDANGERED 2006 COSEWIC COSEPAC COMMITTEE ON THE STATUS OF COMITÉ SUR LA SITUATION ENDANGERED WILDLIFE DES ESPÈCES EN PÉRIL IN CANADA AU CANADA COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows: COSEWIC 2006. COSEWIC assessment and update status report on the Pacific watershrew Sorex bendirii in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 28 pp. (www.sararegistry.gc.ca/status/status_e.cfm). Previous report: Galindo-Leal, C. and J.B. Runciman. 1994. COSEWIC status report on the Pacific water shrew Sorex bendirii in Canada. Committee on the Status of Endangered Wildlife in Canada. 1-33 pp. Production note: COSEWIC would like to acknowledge David Nagorsen for writing the update status report on the Pacific water shrew Sorex bendirii, prepared under contract with Environment Canada, and overseen and edited by Mark Brigham, Co-chair (Terrestrial Mammals), COSEWIC Terrestrial Mammals Species Specialist Subcommittee. For additional copies contact: COSEWIC Secretariat c/o Canadian Wildlife Service Environment Canada Ottawa, ON K1A 0H3 Tel.: (819) 997-4991 / (819) 953-3215 Fax: (819) 994-3684 E-mail: COSEWIC/[email protected] http://www.cosewic.gc.ca Également disponible en français sous le titre Évaluation et Rapport de situation du COSEPAC sur la musaraigne de Bendire (Sorex bendirii) au Canada – Mise à jour. Cover illustration: Pacific water shrew – by Ron Altig. ©Her Majesty the Queen in Right of Canada 2006 Catalogue No. CW69-14/81-2006E-PDF ISBN 0-662-43286-X Recycled paper COSEWIC Assessment Summary Assessment Summary – April 2006 Common name Pacific water shrew Scientific name Sorex bendirii Status Endangered Reason for designation The habitat of this rare species, confined to the lower Fraser valley region of British Columbia, continues to decline and fragment as a result of development.There is little chance of rescue. It is extremely rare throughout its range. Occurrence British Columbia Status history Designated Threatened in April 1994 and in May 2000. Status re-examined and designated Endangered in April 2006. Last assessment based on an update status report. iii COSEWIC Executive Summary Pacific Water Shrew Sorex bendirii Species information The Pacific water shrew is the largest North American species of Sorex with a total length of 154 mm and a body mass of 10.6 g. The dorsal pelage ranges from dark brown to black; the undersides are dark brown. The tail is a unicoloured dark brown. The large hind feet have a stiff fringe of hairs up to 1 mm in length. Distribution The Pacific water shrew ranges from northern California through western Oregon and Washington to southwestern British Columbia in Canada. In Canada, the Pacific water shrew is confined to the lower Fraser River valley region in extreme southwestern British Columbia, where it ranges as far east as the Chilliwack River and Harrison Lake. Northern limits of the range are lower elevations (below 800 m) in the Coast Mountains on the north side of the Fraser River. The 142 known occurrence records represent about 44 distinct locations or sites. The extent of occurrence based on historical and recent occurrences is about 3,350 km2. Habitat The Pacific water shrew is associated with skunk cabbage marshes, red alder riparian and stream habitats, and dense wet forests of western redcedar. Most captures are in riparian habitats in close proximity to water. But individuals have been captured 25-350 m away from streams in forest. Although forested habitats are important, it has been found in non-forested grassy habitats bordering ditches and sloughs in British Columbia. There are no specific data on habitat trends and no quantitative data exist for the rate of habitat loss in the past 10 years. But wetlands and forested habitats have declined over the past 100 years. Protected areas are limited to 26 provincial and regional parks. Federal lands within the known range include 4 Department of National Defence properties and about 62 Indian Reserve lands. The amount of habitat on provincial Crown land is small, probably less than 20%. Biology The basic biology of this species has been little studied. It is primarily insectivorous eating insect larvae, slugs, snails, mayfly naiads, and earthworms. At least 25% of the prey iv is aquatic. The Pacific water shrew is semi-aquatic and capable of swimming and diving in water. It can swim continuously for up to 3.5 minutes and dive for up to 60 seconds. The breeding season extends from February to August with females producing two to three litters of five to seven young. The generation time is about one year. Population sizes and trends No estimates of population density exist for this species from any part of its range and the total number of individuals and the number of mature animals in Canada is unknown. The Pacific water shrew appears to be rare throughout its range. Nothing is known about yearly population fluctuations. Long-term population trends can only be inferred from anecdotal accounts and evidence from historical captures. Limiting factors and threats In Canada, the Pacific water shrew’s distribution coincides with a heavily urbanized area undergoing rapid development and habitat change. Rarity, coupled with its restriction to riparian and wetland habitats, make this species susceptible to habitat loss, fragmentation, and degradation from development. Housing, commercial, recreational (such as golf courses), and industrial development reduces forested areas and riparian habitats that border streams or wetlands and degrade habitat from run-off and storm water management. Special significance of the species The Pacific water shrew is a member of the Pacific Coastal faunal element, a group of coastal mammals that range from northern California to British Columbia and southeast Alaska. Existing protection This species was designated Threatened by COSEWIC in 1994. The status was re-examined and confirmed in May 2000. British Columbia has designated this species as S1S2 (critically imperiled or imperiled). The Pacific water shrew is protected from killing or collecting under the provincial Wildlife Act; it is listed as an Identified Wildlife Species under the British Columbia Provincial Forest and Range Practices Act. Riparian habitat protection is also provided by the Riparian Areas Regulation of the provincial Fish Protection Act. The Department of Fisheries and Oceans (DFO) also has a set of guidelines for establishing Fisheries Sensitive Zones that protect fish and fish habitat. The provincial Riparian Areas Regulation and the DFO regulations apply only to streams, creeks, ditches, or wetlands with fish or that are connected to fresh-water ecosystems with fish. None of the Pacific water shrew’s range is in a national park. Its known distributional area includes 5 provincial parks and 26 regional parks. Protected areas on the south side of the Fraser River are small with no connectivity. v COSEWIC HISTORY The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5th 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process. COSEWIC MANDATE The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens. COSEWIC MEMBERSHIP COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species. DEFINITIONS (2006) Wildlife Species A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and it is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years. Extinct (X) A wildlife species that no longer exists. Extirpated (XT) A wildlife species no longer existing in the wild in Canada, but occurring elsewhere. Endangered (E) A wildlife species facing imminent extirpation or extinction. Threatened (T) A wildlife species likely to become endangered if limiting factors are not reversed. Special Concern (SC)* A wildlife species that may become a threatened or an endangered