Keen's long-eared bat (Myotis keenii) COSEWIC assessment and status report: chapter 2

Executive Summary

Keen’s Long-eared Bat
Myotis Keenii

Species information

Keen’s long-eared bat Myotis keenii (Merriam, 1895) is one of 6 morphologically very similar long-eared Myotis bats found in North America. Taxonomically, it is placed in the evotis group along with the western long-eared bat (M. evotis), northern long-eared bat (M. septentrionalis) and southwestern myotis (M. auriculus), although recent mtDNA analysis has demonstrated that it may actually be in a monophyletic group with M. evotis, fringed bat (M. thysanodes) and Miller’s myotis (M. milleri). M. keenii and M. evotis are morphologically so similar that they are impossible to identify in the field, making this species difficult to study in southwestern BC and western Washington where the two are sympatric. Their low mtDNA sequence divergence suggests that M. keenii and M. evotis could be conspecific.

Distribution

Globally, M. keenii has one of the most restricted distributions of any bat in North America, being limited to western Washington State, western British Columbia and southeastern Alaska. It is the only North American bat confined to the Pacific coast. It has been recorded at twenty-five locations in Canada.

Habitat

Ecomorphological characteristics (short, broad wings and long ears) and a high frequency, low intensity echolocation call suggest that M. keenii is adapted to a coastal old growth rainforest environment, although it does not appear to be limited to this habitat. It has also been captured foraging in estuaries, riparian habitats, and urban environments.

M. keenii is known to roost in rock crevices and under boulders, but has also been found roosting in trees and buildings, and under bridges. The only maternity colony described in detail is unusual in that it is associated with hydrothermal activity. At Gandl K’in Gwaayaay, Haida Gwaii, approximately 40 reproductive females take advantage of heated crevices, boulders and a small cave in which to roost and raise their young. The only other known maternity colony was suspected to be in a tree located in a low elevation, southwest-facing cliff at Knoll Hill near Tahsis, Vancouver Island.

The only known hibernacula are on northern Vancouver Island where M. keenii has been found in 8 caves from 3 separate areas.  In the Weymer Creek drainage, 4 species of bats have been captured while ‘swarming’ in August at the entrances of at least 14 high elevation (550 m – 945 m) caves, and M. keenii has been confirmed as hibernating in three of them. Conditions where bats were hibernating were a constant 100% relative humidity and a stable temperature of 2.4 ° – 4.0° C.

Biology

Detailed reproductive information comes from a two-year study of the Gandl K’in Gwaayaay maternity colony on Haida Gwaii. Female M. keenii returned to this colony near the end of May, and parturition occurred during early July. Non-reproductive females and males did not appear to use the nursery roosts before July. Young became volant by early August but continued to use the nursery roosts into early September. Adults left the colony once young were flying.

Reproductive chronology of the bats at the Gandl K’in Gwaayaay maternity colony was variable and dependent on weather conditions. For M. keenii, gestation appeared to be shorter during the cool, wet year of 1999 than during the warm, dry year of 1998. This was attributed to its ability to glean prey, which allowed it to continue to forage under cool, wet conditions when insects were less likely to be flying, and to prey on non-flying invertebrates. Results of faecal analysis supported this conclusion in that M. keenii at Gandl K’in Gwaayaay fed primarily on spiders and Lepidoptera. There was no evidence that food was a limiting factor.

M. keenii is probably long-lived like most other bats. The oldest known M. keenii was 12 years and 11 months old at the time of recapture.

Population sizes and trends

No estimates of population size or trend are available for this species. The maternity colony at Gandl K’in Gwaayaay has remained viable for at least the last 40 years despite extensive scientific collections during the 1960s. Population estimates made during the 1990s indicate that it remained stable between 1991 and 2000. Elsewhere within its range, M. keenii is rarely encountered although this may be due in part, to the problem of identifying it in the field.

Limiting factors and threats

Habitat loss may be an important threat to M. keenii. Although M. keenii does not appear to be limited to coastal old growth forests, it does forage in these habitats. These forests continue to be logged, and patches of old growth forest are becoming scarce.

Disturbance resulting from human activities is also an important threat, as all known hibernacula remain open to recreational cavers. Hibernating bats are particularly vulnerable to disturbance and winter arousal, which are energetically demanding and could exhaust a bat’s fat reserves. While forest harvesting activities near cave entrances do not appear to modify cave microclimate, fallen debris may block access and blasting activities from road construction could arouse hibernating bats.

M. keenii ‘s behaviour of flying close to the ground makes it vulnerable to predation by cats and possibly other mammals such as raccoons, marten, squirrels and rats. It is also vulnerable to predation by deer mice (Peromyscus maniculatus, Peromyscus keeni) during hibernation and when roosting under boulders or in crevices. Owls occasionally prey on bats but the significance of this predator on M. keenii is unknown.

Special significance of the species

M. keenii is of special significance because about 80% of its range occurs within Canada. It is currently the only bat species listed as an Identified Wildlife Species under the Identified Wildlife Management Strategy of the British Columbia Provincial Forest and Range Practices Code.

Existing protection or other status designations

This species is not listed by the IUCN. It was designated as a Species of Special Concern by COSEWIC in 1988 (see Balcombe 1988). The global heritage status rank is G2; national ranks are N1 for theUnited Statesand N1N3 for Canada. M. keenii is ranked SH for both Alaska and Washington States. British Columbia has designated the species as S1S3 and also provides protection from it being killed under the provincial Wildlife Act.

To date, only one Wildlife Habitat Area has been designated (Knoll Hill Cave) under the Forest and Range Practices Code -- it protects a maternity site near Tahsis, Vancouver Island. Nearby, Weymer Cave and White Ridge Provincial Parks protect areas that support M. keenii hibernacula and roosting habitat. The former park has a draft management plan that identifies the need to protect the bat roosts, but also identifies recreational caving, hiking, and tourism as acceptable park activities. The latter park has no management plan. The maternity colony at Gandl K'in Gwaayaay is protected by Gwaii Haanas National Park Reserve and Haida Heritage Site. An area plan has been prepared for the island that documents the re-development of the area while taking into consideration the protection of the colony. Gwaii Haanas staff monitor bat use of the colony and the island for the presence of introduced species.

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. On June 5, 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 and include 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 organizations (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biosystematic Partnership, chaired by the Canadian Museum of Nature), three nonjurisdictional members and the co-chairs of the species specialist and the Aboriginal Traditional Knowledge subcommittees. The committee meets to consider status reports on candidate species.

Definitions (After May 2003)

Species
Any indigenous species, subspecies, variety, or geographically or genetically distinct population of wild fauna and flora.

Extinct (X)
A species that no longer exists.

Extirpated (XT)
A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A species facing imminent extirpation or extinction.

Threatened (T
A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)Footnotea
A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)Footnoteb
A species that has been evaluated and found to be not at risk.

Data Deficient (DD)Footnotec
A species for which there is insufficient scientific information to support status designation.

 

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

 

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