Spotted bat (Euderma maculatum) COSEWIC assessment and status report: chapter 8

Limiting Factors and Threats

Pierson and Rainey (1998) noted that rarity coupled with specialized roosting requirements and a patchy distribution make the Spotted Bat a species of conservation concern throughout its range.

There are no obvious threats to habitats used for foraging and roosting. The availability of suitable roosting sites may be a limiting factor the Spotted Bat in Canada. Sarell and Haney (2000) found that cliff roosts were patchily distributed throughout the southern Okanagan Valley with most separated by 2 km or more. Specific threats to these cliff roosts include rock climbing and helicopter activity near cliffs associated with mountain helicopter training. However, these activities appear to be limited to a few cliffs in the south Okanagan region. Rock quarries, road construction, or forest harvesting at the base of cliffs could also impact roosting Spotted Bats as there is some anecdotal evidence that this species is sensitive noise disturbance (Garcia et al. 1995). Although natural habitats particularly in the southern Okanagan and Similkameen valleys have been modified by agriculture and urban development, the Spotted Bat evidently is flexible in its foraging habitat foraging over hay fields, abandoned fields, and golf courses.

It is unlikely that this species’ moth prey base is limiting. According to Don Lafontaine (pers. obser.), moth diversity in the Okanagan valley is highest in the antelope-brush (Purshia tridentata) and big sagebrush (Artemisia tridentata) steppe. Croplands and orchards are poor in diversity, but they tend to support high densities of a few moth species. In major fruit growing regions such as the Okanagan Valley, pesticides are applied to control agricultural pests. The impact of pesticides on Spotted Bat prey is unknown.

Although disturbance at hibernacula is a major conservation concern for many temperate bats, the location of the Canadian population of Spotted Bats in winter is unknown. Winter surveys of 18 caves and mines within the Canadian range found no hibernating Spotted Bats (Nagorsen et al. 1993). This bat may hibernate in cliff faces within its summer range or migrate to unknown hibernation sites in the United States. Because its day roosts are inaccessible and it forages in flight, predation is rare. There is no evidence that disease is a limiting factor

Page details

Date modified: