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Northern Long-eared Bat

Northern Long-eared BatThe Northern Long-eared Bat (Myotis septentrionalis) is found in many regions of Canada. Although there are numerous records of its presence in eastern Canada and the United States, it has only been recorded sporadically in the west. Presently, the Northern Long-eared Bat is on the Blue List of species that may be at risk in Alberta. 

This particular type of bat has two habitats: a winter hibernation habitat as well as a summer roosting and foraging habitat.
The Northern Long-eared Bat hibernates in caves or abandoned mines during the cold winter months. Within a cave the northern Long-eared bat intermingles with other species of bats, but forms a small proportion of the total hibernating population. Thus, hibernating Northern Long-eared Bats are never abundant. In Alberta, there are two known hibernacula used by Northern Long-eared Bats: Cadomin Cave, and Wood Buffalo National Park. Both of these hibernacula were shared with Little Brown Bats and Long-legged Bats, but specific site preferences within the hibernacula differed among species. In Alberta, bats often reach the hibernacula in late August and early September Hibernation begins when there are no longer sufficient numbers of flying insects to make continued foraging worthwhile (usually after one or two killing frosts in September).

Hanging Bat In general, bats choose hibernaculum sites that provide a relatively constant, low temperature with high humidity and no air currents. Within these sites, Northern Long-eared Bats usually hang singly in small narrow crevices and may therefore be easy to overlook. Despite their inconspicuous roosts, most records of Northern Long-eared Bats are of individuals found during hibernation. Depending on weather conditions, these bats generally begin emerging from the hibernaculum in late April or early May. 

During the summer months the Bats commonly use crevices behind peeling bark or cavities in partially-decayed trees as summer day roosts. Within thick forests, summer activity may be focused along watercourses and small ponds. Similarly, activity may also be high in the vicinity of artificial light sources such as streetlights and yard lights in association with the increased availability of night-flying insects. These isolated habitats fulfill a critical need and may affect choice of summer day roosts and night foraging areas.

During the summer, bats must accumulate enough resources to maintain the high metabolic costs associated with flight, and to gain sufficient fat reserves to hibernate for the winter. Female bats must accumulate greater energy reserves than males in order to produce and care for the offspring. Environmental conditions influence the ability of a female bat to successfully raise an offspring in any given season. When conditions such as high rainfall, cold weather, or windy evenings reduce insect availability, females may not be able to gather enough food and may delay or forego reproducing during that season. 

Young bats (pups) are particularly vulnerable immediately after birth. At this time they are unable to fly and are totally dependent on female for food. Any alteration of the roost that precludes entry or exit of the adults (such as a homeowner blocking a roost entrance) will result in death of the pup. Exclusion practices to remove bats from interior roosts in buildings should not be done between June and mid August. 

Bat inside a cave Unlike other small mammals the Northern Long-eared Bat are relatively long lived. The record age of a Northern Long-eared Bat in the wild is 19 years. Also in contrast to most small mammals, each female bat produces only one young each year. Most mortality in North American bat species occurs in the juvenile age class and many pups do not survive their first year. Additional mortality occurs during the hibernation period. If winters harsh, or if bats cannot obtain the fat reserves necessary to survive this period, they may starve. Juveniles are particularly vulnerable during hibernation because they have relatively short time after their birth to build up fat reserves.

Like all bat species in Canada, the Northern Long-eared Bat feeds exclusively on insects. Myotis bats are generally insectivores, and their diet is limited only by the size of the insects they are capable of catching. Although moths and beetles make up the majority of their diet, mosquitos, black flies, and other noxious pests also are consumed.  The disappearance of suitable food following killing frosts in the fall is the primary factor initiating hibernation. 

Parasites and diseases probably have minimal impact in most insectivorous bat species. However, bats can become infected with rabies virus and thus pose a public health concern. Rabies virus can cause fatal infections in all warm-blooded mammals and birds and is a concern for public safety and livestock health throughout the world. 

Reprinted from Alberta Wildlife Status Report No. 3, with permission from Alberta Sustainable Resource Development.

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