Wildlife At Risk in British Columbia
A brochure series which will eventually include brochures on other Red 
and Blue listed species, including fish, invertebrates and plants, and on 
ecosystems. Produced by the Ministry of Environment, Lands and Parks, 
Wildlife Branch, 780 Blanshard St. Victoria, BC V8V 1X4. For copies of this 
brochure, write to the Wildlife Branch. Funded by Corporate Resource 
Inventory Initiative and Ministry of Environment, Lands and Parks.
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Undiscovered in Canada until 1979, this large bat of the dry southern interior 
is one of the rarest of North American bats.


Why are Spotted Bats at risk?
This spectacular black and white bat is confined to the arid regions of 
western North America from south-central British Columbia to northern 
Mexico. It has a patchy distribution within that range and is one of the 
rarest of North American bats. In British Columbia, it is only found in the 
dry southern and central valleys. It is found nowhere else in Canada.

Within its range in southern British Columbia, the abundance of Spotted 
Bats may be limited by availability of suitable day roosts, foraging terrain, 
food species, climate or other factors. Although rugged terrain is quite 
common, only certain sites might have crevices that are acceptable for 
roosting or nursery use. The bats seem to like cliffs that are well away 
from human activity and there is concern that land development below 
the roosts, or recreational activity on them, could cause the bats to 
abandon these sites.

Advancing residential and other development could also remove or alter 
some of the open ponderosa pine forests, meadows, and marshes where 
Spotted Bats feed. Chemicals used to control crop or forest pests could 
also adversely affect the food supply of these entirely insectivorous bats.

The Spotted Bat is obviously a very specialized animal in terms of its 
behaviour, food habits, and habitat needs. Being secretive and nocturnal, 
it has few natural enemies. However, subtle changes in the environment, 
either natural or human caused, could have a significant impact on the 
sparse populations of this bat in British Columbia.

What is their status?
The Spotted Bat was unknown in Canada until a small population was 
discovered in the southern Okanagan Valley in 1979, extending the 
previously known range northward by 900 kilometres. Additional Spotted 
Bats were discovered in the Similkameen River Valley in 1990, and in the 
Thompson River and Cariboo regions in 1992. In the 
Okanagan-Similkameen area, the species has been recorded north to 
Kelowna and west to Hedley, but is most common from Osoyoos to 
Penticton and near Keremeos. It has also been reported from Lytton to 
Ashcroft along the Thompson River, and in the Cariboo region, from Gang 
Ranch north to Williams Lake, and west to Bull Canyon on the Chilcotin 
River. Only a few bats have been noted in each area. The actual 
population size in British Columbia is not known.

The Spotted Bat is one of a number of wildlife species that, in British 
Columbia, occur only in the dry valleys of the southern and south-central 
interior. Further surveys will likely find it in additional areas, but this 
species appears to be confined to the Bunchgrass, Ponderosa Pine, and 
Interior Douglas fir zones, which in total comprise only about six percent 
of the area of the province.

Recognizing the rarity and vulnerability of the Spotted Bat, BC 
Environment placed it on its 1993 Blue List. Species on this list are 
considered to be vulnerable and at risk, in contrast to those on the Red 
List, which are being considered for legal designation as Threatened or 
Endangered. This species is nationally designated as “Vulnerable” by the 
Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 
The Spotted Bat, like other wildlife, receives general protection against 
harassment, killing or possession under the provincial Wildlife Act. 
However, most habitats used by these bats do not presently receive any 
special protection.

What do they look like?
The Spotted Bat (Euderma maculatum) is a large, unusually coloured bat, 
with a wingspan of about 35 centimetres. The total length of an adult bat is 
around 12 cm, of which slightly less than half is the tail. Adults weigh 
about 20 grams. In comparison, a one dollar coin weighs about 7 grams.

The fur on the back is black, with the three large white spots that give it its 
name located on each shoulder and on the rump, and a patch of white hair 
at the base of each ear. The underside is entirely white with black 
underfur. The Spotted Bat has huge ears, about 4 cm long. They are 
pinkish-gray in colour, and have many transverse ridges or “ribs.” The 
ears are held erect when the bat is in flight, and folded back over the neck 
and upper back when resting. Like all bats, the Spotted has five claws on 
each hind foot and uses these to hang head-down when roosting. The 
claws also enable it to climb on vertical rock faces. Male and female 
Spotted Bats are externally similar. The large size, enormous ears, and 
striking black-and-white colour pattern are so distinctive that this bat 
cannot be confused with any others.

Like most other bats, the Spotted Bat emits echolocation calls to navigate 
in the dark, to locate prey, and possibly to advertise its presence to other 
bats. Unlike most other bats, however, its low frequency call can be heard 
by humans at distances up to 250 metres. The call has been described as 
sounding like “a pebble hitting the highest strings on an opened piano.”

What makes them unique?
The Spotted Bat is not a very social species, and usually roosts and hunts 
alone. Although foraging areas of different individuals may overlap, they 
usually avoid being in the same place at the same time. They do not form 
the large hibernating colonies typical of many other kinds of bats. Social 
interactions appear to be restricted to mother-infant care, and the mating 
of adults.

Most Spotted Bat activity in British Columbia occurs from late April 
through October, although some flying individuals have been captured in 
southern Utah in December and January at temperatures down to 5°C. By 
late October, Spotted Bats in British Columbia have disappeared from 
their summer ranges. Perhaps they hibernate locally, or they may migrate 
south. Diligent bat researchers will, in time, undoubtedly solve this 
mystery.

Like other bats, the Spotted Bat readily becomes torpid (lethargic) when 
temperatures drop, but is easily aroused from this state. The body 
temperature of resting Spotted Bats declines at about the same rate as that 
of their environment, and body temperatures as low as 1°C have been 
recorded. At very high temperatures, blood flow to the ears and wing 
membranes is greatly increased to aid in cooling.

Spotted Bats are predicted to be fairly slow fliers. This is based on their 
rounded wing shape, and relatively heavy body in relation to the surface 
area of the wing. Observations of flying bats support these predictions. 
Although they are capable of slow flying, they are also very agile and are 
able to leap into flight from the ground.

Spotted Bats shun human activity and noise more than other kinds of bats, 
and are seldom found near paved roads or lighted areas. Their sensitivity 
to human-caused disturbance is in need of study.

How do they reproduce?
Spotted Bats are able to reproduce when one year of age, and females 
produce only one offspring per year. Because the mortality rate of adults 
is quite low, this low reproductive rate is normally sufficient to maintain a 
population.

Spotted Bats are believed to mate in the spring and to give birth in solitary 
roosts during June or July. The gestation period is not known. At birth, the 
single young is naked, with its eyes and ears closed, and weighs about 
four grams. A baby Spotted Bat born in captivity was found to nurse 
almost constantly for the first 48 hours. Its mother was gentle and 
attentive, frequently licking it and shielding it with partly outstretched 
wings. The female often flew with the young attached to a nipple, and 
seemed unhindered by the additional weight. In the wild, female Spotted 
Bats probably leave their young in protected crevices when they go on 
their lengthy feeding flights.

Most Spotted Bat mortality is thought to occur when the inexperienced 
young become independent and start foraging on their own. Like so many 
other aspects of the biology of this rare species, the precise timing of 
independence has yet to be determined.

What do they eat?
The Spotted Bat is a relatively specialized feeder, subsisting almost 
entirely on moths. It catches all its prey in the air, in contrast to some bats 
which glean insects from vegetation or the ground. Some moth species can 
hear the high-frequency echolocation calls of many bats, and take evasive 
action to avoid being captured. The Spotted Bat, however, has calls of 
lower frequency which are outside the hearing range of most moths, 
allowing it to successfully capitalize on this widespread source of food. 
These low frequency calls are better than the higher frequency calls of 
other species for finding fairly large prey at long distances, but are 
ineffective for locating small insects. As it swoops in on its prey, the 
Spotted Bat produces a “feeding buzz” which, like its echolocation call, is 
quite audible to our ears.

Radio-tracking studies in the Okanagan Valley indicate that Spotted Bats 
leave their roosts to forage about 15 minutes after sunset, return about two 
hours before sunrise, and spend five to six hours away from the roost. 
They are continuously airborne during this time, flying 5 to 15 m above 
the ground in large elliptical paths. In contrast, many other species of bats 
feed just after dusk and before dawn, and roost during the middle of the 
night. The Okanagan studies revealed that Spotted Bats caught prey on 
about 90 percent of their attacks, and that the time between attacks was 
about 45 seconds. Once a bat has caught a moth, it may bite off and 
discard the wings, legs and antennae before consuming the rest. 

The bats travelled 6 to 10 km from their roosts to their favourite feeding 
places. From May to July, they used the same commuting paths, fed in the 
same locations each night, and returned to the same roost each morning. 
Some foraging was also done while travelling to and from the main 
feeding sites. After early August, the bats became less predictable in their 
movements and did not always use the same roosts and foraging areas as 
in May, June and July. This may have been a response to changes in 
location of major prey species. Spotted Bats forage under a variety of 
conditions including wind, cloud cover, and light showers, but not heavy 
rain.

Where do they live?
In the southwestern United States, the Spotted Bat prefers arid desert, 
scrub and open forest habitat in rugged landscapes, with vertical cliffs or 
canyons for roosting, and with some water features such as springs, lakes, 
or rivers. Water holes seem to be particularly important for this and other 
species of bats in these desert habitats.

In British Columbia, Spotted Bats forage over a wide variety of forest, 
shrub, hayfield, rock and wetland habitats. Studies in the Okanagan-
Similkameen area indicated a preference for open areas of ponderosa pine 
forest and marshes. These bats have only been found at low elevations in 
this area. Foraging locations include Vaseux Lake, Inkaneep Provincial 
Park, Blue Lake, Madden Lake, Keremeos and lower Ashnola River. 
During summer, they roost individually by day in the crevices of vertical 
cliffs or canyon walls, often 100 m or more high. These cliffs and canyons 
are also used for rearing young. Crevices occupied by the bats are 2.0 to 
5.5 cm wide. Okanagan roosting cliffs may be up to 10 km away from 
regularly used foraging sites; roosts with the highest Spotted Bat 
abundance are Gallagher Bluff, Vaseux Canyon, McIntyre Bluff, and 
Spotted Bluff. Spotted Bats may sometimes be heard foraging along the 
dykes near the Osoyoos oxbows, or at the Vaseux Lake Bird Sanctuary.

In the Thompson and Cariboo areas, foraging habitats of Spotted Bats 
include arid sagebrush and Douglas fir uplands (usually near wetlands or 
rivers), riparian cottonwood shrub stands, hayfields, and abandoned 
pastures, in the vicinity of steep cliffs.

What can we do?
Much can be done to protect and manage the Spotted Bat in spite of a lack 
of detailed knowledge of its distribution, abundance, key habitats, and 
forage resources. However, the information base for Spotted Bats in the 
province must be improved. BC Environment and the provincial Habitat 
Conservation Fund, together with other agencies such as the World 
Wildlife Fund and Nature Trust of British Columbia, have supported 
recent research by university and museum scientists. This has focused on 
the ecology of Spotted Bat roosting and foraging behaviour, identification 
of critical habitats in the Okanagan and Similkameen valleys, and 
determination of the distribution and northern extent of the species. 
Several important foraging and roosting habitats have been identified in 
these areas. Although cliff roosts are relatively secure, there are plans to 
designate key sites as protected areas to prevent inadvertent disturbance 
by rock climbers or other recreationists. Further research and inventory 
are planned to improve the present sketchy picture of Spotted Bat 
distribution and abundance.

In addition, further studies are needed to determine whether human 
activities and land uses are in fact a threat to the continued existence of 
this little-known but valued member of our fauna. Concerned naturalists 
and the general public are encouraged to report sightings or calls of the 
Spotted Bat to Wildlife Branch staff, and to support programs aimed at 
preservation of this unusual and vulnerable mammal.

Around the world, disturbance of roosts, use of pesticides, forest cutting, 
and other activities have caused downward trends in many bat species 
and populations. In British Columbia, half of our 16 bat species are 
considered to be at risk, and are on either the Red or Blue lists. Bats in 
general are a neglected group, worthy of increased conservation effort.