Rogue bat: Just hanging out or a sign of disease?

Bats are important and fascinating animals. They eat tons of insect pests; keeping our crops and forests healthy and saving us billions of dollars in agricultural pest control each year. Several Canadian bat species are federally listed as endangered under the Species at Risk Act (SARA), increasing our responsibility to keep bats safe while also looking after our own health.

Photo courtesy of Jordi Segers

We’re always taught to be on the lookout for strange or abnormal behaviour in animals which can signal that an animal is sick. For bats in Canada, this generally means keeping an eye out for signs of rabies, which is a zoonotic disease that can affect both bats and humans (in addition to other mammals).  Abnormal behaviours in bats indicating a potential rabies infection often includes the following descriptors: daytime activity, found on the ground, unable to fly, or lack defensive or evasive actions when people attempt to handle them (Note: bats should only be touched if absolutely necessary and while wearing sufficiently protective gloves). But what exactly does this all mean? Bat biology sometimes prevents these behaviours from being simply defined. So let’s break it down:

No Defensive Behaviours When Threatened

This point is one of the easier ones to define. If a bat is slow to respond and does not defend itself when threatened by humans or other animals, it could be unwell. HOWEVER, this depends entirely on the time of year. When bats are hibernating, they are going to be unresponsive or very slow to react to a disturbance. This is also true for certain times of year when the temperature is low and bats go into what is known as “torpor”, a temporary state of decreased metabolic activity. For example, if a bat emerges from hibernation in the spring when it is warm, but then the temperature drops again, the bat might go into torpor. If a bat is found roosting on the side of a building during or after such weather conditions, it may not respond well to stimuli, and when encouraged, it may not be able to fly. If this is the case, the bat should be left alone and observed for a few days to see if it does become active and goes out to forage when the temperature increases. If it does, then it is acting completely normal. However, if it remains unresponsive in warmer temperatures, then this may be considered abnormal behaviour and a wildlife professional should be consulted and may need to euthanise the bat.

Unable to Fly

If a bat is in hibernation or torpor, it is not going to be able to fly properly. However, if a bat is observed over the course of several days and it continuously does not appear to fly at dusk on warm nights (approximately 10°C or above), then this may be a sign that the bat is injured or sick. If this is the case, a wildlife professional should be consulted and the bat may need to be euthanised.

Found on the Ground

If a bat is found on the ground, it may be a sign of a sick bat OR it could indicate that it is a juvenile bat still relatively new to flying that has not quite nailed the perfect swoop yet. Juvenile bats that are born in the summer typically become “volant” (able to fly) around three weeks after birth, which generally is sometime from late July to early August for our Canadian bat species. At this time of year, it is common to hear reports of bats being found on the ground outside, on the floor of houses, and elsewhere. In many instances, these are simply juvenile bats making their first attempts at flying. Especially during this period of time, a bat found on the ground does not necessarily indicate that the bat is sick. If a bat is found on the ground and there is no risk of human or domestic animal contact, it should be placed (wearing appropriately protective gloves) in a location where the bat will be safe and there is no chance for contact with people or animals. Suitable locations may include the trunk or branch of a nearby tree, or on a ledge or wall of an adjacent building. Subsequently, the bat can be observed for a few days to see whether or not it displays other signs of disease (e.g., it does not go out to forage on nights of good weather). If so, a wildlife professional should be consulted and euthanasia may need to occur.

Daytime Observations

Bats are nocturnal, and typically do not fly during daylight hours if they are healthy. However, bats roosting outside in the daylight are a fairly common occurrence in the spring when bats emerge from hibernation and move to their summer roost sites (May-June), and again in the late summer and fall (August-October) when they move from their summer roost sites back to their hibernation sites. When the bats are in transit at these times of year, they may stop over to roost for a day or two in what we may consider to be an unusual place. Some of their favourite spots include the walls of warm brick buildings and the soft folds of patio umbrellas. After a few days, the bats typically move on without needing any encouragement from us. If the weather is not too cold (i.e., torpor-inducing), the bat will likely go out to forage after dusk before returning to its temporary roost spot at dawn the next day. If the bat does not continue to forage on nights of good weather, then this could be considered abnormal behaviour. An additional consideration would be if bats are observed roosting outside in the daytime in below 0ºC temperatures during the hibernation season (November-April). This may indicate that the bat is infected with white-nose syndrome (WNS), or is sick from other causes, and a wildlife professional should be consulted to determine if euthanasia is required.

Bats should NOT be euthanised in the following situations without further assessment:

  • A bat is found roosting on the outside of a building in the daytime with NO known or suspected contact with a human and/or domestic animal.
  • A bat is found in a public place with NO known or suspected contact with a human and/or domestic animal.

Bats should be euthanised immediately and submitted for testing in the following situations:

  • There has been known contact between a bat and a human and/or domestic animal.
  • A bat has been found in a room with an unattended child, a sleeping person, a mentally impaired person, or a person under the influence of drugs or alcohol to the extent that it could impair their judgment.
  • The bat is suffering from severe and obvious trauma (g., a broken wing).

If there is even suspected contact with a bat and a human and/or domestic animal, then the appropriate health authorities (i.e., provincial health department and/or provincial veterinarian) should be contacted immediately and the bat should be kept. If the bat is still alive, keep it in a secure container with small air holes. If the bat is already dead, double bag it and put it in a safe place away from people and animals. Remember to wear sufficiently protective gloves when handling bats that are either dead or alive. Euthanised bats that have not come into contact with a human and/or domestic animal can be submitted to the CWHC by contacting the Regional Centre nearest you:

Submitted by:

Tessa McBurney, CWHC-Atlantic

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