Evaluating Relocation as a Means to Deal with Nuisance Wildlife

March 5th, 2012 | Research

By: Curtis Bosson

It is necessary to understand and to think critically about all aspects of live-trapping. The live-capture of an animal may solve one problem, but it introduces another. That is, what will be done with the captured animal?

In 2010, I received a research grant from CAHT to explore the effectiveness and animal welfare outcome of one solution to this problem: relocation. The main goals of the project were to 1) relocate a common animal species and then track and analyse their spatial movements, and 2) recapture relocated animals and observe any changes to their health.

Eastern grey squirrels were used as a model species for the research. These squirrels are highly visible and common in Canada, and it has been suggested that they may possess homing abilities. Do not be fooled by their moniker (eastern grey squirrel), these small mammals live in the west as well as in the east, and they are almost as likely to be black as they are to be grey. The antics of these curious and apparently intelligent back-yard denizens delight many homeowners, as they are quite clever and can navigate through complex obstacles in their quest for food. However, their close relationship with humans means that they sometimes become a nuisance, which means that steps are taken to remove and exclude these animals from the home.

A relocated animal may find its way back to where it was captured (homing ability), be at risk of exposure to heat and cold due to a failure to find an adequate den, or be at risk of encountering more hazards, like roadways and predators, as it travels longer than normal distances. Moreover, if it meets a member of the same species, the resulting interaction is unpredictable, although if the species is territorial it is almost certain that the exchange will be an aggressive one. Thus, relocation may cause undue stress on the animal and perhaps cause death.

The Ontario Ministry of Natural Resources’ (OMNR) Animal Care Committee approved the research methods that I used,  and the study area was approved by the OMNR’s Guelph district office. To track released grey squirrels, I attached a radio-transmitting collar to 40 grey squirrels in Hamilton, ON.  Half of these squirrels were relocated to a forest having suitable habitat for grey squirrels more than 5 km away from the trap site. The collars each weighed 5.6 g and emitted a weak radio-frequency pulse that I detected using a hand held antenna and a portable receiver. The collars allowed me to track the squirrels as they went about the business of adjusting to their new environment. Each squirrel was tracked and located every other day for a 4-8 week period.

The results of my studies were interesting, and provided insight into the lifestyle of grey squirrels. First, I was quite surprised to observe that even control non-relocated grey squirrels sometimes traveled very long distances. The grey squirrel you see at your back yard bird feeder may be 2 km from home! Some control squirrels also “stayed overnight” a few kilometers from home, only to return some days later. Since grey squirrels are not territorial, they may share food and shelter, and thus they can usually enter the home area of other squirrels with impunity.

This apparently gives them some ability to move about in the landscape unharassed by other squirrels. Second, relocated grey squirrels moved longer distances than non-relocated squirrels as expected, because of the need to find food and shelter. However, I found that the relocated squirrels had good survival and minimal health issues (measured using weight change and stress hormone) after 4-8 weeks, perhaps because many were able to find shelter and had settled into a new home area. Only one relocated squirrel was able to find its way home although it took several weeks.

The main limitation of this research is the duration and season of tracking. These animals were relocated during the summer season but the results of this study may have differed had the animals been relocated during the winter season, when food and suitable nest sites are harder to find. It would be interesting to find out what the effects of relocation are on a territorial species, such as red squirrels, as these might be different. However, anyone considering relocation of nuisance animals should first consult with their local natural resources office, as this is illegal to do in some provinces (e.g. a relocation greater than 1 km is not allowed in Ontario).