SEPAQ | Fewer deer, more biodiversity

SEPAQ has seriously reduced the number of deer in the Îles-de-Boucherville and Mont-Saint-Bruno parks. It now remains to be seen at what pace the vegetation will regain its rights.

“It will take a few years and we will have to get down on all fours at the beginning to achieve it because it will be small seedlings that will establish themselves,” says Jean-Pierre Tremblay, professor in the biology department of the University. Laval.

The Îles-de-Boucherville and Mont-Saint Bruno parks had a serious problem with deer overpopulation (or white-tailed deer, to be more exact). In the winter of 2022-2023, 436 deer were recorded at Parc des Îles-de-Boucherville and 353 at Parc du Mont-Saint-Bruno.

However, the optimal density is 5 deer per square kilometer. We can go up to 10. Given its size, the Îles-de-Boucherville park should only be home to 40 to 80 deer. For the Mont-Saint-Bruno park, we are talking about 45 to 90 deer.

Such overpopulation has consequences on the biodiversity of these parks: the deer, in excessive numbers, graze on all the shoots. In the Îles-de-Boucherville park, we have installed a few “exclosures”, which protect the vegetation against the greed of deer.

“When you look at the diversity of vegetation that is inside these exclosures, when you see the height of the shoots, you understand the loss of biodiversity in the territory outside the exclosures,” argues Simon Boivin, spokesperson for SEPAQ.

He also compares Mont-Saint-Bruno Park to Oka Park, which does not have the same problem of deer overpopulation.

“In Oka, in spring we see a carpet of white trilliums, a flower of which we have almost lost track in Mont-Saint-Bruno. »

The latter park has practically lost what is called the low shrub layer, or the first meter of vegetation from the ground. It was a popular environment for species like the blue warbler, which has almost disappeared from Mont-Saint-Bruno.

Jean-Pierre Tremblay notes that invasive plants, such as alder-leaved buckthorn, were able to proliferate because they were resistant to deer browsing.

Last December, SEPAQ called on a firm of experts who followed the method recommended by the Canadian Council on Animal Care and the American Veterinary Medical and carried out the slaughter of 319 deer at Parc des Îles- de-Boucherville and 80 deer at Mont-Saint-Bruno Park.

The generous hunters program of the Quebec Federation of Hunters and Fishermen sent 14,000 pounds of venison to food banks, which represents more than 89,000 portions.

However, with the births this spring, the density is still far too high in both parks.

The Healthy Parks project, which brings together organizations, municipalities and scientists from different universities, will document the impacts of these operations. Jean-Pierre Tremblay’s team has just placed groups of sentinel plants, namely red oak shoots, in Mont-Saint-Bruno and silver maple shoots in the Îles-de-Boucherville, in order to monitor the degree monthly. grazing and survival rate.

Last year, SEPAQ followed the protocol proposed by Mr. Tremblay and placed the first groups of sentinel plants in the two parks.

“This allows us to have a zero year, before the reduction operation,” indicates Simon Boivin. I don’t have the exact figures, but it was covered up pretty quickly. »

Martin Leclerc, associate professor in the biology department of the University of Sherbrooke, is developing a research program on the movements of deer in the various parks of the metropolitan region.

“We don’t know much about the movements of white-tailed deer in a peri-urban matrix,” he says. All around the parks there is a lot of agriculture, roads, highways, residential neighborhoods. We want to know how the deer move within the park, but also how they use nearby habitats. »

Researchers will install GPS collars on the necks of deer in various parks in the region. It will be interesting to see if deer from outside the parks will replace those that were killed, particularly in Mont-Saint-Bruno.

“It is possible that travel will be difficult, for example because of Highway 30 and Highway 20,” says Mr. Leclerc. There has been a reduction in density, but that doesn’t mean it will fill up quickly. The vegetation has probably been degraded, maybe it’s not as attractive to deer. »