Raccoons may be Toronto’s unofficial mascot, but the furry creatures that plunder our green bins are far from the only wild animals that live among us.
“Toronto has a lot of wildlife,” says Tiziana Gelmi Candusso, postdoctoral researcher in the University of Toronto‘s department of ecology and evolutionary biology (EEB) and School of Cities in the Faculty of Arts & Science.
Using "camera traps,” Gelmi Candusso studies how urban mammals select their habitat, how they travel and how different species interact – both through animal-animal and plant-animal interactions.
“We don’t always see them because they‘re mainly nocturnal, but we have so many species of mammals detected in our cameras, from small chipmunks to large deer,” she says. “Most are in the ravine system and because we have such an intricate ravine system in the city, many species are present virtually everywhere.”
The remote cameras used by Gelmi Candusso and her colleagues are placed in the field, with shutters triggered by the movement of animals. They offer advantages over research tools such as GPS collars – which require animal trapping – and labour-intensive data-gathering techniques that depend on collecting scat or hair samples.
In a paper published in the journal Food Webs, Gelmi Candusso and her colleagues describe how they tested the effectiveness of these devices in gathering data about coyote and fox predation.
Gelmi Candusso‘s co-authors on the paper included graduate students Chris Brimacombe and Germain Collinge Ménard, as well as University Professor Marie-Josée Fortin – all with EEB. Gelmi-Candusso is a member of Fortin’s lab and is also funded through the Deutsche Forschungsgemeinschaft Research Fellowship, Fortin Canada Research Chair and a contribution by Péter Molnár, an associate professor at U of T Scarborough. Since May, Gelmi Candusso has also been part of the School of Cities postdoctoral fellowship program.
The team used 33 cameras located throughout the Greater Toronto Area. Many were located along the shore of Lake Ontario east of downtown, the Don River valley and the Humber River valley. Their study looked at images captured between October 2020 to September 2021. That included 2361 images of foxes and 1195 of coyotes.
Out of those, Gelmi Candusso and her collaborators found 43 images in which coyotes and foxes carried prey in their mouths. For coyotes, that mostly meant mice, voles, rabbits and squirrels; for foxes, it was birds, rabbits, squirrels and small rodents.
They also looked at separate images of predators and prey species that were taken by the same camera less than five minutes apart, reasoning that the proximity of the animals could lead to a predation event. They found 299 such encounters.
In analyzing their photographic “catch,” Gelmi Candusso and her collaborators found their camera trap data to be consistent with previous studies using other data-collection methods. They also found that the predation and potential predation images were complementary, as predation images underestimated the number of large mammals caught, and potential encounter events underestimated the number of small mammals caught.