The return of bison to Banff National Park, and keeping them there

Submitted by editor on 15 December 2020. Get the paper!

By David Laskin

After nearly a 150-year absence, 31 plains bison (Bison bison) were recently reintroduced to a 1200 km2 wilderness area in the heart of Banff National Park, Canada. As North America’s largest land mammal, the return of these animals aims to restore ecosystem balance as many species currently in the park co-evolved with bison over millennia. Once numbering in the tens of millions, overhunting in the 1800’s left fewer than 1000 bison on the continent.

Reintroductions have become an increasingly effective conservation strategy for extirpated species, but unsurprisingly they are met with many challenges – especially if the species are large mammals with a tendency to roam. We used a number of strategies to anchor the herd to the target reintroduction zone, and one of them was to strategically place discrete sections of drift-fence at locations along the zone boundary. However, introducing fences to a wilderness landscape is potentially problematic and presented us with the challenge of designing a fence that would effectively keep bison in while letting other wildlife pass through.

In our paper we addressed this seemingly contradictory objective by testing six different fence designs and their varying permeability to wildlife. Using a remote camera network we observed and quantified the crossing success of 12 sympatric mammal species that share the reintroduction zone with the bison. We also used GPS collar telemetry to assess the effects of the fences on the broad-scale movement of wolves and elk.

We recorded 6104 wildlife-fence interactions and found a single design that maximizes permeability for several species with diverse crossing strategies, but can be adjusted to effectively contain bison when they are in the area. We also found that adding fences to the landscape did not affect wolf or elk movements at a broader-scale – even when the fences were deployed in less-permeable configurations.

It is approaching three years since the bison were released and the herd is now thriving within the park. The drift fences have been a critical component in this success and have been one of several critical tools in helping the herd develop site fidelity to the reintroduction zone. We are optimistic that our low-impact fence design can be employed in reintroductions elsewhere as this conservation strategy gains momentum around the world (photo credits: Karsten Heuer).