Observations of Wood Bison Swimming across the Liard River, Northwest Territories, Canada

Abstract

ABSTRACT. We observed a group of 18 wood bison, of mixed sex and age classes, swimming across a 1.7 km wide section of the Liard River on 16 July 2002. Water levels and flow rates were above the long-term average for that time of year, and there was a river current of 14 -16 km/h. The animals took at least 27 minutes to negotiate their 3.6 km swim. Younger animals were able to keep more of their head and body above the water level than older mature males. Calves of the year, observed swimming across a secondary channel of the river on 15 July 2003, had only their heads above water. Bison are capable of swimming across lakes and rivers (Wood Buffalo National Park, Yellowstone National Park), but well-documented cases of bison navigating rapidly flowing northern rivers are rare. Open-water crossings of the Liard River are important to the ecology of the Nahanni wood bison population, especially since seismic activity in the Liard River Valley is likely to increase.

Late PleistoceneBison antiquusfrom Orcas Island, Washington, and the biogeographic importance of an early postglacial land mammal dispersal corridor from the mainland to Vancouver Island

“…Wood bison were observed swimming 3.6 km across Liard River, with a current of 14-16 km/h. Mature males had more difficulty keeping their heads above water than did subadults, but the group swam at least 27 min (Larter et al, 2003). Other insular bovids must have swum across salt water (Croft et al, 2006).…”

Individual-based seasonal habitat selection in a forest-dwelling population of reintroduced bison Bison bison

“…During summer, bison consistently selected fluvial habitats such as riverine gravel bars and islands, where sedges and willows grow (Larter et al 2003). Nahanni bison frequent the Liard River corridor and regularly cross the river to reach riparian foraging areas, despite the risk of drowning (Larter et al 2003, Thomas et al 2021). The strong association of Nahanni bison with riverine habitat is a unique aspect of their ecology, and is likely an adaptation to low forage availability.…”

Insular mammalian fauna dynamics and paleogeography: A lesson from the Western Mediterranean islands

“…Most terrestrial animals show a low swimming ability, or are able to float but only for very short distances, as for instance some primates (Riopelle & Hubbard 1982;Zinner et al 2009;Bender & Bender 2013), antelopes (Cotterill 2003), large bo-vids (e.g. Larter et al 2003;Wilson et al 2009) and a few suids (Oliver et al 1993) sometimes do. Horses can swim over very short distances, but swimming imposes considerable physiological demands and they have neither strong swimming skills nor the propensity to venture into water (Thomas et al 1980;Tokuri et al 1999).…”