Abstract
Interest in bison (Bison bison, B. bonasus) conservation and restoration continues to grow globally. In Canada, plains bison (B. b. bison) are threatened, occupying less than 0.5% of their former range. The largest threat to their recovery is the lack of habitat in which they are considered compatible with current land uses. Fences and direct management make range expansion by most bison impossible. Reintroduction of bison into previously occupied areas that remain suitable, therefore, is critical for bison recovery in North America. Banff National Park is recognized as historical range of plains bison and has been identified as a potential site for reintroduction of a wild population. To evaluate habitat quality and assess if there is sufficient habitat for a breeding population, we developed a Habitat Suitability Index (HSI) model for the proposed reintroduction and surrounding areas in Banff National Park (Banff). We then synthesize previous studies on habitat relationships, forage availability, bison energetics and snowfall scenarios to estimate nutritional carrying capacity. Considering constraints on nutritional carrying capacity, the most realistic scenario that we evaluated resulted in an estimated maximum bison density of 0.48 bison/km2. This corresponds to sufficient habitat to support at least 600 to 1000 plains bison, which could be one of the largest 10 plains bison populations in North America. Within Banff, there is spatial variation in predicted bison habitat suitability and population size that suggests one potential reintroduction site as the most likely to be successful from a habitat perspective. The successful reintroduction of bison into Banff would represent a significant global step towards conserving this iconic species, and our approach provides a useful template for evaluating potential habitat for other endangered species reintroductions into their former range.
Highlights
Few free-ranging wild bison (Bison bison, Bison bonasus) populations currently occur in North America (n = 27) and Eurasia (n = 36)[1,2], and there has been growing interest in restoringPLOS ONE | DOI:10.1371/journal.pone.0150065 February 24, 2016Predicting Bison Habitat and Population Size in study design, data collection and analysis, decision to publish, or preparation of the manuscript
On winter, assuming that this was the season that sets the upper limit on bison population size [28,29]
We focused on winter under the assumption that this was the season that sets the upper limit on bison population size [28,29]
Summary
It is possible that habitat could be inadequate in winter because of snow-depth effects on forage availability, in which case the reintroduction area in Banff would not be able to support a large, year-round bison population. Answering these questions is important for management because if there is insufficient amount and quality of habitat during winter in Banff, bison may migrate outside Banff more frequently in search of suitable habitat [37]. Our approach provides a valuable example of evaluating potential habitat for large herbivore reintroductions to areas of their former range
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