The role of herbivores in Great Plains conservation: comparative ecology of bison and cattle

Abstract

Abstract. The Great Plains of North America evolved with significant influence from bison (Bison bison), but is presently dominated by cattle (Bos taurus). While there are a variety of opinions concerning differences between these two species, there is a lack of scientific comparisons, including those that incorporate important ecological variation. We developed a framework to study and compare the grazing behavior and effects of bison and cattle within grassland ecosystems. Environmental (e.g., resource distribution, disturbance) and animal (e.g., number, social organization) factors play a critical role in determining grazing effects and should be incorporated into discussions that compare the effects of bison and cattle. Using this framework we specifically compare the grazing behavior of both species in tallgrass prairie and discuss the implications of these differences in the context of conservation. We collared bison and cattle with global positioning systems and used resource selection functions to estimate the importance of various environmental factors on site selection. Both species preferred recently burned areas and avoided steeper slopes. Cattle selected areas that were closer to water, while bison were not limited by distance to water; cattle also preferred areas with woody vegetation, while bison avoided them. Incorporating broad scale environmental complexity allows for an effective comparison of ecological differences between bison and cattle. While there are similarities and differences in these species, a comprehensive analysis of all conditions and scenarios is not possible. It is clear, however, that the greatest differences between these species will likely be evident from broad scale studies across complex landscapes. In addition to species, conservation and land managers need to consider other environmental factors that are critical to grazing effects and overall conservation.

Identifying the water sources consumed by bison: implications for large mammalian grazers worldwide

“…For an animal with a mean weight of 250 kg, cattle require on average 30 L per day per individual, but this amount varied over time (Duesterhaus et al 2008). In a study of the comparative ecology of cattle and bison in tallgrass prairie in Oklahoma, USA, Allred et al (2011) showed cattle foraging close to permanent water sources, while bison spent more time at greater distances from permanent water sources. These authors concluded that ephemeral water sources may constitute an important fraction of the total drinking water consumed by bison (Allred et al 2011).…”

“…In a study of the comparative ecology of cattle and bison in tallgrass prairie in Oklahoma, USA, Allred et al (2011) showed cattle foraging close to permanent water sources, while bison spent more time at greater distances from permanent water sources. These authors concluded that ephemeral water sources may constitute an important fraction of the total drinking water consumed by bison (Allred et al 2011). Our results support Allred et al (2011) and highlight the significance of bison wallows as rainfall catchments.…”

“…At the landscape-scale, the often patchy distribution of resource availability over time drives distribution patterns of large herbivores (Fryxell 1991, Bailey et al 1996, Wilmshurst et al 1999, Allred et al 2011, Smit 2011). Forage quality for large herbivores can be constrained by access to reliable water sources (Bailey et al 1996, Redfern et al 2003.…”

“…For example, presumed drinking water sources have been reported using visual observations of herd habitat selection (Coppock et al 1983, Bergstrom and Skarpe 1999, de Leeuw et al 2001, camera traps (Whiting et al 2010), aerial census (Western 1975, Redfern et al 2003, and distances to water calculated using GPS collars (Fortin et al 2003, Allred et al 2011, Dancose et al 2011, Cain et al 2012. These techniques provide a template for presumed water-use by grazers based on the assumption that the water consumed comes from either the most abundant or most proximal water source to the animal's location.…”

“…Bison currently occur within constrained and managed geographic ranges, yet seasonal patterns of resource availability are likely to drive resource selection, consumption, and energetics (Rutley and Hudson 2000, Bergman et al 2001, Allred et al 2011. Bison movements across the landscape commonly reflect selective grazing preferences to maximize forage quality (Coppock et al 1983, Knapp et al 1999).…”