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Dustin H. Ranglack Ph.D. Candidate dhranglack@gmail.com @dhranglack
Competition on the range: Science vs. perception in a bison-cattle conflict in the western USA Dustin H. Ranglack, Susan Durham, and Johan T. du Toit Genome.gov Tringa.org Dustin H. Ranglack Ph.D. Candidate @dhranglack
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@dhranglack Introduction Integration of local ecological knowledge (LEK) into adaptive management But science is still needed nature.org
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Wildlife-livestock conflict
@dhranglack Wildlife-livestock conflict World-wide negative view towards native large herbivores Disease Competition Near eradication of many wildlife species Ryan Sensenig
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@dhranglack Bison Currently ~500,000 ~20,000 in conservation herds Intensively managed; fragmented landscapes; cattle introgression Perceived competition with livestock limiting large-scale restoration
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@dhranglack Predictions If bison significantly reduce forage availability for cattle: Bison visitation a significant predictor of grass biomass depletion If bison are the main wildlife competitor with cattle for grazing resources: Bison and cattle the two predominant grass consumers
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Study site Henry Mountains (HM) Colorado Plateau Arid/semi-arid
@dhranglack Study site Henry Mountains (HM) Colorado Plateau Arid/semi-arid Isolated Public land (BLM) Desert grassland/shrubland PJ and mixed conifer forest Subalpine grassland and aspen
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HM bison Introduced in 1940s Co-mingle with cattle Free-ranging
@dhranglack HM bison Introduced in 1940s Free-ranging Genetically pure Disease Free Huntable ~325 adults post-hunt Co-mingle with cattle
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@dhranglack HM bison conflict Drought
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Other HM grazers Lagomorphs Black-tailed jackrabbits
@dhranglack Other HM grazers Lagomorphs Black-tailed jackrabbits Desert cottontail rabbits Bill Bouton Alan Vernon
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@dhranglack Goals Measure rancher perceptions of wildlife-livestock conflict in the HM Determine relative impacts of bison, cattle, and lagomorphs on HM rangeland
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Rancher survey Questionnaire mailed to 21 ranchers
@dhranglack Rancher survey Questionnaire mailed to 21 ranchers What are the biggest issues? Main wildlife competitors? Predator control?
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Rancher survey 12 responses (57.1% of ranchers; 70.9% of cattle)
@dhranglack Rancher survey 12 responses (57.1% of ranchers; 70.9% of cattle) Competition for forage biggest concern Wildlife competitors (high=3, low=1) Bison: Mean: 2.18, SE: 0.25 Lagomorphs: Mean: 1.11, SE: 0.11 All felt that coyotes should be controlled
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@dhranglack Exclosure sites
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Experimental design At each site (n=20):
@dhranglack Experimental design At each site (n=20): 1 - 8’x8’ exclosure (bison + cattle out) 1 - 8’x8’ exclosure (bison + cattle + lagomorphs out) 1 - 8’x8’ reference plot (all grazers in) Total of 40 exclosures and 20 reference plots
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@dhranglack Site layout
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Data collection Oct. 2011: set up Oct. 2012: clipped
@dhranglack Data collection Oct. 2011: set up Oct. 2012: clipped Separated into grass, forb, shrub, cactus Dried and weighed
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@dhranglack October 2011, Site #19 Partial Exclosure Full Exclosure
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@dhranglack October 2012, Site # 19 Partial exclosure Full exclosure
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@dhranglack Predictions Bison visitation a significant predictor of grass biomass depletion Bison and cattle the two predominant grass consumers
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@dhranglack Bison 44 GPS collars deployed on HM bison
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Bison RDI RDI: Relative Density Index RDIi = Si/A
@dhranglack Bison RDI RDI: Relative Density Index RDIi = Si/A Si = bison locations / sq. km around site i A = bison locations/ sq. km in the area comprising the habitat in which site i occurs Log transformed for analysis
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Bison RDI RDI >0: higher than expected bison use
@dhranglack Bison RDI RDI >0: higher than expected bison use RDI <0: lower than expected bison use Sam Abell
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@dhranglack Expected Prediction 1
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@dhranglack Observed
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@dhranglack Prediction 1 Bison visitation a significant predictor of grass biomass depletion
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@dhranglack Predictions Bison visitation a significant predictor of grass biomass depletion Bison and cattle the two predominant grass consumers
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@dhranglack One-way, RBD ANOVA Significant differences among reference, partial, and full exclosures (p < 0.05) Large herbivores = 13.9 g/m2 (p = 0.005) Lagomorphs = g/m2 (p = 0.048) How much of the large herbivore effect is due to bison vs cattle? Using ‘animal days’ to determine the relative impacts of each.
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Animal days (# of individuals) * (# of days in the area)
@dhranglack Animal days (# of individuals) * (# of days in the area) Bison = 21,415 days Cattle = 81,949 days
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Grass use Cattle: 11.0 g/m2 Lagomorphs: 7.2 g/m2 Bison: 2.9 g/m2
@dhranglack Grass use Cattle: 11.0 g/m2 Lagomorphs: 7.2 g/m2 Bison: 2.9 g/m2 James Marvin Phelps
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@dhranglack Overall grass use
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Prediction 2 Bison and cattle the two predominant grass consumers
@dhranglack Prediction 2 Bison and cattle the two predominant grass consumers
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Adaptive management Integrating LEK must be done carefully
@dhranglack Adaptive management Integrating LEK must be done carefully While useful in many cases, it might be: based on misunderstanding not matched with current conditions biased to suit political needs Management decision based on perceptions are unlikely to lead to a satisfactory outcome Science should provide direction
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Discussion Trophic cascade from predator removal?
@dhranglack Discussion Trophic cascade from predator removal? $1.35 M spent annually in Utah on predator control Hope for bison restoration Impacts on cattle overstated
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@dhranglack Acknowledgements Chris Holcomb
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