• We detected prey items at 231 of the 258 sites investigated (89.5%).

• The 5 most prevalent items detected in the diet of lions were: mule deer 61.1%,

feral horse (Equus caballus) 11.6%, coyote (Canis latrans) 7.9%, birds 4.1%, and

pronghorn 3.4%.

• One lion’s diet (M166) was strikingly dissimilar to other individuals (Figure 3).

Results

Diet Composition of Mountain Lions on the Modoc Plateau Jon Ewanyk1,2, David Garcelon1, Micaela Szykman Gunther2

1Institute for Wildlife Studies, 140 H St. Blue Lake, CA 95525; 2Humboldt State University, 1 Harpst St. Arcata, CA 95521

• The primary prey of mountain lions (Puma concolor) across western North

America are mule deer (Odocoileus hemionus)1 and elk (Cervus canadensis)2.

Mountain lions have also been documented feeding on an extensive variety of

secondary prey items3,4.

• Mountain lions have not been widely studied in the northeastern region of

California, and very little is known about their prey habits in this area.

• In a 2014–16 study, the Institute for Wildlife Studies found that 62% of known

mortalities (n=17) for collared adult female pronghorn (Antilocapra americana)

on the Modoc Plateau were attributed to mountain lions (Figure 1).

• Established gray wolf (Canis lupis) packs exist north, south, and west of the

Modoc Plateau and multiple individuals have traversed through the study area.

• After wolves recolonized Banff National Park, mountain lions were documented

shifting from their primary prey to secondary and alternative prey items5.

• Mule deer were the primary prey of mountain lions in this region.

• If M166, who preyed almost exclusively on feral horses, is removed as an outlier,

the diet composition would shift to 69.07% mule deer and feral horses would

represent 1.27% of the diet (Figures 3 & 4).

• GPS clusters were biased toward larger prey items, therefore some smaller prey

items were likely underrepresented.

• We did not detect any mountain lions that specialized in pronghorn, but found

that several lions consume them. As a result, we do not believe that pronghorn

determine the distribution or numbers of lions on the Modoc Plateau.

Discussion

Introduction

• 21 mountain lions (14 male, 7 female) were captured using box traps or hounds

and were fitted with GPS collars which uploaded locations daily.

• GPS clusters (spatially aggregated GPS points) were used to search for large prey

items of mountain lions.

• GPS locations occurring within 50 m over the course of a 6-hr time span, with at

least one point occurring nocturnally were considered a GPS cluster.

Methods

• The study area consists of a portion

of the Modoc Plateau, that is

encompassed within Modoc and

Lassen counties in the northeast

corner of California and is

approximately 23,110 km2(Figure 2).

• The Modoc Plateau is a series of large

tablelands sculpted from volcanic lava

rock, dominated by sagebrush-steppe

habitat with intermixed western

juniper (Juniperus occidentalis).

Study Area

• Establish a baseline diet composition of mountain lions in the unstudied Modoc

Plateau population prior to the establishment of wolves.

• Determine if there are significant differences in diet between individuals.

• To obtain a better understanding of what percentage of mountain lion diet is

comprised of pronghorn.

Objectives

Acknowledgements:

We are grateful for the assistance of Randy Bacon, Matt Brinkman, Colton Wise, Jeff Davis and Justin Dellinger in capturing and collaring the lions

included in this study. We thank Dr. William T. Bean and Pairsa Belamaric of Humboldt State University, for advice on analysis, and Steffen Peterson

and Richard Shinn of California Department of Fish and Wildlife for their project support. Dr. Brian Hudgens and Douglas Page of the Institute for

Wildlife Studies provided helpful comments on the poster.

Literature Cited: 1Ackerman, B. B., F. G. Lindzey, and T. P. Hemker. 1984. Cougar Food Habits in Southern Utah. Journal of Wildlife Management 48:147. 2Hornocker, M. G. 1970. An analysis of lion predation upon mule deer and elk in the Idaho Primitive Area. Wildlife Monographs 3–39. 3Iriarte, J. A., W. L. Franklin, W. E. Johnson, and K. H. Redford. 1990. Biogeographic variation of food habits and body size of the America puma. Oecologia 85:185–190. 4Robinette, W. L., J. S. Gashwiler, and O. W. Morris. 1959. Food Habits of the Cougar in Utah and Nevada. Journal of Wildlife Management 23:261. 5Kortello, A. D., Thomas E. Hurd, and Dennis L. Murray. 2007. Interactions between cougars (Puma concolor) and gray wolves (Canis lupus) in Banff National Park, Alberta. Écoscience 14:2, 214–222. 6Horn, S. H. 1966. Measurement of “overlap” in comparative ecological studies. American Naturalist 100:419-424.

Figure 4. Diet composition of the 15 individuals with ≥5 clusters investigated, as well as the total diet composition for all lions.

Figure 1. A radio collared pronghorn that was killed and cached by a mountain lion.

Figure 2. The study area illustrating 95% Kernel Density home ranges of collared mountain lions.

Management Implications • Once wolves are established in the study area, wildlife managers will have the

ability to asses diet changes within this population of mountain lions.

• We conducted habitat surveys at kill sites to better understand the habitat

characteristics lions are selecting. These data could be used to inform habitat

management, which may reduce the risk of lion predation to game species.

Figure 3. Morisita’s index of overlap, displaying the variation in diet between individuals. Maximum variation=0, maximum similarity=16. Sex of the individuals (M=male; F=female) is represented by the letter within the ID. Individual M166 highlighted for emphasis.

F158 1.00

F159 0.77 1.00

F163 0.84 0.94 1.00

F164 0.88 0.96 0.95 1.00

F180 0.72 0.99 0.91 0.94 1.00

F182 0.72 0.99 0.91 0.94 1.00 1.00

M157 0.81 0.97 0.98 0.96 0.95 0.95 1.00

M160 0.84 0.72 0.86 0.80 0.67 0.67 0.81 1.00

M161 0.85 0.98 0.96 0.98 0.96 0.96 0.97 0.77 1.00

M166 0.01 0.00 0.00 0.04 0.00 0.00 0.00 0.08 0.01 1.00

M168 0.72 0.99 0.91 0.94 1.00 1.00 0.95 0.67 0.96 0.00 1.00

M178 0.66 0.61 0.66 0.72 0.59 0.59 0.67 0.55 0.63 0.01 0.59 1.00

M179 0.77 0.98 0.92 0.95 0.97 0.97 0.98 0.72 0.97 0.01 0.97 0.68 1.00

M181 0.18 0.20 0.24 0.20 0.18 0.18 0.22 0.22 0.20 0.00 0.18 0.13 0.19 1.00

M184 0.65 0.54 0.66 0.63 0.51 0.51 0.61 0.78 0.59 0.00 0.51 0.59 0.55 0.16 1.00

ID F158 F159 F163 F164 F180 F182 M157 M160 M161 M166 M168 M178 M179 M181 M184