Research Cooperators - University of Idaho

Research Cooperators

Influence of Cattle Grazing on Feeding Site

Selection by Rocky Mountain Elk

Kelly K. Crane, University of Idaho, Michael A. Smith, University of Wyoming,

Jeffrey C. Mosley, Tracy K. Brewer, Wendy L. Torstenson

and Michael W. Tess, Montana State University

Previous Research

? Interspecific Interactions Between Cattle and Elk

¨CDue to similarity in diet and habitat selection there is the

potential for both competitive (Coe et al. 2001, Mackie

1978) and complementary (Gordon 1988, Jourdonnais

and Bedunah 1990) interactions between cattle and elk.

? Prescriptive Cattle Grazing to Improve Forage

Conditions for Elk

¨C Improvements in nutritive quality of forage plants

in response to spring grazing (Clark et al. 2000).

¨C Previous grazing improves the quantity and

availability of preferred portions of forage plants

(Gordon 1988, Clark et al. 1998).

? Southfork Ranch

? Northfork Ranch

? Wapiti Ridge Coordinated Resource

Management Team

? Montana State University Department of

Animal and Range Sciences

? University of Wyoming Department of

Renewable Resources and Cooperative

Extension Service

Forage Conditioning for Elk:

Remaining Questions

? Do elk respond to cattle grazing mediated variability

in forage conditions at a landscape scale?

? Is ¡°previous cattle grazing¡± a significant habitat

attribute

ib when

h other

h variables

i bl are considered?

id d?

? What is the influence of cattle grazing intensity on

elk feeding site selection?

? Does dispersed cattle grazing in the summer

influence feeding site selection by elk during

subsequent fall, winter and spring seasons?

Research Objectives

? Characterize the mosaic of residual forage

conditions which result from dispersed summer

cattle grazing on foothill rangelands.

p

of ¡°previous

p

cattle

? Assess the relative importance

grazing intensity¡± as a predictor of elk feeding site

selection.

? Determine seasonal elk feeding site selection

patterns in relation to the availability of sites which

were heavily, moderately, lightly or ungrazed by

cattle during the preceding summer.

1

Study Area

Northfork

Ranch

Southfork

Ranch

Research Study Sites

Rattlesnake ¨C 24,000 ha

Diamond Bar ¨C 8,000 ha

Rock Creek ¨C 11,000 ha

Field Research Methods: Cattle Grazing

Intensity

? Systematic Ocular Estimates of Residual Forage

?

?

?

?

Heavy (> 61% utilization)

Moderate (31 ¨C 60% utilization)

Light (11 ¨C 30% utilization)

Ungrazed (< 11% utilization)

? Complete Inventory

? Utilization Sampling

Field Research Methods: Elk Diets

? Systematic sampling of elk feces

? Monthly samples of ¡°fresh¡± fecal material from each study site

? Individual sample = random composite of 5 ¡°piles¡± from 3 sites

? Each composite yielded 5 microscope slides w/ 25 fields of

view (100x)

? Microhistological analyses to

determine percent cover of

discernable plant fragments

? Plant species represented in

elk diets and habitats

selected as feeding sites.

2

Field Research Methods: Elk Feeding

Site Selection

? Monthly Aerial Inventories of Study Sites

Data Analyses: Habitat Attributes

? Aspect

? Percent Slope

? Flights Coincided with

A.M. Feeding Bout

? Elevation

? Distance to Ranch Roads

? Non-Forested Habitats

? Distance to County Roads

? Distance to Forested Cover

? Instantaneous

Observations of Groups

of Elk (activity,snow,..)

Elk Observations (n = 795)

T test (alpha = 0.05)

T-test

0 05)

Random Sites (n = 600)

? Previous Summer Cattle

Grazing Intensity

? Geographic Location (G.P.S.)

Data Analyses: Relative Importance of Cattle

Grazing Intensity in Elk Feeding Site Selection

Data Analyses: Feeding Site Selection by Elk

Binary Logistic Regression: Describes the

relationship between a dichotomous response

variable (dependent) and explanatory (independent)

variables.

Chi-Square Analyses and Selection Ratios:

Describes the ratio of the proportion of use to

the proportion of availability

Our Logistic Model:

Independent Variables

Use

Aspect

Elevation

Roads

Cover

Slope

Grazing

Binary Dependent Variable

0 = Randomly located Sites

1 = Elk Feeding Sites

- VS -

Availability

Results: Habitat Attributes

Elk Feeding

Sites

Randomly

Located Sites

SE

Mean

SE

P-Value

Aspect

170.39

3.60

151.12

4.12

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