How does predation risk and forage quality/quantity affect white-tailed deer and elk behavior, and selection for high-value crops?

How can we reduce the damages that these ungulates cause to agriculture?


In North America, ungulates cause more damage to agricultural crops than any other vertebrates. As the human footprint on the landscape and ungulates abundance jointly continue to increase in many regions of western North America, ungulate depredation complaints will likely rise as well. But effective and economical long-term solutions to the depredation problem continue to be elusive, despite decades of research.

In the Clearwater Region of Idaho, a highly productive agricultural area, white-tailed deer are thought to cause significant damage to high-value crops, yet the ecology of Clearwater white-tails remains unstudied, making prevention of deer depredation challenging.

Likewise, in Southern Idaho, elk can cause considerable damage to high-value crops, and elk damage appears to be escalating.

Many solutions have been proposed and tested to reduce ungulate depredation of valuable crops, with mixed success. Treatments typically aim to alter damages to crops by changing ungulate behavior or density. Ungulate density is typically reduced via targeted hunting (e.g., by issuance of depredation permits), but given the high fecundity of ungulates in agricultural systems, and their impressive movement capability, resulting density reductions may be be localized and temporary. As a result, treatments designed to cause changes to ungulate behavior are often used instead of or in addition to targeted hunting. 

Such behavior-modifying treatments can be broadly classified as either fear-increasing, or nutrition-reducing. Fear-increasing treatments include: crop protection dogs; techniques such as application of scents designed to mimic predator odors; playback of sounds that mimic predators or are very noisy and could reduce deer ability to hear predators; and visual and auditory stimuli that do not mimic predators but are designed to startle deer regardless. Nutrition-reducing treatments include: applications of bitter or foul-tasting compounds, including natural tannins, to crops.

Our research project will develop creative management tools for reducing ungulate depredation of crops in Idaho. The goal of the program is to determine how various management treatments affect ungulate behavior and subsequent crop damage, with the goal of identifying the most effective actions for reducing deer damage to agriculture in the region. Primary research objectives are as follows:

1)    Characterize hierarchical deer and elk behavioral response to treatments using GPS collared deer, from activity budgets, to movement patterns and habitat selection, to home range location and composition.

2)    Measure changes in ungulate depredation on crops using exclosures and novel aerial survey techniques.