Do mule deer surf peaks in forage quality while on summer range?

Area of Science:

• Ecology
• Animal Behavior
• Wildlife Management

Background:

• Migratory ungulates, like mule deer, often follow emerging plant waves for optimal nutrition.
• The "green-wave surfing" hypothesis suggests animals track forage quality peaks during migration.
• Less is known about whether ungulates can "microsurf" on high-quality forage within summer ranges.

Purpose of the Study:

• To investigate if temperate ungulates optimize high-quality forage use on summer ranges.
• To evaluate changes in forage (crude protein, digestible energy, abundance) with plant phenology.
• To determine if mule deer alter diets based on plant-specific phenological changes.

Main Methods:

• Studied a partially migratory mule deer population in Wyoming, USA.
• Assessed forage quality (crude protein, digestible energy) and abundance throughout the growing season.
• Analyzed deer diet shifts in relation to plant phenology and forage quality rankings.

Main Results:

• Forage quality declined as plant phenology progressed, supporting the Forage Maturation Hypothesis.
• Heterogeneous declines in forage quality across plant species enabled "microsurfing."
• Mule deer altered their diets, prioritizing plants like Rosa woodsii and Purshia tridentata when forage quality peaked.

Conclusions:

• Mule deer demonstrate potential for "microsurfing" on summer ranges by exploiting phenological diversity.
• Remote sensing is validated as an accurate tool for assessing peak forage quality in shrublands and montane habitats.
• Understanding microsurfing behavior is crucial for effective wildlife management and habitat conservation.