How readily will sheep walk for a preferred forage?

Area of Science:

• Animal behavior
• Foraging ecology
• Decision-making under constraints

Background:

• Understanding animal foraging decisions is crucial for ecology and conservation.
• Sheep (ewes) exhibit complex choices between food sources of varying quality and accessibility.
• Previous research indicates animals balance energy intake with expenditure during foraging.

Purpose of the Study:

• To investigate how ewes balance hay quality against the cost (distance and quantity) of procurement.
• To determine the key factors influencing ewes' choice between freely available poor-quality hay and limited good-quality hay.
• To model the relationship between reward-to-distance ratio and preference for high-value food resources.

Main Methods:

• Ewes were presented with a choice between freely available poor-quality hay and good-quality hay requiring travel.
• The distance to good hay (23m or 46m) and the reward quantity (2-32g) were systematically varied.
• Ewe preference for good hay was quantified and correlated with the reward-to-distance ratio.

Main Results:

• Ewe reluctance to travel for good hay increased as the reward quantity decreased.
• Preference for good hay decreased with increased travel distance for a fixed reward.
• Average preference for good hay did not differ when the reward-to-distance ratio was constant.
• A predictive model incorporating reward-to-distance ratio explained 85% of the variation in ewe choice.

Conclusions:

• Ewe foraging behavior is primarily dictated by the 'procurement cost' (reward-to-distance ratio) of high-quality food.
• Suboptimal choices may arise from environmental conditions, sensory limitations, or a preference for dietary diversity.
• Ewes allocate foraging effort based on the edible biomass available relative to the travel distance to a resource patch.