LEARNING-THROUGH-FORAGING-CONSEQUENCES: A MECHANISM OF FEEDING NICHE SEPARATION IN SYMPATRIC RUMINANTS

Authors: Kronberg, Scott; WALKER, JOHN - TX A&M UNIV,SAN ANGELO

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2007
Publication Date: 3/15/2007
Citation: Kronberg, S.L., Walker, J.W. 2007. Learning-through-foraging-consequences: a mechanism of feeding niche separation in sympatric ruminants. Rangeland Ecol. Manage. 60:195-198.

Interpretive Summary: Explanations for why sympatric ruminant species select diets composed of different plant species or plant parts have been controversial. We suggest that a more complete explanation for these differences is based on learning from the consequences of foraging, which includes the influences that inter- and intra-specific differences in morphology, physiology, and experience have on diet selection. Learning to minimize intake of certain plants is one aspect of learning from foraging consequences and is illustrated by results from a 3-day trial we conducted with cattle (Bos tarus), sheep (Ovis aries), and goats (Capra hircus) and the forb leafy spurge (Euphorbia esula). Ten animals of each species were randomly divided into 2 equal-sized groups. After a pre-trial adjustment period, the control group for each species received, via stomach tube on days 1 and 2, ground air-dried crested wheatgrass after eating a novel food (NF; rolled corn) and the treatment group for each species received ground air-dried leafy spurge after eating the NF. Novel feed intake on days 2 and 3 was expressed as a percent of NF intake on day 1 and it declined considerably for cattle and sheep dosed with leafy spurge but did not decline for goats receiving leafy spurge. These results indicate that leafy spurge elicited aversive feeding responses from cattle and sheep but not from goats. Consequently, cattle and sheep learned to reduce their intake of the NF feed when it was associated with leafy spurge. These results are consistent with field observations that goats graze leafy spurge readily, cattle generally graze little if any of it, and sheep graze it reluctantly in the area where leafy spurge was harvested for this trial. Learning from foraging consequences offers an explanation for the unique diets of sympatric ruminant species.

Technical Abstract: Explanations for why sympatric ruminant species select diets composed of different plant species or plant parts have been controversial. We suggest that a more complete explanation for these differences is based on learning from the consequences of foraging, which includes the influences that inter- and intra-specific differences in morphology, physiology, and experience have on diet selection. Learning to minimize intake of certain plants is one aspect of learning from foraging consequences and is illustrated by results from a 3-day trial we conducted with cattle (Bos tarus), sheep (Ovis aries), and goats (Capra hircus) and the forb leafy spurge (Euphorbia esula). Ten animals of each species were randomly divided into 2 equal-sized groups. After a pre-trial adjustment period, the control group for each species received, via stomach tube on days 1 and 2, ground air-dried crested wheatgrass after eating a novel food (NF; rolled corn) and the treatment group for each species received ground air-dried leafy spurge after eating the NF. Novel feed intake on days 2 and 3 was expressed as a percent of NF intake on day 1 and it declined considerably for cattle and sheep dosed with leafy spurge but did not decline for goats receiving leafy spurge (P = 0.001). These results indicate that leafy spurge elicited aversive feeding responses from cattle and sheep but not from goats. Consequently, cattle and sheep learned to reduce their intake of the NF feed when it was associated with leafy spurge. These results are consistent with field observations that goats graze leafy spurge readily, cattle generally graze little if any of it, and sheep graze it reluctantly in the area where leafy spurge was harvested for this trial. Learning from foraging consequences offers an explanation for the unique diets of sympatric ruminant species.