Predatory plants and patchy cows: modeling cattle interactions with toxic larkspur amid variable heterogeneity

Abstract

8The most common explanations for the evolution and persistence of herd behavior in large 9 herbivores relate to decreased risk of predation. However, poisonous plants such as larkspur 10 (Delphinium spp.) can present a threat comparable to predation. In the western United States, 11 larkspur diminishes the economic and ecological sustainability of cattle production by killing 12 valuable animals and restricting management options. Recommendations for mitigating losses 13 have long focused on seasonal avoidance of pastures with larkspur, despite little evidence that 14 this is practical or effective. Our ongoing research points to the cattle herd itself as the potential 15 solution to this seemingly intractable challenge and suggests that larkspur and forage patchiness 16 may drive deaths. In this paper, we present an agent-based model that incorporates neutral 17 landscape models to assess the interaction between plant patchiness and herd behavior within the 18 context of poisonous plants as predator and cattle as prey. The simulation results indicate that 19 larkspur patchiness is indeed a driver of toxicosis and that highly cohesive herds can greatly 20 reduce the risk of death in even the most dangerous circumstances. By placing the results in 21 context with existing theories about the utility of herds, we demonstrate that grouping in large 22 herbivores can be an adaptive response to patchily distributed poisonous plants. Lastly, our 23 results hold significant management-relevant insight, both for cattle producers managing grazing 24 in larkspur habitat and in general as a call to reconsider the manifold benefits of herd behavior 25 among domestic herbivores. 26