Coyotes as effective seed dispersers: an experimental evaluation of gut passage time and seed viability of 3 fruits commonly consumed by coyotes

John P. Draper, Utah State University, Logan, UT, Trisha B Atwood and Karin M. Kettenring, Watershed Sciences, Utah State University, Logan, UT, Noelle G. Beckman, Department of Biology and Ecology Center, Utah State University, Logan, UT, Julie K. Young, National Wildlife Research Center, USDA, Logan, UT, Julie K. Young, Wildland Resources, Utah State University, Logan, UT

Background/Question/Methods
Seed dispersal is an important and necessary process for sexually reproducing plant species, allowing for gene flow within and between populations, improved reproduction, and colonization of new and changing landscapes. Effective seed dispersal necessitates the deposition of a sufficient number of viable seeds in suitable locations for germination and recruitment often by a dispersal mutualist. Many members of the Mammalian order Carnivora are highly omnivorous consuming large volumes of fruit and in turn distributing their seeds on the landscape. Coyotes are particularly omnivorous and experiencing substantial range expansion, and population density increases within their historic range, providing both a possibly novel seed dispersal relationship and a large quantity of long-distance dispersal events. To test the potential dispersal distance and the quality of seeds dispersed by coyotes we fed three plant species commonly consumed in the wild (Amelanchier alnifolia, Celtis ehrenbergiana, and Juniperus osteosperma) to captive coyotes. We compared gut passage time between a control feeding of their standard diet and two proportions of fruit mixed in with their standard diet. Post consumption seed viability, emergence rate, and emergence timing were measured for all diet ratio, plant species, and gut passage time combinations. Seedling emergence rate and timing was compared between whole scats and seeds removed from scats to simulate secondary dispersal by rodents. We also tested if gut passage was sufficient to break dormancy for plant species that usually require cold stratification for germination (Amelanchier alnifolia and Juniperus osteosperma).
Results/Conclusions
We found that the gut passage time was unchanged with the inclusion of fruit in the diet of coyotes, with gut passage taking between 4 and 24 hours with most depositions taking place greater than 8 hours after consumption. Seed viability was unaffected for all three species, across all treatment combinations. Seedling emergence for Celtis ehrengergiana was similarly unaffected by gut passage and seeds removed to simulate secondary dispersal had a 22% higher emergence ratio (± 8.2%) and emerged 7 days earlier (± 5 days). Gut passage alone was not sufficient to break dormancy for either Amelanchier alnifolia or Juniperus osteosperma. Our results support the hypothesis that coyotes are effective seed dispersers with the potential to deposit a large volume of viable seeds capable of germination. With regular gut passage times of up to 24 hours coyotes can also be regularly dispersing seeds many kilometers aiding in the colonization of changing landscapes.