Netleaf hackberry (Celtis reticulata) is a deciduous shrub native to the southwestern United States and northern Mexico. Individual shrubs can be long-lived, but newly-established stands of hackberry are rare. The lack of juvenile hackberry in the wild could be due to low germination rates reported in both laboratory and field settings. The seeds of hackberry are embedded in drupes that are an important food source for animals. We hypothesized that passage through the digestive tract of a coyote would increase germination rates of C. reticulata. To test this hypothesis, we collected 17 coyote scats containing visible hackberry fruits from along the Bonneville Shoreline Trail east of Provo, Utah. We found the closest hackberry shrub to each scat-collection site and picked a sample of fresh fruits from it. All samples were cleaned, cold stratified, and then planted into cone-tainers in a greenhouse. We sowed 20 seeds from each of the 17 coyote scats and 20 seeds from the fresh fruits collected from the 17 nearby hackberry shrubs for a total of 680 seeds. On watering days, we checked for newly-germinated hackberries and recorded their date of emergence. Near the end of the experiment, we measured the height of each seedling.
Results/Conclusions
The germination rate of hackberry seeds that had passed through the digestive tract of a coyote did not differ from the germination rate of seeds from fresh-picked fruit (42.7% vs. 46.5%, respectively; Χ2 = 0.558, df = 1, p = 0.455). However, on average, the coyote-treatment seeds took just over half as many days to germinate as did the seeds from fresh-picked (undigested) fruit (35 days vs. 69 days, respectively; p < 0.001). The seedlings from coyote-treatment seeds were 9.5% taller than were the seedlings derived from seeds from undigested fruit (6.4 cm vs. 5.8 cm, respectively; p < 0.001). Our results show that consumption by coyotes can benefit hackberries by enabling their seeds to germinate earlier in the year when conditions for establishment are good. The earlier start on germination that coyote-ingested hackberries get translates to increased height and likely a higher rate of survival in the field.