Mesopredator frugivory has no effect on seed viability and emergence under experimental conditions

Abstract

Members of the order Carnivora are a unique and important seed disperser who consume and deposit undamaged seeds while providing regular long-distance seed dispersal opportunities. Some members of Carnivora, such as coyotes (Canis latrans), are undergoing range expansions which may help the plant species they consume colonize new locations or replace dispersal services provided by recently extirpated species. In this study, we evaluated aspects of the seed dispersal effectiveness of coyotes and gut passage time to determine the potential dispersal distances for three commonly consumed and commonly occurring plant species (Amelanchier alnifolia, Celtis ehrenbergiana, and Juniperus osteosperma). We also investigated the potential effects of secondary dispersal of seeds away from scats by comparing seedling emergence from whole scats to those where seeds were first removed from scats. We found that seeds generally took between 4 and 24 h to pass through the digestive tract of coyotes, which could result in regular seed dispersal up to 7 km. Gut passage through coyotes had no effect on seed viability or emergence for any of the three plant species, including that gut passage for A. alnifolia and J. osteosperma does not replace cold stratification for breaking physiological dormancy. By simulating secondary dispersal, we found that 22% (AE8.2%) more C. ehrenbergiana seedlings emerged when seeds were removed from scats and those seedlings emerged 7 d earlier (AE5 d) compared to seeds that remained in the coyote scat. Coyotes are effective seed dispersers, with the potential for regular long-distance dispersal services and for providing opportunities for secondary seed dispersal, which could aid in climate migration or serve to replace extirpated dispersal mutualists.

Coyote and porcupine spread Russian olive seeds through endozoochory

“…Thus, depending on coyote bowel movement speeds, they have the potential to spread Russian olive seeds a long distance from the source tree. For example, coyotes have been shown to pass other plant seeds up to 24 hours after consumption and deposit them up to 7 km away (Draper et al 2021). Numerous plants have been documented to germinate from coyote scat prior to this experiment (Cypher and Cypher.…”

“…For example, coyotes have been shown to pass other plant seeds up to 24 hours after consumption and deposit them up to 7 km away (Draper et al 2021). Numerous plants have been documented to germinate from coyote scat prior to this experiment (Cypher and Cypher.…”

Frugivory and Seed Dispersal by Carnivorans

“…For example, one study found that an increase in fruit in brown bear (Ursus arctos) diets reduced the average gut-passage time from 14.5 to 6.5 h (Elfström et al, 2013). Conversely, there was no effect of the proportion of fruit in the diet on gut-passage times for coyotes (Draper et al, 2021). Though gut-passage time may be altered when consuming fruit for some species (both decreasing and increasing gut-passage time, Cipollini and Levey, 1997), passage times remain on the order of hours suggesting that regardless of how much fruit was consumed, Carnivorans physiology can accommodate long dispersal distances.…”

“…Furthermore, the behaviors, life-history traits, and physiology of Carnivora make them distinct from other dispersers. For example, Carnivora often maintain large home ranges (i.e., ursids, Graham and Stenhouse, 2014), gut passage times are long (Escribano-Avila et al, 2014;Draper et al, 2021) which will affect the patterns of seedfall across landscapes and the consequences of those patterns in ways that differ from other frugivores (Schupp and Fuentes, 1995;Jordano et al, 2007;Martínez et al, 2008). Differences in seed disperser gut-passage time and post-consumption movement can influence dispersal distances, while their habitat use and defecation patterns can influence micro-site characteristics and degree of seed clumping that will influence plant recruitment.…”

The important role of animal social status in vertebrate seed dispersal

“…This variation in seed dispersal may be most evident in two general types of systems: 1) where fruit is a supplementary food item that is less preferred to a food item that can be defended by dominant individuals, leading to greater quantities of seeds dispersed by subordinate individuals supplementing their diets with fruit and 2) where fruit is the preferred food item that is defended by dominant individuals, leading to greater quantities of seeds dispersed by dominant individuals than subordinates (Figure 1). For example, coyotes (Canis latrans) are social carnivores with highly variable diets that often include fruit (Mastro, 2011;Parker, 1995), and fruit consumption by coyotes can provide seed-dispersal services for a wide range of plant species across North America (Bartel & Orrock, 2021;Cypher & Cypher, 1999;Draper et al, 2021;Roehm & Moran, 2013;Willson, 1993) et al, 1996), it is likely that subordinate individuals consume greater amounts of fruit (a secondary food item), transporting substantially greater quantities of seeds than dominant individuals (Figure 1). Because transient (less-dominant) coyotes also have reduced access to ungulate carcasses than territorial (more-dominant) individuals (Gese, 2001), it is likely that resident status is an important predictor of individual fruit consumption, and subsequent seed dispersal, in coyote populations.…”