Social status affects the quantity of seeds dispersed
Social status is often predictably related to an individual’s ability to monopolize preferred food items (Ward & Webster 2016a), which likely generates intraspecific variation among dispersal agents in the quantity of seeds they disperse. This variation in seed dispersal may be most evident in systems where fruit is a supplementary food item that is less preferred to a food item that can be monopolized by dominant individuals, leading to greater quantity of seeds dispersed by subordinate individuals supplementing their diets with fruit. For example, coyotes (Canis latrans ) are social carnivores with highly variable diets that often include fruit (Parker 1995; Mastro 2011), and fruit consumption by coyotes can provide seed-dispersal services for a wide range of plant species across North America (Willson 1993; Cypher & Cypher 1999; Roehm & Moran 2013; Bartel & Orrock 2021; Draper et al. 2021). Since coyote dominance hierarchies affect individual access to carrion (i.e., dominant individuals have greater access than subordinates; Gese et al. 1996; Atwood and Gese 2008), it is likely that subordinate individuals consume greater amounts of fruit (a secondary food item), transporting substantially greater quantities of seeds than dominant individuals (Fig. 1). Since 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. Moreover, social status related to space use is also likely to affect dispersal distance (see below).
It may be quite common that subordinate individuals disperse substantially more seeds than dominant individuals within carnivore populations (Box 1) as well as many primate populations where social status is known to dictate individual diet breadth. For example, in Kenya, higher-ranking female vervets (Cercopithecus aethiops ) consumed significantly less fruit than lower-ranking females (Isbellet al. 1999). This difference in diet is thought to be a result of higher-ranking females monopolizing fungi, a larger component of higher-ranking female diets, due to its abundance in restricted areas (Isbell et al. 1999). Rank differences in seed-dispersal efficacy may also be the opposite in primate populations where fruit is both preferred and can be monopolized by high-ranking individuals. In both blue monkeys (Cercopithecus mitis stuhlmanni ) and chimpanzees (Pan troglodytes ), high-ranking individuals consume significantly more fruit than low-ranking individuals, which consume significantly more foliage (Pazol & Cords 2005; Murray et al.2006). Predicting how dominant and subordinate individuals vary in effectiveness as seed-dispersal agents therefore requires an understanding of which food item (fruit or an alternative resource) is both preferred and monopolizable by dominant individuals (Fig. 1).