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).