Social queuing in animal societies: a dynamic model of reproductive skew

Abstract

Previously developed models of reproductive skew have overlooked one of the main reasons why subordinates might remain in a group despite restricted opportunities to breed: the possibility of social queuing, i.e. acquiring dominant status in the future. Here, we present a dynamic ESS model of skew in animal societies that incorporates both immediate and future ¢tness consequences of the decisions taken by group members, based on their probability of surviving from one season to the next (when postbreeding survival probabilities drop to zero, our analysis reduces to the model produced by Reeve and Ratnieks in 1993, which considered only a single breeding season). This allows us to compare the delayed bene¢ts of philopatry and the immediate opportunities for independent breeding. We show that delayed bene¢ts greatly reduce the need for dominants to o¡er reproductive concessions to retain subordinates peacefully in the group. Moreover, this e¡ect is strong enough that di¡erences in survival have a much greater impact on the group structure than di¡erences in other parameters, such as relatedness. When the possibility of acceding to dominant status is taken into account, groups where the dominant completely monopolizes reproduction can be stable, even if they consist of unrelated individuals, and even if subordinates have a reasonably high probability of winning a ¢ght for dominance. Finally, we show that stable groups are possible even if association leads to a decrease in current productivity. Subordinates may still stand to gain from group membership under these circumstances, as acquiring breeding positions by queuing may be more e¤cient than the attempt to establish a new territory. At the same time, the dominant may be unable to exclude unwelcome subordinates, may enjoy increased survival when they are present, or may gain indirect bene¢ts from allowing relatives to stay and queue for dominance. We conclude that reproductive skew in animal groups, ranging from eusocial insect colonies to mating aggregations (leks), will be strongly in£uenced by the future prospects of group members.

The lemur syndrome unresolved: extreme male reproductive skew in sifakas (Propithecus verreauxi), a sexually monomorphic primate with female dominance

“…Given this observed reproductive skew in favor of dominant males, it remains puzzling why subordinate males do not attempt takeovers more often. One possibility is that they are queuing for the alpha position (Kokko and Johnstone 1999;Cant and English 2006), as for example mountain gorillas (Bradley et al 2005) or spotted hyenas (East and Hofer 2001), but adult mortality rates are low, and sifaka life span may reach up to 30 years (Richard et al 2002). The potential success of this tactic can therefore not be evaluated with the available data.…”

A skew model for the evolution of sociality via manipulation: why it is better to be feared than loved

“…The expanded range of assumptions includes situations with (i) incomplete control of subordinates by dominants (Reeve et al 1998), (ii) variable brood sizes and costs of reproduction for dominants (Cant 1998;, or (iii) multiple subordinates , and the range of behavioural options now allows for (i) inheritance by subordinates (Kokko & Johnstone 1999;Ragsdale 1999), or (ii) eviction of subordinates by dominants . Most of these models yield predictions which di¡er considerably from those of the original skew models and, in some cases, their predictions accord well with data from natural populations of social animals (e.g.…”

Adaptive Advantages of Cooperative Courtship for Subordinate Male Lance‐Tailed Manakins

“…: Kriitzen et al 2004; Meleagris gallopavo: Watts and Stokes 1971;Krakauer 2005;Philomachuspugnax: van Rhijn 1973;Lank et al 2002;Chiroxiphia manakins: Sick 1967). Ecological benefits from cooperative foraging or territoriality are shared among members of a group; in contrast, the reproductive benefits of alliances formed to attract mates are not usually distributed evenly among members of the coalition (Kokko and Johnstone 1999). Such reproductive coalitions are therefore ideal for investigating the complex series of costs and benefits that interact to determine whether subordinate individuals cooperate.…”