Early ideas on 'market effects' (Noë et al. 1991) were inspired by data from studies of 'helpers-at-the nest', such as Uli Reyer's study of the pied kingfisher (Reyer 1984; 1986).

Cooperative breeding seemed to be a prime example of a system in which market effects could be expected:

  • there are two clear classes of traders: breeders and helpers
  •  both classes can offer commodities: help in raising offspring and access to resources (notably to territories and shelter)
  •  the membership of one class (the helpers) is variable

Thus: if individual helpers are less valuable to the breeders when their numbers increase, we should see less tolerance towards helpers, more pressure to deliver food and so forth.

A drawback of this system is that helpers are often closely related to breeders. Kin selection is expected to temper aggression of breeders towards helpers, obscuring market effects.

Recently some examples of the use of the biological market paradigm in cooperative breeding have been published: Bergmüller et al. (2005) on cichlid fish, Löttker et al. (2007) on tamarins and Kutsukake & Clutton-Brock (2008) on meerkats (Suricata), a mongoose.

 

The latter study is especially interesting, because it is an explicit test of the paradigm and – to my relief – provides strong support. From the abstract: As predicted, the number of subordinates in a group was positively associated with the aggression frequency by the dominant male and with the submission frequency by the subordinate males.

 

 

References

Bergmuller R, Heg D, Peer K, Taborsky M (2005) Extended safe havens and between-group dispersal of helpers in a cooperatively breeding cichlid. Behaviour 142: 1643-1667

Löttker P, Huck M, Zinner DP, Heymann EW (2007) Grooming relationships between breeding females and adult group members in cooperatively breeding moustached tamarins (Saguinus mystax). American Journal of Primatology 69: 1-14

Noë R, van Schaik CP, van Hooff JARAM (1991) The market effect: an explanation for pay-off asymmetries among collaborating animals. Ethology 87: 97-118

Kutsukake N, Clutton-Brock TH (2008) The number of subordinates moderates intrasexual competition among males in cooperatively breeding meerkats. Proceedings of the Royal Society B: Biological Sciences 275: 209-216

Reyer HU (1984) Investment and relatedness: a cost/benefit analysis of breeding and helping in the pied kingfisher (Ceryle rudis). Animal Behaviour 32: 1163-1178

Reyer H-U (1986) Breeder-helper-interactions in the pied kingfisher reflect the costs and benefits of cooperative breeding. Behaviour 96: 277-303