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

Several 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; 2010) on meerkats (Suricata), a South-African mongoose species.

The latter study is especially interesting, because it is an explicit test of the paradigm and – to my relief – provides strong support.

From the Kutsukake & Clutton-Brock 2008 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.

From the Kutsukake & Clutton-Brock 2010 abstract: This result is consistent with the biological market theory, which predicts that the value of subordinates is dependent on group size and that subordinates will alter grooming efforts accordingly.

Note that the same result was found in red-fronted lemurs by Port et al. (Anim Behav 2008) - see my page on Grooming in primates and in an experiment with cooperatively breeding cichlid fish (Neolamprologus pulcher) by Hellmann etal (2015) - see reference & link to ScoopIt-page below.  

More recently, a very interesting experimental study with paper wasps was added to this list (Grinsted & Field 2017). In this study it is not the ratio breeders-helpers that is manipulated, but rather the outside options for the helpers in the form of vacant nest sites and additional floaters that could become helpers at new nests. A quote from this study: To summarize our main findings: our first result is that females have a choice of partners when they form social groups, confirming the potential for a market in this species. Our second result is that increasing the availability of outside options for subordinates leads to them decreasing their foraging effort within groups. These results are in accordance with predictions from biological market theory: that increased competition among dominants for cooperative partners will induce them to accept a lower price for group membership. Our findings imply that it is necessary to take market forces and specifically outside options into consideration when predicting the amount of help provided in cooperative societies.