Copyright © 2007 The Association for the Study of Animal Behaviour Published by Elsevier Ltd.
Payment for sex in a macaque mating market
In primate sexual relationships, males and females can cooperate through social trade. Market-like trading of sexual activity has been theorized, but no data have yet been presented that clearly show its existence. I collected data to test whether biological market theory could account for exchanges of male-to-female grooming and sexual activity in longtailed macaques. I explored male-to-female grooming, rates of sexual activity, and grooming–mating interchanges, which were male-to-female grooming bouts that directly involved mating. Male-to-female grooming mainly occurred when females were sexually active, and males groomed females longer per bout when mating, inspection, or presentation of female hindquarters was involved. Moreover, male-to-female grooming was associated with an increase in female rates for all forms of sexual activity, where in contrast, female-to-male grooming was associated with decreased rates of mating in the groomed males. Males did not preferentially mate with swollen females or invest more grooming in them during grooming–mating interchanges, as swellings did not seem to be a reliable indicator of female fertility. Rank status was correlated with grooming payment during grooming–mating interchanges in favour of higher-ranked males and females. In support of a biological market interpretation, the amount of grooming a male performed on a female during grooming–mating interchanges was related to the current supply of females around the interaction. The results provided evidence of a grooming–mating trade that was influenced by a mating market.
Keywords: biological markets; grooming; interchange; Macaca fascicularis; macaque; mating; sex; social exchange
Correspondence and present address: M. D. Gumert, Division of Psychology, School of Humanities, Nanyang Technological University, Singapore, 639798. Correspondence and present address: M. D. Gumert, Division of Psychology, School of Humanities, Nanyang Technological University, Singapore, 639798.
Department of Biology, Hiram College, Hiram, OH, U.S.A.Department of Psychology, Hiram College, Hiram, OH, U.S.A.Received 18 September 2006; revised 26 October 2006; accepted 13 March 2007. MS. number: A10560R. Available online 5 November 2007.
Javaneraaffe

 Forscher aus Singapur haben bei der 20-monatigen Beobachtung freilebender Javaneraffen in der Provinz Kalimantan Tengah auf Indonesien laut der wissenschaftlichen Zeitschrift „New Scientist“ (Ausgabe 2637 vom 2. Januar 2008) eine Entdeckung gemacht: Affenmännchen werden von Affenweibchen nach einer Fellpflege, deren Dauer von der Anzahl an Weibchen und Männchen abhängt, jedoch zwischen acht und 16 Minuten liegt, mit Sex belohnt. Dabei dauerte die Entlausung länger, wenn weniger Weibchen anwesend waren. Durchschnittlich vollzogen die Weibchen anderthalbmal pro Stunde Geschlechtsverkehr. Nach ausgiebiger Fellpflege stieg dies auf dreieinhalbmal, dabei meist mit den pflegenden Männchen.

Forscher Michael Grumert vermutet, dass das in früheren Studien nicht entdeckt werden konnte, da in diesen in Gefangenschaft lebende Affen untersucht wurden. Seine Forschungsergebnisse wurden im November 2007 im Journal „Animal Behaviour“ (Band 74, Seite 1655 bis 1667) im Internet veröffentlicht. Die bisher einzige andere Studie, die einen Zusammenhang zwischen „Marktwirtschaft“ und tierischem Paarungsverhalten aufzeigte, befasste sich mit Waldmäusen.