Paper: Grooming reciprocation among female primates - a meta-analysis

Biology Letters
ISSN: 1744-9561 (Paper) 1744-957X (Online)
Issue: FirstCite Early Online Publishing
DOI: 10.1098/rsbl.2007.0506

----------------------------------------------------------------------------

Animal behaviour

Grooming reciprocation among female primates: a meta-analysis

Gabriele Schino1, * & Filippo Aureli2

1Istituto di Scienze e Tecnologie della Cognizione, Consiglio Nazionale
delle Ricerche, 00197 Roma, Italy
2Research Centre in Evolutionary Anthropology and Palaeoecology, School of
Biological and Earth Sciences, Liverpool John Moores University, Liverpool
L3 3AF, UK

*Author and address for correspondence: Via Lucilio 36, 00136 Roma, Italy
gschino@xxxxxxxxxxxxxxxx


Received 9 October 2007; Accepted 24 October 2007

----------------------------------------------------------------------------

Abstract
The theory of reciprocal altruism offers an explanation for the evolution of
altruistic behaviours among unrelated animals. Among primates, grooming is
one of the most common altruistic behaviours. Primates have been suggested
to exchange grooming both for itself and for rank-related benefits. While
previous meta-analyses have shown that they direct their grooming up the
hierarchy and exchange it for agonistic support, no comprehensive evaluation
of grooming reciprocation has been made. Here we report on a meta-analysis
of grooming reciprocation among female primates based on 48 social groups
belonging to 22 different species and 12 genera. The results of this
meta-analysis showed that female primates groom preferentially those group
mates that groom them most. To the extent allowed by the availability of
kinship data, this result holds true when controlling for maternal kinship.
These results, together with previous findings, suggest that primates are
indeed able to exchange grooming both for itself and for different
rank-related benefits.

Keywords: reciprocation; altruism; grooming; primates

----------------------------------------------------------------------------

1. Introduction

Altruistic behaviours, that is those that benefit the recipient at some cost
to the donor, defied evolutionary explanations until the formulation of kin
selection theory (Fisher 1930; Haldane 1932; Hamilton 1964) and reciprocal
altruism theory (Trivers 1971), that provided evolutionary explanations of
altruism among related and unrelated animals, respectively.

However, while evidence for kin selection in favouring altruism among
relatives is robust (Griffin & West 2002), evidence for reciprocal altruism
is much weaker. Relatively few examples of reciprocal altruism have been
published, and these have often been difficult to replicate (Packer 1977;
Wilkinson 1984; Milinski 1987; Bercovitch 1988; Dugatkin 1988).

Allogrooming (grooming, hereafter) is possibly the most common primate
affiliative behaviour and is also observed in non-primates (e.g. Wilkinson
1986; Mooring et al. 2004). It is generally considered to be altruistic, in
that it provides benefits to the recipient in terms of removal of
ectoparasites, release of beta-endorphines and reduction of tension (Schino
et al. 1988; Keverne et al. 1989; Aureli et al. 1999; Zamma 2002). Its
costs, however, are less clear (Dunbar & Sharman 1984; Maestripieri 1993).
The study of grooming has had a pivotal role in our understanding of the
evolution of reciprocal altruism (e.g. Seyfarth & Cheney 1984).

Demonstrating reciprocal altruism requires showing the existence of a
contingency between giving and receiving (Olendorf et al. 2004).
Traditionally, this has been interpreted as a (relatively) short-term
temporal contingency. For example, both Seyfarth & Cheney (1984) and
Hemelrijk (1994) showed that previous grooming may increase the probability
of agonistic support, and both Barrett et al. (1999) and Manson et al.
(2004) showed that monkeys time-match grooming given and received during
each grooming session.

Group living animals, however, do not make their behavioural decisions
exclusively in the context of short-term dyadic interactions, because a
further level of complexity is added by the possibility of exerting partner
choice, that is of deciding which partner to interact with (Noë &
Hammerstein 1995; Noë 2001). While classical reciprocal altruism theory
(Trivers 1971) interpreted partner choice mostly in terms of detection of
cheaters, more recent biological market approaches emphasized the varying
balance between giving and receiving that is due to economic forces such as
fluctuating demand/offer ratios (e.g. Henzi & Barrett 2002; Slater et al.
2007). Within this framework, it becomes important to test how animals
distribute their altruistic behaviours (e.g. grooming) among their group
mates, that is to investigate their quantitative partner choices.

Grooming offers a unique possibility in this respect, as it is commonly and
easily observed. Indeed, data on the distribution of grooming are frequently
published, and correlations between giving and receiving have been reported,
suggesting the maintenance of a long-term balance (e.g. Silk et al. 2006).
We thus capitalized on the availability of published grooming data and used
modern meta-analytical techniques to test whether female primates
reciprocate the overall amount of grooming they receive, that is whether
they exert partner choice by grooming preferentially those individuals that
groom them most.

Source: The Royal Society [Open Access Paper]
http://www.journals.royalsoc.ac.uk/content/j577hu5rk7h7770q/fulltext.html
Posted by
Robert Karl Stonjek


.