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females expose the chest, face, and belly less often to higher-ranking females
than vice versa. Male-male dyads almost never groomed the face, chest, and
belly. Similarly the face, chest, and belly were underrepresented in grooming
between individuals that groomed each other less frequently. One interpreta-
tion is that recipients of grooming expose less vulnerable parts of their body to,
and avoid eye contact with, individuals they perceive as potentially dangerous
(Moser et al. 1991; Borries 1992). Another analysis of the form, distribution,
and context of social grooming was undertaken in two groups of Tonkean
macaques (
Macaca tonkeana
) by Thierry et al. (1990). They found that kinship
and dominance role had no effect on the form or distribution of social groom-
ing among adult females, the most common class of individuals to be observed
grooming.
The caveat that no one method of disentangling social relationships is uni-
versally appropriate has been stressed by Dunbar (1976). For example, in a
study of grooming in three species of macaques, Schino et al. (1988) found
that whereas frequency and total duration of grooming were highly correlated,
there was low correlation between its total duration and mean duration, and
frequency and mean duration were not correlated. A closer inspection of the
data also revealed that even this general equivalence between measures of fre-
quency and total duration did not always hold within specific grooming rela-
tionships. In general, frequency is a measure of initiation and mean duration
is a measure of continuation. In Schino et al.'s case, both measures were needed
to interpret adequately the macaques' society.
Not surprisingly, one important stimulus for grooming in rodents is soiled
fur (Geyer and Kornet 1982). However, because grooming can be undertaken
alone or mutually, it has social implications transcending cleanliness. Stopka
and Macdonald (in press) used a similar approach to Hemelrijk and Ek's
(1991) analysis of grooming in captive chimpanzees to examine patterns of
reciprocity in grooming among wood mice (
Apodemus sylvaticus
). A powerful
method for investigating this involved row-wise matrix correlation and the
Mantel test (de Vries et al. 1993). Allogrooming was less common than auto-
grooming and was most commonly directed by male wood mice to females.
Having described a social network in grooming, Markov chain analysis then
revealed that the termination rate of female contact behavior (expressed as her
tendency to flee the male's attentions) depended largely on the male's tendency
to terminate allogrooming. The pattern of transition rates from one behavior
to another revealed that the most common transition was from allogrooming
of the female by the male to male nasoanal contact with the female. This indi-
cates the motivation underlying the male's tendency to allogroom females:
