Wiley, R. H., L. Steadman, L. Chadwick, and L. Wollerman. 1999.
Social inertia in white-throated sparrows results from recognition
of opponents. Animal Behaviour 57: 453-463.
Social inertia is a term for the stability of dominance relationships
despite changes in the intrinsic dominating abilities of opponents. In a
standard test for social inertia, low-ranking birds in an established
hierarchy receive implants with testosterone (treated) and high-ranking
birds receive empty implants (untreated). Social inertia occurs when the
treated birds remain subordinate to untreated opponents in these groups,
despite evidence that similarly treated birds dominate untreated
All previous demonstrations of social inertia have returned treated and
untreated birds to their original aviaries and opponents and thus have not
separated effects of familiarity with the location from those of
familiarity with opponents.
The present experiment investigated social inertia in 16 groups of
white-throated sparrows Zonotrichia albicollis.
When low-ranking treated birds were placed in new aviaries with
familiar high-ranking untreated opponents (treatment S, same opponents),
dominance relationships showed social inertia.
When such birds were placed in new aviaries with unfamiliar opponents
(treatment N, new opponents), testosterone influenced dominance.
When groups of high-ranking untreated birds acquainted with each other
were placed with unfamiliar treated opponents (treatment G, grouped
dominants), coat-tail effects sometimes outweighed the effects of
Social inertia in this species is thus a result of familiarity with
opponents, rather than familiarity with locations of encounters.
Measurements of aggressive tendencies confirmed a previous report that
social inertia suppresses activation of aggression by testosterone.
White-throated sparrows can thus recognize their opponents, and this
ability affects the expression of both dominance and aggression.
STATUS SIGNALS AND RECOGNITION OF OPPONENTS (from the Discussion)
Studies of status signalling in a congener of the white-throated sparrow,
the Harris' sparrow Zonotrichia querula, have included
manipulations of hormonal state or appearance or both (a double
treatment). For instance, one individual implanted with testosterone and
then released where it had been captured failed to increase in dominance;
in contrast, two others observed before and after they were both implanted
and painted to look like older males did increase in rank (Rohwer & Rohwer
The bird that was only implanted received more attacks from dominant
opponents but apparently did not initiate any more attacks (Rohwer &
Rohwer 1978). In white-throated sparrows, some implanted birds returned
to wild flocks also engage in more frequent aggression, in part initiated
by themselves (Archawaranon et al. 1991). Birds released into wild flocks
confront opponents that no doubt vary in familiarity. Presumably, as in
stage III of the present experiment, testosterone activates aggression
when opponents are unfamiliar with each other.
Painting a bird might well affect its previous acquaintances' ability to
recognize it. This new situation might also quickly affect the subject's
behaviour. As a result, the rise in dominance of Harris' sparrows
following double treatment (with both implants and paint) might result
either from direct effects of the painting on its status signals or from
indirect effects of the painting on recognition of opponents. In the
latter case, when recognition is diminished, testosterone could produce an
increase in dominance.
Such double-treatment experiments might thus be explained by the effects
of testosterone on the behaviour of unfamiliar opponents, in effect by an
absence of social inertia.
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