Md. Jennions et Pry. Backwell, RESIDENCY AND SIZE AFFECT FIGHT DURATION AND OUTCOME IN THE FIDDLER-CRAB UCA ANNULIPES, Biological Journal of the Linnean Society, 57(4), 1996, pp. 293-306
We performed a field experiment to investigate the effect of carapace
width, major cheliped length and burrow ownership on the fighting succ
ess of male fiddler crabs (Uca annulipes). We removed males from their
burrows and released them back into the colony (n = 82). Released mal
es tended to initiate encounters with burrow owners slightly smaller t
han themselves. Several general predictions of Sequential Assessment G
ame models of contest behaviour were supported: (1) residents won more
encounters; (2) intruders were more likely to ruin when larger than r
esidents. When body size (carapace width) was controlled for, intruder
s with relatively large claws for their body size were more likely to
win contests; (3) the duration of encounters was related to the size d
ifference between males; (4) encounters won by the larger male were of
shorter duration than those won by the smaller male; (5) encounters w
on by the resident tended to be of shorter duration than those won by
intruders (P = 0.07); (6) on average, encounter duration was longer wh
en the intruder was larger than the resident. However, the encounters
we documented began with seemingly costly behaviour such as pushing an
d the inter-locking of daws and did not unambiguously escalate from in
itial low cost behaviours. Sequential assessment of relative fighting
ability may therefore not have been occurring. Prior visual assessment
of opponents' fighting ability, followed by 'all-out fights' during p
hysical encounters may also provide a plausible explanation for our re
sults. (C) 1996 The Linnean Society of London