M. Takahashi et al., Burrow defense behaviors in a sand-bubbler crab: Scopimera globosa, in relation to body size and prior, residence, J ETHOL, 19(2), 2001, pp. 93-96
The burrow defense behaviors in a sand-bubbler crab, Scopimera globosa, liv
ing on a tidal flat, were experimentally examined. Body size and prior resi
dence influenced the results of struggles for the burrows, and large indivi
duals or the burrow owners won in most cases when the intruders were not si
gnificantly larger than the owners. Most large owners defended their burrow
s by directly fighting their opponents. On the other hand, small owners def
ended their burrows in three different ways. (1) Owners fought directly aga
inst same-sized or smaller intruders. For larger intruders, (2) most owners
returned to their burrows when the owner was nearer to the burrow than the
intruder (returning behavior), and (3) owners sat motionless when the intr
uder was nearer to the burrow than the owner (sitting behavior). Success ra
tios of the three types of burrow defense were 38.2%, 88.5%, and 100%, resp
ectively, It was considered that sitting behavior of the cryptically colore
d S. globosa has evolved because intruders cannot see motionless owners and
consequently cannot detect the owner's burrow.