R. Houtman et Lm. Dill, THE INFLUENCE OF SUBSTRATE COLOR ON THE ALARM RESPONSE OF TIDEPOOL SCULPINS (OLIGOCOTTUS-MACULOSUS, PISCES, COTTIDAE), Ethology, 96(2), 1994, pp. 147-154
For animals that use crypsis to avoid predators, immobility reduces th
e risk of detection. The magnitude of this immobility benefit depends
upon the probability that a predator is present, since a predator must
be present for crypsis to be valuable. Thus, cryptic animals typicall
y reduce their movement rates upon detection of a nearby predator or s
igns of its activity. Such a response occurs in tidepool sculpins (Oli
gocottus maculosus) when presented with water-borne compounds released
from the skin of injured conspecifics (HUGIE et al. 1991). The benefi
t of immobility should also depend upon the animal's background, or su
bstrate, since animals on a matching substrate achieve a higher level
of crypticity than those on a nonmatching substrate, and have more to
gain by remaining still. Therefore, we predicted that the response of
tidepool sculpins to conspecific skin extract would involve a greater
reduction in movement rates for fish on sand (matching) than for those
on white (nonmatching) substrate. The results of a laboratory experim
ent supported this prediction, with fish on sand showing a large decre
ase in movement rates in response to skin extract, while the movement
rates of those on white substrate remained unchanged.