Deception in visual and chemical communication in crustaceans

Abstract

Deception in animal communication occurs when one animal causes another to respond to a condition that does not exist or to fail to respond to one that does. Signals that bluff produce the first kind of error, behavior that hides causes the second, and both are common in visual communication by crustaceans. In contrast, crustacean chemical communication may usually be honest because the communicative chemicals typically are byproducts of the biochemical mechanisms by which crustaceans are built and operate. These cues, which often are released in urine, reliably reveal an individual's identity, sex, reproductive state, and condition. There are, however, opportunities for deception by bluffing and by hiding in the chemical channel. Bluffing may occur when dominance relationships are learned and individuals recognize each other. Subordinates may avoid known dominants even after the condition of the dominant has declined and it is no longer able to win a fight with the subordinate. Frequent probing by subordinates should check such bluffing. Hiding in the chemical channel may occur in escalated fights in which one animal fails to chemically announce its intent to strike and wins by delivering a blind-side punch to an unprepared opponent. Receptive female crabs and lobsters may also withhold cues of their receptivity to avoid courtship by some males, yet direct the same cues to preferred potential mates. In species with multiple male morphs, we speculate that subordinate males may hide from dominants by withholding male odors or mimicking female odors. In species with internal fertilization we also suggest that male seminal fluids may contain chemicals that affect female reproductive processes and bias the rate the male's sperm fertilize the female's eggs. Detecting deception in chemical communication will be very challenging, but we encourage crustacean researchers to keep this possibility in mind when examining signaling behavior via chemicals.