Behavioral Evidence for a Chemical Disturbance Cue in Bat Rays (Myliobatis californica)

The release of waterborne chemical cues is a well-documented anti-predator strategy in teleost fish, allowing individuals to detect, and respond to, predation threats. However, little is known about whether an ancient group of fishes, elasmobranchs, employ similar mechanisms to communicate predation risk. Here, we experimentally investigate the behavioral and physiological responses of Bat rays (Myliobatis californica) following the manipulation of an upstream conspecific. Specifically, we examined whether Bat rays receiving water from an upstream conspecific that had been physically chased with a stick for 30 s, simulating a non-injurious predation disturbance, exhibited changes in activity levels and physiological stress markers. Receiving Bat rays increased their velocity by approximately 3 cm/s (~21%) compared to their pre-exposure state, whereas Control rays showed no significant change. Receivers also exhibited a significant shift toward active swimming behaviors, while Controls spent more time in passive behaviors. This shift was positively correlated with velocity, reinforcing that exposure to waterborne disturbance cues from a distressed conspecific triggered increased activity. Physiological measurements showed no significant differences between groups in glucose, β-HB, lactate, or pH levels. We suggest the activity increase corresponds with a flight-type response to predation risk. These findings reveal a previously undocumented communication mechanism in marine predators, contributing to a broader understanding elasmobranch behavior and physiology.