Homing in the New Zealand eagle ray, Myliobatis tenuicaudatus

Abstract

Homing after experimental displacement is widespread among bony fishes but has only been documented in two species of elasmobranchs, lemon sharks, Negaprion brevirostris, and Port Jackson sharks, Heterodontus portusjacksoni. To test if a species of batoid was capable of homing, New Zealand eagle rays, Myliobatis tenuicaudatus, were experimentally displaced 1.3–9.4 km from the Whangateau Estuary, where they feed, rest and are protected from predators. Significantly more rays returned to the estuary than expected by chance (seven out of eleven rays). The present study demonstrated for the first time that rays are capable of homing after experimental displacement. Homing success was not predicted by day or night capture, displacement distance, ray size, water depth at the displacement site or time in captivity. The homing rates and speeds of the rays were lower than those recorded for sharks, possibly due to a disparity in motivation and behavioural differences. Analysis of active tracks for associations with potential navigational stimuli may indicate which stimuli the rays use to home.