Orienting behaviour during aerial and underwater visual discrimination by the mink (Mustela vison schreber)

Orienting responses by mink during aerial and underwater visual discrimination tests were most frequent when the grating lines subtended angles at the eye near the visual threshold angle. Factorial analysis showed that in air and in water at ranges from 10 to 90 cm most responses occurred at 30 cm discrimination distance and more occurred to marginally supra-threshold than to marginally sub-threshold stimuli. Between media, more responses occurred in air than in water. At longer ranges the mink oriented less readily than at 30 cm but if orienting occurred better discrimination followed than if the mink did not orient.