The Neotropical catfish Pterygoplichthys pardalis produces a harsh stridulation sound upon manual capture. This stridulation sound is made on the abduction of the pectoral fin spine, and is accomplished by friction of a ridged dorsal condyle against a rough spinal fossa of the cleithrum in the pectoral girdle. The sound produced has an average frequency of 121 Hz, and is used with other anti-predator adaptations such as bony subdermal armor and defensive fin-spreading. Pterygoplichthys pardalis does not display behavioral modification in response to conspecific stridulation sound, and therefore it is likely that stridulation sound in P. pardalis is being used as a predator deterrent.