As stated in
McCormick and Manassa (2008), bobbing has been shown
to occur as a defensive response (Gnatholepis anjerensis
and Coryphopterus nichlosii: Smith and Lawrence 1992),
but the behavior could also be a means of enhancing visual
risk assessment (Smith 1989) or acquiring chemical
information, as well as functioning both as a signal to
predators that they have been seen and to alert conspecifics
to the presence of an active predator (Smith and Smith
1989).