Divergent Receiver Responses to Components of Multimodal Signals in Two Foot-Flagging Frog Species

Abstract

Multimodal communication of acoustic and visual signals serves a vital role in the mating system of anuran amphibians. To understand signal evolution and function in multimodal signal design it is critical to test receiver responses to unimodal signal components versus multimodal composite signals. We investigated two anuran species displaying a conspicuous foot-flagging behavior in addition to or in combination with advertisement calls while announcing their signaling sites to conspecifics. To investigate the conspicuousness of the foot-flagging signals, we measured and compared spectral reflectance of foot webbings of Micrixalus saxicola and Staurois parvus using a spectrophotometer. We performed behavioral field experiments using a model frog including an extendable leg combined with acoustic playbacks to test receiver responses to acoustic, visual and combined audio-visual stimuli. Our results indicated that the foot webbings of S. parvus achieved a 13 times higher contrast against their visual background than feet of M. saxicola. The main response to all experimental stimuli in S. parvus was foot flagging, whereas M. saxicola responded primarily with calls but never foot flagged. Together these across-species differences suggest that in S. parvus foot-flagging behavior is applied as a salient and frequently used communicative signal during agonistic behavior, whereas we propose it constitutes an evolutionary nascent state in ritualization of the current fighting behavior in M. saxicola.

DNA barcoding reveals unprecedented diversity in Dancing Frogs of India (Micrixalidae, Micrixalus): a taxonomic revision with description of 14 new species

“…To stabilize this name, we herein designate a specimen that is most comparable with the original description as the neotype of Philautus (= Micrixalus) kottigeharensis Rao, 1937. This species was identified as Micrixalus saxicola by Gururaja (2010) and Preininger et al (2013aPreininger et al ( , 2013b, and as Micrixalus aff. saxicola by Preininger et al (2013c).…”

“…Studies have reported habitat features (Reddy et al, 2002), foot-flagging (Krishna and Krishna, 2006;Malhotra and Davis, 1991;Vasudevan, 2001) and reproductive behaviour (Gururaja, 2010) in Micrixalus species, and a few have specifically dealt with visual and acoustic communication in these frogs (Preininger et al, 2013a(Preininger et al, , 2013b(Preininger et al, , 2013c. However, all of these studies concentrated only on two species, M. fuscus and M. 'saxicola', and there is no information available for other species in the genus.…”

Increased androgenic sensitivity in the hind limb muscular system marks the evolution of a derived gestural display

“…22 and 23). Prior studies suggest that S. parvus use calls as longer-range advertisement signals, whereas they use foot flags predominantly as close-range signals to other males in competition for breeding sites (22,25). Thus, in this species, acoustic and visual displays are used in concert as a multimodal signal, or at least a simultaneous and/or sequential combination of signals necessary for appropriate intraspecific communication (22,26).…”

Multimodal cues improve prey localization under complex environmental conditions

“…Males of some frog species that call near forest streams, for example, show elaborate foot-waving displays [16,17]. These displays are thought to have evolved in response to high levels of acoustic background noise to increase their detection by prospective females.…”