Real estate ads in Emei music frog vocalizations: female preference for calls emanating from burrows

Abstract

During female mate choice, both the male's phenotype and resources (e.g. his nest) contribute to the chooser's fitness. Animals other than humans are not known to advertise resource characteristics to potential mates through vocal communication; although in some species of anurans and birds, females do evaluate male qualities through vocal communication. Here, we demonstrate that calls of the male Emei music frog (Babina dauchina), vocalizing from male-built nests, reflect nest structure information that can be recognized by females. Inside-nest calls consisted of notes with energy concentrated at lower frequency ranges and longer note durations when compared with outside-nest calls. Centre frequencies and note durations of the inside calls positively correlate with the area of the burrow entrance and the depth of the burrow, respectively. When given a choice between outside and inside calls played back alternately, more than 70 per cent of the females (33/47) chose inside calls. These results demonstrate that males of this species faithfully advertise whether or not they possess a nest to potential mates by vocal communication, which probably facilitates optimal mate selection by females. These results revealed a novel function of advertisement calls, which is consistent with the wide variation in both call complexity and social behaviour within amphibians.

Right ear advantage for vocal communication in frogs results from both structural asymmetry and attention modulation

“…In general, either increases or decreases in power output within the delta, alpha and beta bands, over time, matched closely the dynamic properties of the acoustic signals presented as well as the previously described time course of decision-making during mate choice in female music frogs [36]. Moreover, these significant differences in EEG output including differences in the EEG theta band among the four acoustic stimuli only appeared in the left mesencephalon.…”

“…Notably, the relative delta power in the music frog declines with time in the left mesencephalon, especially in response to HSA calls, consistent with the idea that active neural processing results in a decrease in low frequency EEG power and an increase in high frequency power [48,49]. These dynamics might reflect the fact that Babina females in the reproductive stage exhibit a high level of approach behavior when listening to HSA calls [36].…”

“…daunchina males produce advertisement calls during the breeding season both from within nest burrows the male has made and from outside the burrows. The resonant properties of the burrow alter some of the call acoustics, and phonotaxis experiments show that females in the reproductive stage prefer male calls produced from inside burrows [36]. Calls recorded from males within burrows were regarded as highly sexually attractive (HSA) while those produced from outside the burrow were regarded as possessing low sexual attractiveness (LSA).…”

“…Both HSA and LSA calls contained five notes recorded from the same individual with both temporal and frequency parameters close to average values for the population. Moreover, the call stimuli were one of five pairs used in a previous phonotaxis study which demonstrated that females responded preferentially to this specific HSA call exemplar versus the LSA call exemplar [36]. WN was constructed as a consecutive "call" and its duration was the average of the durations of the HSA and LSA calls (about 1.2 s), containing a 15 ms period with sinusoidal rise-fall characteristics.…”

“…The four stimuli were presented to females in a randomized sequence, in which each stimulation continued for 10 min with 4 s inter-stimulus intervals between each call presentation, approximately equal to the mean natural inter-call intervals of B. daunchina [36]. Each 10 min stimulation period except for the silence stimulus was followed by an hour silent period, and all stimuli except for silence were equalized for intensity (65 dB SPL, re 20 Pa; Aihua, AWA6291; Hangzhou, China; measured at the center of the tank).…”