Old World frog and bird vocalizations contain prominent ultrasonic harmonics

Abstract

Several groups of mammals such as bats, dolphins and whales are known to produce ultrasonic signals which are used for navigation and hunting by means of echolocation, as well as for communication. In contrast, frogs and birds produce sounds during night- and day-time hours that are audible to humans; their sounds are so pervasive that together with those of insects, they are considered the primary sounds of nature. Here we show that an Old World frog (Amolops tormotus) and an oscine songbird (Abroscopus albogularis) living near noisy streams reliably produce acoustic signals that contain prominent ultrasonic harmonics. Our findings provide the first evidence that anurans and passerines are capable of generating tonal ultrasonic call components and should stimulate the quest for additional ultrasonic species.

Inner ear anatomy is a proxy for deducing auditory capability and behaviour in reptiles and birds

“…In theory, these ECD dimensions should provide a basis for inferring hearing sensitivity, which in turn has behavioural implications. For example, vocalizing vertebrates generally produce vocal frequencies within the range of their hearing (Konshi 1970;Brown & Waser 1984;Endler 1992;Narins et al 2004), so estimates of hearing frequency range may be informative about the presence of vocalization and likely vocalization frequencies in extinct taxa (Evans 1936;Manley 1973). These estimates may also provide information about sociality and vocal complexity, since vocal communication tends to be more complex in species that form large, socially intricate aggregations (Evans 1936;Blumstein 1997).…”

Ultrasonic signalling by a Bornean frog

“…In contrast, the DF of the calls of the other 'ultrasonic' frog, O. tormota, are consistently within the audible range, 5-9 kHz (Feng et al 2002;Narins et al 2004). To our knowledge, H. cavitympanum and the blue-throated hummingbird (Lapornis clemenciae; Pytte et al 2004) are the only non-mammalian vertebrates shown to produce structurally independent ultrasonic signals (i.e.…”

“…Among the most striking examples is Odorrana tormota (previously Amolops tormotus), a frog found in two provinces of central China (Zhou & Adler 1993). This species has unusually high-pitched calls containing substantial energy in the ultrasonic frequency range (above 20 kHz), and its hearing extends from less than or equal to 1 kHz to approximately 35 kHz (Narins et al 2004;Feng et al 2006), dramatically exceeding previously reported upper limits of anuran frequency sensitivity (e.g. 8 kHz, Loftus-Hills & Johnstone 1970;5 kHz, Fay 1988).…”

“…8 kHz, Loftus-Hills & Johnstone 1970;5 kHz, Fay 1988). Playback experiments demonstrate that the ultrasonic elements are behaviourally relevant and may be used to avoid masking by broadband but predominately low-frequency stream noise in their habitat (Narins et al 2004;Feng et al 2006). Odorrana tormota is the first nonmammalian vertebrate shown to communicate with ultrasound, and its use of this high-frequency channel for intraspecific acoustic communication challenges current understanding of frog sound production and reception mechanisms.…”

Inner ear morphological correlates of ultrasonic hearing in frogs

“…The Odorrana and Huia genera are from distinct evolutionary lineages (Stuart, 2008) suggesting that the frogs converged on the ability to detect extraordinarily high frequencies. All three species are torrent frogs; they inhabit rapid-flowing hill or mountain streams, and call alongside rushing water that produces an abundance of broadband, predominately low-frequency, background noise (Feng et al, 2002;Narins et al, 2004;. The convergence of O. tormota and H. cavitympanum on ultrasonic communication may have resulted from parallel selection pressure to place acoustic signals within relatively noise-free windows of their environments' ambient spectra .…”