The mechanics of sound production in the puff adder Bitis arietans (Serpentes: viperidae) and the information content of the snake hiss

Abstract

Puff adders (Bitis arietans), like many other snakes, hiss as part of their defensive repertoire. In B. arietans, the hisses have a clear quadraphasic pattern consisting of an initial exhalatory hiss, a brief transitional pause, an inhalatory hiss and a rest or breath-holding phase. Simultaneous recordings of body diameter, electrical activity in the intrinsic laryngeal musculature, airflow through the nasal passageway and sound production revealed that the anterior respiratory tract plays a passive role in hissing and that the costal pump is responsible for generating the quadraphasic pattern. During hissing, B. arietans uses the same mechanics previously described for normal respiratory ventilation in snakes. Analyses of artificial hisses reveal that the anterior respiratory tract of B. arietans has little ability to modify an exhalant airstream acoustically. The combination of the simple ventilatory mechanics used during hissing and the lack of acoustic modification of the exhalant airstream results in the production of an acoustically simple hiss. Cross-correlation matrix analyses of a variety of snake hisses showed a high degree of acoustic similarity between the sounds, almost approaching the levels determined for white noise. This high level of acoustic similarity reflects the low level of acoustic specialization within the sounds produced by snakes and the low potential for encoded information content.

Chinese striped-neck turtles vocalize underwater and show differences in peak frequency among different age and sex groups

“…There is a lack of hearing research on Chinese striped-neck turtles; thus, further studies are needed to determine whether the turtles can hear their own high-frequency signals, or if it is just a potential functional signal redundancy as observed for some of the vocalizations of Alligator sinensis ( Todd, 2007 ; Wang et al, 2007 ; Wang et al, 2009 ). Snakes can produce sounds up to 10 kHz, which is well above their hearing range; however, the low level of acoustic specialization within the sounds produced by snakes and the low potential for encoded information content indicate limited communication capabilities ( Young et al, 1999 ; Young, 2003 ). It was reported that Ptyas mucosus may be an acoustic Batesian mimic of the king cobra, Ophiophagus hannah ( Young, Solomon & Abishahin, 1999 ).…”

Exploring Sound Emission of the Lizard Pristidactylus valeriae

“…Pristidactylus valeriae hissed under predation risk, but some sound characteristics were treatment and sex-dependent since; for example, hisses emitted under threat were longer than those emitted under capture. Even if hisses only involve normal respiratory movements [52], prolonged and forced movements might require extra energy. In this context, emitting longer hisses when there is more probability to survive, threat vs. capture, may provide honest information on endurance to fight or escape, e.g., [53] and thus increase the chances to deter the predator.…”

“…Hisses are sounds with a simple structure and, at least for snakes, data show that they have high similarities across species [52]. In light of this, and considering that vocalizations uttered under predation risk tend to be conservative across taxa, e.g., [62,63], it can be hypothesized that hisses of Pristidactylus species may be similar across taxa.…”