5 Memorandum : Vibration effects on amphibians (Leiopelmatid frogs) 64524 Vibration effects_memorandum (15 June 2022)_Final Rev 0 are also responsible for sensing seismic (vibration) signals (Narins & Lewis, 1985; Christensen-Dalsgaard & Narins, 1993; Christensen-Dalsgaard & Jørgensen, 1996). The pathway for substrate vibration sensing occurs via the operculum, a cartilaginous disc that is in physical contact within in the oval window of the inner ear in amphibians (i.e., their movement is coupled), which transfers substrate vibrations to the inner ear organs. Because the inner ear structures are responsible for sensing vibration signals, it is not essential that the structures of the middle ear are present. Indeed, studies on ‘earless’ amphibian species (species lacking a middle ear) demonstrate sufficient ability to sense vibration and some groups (e.g., bufonids) show vibrational sensitivities equivalent to ‘eared’ species (Womack et al. 2017 and refs within). It has been postulated that the loss of the middle ear could allow freer movement of the operculum, increasing sensitivity to substrate vibrations in ‘earless’ species (Gridi-Papp & Narins, 2010). Furthermore, species-specific extratympanic pathways, including lung pathway, opercularis pathway, and/ or bone pathways (e.g., skull conduction enhanced by resonation of the oral cavity, lowering head to contact floor, or transmitted to the inner ear fluid directly by the skeletal system along the entire spine) may also be utilised to sense vibration in ‘earless’ species (Gridi-Papp & Narins, 2010; Pereyra et al., 2016). Such substrate vibrations that travel through the ground or plants have been suggested as important communication mechanisms for some ‘earless’ species (Womack et al., 2017). It is important to note that the above observations are general in nature, and there appear to be no studies that explore whether and how leiopelmatid frogs (including Archey’s frogs) perceive vibrations, including those that are not associated with noise. 5.1 Effects of vibration on animal behaviour There is a growing body of evidence on behavioural and physiological responses to vibration stimuli in animals (e.g., rodents - Reynolds et al., 2018; poultry - Scott, 1994; bats - Snyder et al., 2015; and frogs - Felt et al., 2012; Márquez et al., 2016; and Caorsi et al., 2017; 2019). Studies on rodents have demonstrated that vibration can cause alterations in reproduction as well as mortality and morbidity in other laboratory species, including frogs (Garner et al., 2018). Nevertheless, while anthropogenic substrate vibrations could be sources of mechanical disturbance for animals, including frogs, that disrupt behaviour this field is still in its infancy is poorly understood (Caorsi et al., 2019). With respect to amphibians, while there have been studies examining the impacts of noise (e.g., traffic noise) on behaviour, very few studies have investigated vibration effects. Amphibian response to vibrations is most readily demonstrated in calling or vocalising species, by reduced male calling rates in response to anthropogenic seismic activity (Gridi-Papp & Narins, 2010; Mazerolle et al., 2015; Caorsi et al., 2019). For example, the call frequency reduces or ceases in response to an observer walking at a few meters distance, but not in response to observer-emitted vocalisations (Gridi-Papp & Narins, 2010). Caorsi et al. (2017; 2019) investigated the effects of seismic sources associated with traffic and wind turbines on frogs and demonstrated a significant reduction in call rate by males and a clear negative effect of anthropogenic vibrations on anuran communication. However, such effects are not relevant for
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