4 Memorandum : Vibration effects on amphibians (Leiopelmatid frogs) 64524 Vibration effects_memorandum (15 June 2022)_Final Rev 0 Unlike Archey’s frog, Hochstetter’s frog are strongly associated with streams and take refuge during the day in damp crevices, under stones, in rock piles or under logs, and in thick leaf litter packs within or immediately adjacent to the water column. Though, they are occasionally found long distances away from streams in damp native forest, where they refuge beneath logs, rocks, and dense leaf litter. Hochstetter’s and Archey’s frogs are occasionally found together under the same terrestrial refuges in damp native forest. Hochstetter’s frog occurs only in the North Island, in fragmented populations from Northland (south of Whangarei) to Waikato (Maungatautari) and the Coromandel Peninsula, and on East Cape. It also occurs on Great Barrier Island (Aotea Island). Hochstetter’s frog is currently classified as “At Risk – Declining” under the New Zealand Threat Classification System (Townsend et al, 2008; Burns et al., 2018), based on a 2017 national population estimate of > 100,000 mature individuals and a predicted decline 10–70% over three generations8. It has an IUCN Red List listing of “Least Concern” (100, 000 mature individuals) with an ongoing decreasing (at least 10%) population trajectory. 4.1 Seismic (vibration) detection by animals Vibration is a form of energy that travels in waves that can be physically felt. These waves are oscillatory in nature and have both an amplitude and frequency. The amplitude contributes to the intensity of the vibration and is represented by how far the peak of the wave moves past the position of equilibrium. Frequency is the amount of time that it takes to complete one cycle from a point on one wave to the same point on the next wave (measured in Hertz). The magnitude of vibration can be measured in relation to the amplitude by displacement from the point of equilibrium (often measured in millimetres), the velocity of wave movement (quantified in mm/s) or acceleration past the neutral point measured in meters per second squared (mm/s2) (Reynolds et al., 2018). Different species perceive vibration to a lesser or greater degree depending on the frequency (Hz) of the vibration. For example, Norton et al. (2011) demonstrated that small rodents (rats and mice) are more likely to be affected by vibration in frequency ranges generated by a vibration source as compared with humans. This also highlights that the degree of perception is dependent on the size of an animal. In addition to the frequency of vibration, other factors that will determine the effects on animals include magnitude, duration, whether the vibration is directed at the whole body or is localized, and potentially individual variation in perception across species or within the same species. Amphibians are highly sensitive to air-borne sound and among terrestrial vertebrates, are the most sensitive to vibrations (Caorsi et al., 2019). Typically, the tympanic middle ear and inner ear structures of anurans function to detect airborne sound by transferring sound energy to fluid vibrations sensed by hair cells in the inner ear (Pereyra et al., 2016). These structures, and specifically those associated with the inner ear (i.e., three organs: the amphibian papilla, the basilar papilla and the sacculus; Caorsi et al., 2019), 8 https://nztcs.org.nz/assessments/24936
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