3 Memorandum : Vibration effects on amphibians (Leiopelmatid frogs) 64524 Vibration effects_memorandum (15 June 2022)_Final Rev 0 The male guards (broods) the eggs for a period of 6–9 weeks6 by sitting high over the eggs with body raised and both fore- and hind-limbs outstretched. The function of egg brooding behaviour in Archey’s frog is poorly studied but may represent a strategy to keep the eggs moist (possibly via urinary excretion) (Stephenson, 1961). Indeed, male Archey’s frogs with eggs or hatchlings store water reserves, presumably for maintaining the necessary hydric environment at the nest site (Bell, 1985). Other possible reasons might be to reduce the incidence of fungal or bacterial infection through transfer of chemicals from the adult to eggs, and/ or to protect the eggs from predators. Whatever the function, the males have a strong behavioural predisposition to brood over this period of the lifecycle. Male frogs continue to brood eggs until they hatch and the tiny, tailed froglets then climb onto the back of the male who carries them for up to six weeks while they complete their development (dorsal brooding) (Bell, 1978; 1985). Sexual maturity is reached at 3–4 years of age and generation time is approximately 8–10 years. The lifespan of Archey’s frog may be more than 35 years. Like all Leiopelmatid frogs (of which there are three species), Archey’s frog possess primitive traits that distinguish them from all other species of frogs. These traits include vestigial tail-wagging (caudalipuboischiotibialis) muscles, cartilaginous inscriptional ribs, the presence of amphicoelous vertebrae, and nine presacral vertebrae (most frogs have eight). In addition, leiopelmatid frogs lack structures of the middle ear (e.g., tympanic membranes, columella), eustachian tubes and vocal sacs (Stephenson, 1961; Bell, 2010). This limits their ability to ‘hear sound’ and vocalise compared to most other frogs that usually emit loud social calls during the mating season. The absence of anatomical structures for communication suggests that chemosensory signals might be important in leiopelmatid frog communication (i.e., communication like that of salamanders, using chemosignals to recognise the size and individuality of their conspecifics). Furthermore, seismic (vibration) signals may play an important role in communication or behavioural response, as this is seen in other ‘earless’ anurans (Womack et al., 2017). Archey’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 5,000– 20,000 mature individuals and a predicted decline 10–30% over three generations7. It is listed as “Critically Endangered” (A2ab) on the IUCN Red List based on a dramatic (≥ 80%) population reduction over 10 years or three generations and a presently stable population trend (low confidence). 3.1 Biology and ecology of Hochstetter’s frog (Leiopelma hochstetteri) The biology and ecology of Hochstetter’s frog (L. hochstetteri) are markedly different that of Archey’s frog. Hochstetter’s frog is semiaquatic, usually living in and on the edges of small, shaded stream tributaries and their reproductive strategy involves laying eggs (up to 22 in number) in shallow depressions with trickling water on the edges of streams. The eggs hatch at a relatively early development stage into larvae with partially developed limbs and well-developed tail fins that enable them to swim. They do not feed and remain in the shallow water while they develop into small frogs (Bell, 1985). 6 Captive observation. 7 https://nztcs.org.nz/assessments/24936
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