Boffa Miskell Ltd | Waihi North Project | Terrestrial Ecology Values and Effects of the WUG | 22 June 2022 47 6.2.2 Terrestrial Invertebrates Noise Noise may potentially be disruptive for invertebrates that communicate by sound by interfering with their perception of natural sounds (masking). Given that the change to the noise environment described below is minimal (i.e. the modelled noise is close to measured ambient noise levels), the likely behavioural response of invertebrates is either no response, aversion (if the individual is mobile), or adaptation to compensate for increased background noise. There are very few studies that examine the effects of noise on invertebrate species in New Zealand. However, the New Zealand tree wētā (Hemideina spp.) readily communicates by stridulation24 that produces a low frequency chirping sound. These sounds are important in social behaviour, for both aggressive and mating interactions (Ewers and Cowley 2005). In contrast, ground wētā (Hemiandrus spp.) primarily communicate using vibration signals as they lack tympanal hearing organs. Both ground wētā and tree wētā are common in Coromandel Forest Park. Vibration Responses to vibrations are understudied in the scientific literature, but it is understood that ground wētā (Hemiandrus spp.) primarily communicate using vibration signals. Ground wētā burrow in soil and mate on leaf litter which also transmits signal vibrations. Males also use vibrational signals to defend their burrows and territory. Vibrations produced are sexually dimorphic (Hill, 2001; Gwynne, 2004). Tree wētā have a suite of tibial organs which allow them to sense both substrate vibrations and air borne sound (Strauß et al. 2017). Tree wētā produce vibrations on mānuka trees as a method of mate locating (Hill, 2001). Both ground wētā and tree wētā are common in Coromandel Forest Park. Vibrations that are infrequent and short in duration are unlikely to meaningfully impact wētā communication and behaviour as they are typically active for many hours at a time. 6.2.3 Native Frogs Noise Archey’s frogs do not have inner ear structures and their sensitivity to airborne sounds is limited. Leiopelmatid frogs do not appear to communicate by vocalisation so the noise associated with the construction and operation of the vent raises and WUG, respectively, may have little impact on their behaviour or communication. Archey’s frogs are nocturnal, and construction of the vent raises would be undertaken during the day, outside of their typical active period. Noise associated with the fan when vents are operational would be continuous. Taking a conservative approach, their response to noise disturbance may include freezing while out of a refuge, resulting in heightened predation risk; or reluctance to emerge from a refuge resulting in inability to find prey / mates. Modelling of noise levels indicates that operational noise associated with the vent raises will be comparable with ambient noise levels. Vibration Archey’s and Hochstetter’s frogs are sit and wait predators that remain stationary for long periods. They may be sensitive to vibration if they use it to detect prey, or if vibrations from natural sources act as behavioural cues (e.g. rainfall vibration as a cue to emerge) although this 24 Vibration produced by rubbing two parts of the body together. In the case of wētā, sounds is produced by rubbing a scraper on the hind legs against a file on the side of the body. Giant wētā also communicate by stridulation, but their known range does not include the Coromandel.
RkJQdWJsaXNoZXIy MjE2NDg3