Hearing sensitivity in context: Conservation implications for a highly vocal endangered species

Abstract

a b s t r a c tHearing sensitivity is a fundamental determinant of a species' vulnerability to anthropogenic noise, however little is known about the hearing capacities of most conservation dependent species. When audiometric data are integrated with other aspects of species' acoustic ecology, life history, and characteristic habitat topography and soundscape, predictions can be made regarding probable vulnerability to the negative impacts of different types of anthropogenic noise. Here we used an adaptive psychoacoustic technique to measure hearing thresholds in the endangered giant panda; a species that uses acoustic communication to coordinate reproduction. Our results suggest that giant pandas have functional hearing into the ultrasonic range, with good sensitivity between 10.0 and 16.0 kHz, and best sensitivity measured at 12.5-14.0 kHz. We estimated the lower and upper limits of functional hearing as 0.10 and 70.0 kHz respectively. While these results suggest that panda hearing is similar to that of some other terrestrial carnivores, panda hearing thresholds above 14.0 kHz were significantly lower (i.e., more sensitive) than those of the polar bear, the only other bear species for which data are available. We discuss the implications of this divergence, as well as the relationship between hearing sensitivity and the spectral parameters of panda vocalizations. We suggest that these data, placed in context, can be used towards the development of a sensory-based model of noise disturbance for the species.

Sound transmission in a bamboo forest and its implications for information transfer in giant panda (Ailuropoda melanoleuca) bleats

“…Imaging studies are now required to determine whether the giant panda has evolved a specialized epi-laryngeal tube that is compatible with the production of a high amplitude formant at around 3 kHz. Interestingly, a recent behavioural test of the giant panda’s auditory capabilities also revealed increased hearing sensitivity around 500 Hz and 2000 Hz 62 , which corresponds approximately with the lowest amplitude frequency components of bleats at 40 m, F0 and F4. Hence, this species’ hearing sensitivity may also reflect selection pressures to perceive information encoded by F0 and F4 in the contexts of identity cueing.…”

Giant panda (Ailuropoda melanoleuca) neonates use broadband calls to communicate with their mothers

“…Adult pandas are most sensitive to frequencies between 12.5 and 14.0 kHz and can even hear frequencies up to 70 kHz (Owen et al 2016). Therefore, even the extremely high-pitched vocalizations of neonates fall well within the mother's operational hearing range (Koester et al 1998).…”

“…For the first 4-5 weeks of their lives, neonates are very vocal (Zhu et al 2001), but will emit fewer calls from approximately 2 weeks of age onward, when the mother starts feeding again, and thus leaves her cub for increasingly longer periods of time (Zhu et al 2001). The functional hearing range of adult pandas has been estimated to extend from 0.1 to 70 kHz with good sensitivity between 10.0 and 16.0 kHz, and best sensitivity measured at 12.5-14.0 kHz (Owen et al 2016), making pandas a suitable model species to investigate the potential occurrence and behavioral relevance of neonate broadband calls.…”

“…The functional hearing range of adult pandas has been estimated to extend from 0.1 to 70 kHz with good sensitivity between 10.0 and 16.0 kHz, and best sensitivity measured at 12.5–14.0 kHz (Owen et al. 2016), making pandas a suitable model species to investigate the potential occurrence and behavioral relevance of neonate broadband calls.…”

Acoustic recordings provide detailed information regarding the behavior of cryptic wildlife to support conservation translocations

“…Understanding the degree to which released pandas are encountering human infrastructure and activities is also a priority for understanding the experience of release candidates and the challenges they face 37 . Indeed exposure to noisy anthropogenic activities (e.g., vehicle traffic, resource extraction) may be readily identified and panda specific audibility interpreted 45 via acoustic monitoring, as could be the sounds of herding activities. While reserves offer a degree of protection and appropriate habitat, human activities are common and pandas may move outside the boundaries of reserves post-release.…”