The axolotl (Ambystoma mexicanum) has been used as a model organism for studying development, genetics, and regeneration. Although the sensory hair cells of the lateral line of this species have been shown to be able to regenerate, it is not known whether this also occurs in the inner ear. In fact, little is known about the hearing capabilities of the axolotl or other salamander species. I recorded auditory evoked potentials (AEPs) of six axolotls at eleven frequencies (0.1, 0.25, 0.4, 0.6, 0.8, 1, 1.5, 2, 3, 4, and 6 kHz) in order to produce baseline audiograms of underwater pressure sensitivity. Individuals were then subjected to a 48-hour, 150 Hz sound exposure at approximately 170 dB (re 1 μPa). AEPs were then performed to measure hearing thresholds immediately after sound exposure and at 2, 4, and 8 days post-sound exposure (DPSE). In the baseline audiogram, axolotls were most sensitive at 600 Hz, with an additional peak of sensitivity at 3 kHz. Following sound exposure, axolotls experienced a 6 to 12 dB temporary threshold shift (TTS) after sound exposure, with TTS being greatest at low frequencies near the 150 Hz stimulus frequency (i.e., 100 and 250 Hz). Hearing sensitivity returned to control levels within 8 DPSE. This indicates that axolotls do possess the ability to recover hearing sensitivity after damage following acoustical trauma. This study is the first to document hearing loss in the axolotl. Future studies are needed to correlate this hearing loss and recovery to sensory hair cell loss and regeneration in the axolotl inner ear.

No description available.

Although the effects of noise on children’s learning in school classrooms is well documented, there is very little on the effects of noise on preschool children. There are strict legal requirements for the daily noise exposure an adult worker can received in the workplace but nothing to control the noise children can receive in school and early education. There is also little or no data on how sound affects a child, compared to an adult. The early years of life are critical for the development of speech, hearing and auditory processes, as well as being the most vulnerable time for middle ear infections. This work sets out to determine the typical noise levels in early childhood centres and the effects on a range of children and their teachers. Reverberation times in most centres were found to well exceed the 0.6 seconds prescribed by the Australasian standard for schools and learning spaces. Very high levels of noise were recorded in a number of centres with a significant number of children and staff members, exceeding the maximum daily sound exposure of 100% permitted for workers in industry. A range of special needs children were identified as being particularly at-risk to noise, with the most adverse outcomes reported for those experiencing sensory integration disorder. Yet, even though high levels of noise were recorded, the majority of respondents in a survey of teachers rated the lack of sufficient space for the number of children present as the main issue, and inclement weather as the greatest environmental condition contributing to noise (by confining children indoors, especially over long periods of time). Hearing tests on the children were not permitted under the strict human ethics criteria to which this study had to conform, but simple hearing tests on a small group of teachers, revealed that hearing loss could be a serious occupational health issue. The legal issues of noise control and management in early childhood education have been addressed in this thesis, current legal frameworks reviewed, and recommendations presented for future consideration.

No description available.

Species distribution maps can provide important information to focus conservation efforts and enable spatial management of human activities. Two sympatric marine predators, grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina), have overlapping ranges but contrasting population dynamics around the UK; whilst grey seals have generally increased, harbour seals have shown significant regional declines. A robust analytical methodology was developed to produce maps of grey and harbour seal usage estimates with corresponding uncertainty, and scales of spatial partitioning between the species were found. Throughout their range, both grey and harbour seals spend the majority of their time within 50 km of the coast. The scalability of the analytical approach was enhanced and environmental information to enable spatial predictions was included. The resultant maps have been applied to inform consent and licensing of marine renewable developments of wind farms and tidal turbines. For harbour seals around Orkney, northern Scotland, distance from haul out, proportion of sand in seabed sediment, and annual mean power were important predictors of space-use. Utilising seal usage maps, a framework was produced to allow shipping noise, an important marine anthropogenic stressor, to be explicitly incorporated into spatial planning. Potentially sensitive areas were identified through quantifying risk of exposure of shipping traffic to marine species. Individual noise exposure was predicted with associated uncertainty in an area with varying rates of co-occurrence. Across the UK, spatial overlap was highest within 50 km of the coast, close to seal haul outs. Areas identified with high risk of exposure included 11 Special Areas of Conservation (from a possible 25). Risk to harbour seal populations was highest, affecting half of all SACs associated with the species. For 20 of 28 animals in the acoustic exposure study, 95% CI for M-weighted cumulative Sound Exposure Levels had upper bounds above levels known to induce Temporary Threshold Shift. Predictions of broadband received sound pressure levels were underestimated on average by 0.7 dB re 1μPa (± 3.3). An analytical methodology was derived to allow ecological maps to be quantitatively compared. The Structural Similarity (SSIM) index was enhanced to incorporate uncertainty from underlying spatial models, and a software algorithm was developed to correct for internal edge effects so that loss of spatial information from the map comparison was limited. The application of the approach was demonstrated using a case study of sperm whales (Physeter macrocephalus, Linneaus 1758) in the Mediterranean Sea to identify areas where local-scale differences in space-use between groups and singleton whales occurred. SSIM is applicable to a broad range of spatial ecological data, providing a novel tool for map comparison.