Effects of Flight Noise From Jet Aircraft and Sonic Booms On Hearing, Behavior, Heart Rate and Oxygen Consumption of Desert Tortoises (Gopherus Agassizii)
Abstract
The effects of simulated subsonic (94.6-114.2 dB CSEL) and supersonic (0.25-6 psf) aircraft noise on 14 desert tortoises, Gopherus Agassizii were studied. Auditory thresholds of the most sensitive individuals at 250 Hz were 17.5 dB SPL. Thresholds averaged 34 dB SPL at 250 Hz for the 11 individuals tested. No significant temporary threshold shift (TTS) was detected after worst-case exposure to subsonic aircraft noise or 2-6 psf simulated booms. TTS ranging from 5-20 dB was measured in 5 of 9 individuals after exposure to 10-6 psf booms (recovery >45 min and <48 hr). Tortoises were trained to walk voluntarily on a treadmill and fitted with small mask for measurements of O2 consumption. V02 at rest averaged 1.472 1.472 ml/min/kg/ (s.d.=0.410). Resting heart rate averaged 11.82 BPM (s.d. = 3.91). Exercising heart rate ranged from 10 BPM to 42 BPM, averaging 30 BPM. There was no increase in blood lactate levels during or post-exercise. The most extreme response to simulated subsonic aircraft noise was a typical reptilian defensive response - freezing - for up to 113 minutes. After the initial exposure, bouts were short (<^5 min); thereafter, the tortoise entered a milder defensive state (head withdrawals, alerting, less climbing or digging). Averaged heart rate declined 7-8% decrease during exposures, corresponding to the shift in behavior. Responses to sonic booms were limited to brief bouts of alerting.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1999
- Accession Number
- ADA367285
Entities
People
- Ann E. Bowles
- Erik Berg
- Larry Wolski
- Lisa Starke
- Scott Eckert