Critical ratios in harbor porpoises (Phocoena phocoena) for tonal signals between 0.315 and 150 kHz in random Gaussian white noise

Abstract

A psychoacoustic behavioral technique was used to determine the critical ratios (CRs) of two harbor porpoises for tonal signals with frequencies between 0.315 and 150 kHz, in random Gaussian white noise. The masked 50% detection hearing thresholds were measured using a "go/no-go" response paradigm and an up-down staircase psychometric method. CRs were determined at one masking noise level for each test frequency and were similar in both animals. For signals between 0.315 and 4 kHz, the CRs were relatively constant at around 18 dB. Between 4 and 150 kHz the CR increased gradually from 18 to 39 dB ( approximately 3.3 dB/octave). Generally harbor porpoises can detect tonal signals in Gaussian white noise slightly better than most odontocetes tested so far. By combining the mean CRs found in the present study with the spectrum level of the background noise levels at sea, the basic audiogram, and the directivity index, the detection threshold levels of harbor porpoises for tonal signals in various sea states can be calculated.

Audiogram and auditory critical ratios of two Florida manatees (Trichechus manatus latirostris)

“…This response may lead to the manatee crossing a boat path, and is supportive of boat slow speed zones in manatee habitat, so that if there is a collision, it is less likely to result in death (Calleson and Frohlich, 2007). (Terhune and Ronald, 1975), bottlenose dolphin (plus signs) (Johnson, 1968), false killer whale (open triangles) (Thomas et al, 1990) and harbor porpoise (asterisks) (Kastelein et al, 2009). The dashed line represents the 10% energy level, calculated as 10ϫlog(frequencyϫ0.1).…”

“…The 10% energy curve that is plotted on the graph is approximately followed by most mammals for which there are critical ratio measurements compiled in Fay (Fay, 1988). The critical ratios for the ringed seal (Pusa hispida), bottlenose dolphin (Tursiops truncatus), false killer whale (Pseudorca crassidens) and harbor porpoise (Phocoena phocoena) are shown for comparison (Terhune and Ronald, 1975;Johnson, 1968;Thomas et al, 1990;Kastelein et al, 2009). Manatees possess critical ratios that are relatively quite low, with most below the 10% energy curve, especially at 8kHz.…”

Brief Behavioral Response Threshold Level of a Harbor Porpoise (Phocoena phocoena) to an Impulsive Sound

“…The study was conducted with only one animal, but his hearing was very similar to that of another male harbor porpoise of the same age (Kastelein et al, 2009) and to that of another male (Kastelein et al, 2002(Kastelein et al, , 2010, and so, it was likely to be representative for harbor porpoises. After each session, the animal's behavior immediately returned to normal.…”

“…His body mass was around 38 kg, his body length around 142 cm, and his girth at axilla around 75 cm. His hearing was assumed to be representative of animals his species and age because hearing data obtained from him shortly prior to the present study were similar to those from other young male harbor porpoises (Kastelein et al, 2009(Kastelein et al, , 2010. The animal received between 2.3 and 3.0 kg of thawed fish/d, equally divided over four meals.…”

“…Data on the effects of noise on the harbor porpoise (Phocoena phocoena) are of particular interest because it has a wide distribution area in the northern hemisphere, the most acute hearing so far quantified in a marine mammal species, and functional hearing over a very wide frequency range (Kastelein et al, 2002(Kastelein et al, , 2009(Kastelein et al, , 2010. The harbor porpoise detection threshold sound exposure level (SEL) for an impulsive sound has been established (Kastelein et al, 2012b).…”