Underwater detection of tonal signals between 0.125 and 100kHz by harbor seals (Phoca vitulina)

Abstract

The underwater hearing sensitivities of two 1-year-old female harbor seals were quantified in a pool built for acoustic research, using a behavioral psychoacoustic technique. The animals were trained to respond when they detected an acoustic signal and not to respond when they did not (go/no-go response). Pure tones (0.125-0.25 kHz) and narrowband frequency modulated (tonal) signals (center frequencies 0.5-100 kHz) of 900 ms duration were tested. Thresholds at each frequency were measured using the up-down staircase method and defined as the stimulus level resulting in a 50% detection rate. The audiograms of the two seals did not differ statistically: both plots showed the typical mammalian U-shape, but with a wide and flat bottom. Maximum sensitivity (54 dB re 1 microPa, rms) occurred at 1 kHz. The frequency range of best hearing (within 10 dB of maximum sensitivity) was from 0.5 to 40 kHz (6(1/3) octaves). Higher hearing thresholds (indicating poorer sensitivity) were observed below 1 and above 40 kHz. Thresholds below 4 kHz were lower than those previously described for harbor seals, which demonstrates the importance of using quiet facilities, built specifically for acoustic research, for hearing studies in marine mammals. The results suggest that under unmasked conditions many anthropogenic noise sources and sounds from conspecifics are audible to harbor seals at greater ranges than formerly believed.

Amphibious hearing in spotted seals (Phoca largha): underwater audiograms, aerial audiograms and critical ratio measurements

“…The Journal of Experimental Biology (2014) The spotted seal underwater audiograms obtained in this study agree well with published thresholds for the harbor seal (Møhl, 1968;Terhune, 1988;Kastelein et al, 2009;Reichmuth et al, 2013). However, the spotted seal hearing thresholds are considerably lower than existing underwater data for other Arctic seals.…”

“…In terms of sound reception, some auditory data exist for harp (Pagophilus groenlandicus) (Terhune and Ronald, 1971;Terhune and Ronald, 1972) and ringed seals (Pusa hispida) (Terhune and Ronald, 1975a;Terhune and Ronald, 1975b), but there are few measurements below 1 kHz where industrial and shipping noises typically occur (Wenz, 1962;Richardson et al, 1995). The most comprehensive data exist for the closely related, but more temperate living, harbor seal (Phoca vitulina) (Møhl, 1968;Terhune, 1988;Terhune, 1991;Kastak and Schusterman, 1998;Wolski et al, 2003;Southall et al, 2005;Kastelein et al, 2009;Reichmuth et al, 2013). However, because the phylogenetic relationships among the 10 species of northern seals are incompletely resolved (Berta and Churchill, 2012), the validity of extrapolating hearing capabilities across species in this group remains unclear.…”

Amphibious hearing in ringed seals (Pusa hispida): underwater audiograms, aerial audiograms and critical ratio measurements

“…The audiograms for the two subjects are in good agreement from 0.1 to 25.6 kHz, above which the adult male (Natchek) exhibits apparent high-frequency hearing loss. The thresholds of the young female (Nayak) are quite similar to those reported recently for harbor (Kastelein et al, 2009;Reichmuth et al, 2013) and spotted seals (Sills et al, 2014) across the hearing range. In contrast to historical data, these ringed seal audiograms are consistent with the hypothesis of a functional hearing group for northern seals.…”

“…The northern seals (subfamily Phocinae) include the ringed, Baikal (Pusa sibirica), Caspian (Pusa caspica), spotted (Phoca largha), harbor (Phoca vitulina), grey (Halichoerus grypus), ribbon (Histriophoca fasciata), harp (Pagophilus groenlandicus), hooded (Cystophora cristata) and bearded seals (Erignathus barbatus). Among these species, hearing thresholds are currently available for spotted (Sills et al, 2014), harbor (Møhl, 1968a;Terhune, 1988Terhune, , 1991Kastak and Schusterman, 1998;Wolski et al, 2003;Southall et al, 2005;Kastelein et al, 2009;Reichmuth et al, 2013), Caspian (Babushina, 1997), harp (Terhune and Ronald, 1972) and ringed seals (Terhune and Ronald, 1975a). Of note relative to the present study, however, is that sensitivity data for ringed, harp and Caspian seals do not extend to the low frequencies, and ringed seal hearing has only been studied in water.…”

Seal monitoring and evaluation for the Gemini offshore windfarm: Tconstruction - 2015 report

“…This device produced sounds at ultra-sonic frequencies (60-150 kHz), which were higher than could be detected by seals, whose frequency range for best hearing is 0.5 to 40 kHz (Kastelein et al 2009). The…”