254
Marine Mammal Physiology: Requisites for Ocean Living
140
120
100
Walrus
California sea lion
Steller sea lion
Northern fur seal
Harbor seal
Spotted seal
Northern elephant seal
80
60
Threshold (dB re 1 µPa)
Threshold (dB re 20 µPa)
40
(a)
(b)
40
80
60
20
0
–20
0.1
1
10
100
Frequency (kHz)
Underwater
Aerial
Figure 11.4 (See color insert.) Underwater (a) and aerial (b) hearing thresholds for selected pinniped species. All audiograms were obtained using behavioral methods. The two plots are shown
with identical x-axes to emphasize the differences in frequency range of hearing between air and
water. Note the difference in reference pressures for underwater (1 μPa) and aerial (20 μPa) thresholds. Studies for which underwater thresholds are shown: California sea lion (Reichmuth et al. 2013),
Steller sea lion (Kastelein et al. 2005), northern fur seal (Moore and Schusterman 1987), harbor seal
(Reichmuth et al. 2013), spotted seal (Sills et al. 2014), northern elephant seal (Kastak and Schusterman
1999), and walrus (Kastelein et al. 2002). Aerial studies: California sea lion (Reichmuth and Southall,
2012), Steller sea lion (Mulsow and Reichmuth 2010), northern fur seal (Moore and Schusterman
1987), harbor seal (Reichmuth et al. 2013), spotted seal (Sills et al. 2014), and northern elephant seal
(Reichmuth et al. 2013).