Spectral sensitivity in two species of pinnipeds (Phoca vitulina and Otaria flavescens)

Spectral sensitivity was measured in air in the light adapted stare in two harbor seals and a South American sea lion using a behavioral training technique. Increment thresholds were determined in a spectral range from 390 nm to 670 nm in a Simultaneous two-choice discrimination task. The spectral sensitivity curves show two maxima in sensitivity, one main peak with a maximum around 500 nm in the harbor seal and around 550 rim in the South American sea lion, and a second, smaller Peak with a maximum in the range of 410 nm in both species. The broad shape and the position of the maximum of the spectral Sensitivity Curve Of the harbor seals Suggests that even under photopic conditions both rods and cones are contributing to the measurements since harbor seals possess only one cone type. The maximum sensitivity in the green part of the spectrum may indicate an adaptation to a Specific underwater environment.