Characterization of pinniped vibrissal type and number

Abstract

Pinnipeds have vibrissae with which they can explore their environment. Two vibrissal parameters that differ in pinnipeds are shape and number. Regarding shape, most phocids have undulated vibrissae, whereas the vibrissae of a few phocids, all otariids and walruses are smooth. As there is disagreement with respect to which phocid vibrissae lack the undulation, we systematically collected information on vibrissal type. We have documented that all eared seals we examined, walruses, Mediterranean monk seals, bearded, and leopard seals have smooth vibrissae. All other phocids have undulated vibrissae, except for Ross seals and Hawaiian monk seals, which have partially undulated vibrissae. Moreover, we quantified and documented the existence of vibrissae from photos revealing otariids to have 20–43 mystacial vibrissae/pad, no rhinal vibrissae, 1–2 supraorbital vibrissae above each eye, and phocids to have 15–97 mystacial vibrissae/pad, 0–2 rhinal vibrissae/nostril, 1–9 supraorbital vibrissae above each eye, all averages determined from counts made from photos. Walruses have the maximum number of mystacial vibrissae amounting to 198 vibrissae/pad on average, but almost all walruses lack rhinal and supraorbital vibrissae. Vibrissae were found at the upper lip and on the lower jaw in some pinnipeds.