Vocal changes as indicators of pain in harbor seal pups (Phoca vitulina)

Abstract

Vocalizations are potential indicators of pain in animals. We recorded and analyzed spectrographically the vocalizations of harbor seal pups (Phoca vitulina) before, during, and after the routine procedures of flipper tagging and microchipping prior to release from a rehabilitation facility in British Columbia, Canada. It is standard practice for these procedures to be done without analgesia. In Experiment 1, we compared vocalizations before and after the procedures (n = 21); in Experiment 2, we compared vocalizations in response to real and sham procedures (n = 10). In Experiment 1, seals produced more vocalizations, and peak frequency was higher, after tagging and after microchipping. In Experiment 2, seals also produced more vocalizations after real but not after sham tagging and microchipping. The average peak frequency was higher after each procedure, but not after each sham procedure. These results suggest that an increase in the number and peak frequency of vocalizations are indicators of pain in seal pups. The results also suggest that analgesia, when feasible, should be considered for harbor seal pups undergoing routine flipper tagging and microchipping.