ABSTRACT: The use of biochemical analyses of whiskers to address ecological and physiological questions requires an understanding of whisker growth dynamics. To expand comparative data for phocid seals, we report fine-scale growth patterns, retention times, and temporal patterns of whisker loss for 3 captive seals using direct and photogrammetric methods. The ringed seal Pusa hispida, bearded seal Erignathus barbatus, and Hawaiian monk seal Neomonachus schauinslandi all showed rapid regrowth following whisker loss, with maximum growth rates of 0.15 to 0.20 cm d^-1. After this initial growth period, tissue deposition rates contrasted between the smallest species—the ringed seal—and the other 2 species. Ringed seal whiskers exhibited an asymptotic growth pattern typical of other phocids, whereas growth of bearded and monk seal whiskers continued at a slow, linear rate until shedding. The ringed seal had a seasonal pattern of whisker loss that coincided with the timing of the annual pelage molt, whereas there was no temporal pattern of whisker loss for the other 2 species. The rapid-to-slow growth of bearded and monk seal whiskers is unique within the phocid lineage, along with the presence of smooth rather than undulated whiskers in these species. In light of phylogenetic differences in growth and shedding patterns, extrapolation of whisker growth to related species requires careful consideration.