Growth and shedding of captive harp seal (Pagophilus groenlandicus) vibrissae over one year

The harp seal (Pagophilus groenlandicus) is the most abundant marine mammal in the Northwest Atlantic. Climate change negatively affects the sea ice that the species needs for pupping and moulting, while also altering the composition and availability of the species’ prey. Analyzing vibrissae for biological and chemical markers can aid in understanding the overall health, movements, and interactions of the animal with the environment. In this study, I examined growth and shedding patterns of mystacial vibrissae using photogrammetry in three captive harp seals over one year. I modelled vibrissa growth using von Bertalanffy growth curves that followed an asymptotic growth profile. Shedding occurred in 24 out of 36 vibrissae across the three seals in March and April, just before the moult of body pelage. Vibrissae grew for a mean of 104 days (SD = 14.4), indicating a period of growth from late March until mid-July. Vibrissa lengths varied greatly, so vibrissae in different positions could not be modelled using the same von Bertalanffy parameter estimates. This research on harp seal vibrissa growth and shedding will be helpful to future ecological and physiological studies including stable isotope analysis, measuring reproductive and stress-related hormones, as well as the accumulation of environmental pollutants.