Shifting Seas: Harp Seals Threatened By Weak Sea Ice

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Thinning, cracking ice is responsible for seal deaths. Image Credit: Colin broug

Can Harp Seals Meet the Challenge of Changing Ice Conditions?

Based on the seals’ experiences during poor ice years, the answer seems to be that seals find it hard to bend much further. Harp seals already lead a tenuous existence that’s well adapted to the current challenging conditions out there on the ice. Any less ice, and entire years of seal pups are lost to the water.

What impact could changing ice conditions have on seal populations? Harp seals breed when they are between three to five years old. If the ice causes the loss of a year of pups, it’s difficult. If a few year classes are lost, this will dramatically impact the ability of the population to breed. There are simply too many older animals.

In an interview with Decoded Science, co-author Dr. Johnston describes the impact of the loss of a year class as an “aging population issue. If several year classes are small or lost, fewer young seals show up to breed and fewer pups are produced. The older seals continue to die at normal rates, and the population becomes top heavy and smaller.”

Harp Seals: What Will the Future Hold?

By the nature of their breeding and nursing habits, harp seals have shown that they are tough and adaptable. But there’s a limit to how much a species can adapt, and they’re already pushing that limit. What can the seals do?

One option might be to move to find better ice conditions. Johnson says that there are seals that are pupping at sites closer to Greenland, but it is unclear whether these are the same seals that would traditionally breed in Eastern Canada.

What is the other option? If year upon year of seals can’t make it to adulthood on thin ice, the other option may be a more limited role of the harp seal population in Eastern Canada’s ecosystems.

References

Johnston, D.W., Bowers, M.T., Friedlaender, A.S., Lavigne, D.M. The Effects of Climate Change on Harp Seals (Pagophilus groenlandicus). (2012). PLoS ONE 7(1): e29158. doi:10.1371/journal.pone.0029158. Accessed January 9, 2012.

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