Landfast ice around Antarctica thickens through the winter and would seal a diving mammal underneath it. Weddell seals prevent that by working at the edges of their breathing holes, swinging the head from side to side and rasping the ice with the forward-projecting canines and incisors.
The cost falls on the teeth. Worn and broken canines are common in older Weddell seals, and severely abraded teeth expose the pulp, allowing infection to reach the jaw. Because a seal that cannot maintain a hole cannot breathe, tooth wear is thought to set a practical ceiling on lifespan in this species, and animals much beyond about twenty years are uncommon.
The strength of that link is not fully pinned down. Ageing seals decline for several reasons at once, and separating dental failure from general senescence requires long-term individual records. The long-running study population in Erebus Bay in McMurdo Sound, followed for decades, is the main source of what is known.