The harbor seal: the most ubiquitous phocid in the Northern hemisphere

True to its name, the harbor (or common) seal (Phoca vitulina) is found in many coastal environments in the northern hemisphere and is perhaps the most wide-ranging pinniped in the world. Harbor seals haul out on many types of coastal or ice environments where they engage principally in resting but also come ashore for pupping and nursing, temperature maintenance, predator avoidance, digestion, and molting. Males may defend underwater territories near haulout sites or foraging areas and use acoustic displays to attract mates or ward off competing males. Mating occurs underwater, and females give birth to a single pup in the boreal spring/summer that is capable of swimming and diving within minutes of birth. Pups are weaned in three to six weeks of birth and often disperse more widely than adults. Although they begin their lives eating slower swimming prey, such as some invertebrates and smaller fish, they eventually become adept predators of fishes and cephalopods in many types of coastal environments. Foraging trips might be a day’s swim from the haulout site or may be two to three weeks duration. Due to their coastal distribution, harbor seals are more susceptible to anthropogenic impacts, such as contaminants, disturbance, human-made structures, and noise pollution. Harbor seals are perhaps the most adaptable phocid to deal with potential climate change issues, given their evolutionary history in the dynamic coastal environments near human populations.