Strandings: Harbor Seals vs. Grey Seals

With Harbor Seal pup season in full swing at the National Marine Life Center, many visitors have been curious about why seals strand. Between the four species of seals that can be found within our harbor, harbor seals and grey seals are the two we primarily rehabilitate.

During the different seasons of the year, stranding events occur for different reasons. Throughout the summer months, harbor seal

pups are priority to give them the best shot at life. Thanks to our partnership with Marine Mammals of Maine, an organization located in Bath, Maine who triages our pups, we are able to rehabilitate malnourished or abandoned pups. While these pups have not experienced life in the water yet and have not been exposed to the numerous threats that come from the ocean, they are vulnerable to predators on land. Due to the nature of parental care for this species, the pups have little protection as the mother returns to the water periodically to feed for herself in between nursing. As a result, if humans get too close to the pup while mom is returning from hunting, she will not return if there are too many people around. Other reasons could be due to maternal abandonment as the mother determines that her pup is not suitable enough to survive and will leave the pup and invest her time and energy elsewhere. After enough time has passed without mom returning, pups will be taken from the beach suffering from malnourishment, and taken into our care to rehabilitate them in the hopes to release them one day.

In the case of grey seals, it could be a variety of different reasons due to either human interaction or environmental impacts. During the

fall and spring months grey seals are taken into our care and here we see physical injuries more often. Compared to the pups that are found along the shoreline, weanlings have experienced life within the ocean and are susceptible to the dangers of the world. Many issues are increasingly arising from plastics and fishing debris resulting from human interactions. Many seals are found and have fishing line or nets around their bodies which can wear them down or suffocate them if around their necks. Other injuries can arise from encounters with boats as seals frequently are found within the harbors and more than likely have associated boats with food. This could be a result from following commercial fishing boats, to which many do, or the public feeding them while unknowingly causing future harm. Nevertheless, close interactions with boats can cause life threatening injuries from the propellers.

While these seals have begun eating fish, which labels them as weanlings, they are also more likely to contain parasites that they receive from their diets. One issue many of us are all sure to be familiar with as well is shark hits. Unfortunately it is a sad part of life, seeing photos of seals injured from shark bites, but it is a natural occurrence.

While it is important to report any seal stranding to local organizations, one must take caution as these are wild animals. Always remain 150 feet away at all times and refrain from taking photos as to avoid any further stress on these animals. Always take the precaution to call a spotting in, but remember these species are mammals as well. They get tired from swimming and must breathe air just like we do, so it is not uncommon to find seals out of water. If a seal pup is found alone on the beach remain as far away as possible. Depending on the species and time of year, mom could be returning from a hunt and see you along the beach. While you may not be causing the pup any harm, this will scare her off and the pup will be indirectly hurt from this.

Take caution along the beaches and keep your children in mind. We wouldn’t want big scary animals poking at our babies!

Posted by Kelsey B.

Kelsey is a summer, 2017 intern at the National Marine Life Center. She just recently graduated from Salem State University with a degree in Marine Biology.