From Pups to Weanlings: What’s on the Menu?


During peak pupping season for Harbor Seals here at NMLC, our patients are fed every four hours beginning at 7am until 11pm.  When Harbor Seal pupping season begins in late spring, we begin to receive our first patients of the season that have either been abandoned by mom due to human interaction, or simply because the mom has the instinct that the pup will not thrive. The pups we receive are maternally dependent pups, so we must take on the role

Jane Goodseal, a premature harbor seal, that is only a few days old.

of mom in teaching them necessary behaviors, but most importantly we must feed them an incredibly nutrient & fat rich formula to ensure they thrive. From the time pups come in up until they begin to become weanlings, they are fed our Pup Formula mixture. Our Pup Formula is a mixture of: milk matrix, oil, water, lactase capsules, and salt. Unlike most mammals, we must tube feed our pups to ensure they are guaranteed all their feed and are absorbing as much nutrients and calories as possible, and when the pups are too young, weak, or sick to eat on their own. This formula provides them with almost 3,000 calories per day! Harbor Seal pups nurse for ~3-4 weeks, and then they begin the transition to weanlings.

When our pups begin the weaning process, their bodies are undergoing drastic changes and becoming lactose intolerant. During this time, we begin feeding them Fish Gruel to prepare them for transitioning to eating whole fish. Our Fish Gruel consists of pedialyte, herring, fish oil, milk matrix, vitamins (marine mammal tab, B1, B-complex, and Vitamin C), and salt. We also begin Fish School with our weanling pups, to teach them to become familiar with fish as well as learning how to hunt them since mom is not there to teach them how to thrive in the wild. This activity is also a great way to engage the animal, spike their curiosity, and hopefully to help them learn to forage less invasively.

Once the weanlings show an increased interest in the herring used during Fish School, as well as actively trying to bite the fish or even consume them, our Animal Care Director Margot

Jane Goodseal after she had learned to swim and eat on her own.

Madden will begin what is known as Assist Feeding. During Assist Feeding, the weanlings will learn how to swallow the herring whole while keeping the fish properly positioned during the feed. Since seals cannot use their flippers to help them position their fish while hunting, it is important that they learn the proper way to position the fish while feeding so they do not injure themselves in the future while hunting in the wild. If you happen to be in our Discovery Center watching the live video during an Assist Feed, you will also notice that she will splash water onto their faces after they have swallowed the fish. This helps the seals learn that they must close their nostrils while swallowing the fish, since they will be hunting solely under water!

Once the seals are proficiently consuming whole herring with little to no assistance from our Animal Care Director, they are moved to our larger pool called DJF (named after donor Douglass J. Fletcher), where they will begin Mass Feeding. Animal Care interns and volunteers will toss in set amounts of whole herring each feed time and observe how well each seal feeds on their own, as well as recording how many herring each seal consumes. This next step helps us determine that the weanling seals are close to being ready for release, at which time they will be Mass Fed live herring to ensure the weanlings can adequately hunt down moving prey. Once these signs have been observed and we have been given approval, we will release our fully-grown patients back into the wild!

Posted by Caitlin J.

Caitlin is a Summer, 2017 Animal Care and Education Intern at the National Marine Life Center. She is a recent graduate of Southeast Missouri State University with a Bachelor of Science in Marine Biology.