G Cover What to do when you see a seal When a marine mammal turns up on the beach, the goal is to avoid unnecessary human intervention ← Related Article Visit The Boston Globe Share on Twitter Share on Facebook Comment on this Scroll to top of page Unlike harbor seals, gray seals congregate in colonies to breed, most notably in Chatham and on Muskeget Island. David L. Ryan/Globe Staff A seal pup in Hull, which New England Aquarium staff rescued in February. David L. Ryan/Globe Staff Adam Kennedy, a rescue biologist for the NewEngland Aquarium, walked past the grey seal pup. David L. Ryan/Globe Staff New England Aquarium staff rescued the pup. David L. Ryan/Globe Staff A grey seal pup on a beach in Hull in February. Unlike whales and dolphins, seals are only semi-aquatic. In other words, it is perfectly natural for them to haul themselves onto shore. David L. Ryan/Globe Staff Seals on Cape Cod’s Monomoy Island. Julia Cumes for the Boston Globe David Nash of Edgartown, a marine mammal volunteer for the New England Aquarium, at South Beach on Martha’s Vineyard, “I’m honored to be part of this network,’’ he says.