Some seal pups are injured and appear to have been abandoned by their mothers - photo courtesy of Anna Drake

UBC Reports | Vol. 54 | No. 6 | Jun. 5, 2008

Diet Doubles Pups’ Survival Rate

By Brian Lin

In a world obsessed with low-calorie diets, Amelia MacRae thinks that more fat may be the key to survival -- for seal pups, that is.

MacRae, a graduate student in the Faculty of Land and Food Systems’ Animal Welfare Program, has been working with the Vancouver Aquarium’s Marine Mammal Rehab Centre to find the best diet for nursing orphaned or abandoned harbour seal pups to health before releasing them back in the wild.

The rehab centre takes in more than 100 harbour seal pups every summer after responding to public reporting of seal strandings.

“Many pups arrive in terrible condition,” says MacRae, a former marine mammal trainer with the aquarium. “Some are injured, some are emaciated and appear to have been abandoned by their mothers often because of human interference.”

Seal pups need to more than double their natal weight by the time they are weaned from their moms. To achieve this, seal milk contains more than 50 per cent fat. In comparison, commercial whole milk contains 3.5 per cent fat.

“There are two widely-used feeds for orphaned harbour seals -- an artificial milk formula and ground-up fish gruel,” says MacRae. “But there has been little evaluation of their nutritional values and how they actually contribute to the growth of seals pups.”

MacRae began comparing the two popular feeds last summer and has found that while neither led to weight gain, seal pups on the milk formula had almost double survival rate. She hypothesizes this may have to do with the milk’s higher caloric content.

This summer, MacRae plans to take the study one step further by introducing heating to the seal nursery. “If the pups don’t have to expend energy to keep warm, we hope they will grow faster and have a better chance of survival once released,” says MacRae. “By applying some simple science we hope to give these unfortunate animals a second chance at life.”