Sea Otter Supermoms
Once hunted to near extinction, sea otters on California’s Central Coast have made a comeback. But a stall in population recovery, with higher than expected deaths among female sea otters, prompted UC Santa Cruz marine biologist Nicole Thometz to investigate.
Thometz discovered the high-energy needs of pups may push their moms beyond their metabolic means. Her findings on “end lactation syndrome” were published in the Journal of Experimental Biology. The study was co-authored by Terrie Williams, professor of ecology and evolutionary biology.
Just to survive in a cold water habitat, these small marine mammals need to eat 25 percent of their body weight in food every day. “But we didn’t know how much more energy a mom needed to provide for her pup,” Thometz said.
To calculate the daily caloric needs of pups, from birth until six months of age, Thometz observed 26 wild sea otters to construct their daily activity budgets. Then, to determine the energetic cost of these activities, she recorded oxygen consumption during activities of seven young otters (in rehabilitation for release back into the wild) at the Monterey Bay Aquarium. Thometz then estimated that moms had to double their energy intake when caring for a large pup. After pregnancy and nursing, females may be too energetically depleted to meet those demands without risking their own lives, she said.
“Sea otters are apex predators in the kelp forest. If we understand what impacts their population, we’ll understand more about our coastal ecosystems,” Thometz said.