Development of an altricial mammal at sea: II. Energy budgets of female sea otters and their pups in Simpson Bay, Alaska Academic Article uri icon


  • © 2016 Elsevier B.V. Lactation is a critical and energetically expensive period of reproduction, especially for female sea otters (Enhydra lutris) and their pups, both of which have resting metabolic rates that are ca. 2.5-fold higher than terrestrial mammals of similar size. The simultaneous energy budgets for female Alaskan sea otters and their pups during the first three months postpartum were calculated based on published activity budgets for wild animals and metabolic rates for specific behaviors of captive sea otters. Pups were classified into three behavioral/size categories: Category 1 (C1) 0–<4 wk. old; Category 2 (C2) 4–<8 wk. old; and Category 3 (C3) 8–12 wk. Energy for growth (Energygrowth) averaged 0.0416 MJ day− 1 for all pups. The combined daily energy expenditure to support resting metabolism and activity (Energyr + a) for C1 and C2 pups was 1.31 and 2.61 MJ day− 1, respectively, of which most (C1: 99%; C2: 84%) was associated with resting-equivalent behaviors (i.e., resting, nursing and being groomed by the female). Energyr + a for C3 pups was 4.62 MJ day− 1 of which 49% was associated with resting-equivalent behaviors, while 35% was associated with active behaviors (i.e., feeding, swimming and grooming). The underlying resting metabolic rate for all behaviors represented 100% of Energyingest for C1, 94% for C2 and 85% for C3 pups. Energyr + a for all females was similar regardless of pup age and averaged 10.88 MJ day− 1 (range 10.79–11.03). Energyr + a for C1 females was associated mainly with self-grooming and pup grooming (30%) and swimming (25%), while only 10% was associated with feeding. Energyr + a for C3 females was mainly associated with feeding (37%) with less energy devoted to swimming (10%) and grooming (14%). Lactation energy (Energylactation) in C3 females was 3.5-fold greater than in C1 females. Ingested energy for C1 females was 19.55 MJ day− 1, which increased to 22.13 MJ day− 1 for C2 females and 26.53 MJ day− 1 for C3 females. As with pups, the underlying resting metabolic rate for all female behaviors represented 70% of Energyingest for C1 females and 72% for C2 and C3 females. Hence, thermogenesis dominated the metabolism of female sea otters as with their pups. These results provide a quantitative picture of the energetics of Alaskan female sea otters and their pups during early pup rearing in a species that has one of the highest mass specific resting metabolic rates of any mammal and the most altricial neonate born at sea.

author list (cited authors)

  • Cortez, M., Goertz, C., Gill, V. A., & Davis, R. W.

citation count

  • 1

publication date

  • August 2016