Physiological response to feeding in little penguins

Area of Science:

• Animal Physiology
• Ecology
• Bioenergetics

Background:

• Specific dynamic action (SDA) is the energy cost of food digestion and assimilation.
• SDA can be a significant component of an animal's daily energy expenditure.
• Penguins forage in cold environments, potentially increasing energy demands for digestion.

Purpose of the Study:

• To quantify specific dynamic action (SDA) in little penguins.
• To determine the relationship between meal size and SDA magnitude.
• To estimate the additional energy cost of food thermoregulation in little penguins.

Main Methods:

• Measured heart rate (fH) and oxygen consumption (VO2) in 12 little penguins.
• Monitored physiological responses during the digestion of a sardine meal.
• Calculated energy expenditure for SDA and estimated thermoregulatory costs.

Main Results:

• Little penguins demonstrated substantial SDA, with energy utilization equivalent to 13.4% of the meal's energy content.
• SDA magnitude was directly proportional to the size of the ingested meal.
• Additional energy expenditure for food warming ranged from 1.6% to 2.3% of meal energy, varying with water temperature.
• Heart rate and oxygen consumption changes during digestion were qualitatively similar, indicating no major circulatory adjustments.

Conclusions:

• Little penguins exhibit significant SDA, a key factor in their energy budget.
• The energy cost of SDA in little penguins is substantial and meal-size dependent.
• Thermoregulation of ingested food represents an additional, significant energetic cost for penguins in cold environments.
• Penguin cardiovascular function is not substantially altered by the digestive state.