How many calories does a penguin need?
Most penguins in zoos and aquariums are kept to the point of satiety, assuming that appropriate environmental conditions replicate and regulate their normal activity cycles and energy needs
Penguins are seabirds of the Southern Hemisphere, distributed in tropical, temperate, subantarctic and high antarctic regions. They comprise 18 species that are collectively considered the most threatened seabirds, with two-thirds of the species considered threatened by the IUCN. Apart from being a key factor in achieving optimal levels of health, growth, reproduction, survival and longevity in wild species under human care, little is known about penguin nutrition.
Today, a combination of requirements for domestic chickens, carnivorous mammals and other fish-eating vertebrates is used as the standard data for formulating diets. In fact, intake rates are largely relied upon when discussing dietary requirements for captive animals. However, energy-dense fish species commonly kept in captivity are likely to restrict food intake, causing the animals to stop consuming the minimum amount of essential nutrients before consuming them.
However, not all facilities maintain the seasonal nature of the environment in terms of photoperiod and temperature. The lack of these features may compromise the ability of the animals to self-regulate consumption or maintain appropriate moulting and breeding rhythms. Even when a seasonal nature of the environment is provided, the natural desire for food may dictate excessive food intake, once the animals have adapted to store nutrients in all circumstances.
To avoid the effect of overfeeding and to guarantee healthy conditions in captive populations, the formulation of the diet should always take into account the energy requirements of the species and its physiological state, which is associated with an appropriate feeding rate.
Field metabolic rates (FMR, measured with doubly labeled water) in breeding Adélie penguins (weighing 3.81 kg) averaged 1.64 ml CO₂, g⁻¹ h⁻¹, 3,896 kJ d⁻tabal¹ and MRBtabol¹. Energy expenditure while in the nest was 2.0 X BMR, and when outside the nest was 5.4 X BMR, including time spent foraging at sea.
These FMRs are higher than those of other penguin species and may reflect the intense foraging effort associated with the relative scarcity of food during our study. The penguins ate only krill (Euphausia superba), primarily medium-sized juveniles, which have a much higher water content, lower lipid content, and relatively lower metabolizable energy content than gravid female krill.
The low water intake suggests that the penguins did not drink much fresh or seawater and that they did not consume enough food to cover their energy expenditure after feeding their chicks. Their body fat consumption during this breeding phase would have been approximately 33 g d⁻¹ to cover the difference. We estimated that 25,500 Adélie penguins using the Arthur Harbour area around Palmer Station would have consumed approximately 27.5 metric tons of krill per day.
Six hundred and twelve penguins (total biomass 2,330 kg) would have consumed approximately the same amount of krill per day as a 48,000 kg Antarctic right whale.
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