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Conservation

Busy penguins strive to find an energy balance.

Sala, J. E., Wilson, R. P., & Quintana, F. (2015). Foraging effort in Magellanic penguins: balancing the energy books for survival? Marine Biology, 162, 501–514. doi:10.1007/s00227-014-2581-9

Photo Credit: Luis Alejandro Bernal Romero, http://aztlek.com

Magellanic penguin family in Chile. Photo Credit: Luis Alejandro Bernal Romero http://aztlek.com

Introduction

We’ve all spent countless hours trying to figure out how to balance all our responsibilities in life, but next time you’re stressing, think of the plight of the penguins. Penguins face many obligations— reproduction, foraging (searching for food), and preening (grooming their feathers), to name a few. Time and energy management becomes crucial during breeding season when new young need special attention to survive the critical early stages.

Among their many responsibilities, the ,Magellanic penguins (Spheniscus magellanicus) of Patagonia face an unusually busy breeding season, involving energy intensive dives to gather food for themselves and their chicks. The depths and durations of these dives determine how much energy is expended by a parent penguin in seeking food for its young.

A recent paper published by Sala et al. in Marine Biology investigates how Magellenic penguins expend their energy, and explores how differences in energy management strategies might relate to population-level trends observed across different colonies. Specifically Sala et al. investigate the hypothesis that penguins with the highest energy expenditure at sea would have the least successful reproductive seasons.

Methods

From 2005 to 2008 researchers monitored four different penguin colonies (groups of penguins) inhabiting four distinct locations along the coast of Argentina, focusing on the chick-rearing season. They attached devices known as accelerometers to the backs of fifty-seven lucky penguins to measure energy expenditure as the birds moved through the sea. Each subject was monitored for one multi-dive foraging trip, totaling almost 30,000 dives.

Results

In support of their original hypothesis, Sala et al. found that population growth for an individual colony correlated inversely with energy expended on foraging. Higher energy output occurs with long, deep dives and more dives per foraging trip. In other words, spending more energy catching food translates to less energy spent raising young. Sala et al. also observed differences in the prey consumed at different locations, consistent with the difference in the depth of the dives.

 

Total energy expended per dive (EEE) (J) as function of maximum dive depth (m) for penguins from each colony (PN Punta Norte, BB Bahía Bustamante, PD Puerto Deseado, PSJ Puerto San Julián. The red lines correspond to the curves that best fit the data. The values (coloured circles) correspond to the overall means for intervals of 5 m depth ± SE

Total energy expended per dive (EEE) (J) as function of maximum dive depth (m) for penguins from each colony (PN Punta Norte, BB Bahía Bustamante, PD Puerto Deseado, PSJ Puerto San Julián, Argentina.

a Total estimated energy expenditure (EEE; kJ ± SE) and b mean metabolic power use (i.e. rate of EEE; W ± SE) for complete foraging trips made by penguins from different colonies as a function of population growth rates at four different breeding sites along the coast of Patagonia. The red lines represent the functions that best fitted to the data and the black dashed lines show the 95 % confidence intervals

a) Total estimated energy expenditure  and b) mean metabolic power use for complete foraging trips made by penguins from different colonies as a function of population growth rates at four different breeding sites along the coast of Patagonia. 

Significance

During the breeding season seabirds must balance their energy budget carefully in order to ensure the highest survival rates for themselves and their new young. Monitoring their energy budget choices helps to explain how the population is changing as a whole based on how many new birds enter the population each year.

Though the data collected in this study do not explain the whole situation of changing populations it does give us insight into potential limitations on population growth.   Monitoring the energetics of penguins, or other animals, can help inform management and conservation decisions as we better understand foraging behavior and its relationship to care of young. In a situation where food may be scarce the trade off between caring for young and searching for food could become critically important for the survival of the population. You may not be able to teach a penguin good time management skills but we can at least try to conserve and manage their populations according their habits.

Sarah Giltz
I am a doctoral candidate in Ecology and Evolutionary Biology at Tulane University. My research focuses on the larval dispersal and development of the blue crab in the Gulf of Mexico.

When not concerning myself with the plight of tiny crustaceans I can be found enjoying life in New Orleans with all the costumes, food, and music that entails.

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