Dolphins burn energy during speedy swims for survival

Life in the ocean requires some very intriguing survival tactics, and dolphins are no exception. Dolphins must strike a balance between searching for prey and hiding from predators. They must also learn to avoid human disturbances, such as ship strikes or being trapped in fishing nets as bycatch. These survival tactics depend on a dolphin’s ability to increase speed and shift into high gear. 

Speed swimming is an exhausting sport that causes animals to burn a lot of energy. Over time, this can deplete energy that is vital for the mammal’s growth and overall health – especially if the dolphin burns more calories than it consumes. This is referred to as energy costs of locomotion (COL), which researchers consider integral to understanding dolphin physiology. 

Studying COL in the wild is difficult. Most findings are limited to estimations of a dolphins’ fluke stroke per minute, which does not provide precise data. 

In a new study led by Duke University, experts have taken a more reliable approach to calculating energy costs of locomotion among dolphins by using overall dynamic body acceleration (ODBA) – an integrated measure of all body motions a dolphin makes during swimming.  “This is the first published study calibrating ODBA with energy expenditure in multiple dolphins,” said study leader Austin Allen.

To do this, the researchers conducted swim trials with six bottlenose dolphins at Dolphin Quest (a zoological facility on Oahu, Hawaii) from 2017 to 2019. The team measured each dolphin’s resting metabolic rate by measuring oxygen consumption after swimming 80-meters, using a device known as a pneumotachometer. Non-invasive biologging tags were used to detect changes in motion throughout the trial, such as slowing down or turning around.  

Over the course of the three-year study, a pattern emerged in the data which found a “significant correlation between oxygen consumption and body acceleration, which suggests ODBA can be a reliable proxy for COL,” said Allen.

The strength of the correlation between ODBA and COL varied among individuals, but the overall relationship can be used to further investigate the energy costs of diving in free-ranging animals where bio-logging data are available. 

The research proved a more efficient approach to measuring dolphin fuel efficiency, which could inform efforts to boost odds of survival. “Working with dolphins in zoos or aquariums is allowing us to use data we’ve already collected using these tags in the field to evaluate the cost of locomotion in wild populations,” explained Allen.

The study is published in the Journal of Experimental Biology.

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By Katherine Bucko, Earth.com Staff Writer