Ecology is the study of how living organisms interact with their environment, and with each other. One of the most commonly studied interactions among different creatures is the flow of ingested energy – in other words, mealtimes.
An investigation into an animal’s eating habits might involve many questions – not just, ‘what does it eat?’ But also, ‘how often?’ And ‘where?’ And ‘at what time of day (or night)?’ And ‘under what conditions might it not eat at all?’
Direct observations can answer some of these questions, but the problem becomes more complicated if all the action occurs underwater – for instance, if you’re talking about harbor seals (or other marine mammals). Harbor seals can dive hundreds of meters underwater to catch the fish and other seafood that make up their diet.
Underwater video footage is one way to spy on harbor seals as they hunt for their meals, but, as a team of researchers who recently reported an alternate method in The Journal of Experimental Biology points out, the presence of the required light source may influence the very behaviors videographers attempt to witness and record during deep dives.
By strapping an accelerometer – a device that measures changes in speed – to the head of a harbor seal using a small neoprene headband, the scientists were able to record a characteristic jerk of the seal’s head each time it captured a fish. The researchers were working with a single harbor seal in a controlled environment for the purpose of testing the accelerometer; however, they say the method has the potential for use in months-long studies in the wild, partly because the battery demands of the accelerometer are so low.
“Such long records of foraging behavior will help us to understand how free-ranging aquatic predators search for and acquire energy from their dynamic environment in time and space,” the scientists write. By answering questions like, ‘when and where do seals find their meals?’ the researchers will be able to investigate the rest of the food web, too.
Harbor seal swimming in shallow water on the California coast.
(Original image by Tewy via Wikimedia Commons)