Researchers Checked the Number of Squids Pilot Whales Ate Each Day— the Results Were Unbelievable
Apparently, whales have a massive appetite. It makes sense considering their large structure and is acceptable as long as it doesn't mess up the food web. It's one thing to consume a large prey, but concerning if the diet almost wipes out an entire population. The short-finned pilot whales enjoy feasting on about 82 and 202 squid per day, which means a total of 73,730 squids are consumed annually by a single whale. If the entire population of 8000 whales is accounted for, then a shocking amount of squid is eaten each year, according to the study published in the Journal of Experimental Biology. Short-finned pilot whales (Globicephala macrorhynchus) are a less explored species of whale that resides in the waters around Hawaii.
Curiosity over the dietary habits of these Hawaiian mammals prompted a team of scientists to experiment by deploying suction cup tags underwater. "Ideally, we attached the tag right behind the blowhole facing the head, so we could see any foraging at depth," said study author William Gough from the University of Hawaiʻi said in a statement, as per EurekAlert. "Short-finned pilot whales are fairly small and quick, so we really have to pick our moment," he added. It turns out that whales are extremely particular about their meals and can literally go to any length to get them. During forage, they can swim about 1,700 meters deep, which requires excess energy because of the pressure at the depths of the ocean.
The rigorous hunt for food clearly builds up their appetite enough to consume 100s of squids in a day. Whales also need to come up to the surface to breathe, which further increases the number of times they have to dive. The researchers found that these Hawaiian whales dive deep into the water from the surface about 39 times in a day. In each dive, they cover an estimated distance of 400-800 meters in about 8-16 minutes: an extremely energy-draining task. Their tales helped the scientists analyze the energy it took them to complete one round of dive. Since tails help marine animals propel forward, the faster the tail wags signifies the speed at which the mammal travels.
The study showed that the whales used 73.8 kilojoules per minute (kJ/min) of energy while diving into the water and 44.4 kJ/min of energy for coming up to the surface. Based on this data, the scientists derived a connection between the number of squids that the whales would have to consume to meet their energy needs. Through hydrophone recordings, the team could determine whenever an individual whale preyed on a squid. Further analysis showed that each whale consumed about four squid with each dive, and one squid provided them with 560kJ of energy.
These numbers helped the scientists determine the estimated number of squids that each whale consumes per day, which is between 82 to 202. So how many squids are consumed by the entire population of the pilot whales around Hawaiʻi? 8000 individuals consume up to 88,000 tonnes of squid each year. But fortunately, the Hawaiian ocean holds far more squids than these whales consume. "These results show that short-finned pilot whales are in relatively good shape in Hawaiʻi, having found an abundant and reliable source of food," Gough added. That's a great confirmation that pilot whale extinction won't happen anytime soon.
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