For the short fin pilot in Hawaii whales (Globicephala macrorhynchus), the whole point is squid. Black marine mammals with bulbous heads They mainly feed on cephalopods and small amounts of fish. But how much squid do they eat?
New estimates show that individual Hawaiian short-finned right whales eat between 82 and 202 squid per day. For the entire population, this is about 88,000 tons per year. The results are described in detail in study published today in the journal Journal of Experimental Biology and can help locals conservation efforts.
Understanding how much food an animal should consume can help scientists understand when a species might be at risk. Humpback whales I can eat it up to 3000 lbs krill, plankton and small fish in one day, and killer whales can eat up to 300 to 500 lbs fish, cephalopods and even other marine mammals per day. Pilot whales in Hawaii dive up to 5,000 feet below the surface in search of food, primarily nutritious squid.
“These animals have been studied around the world, but relatively little is known about them in Hawaiian waters,” study co-author from the University of Hawaii at Manoa. marine biologist William Gough the statement says.
To solve the mystery of how much squid whales eat, Gough teamed up with colleagues from institutions in Spain, Australia and Denmark. They went to the Pacific Ocean and Attached data collection tags with removable suction cup to eight short-finned pilot whales. Each tag had motion sensors, a backlit camera, hydrophones to pick up echolocation clicks, and GPS.
“Short-finned pilot whales are quite small and fast, so we really have to pick our timing,” Gough said. “Ideally, we would attach a tag just behind the blowhole, facing the head, so we could see any prey in the depths.”
The team also flew a drone 82 feet above each whale, filming them from above so the team could determine the size of each animal.
A tagged short-finned whale “picks” other whales in its pod. CREDIT: HIMB Marine Mammal Research Program.
The team then recovered the tags, some of which were floating 50 miles away in rough water. Whales did 118 deep dives to a depth of 2836 meters.. Each of the eight whales surveyed dived approximately 39 times per day.
The team then analyzed the whales' tail impacts as they descended below the surface to see how much energy they expended. Short-finned whales use about 73.8 kilojoules per minute of energy (about 17.6 calories) while diving, compared to just 44.4 kilojoules per minute (about 10.6 calories) at the surface. So how much squid do they need to eat to meet the calorie requirements for diving and foraging?
By listening to echolocation clicks recorded on a hydrophone as the whales intercepted the squid, the team estimated that the mammals ate about four squid per dive. Each squid, when digested, provides them with about 560,000 kilojoules of energy (more than 133,000 calories).
Video from a camera attached to a diving short-finned pilot whale swimming in the depths. The whale was recorded making hunting echolocation clicks just before the flash of light. Echolocation clicks suggest the whale has detected a squid, and the bright object is a cloud of squid ink illuminated by the tag lights as the whale swims through it. CREDIT: HIMB Marine Mammal Research Program.
Gough then calculated that each whale should eat between 82 and 202 squid each day, or as many as 73,730 squid per whale per year.. There are approximately 8,000 short-finned pilot whales in the waters around the Hawaiian Islands, amounting to 88,000 tons of squid each year. Hawaii is home to several species of squid, including Hawaiian bobtail squid. Maintaining healthy squid supplies ensures that the whales will have enough food in the future.
“These results show that short-finned whales in Hawaii are in relatively good shape, having found an abundant and reliable food source,” said Gough, who is optimistic about the future of the whale species.
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