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| An aerial view of Hawaiʻi short-finned pilot whales at the surface. Photo Credit: HIMB Marine Mammal Research Program |
For the first time, scientists have calculated a detailed “energetic budget” for Hawaiʻi‘s short-finned pilot whales, revealing what it takes to power their extreme, 800-meter (2,600-feet) dives for food.
A new study led by the University of Hawaiʻi at Mānoa’s Hawaiʻi Institute of Marine Biology (HIMB) found an average adult whale must eat 142 squid daily to survive, scaling up to 416 million squid annually for the entire population of short-finned pilot whales. This data, published in the Journal of Experimental Biology, provides a new benchmark for protecting the historically understudied marine mammals.
“Pilot whales are one of the only oceanic dolphins that regularly dive to extreme depths—up to 1,000 meters—to find prey,” said William Gough, Marine Mammal Research Program (MMRP) postdoctoral researcher and lead author of the study. “This deep-diving, high-risk foraging strategy requires a delicate balance between the energy they spend and the energy they acquire. Our study is the first step in quantifying that balance for this specific population.”
Understanding precisely how much energy the animals require is essential for understanding how to effectively manage against threats and ensure their survival.
“This detailed scientific data gives Hawaiʻi management agencies a critical tool to monitor how changes in the ocean—from warming waters to ship noise—might push the pilot whales past their survival limit,” said Lars Bejder, MMRP director and co-author of the study.
The deep waters surrounding the Hawaiian Islands are home to a genetically distinct population of short-finned pilot whales. These highly social, toothed whales are not migratory; they remain with their tight-knit, multi-generational families in one region for life. The population forages year-round where they pursue their preferred prey: squid.
Requirements can inform effective management
“Deep-diving species like pilot whales are especially vulnerable to human-induced disturbances, such as noises from ships or changes in ocean temperature, which can disrupt foraging or increase their energetic costs,” said Gough. “If they use more energy than they can find, they face an energy crisis that weakens their health, hurts their ability to fight off disease, and ultimately limits their ability to reproduce and recover the population.”
Despite this inherent vulnerability, the Hawaiian pilot whale population benefits from a stable and abundant squid food source, which may better equip them to cope with environmental disturbances than populations elsewhere.
The team placed advanced Customized Animal Tracking Solutions (CATS) tags on eight short-finned pilot whales off the coast of Lānaʻi between 2021 and 2024. The tags recorded movement, depth and sound, and used 2K cameras with LED headlights to observe the whales in their lightless, 800-meter-deep hunting habitat. The researchers developed a new method to estimate minute changes in energy usage by combining data from tags with body measurements from aerial drone footage.
“Getting to be on the water and close to these animals is an absolute joy,” said Gough. “But the fact that we can see into their world, even at 800 meters and under extreme pressures [80 times that at the surface], and observe them capturing their food in complete darkness, feels unbelievable to me. It’s truly a privilege to document the lives of these elusive, deep-diving whales.”
Title: Daily energetic expenditure and energy consumption of short-finned pilot whales
Authors: William T. Gough, Brijonnay C. Madrigal, Augusta Hollers, Jens J. Currie, Robin W. Baird, Kristi L. West, Andreas Fahlman, Frank E. Fish, Lewis Evans, Martin van Aswegen, Brian Stirling, Aude Pacini, Grace L. Olson, Stephanie H. Stack, Ashley M. Blawas, William A. Walker, and Lars Bejde
Source/Credit: University of Hawaiʻi
Reference Number: mb111425_02