HONOLULU (KHON2) -- If you've spotted a drone surveilling the Pacific Ocean, it might be a drone monitoring nursing humpback whale mothers and their calves. Get Hawaii's latest morning news delivered to your inbox, sign up for News 2 You Biologists from the University of Hawaii at Manoa are taking drone imagery usage to the next level, using the images to compare calf growth and maternal body conditions for humpback whales in Hawaii versus Alaska. Why are drones taking over Hawaii skies? The drone imagery helps biologists fully understand "how mother-calf pairs expend energy across their migratory cycle." “A total of 2,410 measurements were taken from 1,659 individuals, with 405 repeat measurements from 137 lactating females used to track changes in maternal body volume over migration,” explained Martin van Aswegen, Marine Mammal Research Program PhD candidate and lead author of the study.  The study revealed larger humpback whale females produce larger, faster-growing calves. Mother humpbacks in Hawaii "lost 20% of their body volume over 60 days of lactation" while those in Southeast Alaskan feeding grounds had the "slowest rates of weight gain compared to non-lactating females." Researchers also highlighted studies documenting declines in mother-calf encounter rates and birth rates in Hawaii. Other studies showed total reproductive failure in Southeast Alaskan feeding grounds. Officials said the studies were a result of the longest-lasting global marine heatwave, which shifted food webs and reduced the availability of prey in the North Pacific. Find more Hawaii, Oahu, Maui and Kauai news here “This work forms the basis for future studies investigating the energetic demands on humpback whales. These studies will be used to better predict the resilience of large baleen whale species in the face of threats, including disturbance, entanglement, vessel collision, and climate change," explained Lars Bejder, MMRP director and co-author of the study.