Whaling, the practice of hunting whales, dates back to around 3000 BC. The people living in the North Atlantic and North Pacific regions relied on the resources provided by whaling for survival. As populations around the world grew, commercial whaling gained popularity. By the dawn of the Industrial Revolution in the mid-1700s, whaling had become extremely important. Whale blubber, refined into oil, helped propel the Industrial Revolution. Whales throughout the world’s seas and oceans were hunted to the extreme, and many whale species were brought to near extinction.

In response to the dramatic drop in whale populations caused by whaling, the International Whaling Commission (IWC) banned commercial whaling in the 1980s. Humpback whales were just one of the species placed on the Endangered Species List due to over whaling. Significant conservation efforts have helped revitalize populations of many whale species, including the humpback whale. In 2016, the humpback whales that populate the coast from Hawaiʻi to Alaska were removed from the Endangered Species List and are currently classified as “Least Concern.” However, as climate change continues to impact the globe, humpback whale sightings have once again declined.

Researchers from the University of Hawaiʻi at Mānoa’s Marine Mammal Research Program (MMRP) at the Hawaiʻi Institute of Marine Biology have begun using technology like drones to better understand the effects of climate change on humpback whale populations. PhD student Martin van Aswegen, working under the leadership of MMRP director Dr. Lars Bejder, recently published his findings using drones to study humpback whale mothers and their calves migrating from Hawaiʻi to Alaska. The paper, titled Maternal Investment, Body Condition, and Calf Growth in Humpback Whales, was published on December 12, 2024, in the Journal of Physiology.

Martin and a team of fellow researchers began tracking pregnant whales in Hawaiʻi with drones between 2018 and 2022. The whales were followed throughout their pregnancies, through birth, and along their journey to the Alaskan feeding grounds with their newborn calves. Martin explained that using drones, “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.” The drone images were compared to those of whales that were not pregnant or lactating. The drone images provided significant data on the correlation between size and population health.

New whale mothers were shown to be losing weight dramatically compared to those who had not recently given birth. The calves were growing at a healthy rate, while the mothers’ weight continued to decline due to what researchers believe is a combination of natural energy expenditure from migration, birth, and lactation, combined with limited food access. A release from the university states, “Studies document a 76.5% decline in mother-calf encounter rates in Hawaiʻi between 2013 and 2018, with birth rates declining by 80% from 2015 to 2016. In Southeast Alaskan feeding grounds, research reveals total reproductive failure in 2018, with calf survival decreasing tenfold from 2014 to 2019. These observations coincided with the longest-lasting global marine heatwave, which shifted food webs and reduced availability of prey throughout the North Pacific.”

The drone data collected by Martin and his team directly correlated with previous research on birth rates influenced by food availability, conducted by the MMRP. “Our humpback whale health database, comprising 11,000 measurements of 8,500 individual whales in the North Pacific, is being used across several projects within the Marine Mammal Research Program and abroad,” Dr. Bejder said. “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.”

There is still much research to be conducted, but as Martin points out, using drones makes such endeavors feasible. “The surprising part of this study was our ability to find the same individual mothers and calves over great distances and time periods,” he said. “To measure the same whales over 3,000 miles apart, over a period of roughly 200 days, is truly remarkable and provides such valuable data for the questions we were asking.” While significant strides have been made in whale conservation, ongoing challenges such as climate change and shifting food availability highlight the need for continued monitoring and adaptive strategies. As research progresses, the use of innovative technologies like drones offers insights into the complex relationship between humpback whales and their changing environment.

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