糖心视频

The energy required for newborn humpback calves to grow after birth is 38 times greater than what they needed inside the womb according to research from University of Hawai驶i at M膩noa Hawai驶i Institute of Marine Biology (HIMB) in collaboration with Alaska Whale Foundation and other key partners. These findings were in the Marine Ecology Progress Series.

"This study addresses a key piece of the energetic puzzle in estimating the cost of being a humpback whale in the North Pacific: the cost of growth," said Martin Van Aswegen, lead author of the study and postdoctoral researcher at HIMB's Marine Mammal Research Program (MMRP). "While previous research has shown that these whales must grow very large in a short period of time, the actual energetic expense of that accelerated growth remained unknown."

Geared to grow

Research revealed that calves require 6鈥�8 times the daily growth energy of an adult whale, and they achieve 30% of their total lifetime growth in less than their first year of life. In fact, more than 60% of a calf's crucial energy needs for growth occur within the first 150 days of birth.

Humpback mothers must support lactation while fasting in Hawai驶i breeding grounds and then traversing back to their feeding grounds in Alaska. This exposes the mother-calf pair to significant vulnerability when ocean conditions threaten the mother's energy stores.

The study found that a mother's ability to produce a large, healthy calf鈥攐ne more resilient to starvation and environmental stress鈥攈inges directly on her own energy reserves. Smaller females, with lower energy reserves, face trade-offs that constrain how often they can reproduce and how much they can invest in their offspring.

"By quantifying the energetic demands of growing big and strong, we provide crucial insight into how external pressures, including climate change and human disturbance, may affect the survival and resilience of these ocean giants," said van Aswegen.

Warning signs

The study also revealed a worrying trend: Mature humpback whales today are noticeably shorter than historical records, indicating a decline in body size of approximately 1鈥�2 feet since the mid-1900s. Recent signs of humpback population stress in the region include a 76.5% drop in mother-calf sightings and an estimated 80% drop in crude birth rates in Hawai驶i between 2013 and 2018.

These declines coincided with the longest-lasting global marine heat wave, suggesting that low food availability prevented mothers from getting enough energy for the demands of nursing and calf growth. The results affected calves and juveniles, whose higher energy requirements make them highly vulnerable.

"If humpback whales are to survive threats like extreme marine heat waves and other stressors that result from human activity, we need to understand precisely how reproductive females accumulate and allocate energy to support the exponential costs of gestation and lactation," said Lars Bejder, director of MMRP, professor at HIMB, and senior author of the study. "This knowledge is the foundation for making the urgent conservation changes required for the population's future."

Drones and data

The team used drones to take high-resolution aerial photos of more than 1,500 humpback whales in Hawai驶i and Southeast Alaska. They combined drone measurements with historical records and biological samples to acquire a full picture of humpback energy needs throughout their lifespan.

"This noninvasive approach gives us a rare look at whale biology as they live, instead of relying only on historical whaling data from the 1900s," said van Aswegen. "Our humpback whale health database, comprising more than 12,000 measurements of 8,500 individual whales in the North Pacific, is being used across several projects within the Marine Mammal Research Program and abroad."

The data can be used in conjunction with fine-scale behavior and movement data (from biologging tags), reproductive and stress hormone data (from tissue and breath samples), and tissue data derived from postmortem events.