Drone technology uncovers rapid growth in Australian humpbacks
Recent aerial surveys conducted by researchers from Griffith University and the Pacific Whale Foundation have revealed that the eastern Australian population of humpback whales (Megaptera novaeangliae) reaches near‑adult dimensions at a remarkably young age. By attaching drones equipped with laser altimeters above migrating whales in Hervey Bay and Eden, scientists measured the total length of 865 individuals between 2021 and 2024. The data show that five‑year‑old whales are already close to eleven metres long, and by the time they are about 6.6 years old they have attained roughly ninety percent of their final size, which caps at around thirteen metres.
Why historic data fell short
For decades, knowledge of humpback growth curves relied on specimens harvested during the mid‑twentieth‑century whaling era. Between 1949 and 1962, more than twelve thousand whales were taken from Western Australia, yet only a tiny fraction—118 individuals—were recorded as juveniles because a legal minimum length of 10.7 metres effectively excluded younger animals from the catch. Consequently, the classic growth model published by Chittleborough in 1965 was based largely on whales aged five to nineteen years, leaving the earliest stages of development largely inferred rather than measured.
Methodology from the sky
The modern study circumvented those limitations by using drones to obtain precise, non‑invasive measurements. A laser rangefinder logged the drone’s altitude, allowing researchers to convert the visual distance from snout tip to tail notch into exact metres. When a whale passed beneath the drone twice, the two independent readings matched closely, confirming the technique’s reliability. Age estimation combined a photographic catalog of over 8,000 humpbacks—dating back to 1984—with unique tail‑fluke patterns to assign a minimum age to 294 individuals. For the remaining whales, researchers placed them into broad age classes ranging from calf to adult.
Comparisons with northern populations
When juxtaposed with data from the North Pacific and the North‑East Atlantic, the Australian humpbacks’ growth trajectory stands out. In the northern Pacific, a comparable study found that whales need nearly nine years to reach the same proportion of adult length, while Atlantic counterparts take even longer. Despite these differences in growth speed, the ultimate adult size of Australian humpbacks appears unchanged from the whaling era, suggesting that the rapid early growth does not translate into larger final dimensions.
Implications for population recovery
The accelerated growth aligns with a population that has rebounded impressively since the cessation of commercial hunting, expanding at an average of 11 % per year for three decades. Faster attainment of near‑adult size could, in theory, lead to earlier sexual maturity, potentially shortening generational intervals. However, the study did not directly link size to reproductive readiness, and the relationship between length and maturity remains complex in humpbacks.
While the dataset contains relatively few older individuals—making the later‑stage curve less certain—the overall pattern is robust across a range of age‑estimation methods. Researchers caution that cross‑population comparisons must consider environmental, genetic, and ecological variables that could influence growth rates.
These findings underscore the value of drone‑based monitoring for marine megafauna, offering a repeatable, low‑impact means to track vital life‑history parameters that were previously hidden behind historical data gaps.
