Every December through May, the waters around the Ogasawara Islands—a remote archipelago 1,000 kilometers south of Tokyo—transform into one of the world's most thrilling whale watching destinations as thousands of humpback whales breach and dive in the breeding season shallows. Now, scientists have mapped exactly where these magnificent creatures prefer to gather around Chichijima Island, the archipelago's main hub, unveiling the first-ever habitat suitability map for the region and reshaping how conservationists and tourism operators can protect and sustainably share this marine treasure.
For whale watchers, humpback whales are the showstopper species—acrobatic, active, and visible near the surface. But for researchers, the question of which specific areas around Chichijima the whales favor had remained unanswered until now. A collaborative team from Kyoto University, Tokyo University of Marine Science and Technology, and the Ogasawara Whale Watching Association set out to solve that mystery using five years of field data.
The researchers analyzed visual survey records from the Ogasawara Whale Watching Association spanning 2013 and 2015 to 2018, compiling sightings of 234 individual whales organized into 160 distinct groups. They then layered this observational data with underwater topography—water depth, seabed slope, and distance from shore—using two species distribution models to predict where conditions were most favorable for humpbacks. The results, published in the journal Mammal Study, revealed a clear pattern: shallow waters with gentle seabed slopes, conditions most abundant off the island's west coast, emerged as the prime habitat. Water depth proved the strongest predictor of whale presence.
The implications ripple outward in multiple directions. For whale watchers and local tourism operators, the map offers scientific guidance on where to direct boat tours with the highest likelihood of sightings, potentially protecting whales in other regions from excessive pressure. For conservation planners, it provides the first rigorous, visual foundation for marine protection strategies specific to humpbacks in the Ogasawara region. And economically, as Koki Tsujii, the study's lead author, emphasizes, whale watching has become a vital local industry—one that depends entirely on thriving populations.
"Whale watching focused on humpback whales is a thriving activity in the Ogasawara waters, so this species holds significant economic value not only as a component of marine biodiversity but also as a local tourism resource," Tsujii notes. "We aim to scientifically and visually identify suitable habitats in hopes of contributing to the effective conservation of this species."
The research opens doors to deeper investigation. Scientists already know from other regions that different whale groups—mothers with calves, for instance—show distinct habitat preferences, with calf-rearing pairs gravitating toward shallower waters. The team's next phase will be to develop models accounting for these pod compositions and to expand their mapping across the entire Ogasawara archipelago rather than just Chichijima. Each layer of understanding brings the possibility of more nuanced, effective conservation that honors both the whales' needs and the communities that depend on their presence.