The Effect of Ambient Noise on Humpback Whale Breaching Behavior on a Southeast Alaskan Foraging Ground

ABSTRACT Sound plays a central role in the lives of humpback whales ( Megaptera novaeangliae ), but elevated ambient sound levels—from either natural or anthropogenic sources—may interfere with their ability to communicate. While vocal responses to noise have been well‐documented, far less is known about how whales may adjust non‐vocal behaviors such as breaching. We investigated whether humpback whales in Glacier Bay National Park and Preserve (GBNPP), a protected foraging habitat in Southeast Alaska, modify breaching behavior in response to elevated ambient sound levels. Using a combination of long‐term acoustic monitoring and land‐based visual surveys conducted over two humpback whale foraging seasons (2015–2016), we assessed breaching occurrence and frequency in relation to measured ambient sound. We found that higher ambient sound levels were significantly associated with an increased likelihood of breaching and a greater number of breaches per observation period. Notably, this effect was driven by total ambient sound level, not by the presence or proximity of vessels, suggesting that whales respond to acoustic sources equally in this system. Our results support the hypothesis that breaching may function as a compensatory communication strategy when vocal signals are masked, and that this strategy is transferable between sound sources. Our findings underscore the importance of managing ambient sound in sensitive habitats and suggest that low‐noise protected areas like GBNPP may buffer whales from more disruptive effects of ocean noise.