{"id":237032,"date":"2026-07-06T13:16:33","date_gmt":"2026-07-06T23:16:33","guid":{"rendered":"https:\/\/www.hawaii.edu\/news\/?p=237032"},"modified":"2026-07-10T08:13:52","modified_gmt":"2026-07-10T18:13:52","slug":"spinner-dolphins","status":"publish","type":"post","link":"https:\/\/www.hawaii.edu\/news\/2026\/07\/06\/spinner-dolphins\/","title":{"rendered":"Hawaiʻi Island spinner dolphins are producing fewer calves"},"content":{"rendered":"Reading time: <\/span> 3<\/span> minutes<\/span><\/span>
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Mother and calf spinner dolphins. (Photo credit: Fabien Vivier, and research was conducted under National Marine Fisheries Service permit number 21476.)<\/figcaption><\/figure>\n

Unexpectedly low calf numbers within the spinner dolphin population off Hawaiʻi<\/span> Island were revealed in a study led by scientists with the Marine Mammal Research Program<\/a> (MMRP<\/abbr>) at the University of Hawaiʻi<\/span> at Mānoa<\/span> along with national and international collaborators. Their research, published in Endangered Species Research<\/em><\/a>, determined that calves make up only about 9% of the population, a stark contrast to the 17% expected in a healthy, stable population, raising urgent concerns about the long-term survival of this isolated population.<\/p>\n

Viewing spinner dolphins is an attraction of the tourism industry in Hawaiʻi,<\/span> however, those activities put pressure on the marine species. Previous research has shown that this population of dolphins experiences the highest levels of disturbance exposure recorded for dolphins worldwide.<\/p>\n

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Group of spinner dolphins fast traveling. (Photo credit: Fabien Vivier, and research was conducted under National Marine Fisheries Service permit number 21476.)<\/figcaption><\/figure>\n

“The evidence suggests chronic human disturbance—especially tourism and recreational-related interactions during critical dolphin resting periods—as a likely contributing factor affecting reproductive success and calf survival,” said lead author Fabien Vivier, who was a doctoral student at the Hawaiʻi<\/span> Institute of Marine Biology<\/a> in the 糖心视频<\/abbr> Mānoa<\/span> School of Ocean and Earth Science and Technology<\/a> at the time of this work. “The findings support stronger conservation actions, such as time-area closures for human activities, alongside continued long-term monitoring—actions that have long been called for.”<\/p>\n

Drone surveys reveal population trends<\/h2>\n

To reach these conclusions, scientists utilized drone photography to measure the body length of free-swimming dolphins. By combining these aerial measurements with age-length data from stranded spinner dolphins collected by Kristi West, study co-author and researcher with the 糖心视频<\/abbr> Health and Stranding Lab at the 糖心视频<\/abbr> Mānoa<\/span> College of Tropical Agriculture and Human Resilience<\/a>, the team created the first age-length growth curve for this specific population. This allowed them to accurately categorize individuals into calves (under 2 years), juveniles (2–9 years), and adults (over 9 years).<\/p>\n

Age structure is an early indicator of population health and long-term viability. The documented low proportion of calves suggests the spinner dolphin population off Hawaiʻi<\/span> Island may not be replacing itself fast enough, which could lead to future population decline.<\/p>\n

Highly valuable and vulnerable population<\/h2>\n
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Drone view of a large group of approximately 110 individual spinner dolphins. (Photo credit: Fabien Vivier, and research was conducted under National Marine Fisheries Service permit number 21476.)<\/figcaption><\/figure>\n

In Hawaiʻi,<\/span> spinner dolphins are culturally, ecologically and economically important. Research from 2013 estimated that each individual dolphin is valued at more than $3.3 million over its lifetime and collectively, dolphin tourism generates more than $100 million annually for the state\u2019s economy.<\/p>\n

With spinner dolphins following a predictable daily cycle—foraging offshore at night and returning to shallow coastal bays during the day to rest and socialize—they are especially vulnerable to tourism activities in these nearshore habitats.<\/p>\n

“This study provides one of the first population-level demographic signals suggesting those long-term disturbances may now be affecting reproduction and calf survival,” said Professor Lars Bejder, co-author on the study and MMRP<\/abbr> director.<\/p>\n

A call for stronger protections<\/h2>\n

While a 2021 federal rule requires people and vessels to remain at least 50 yards away from the dolphins, experts from the U.S.<\/abbr> Marine Mammal Commission and the Pacific Scientific Review Group have argued that this measure is insufficient. The study authors are calling for stronger conservation actions, specifically time-area closures that would restrict human access to critical resting bays during the day.<\/p>\n

“Understanding these impacts is critical for protecting an isolated local population before declines become irreversible,” Randall Wells, study co-author and director of Brookfield Zoo Chicago\u2019s Sarasota Dolphin Research Program<\/a>. “We hope this work provides the science-based evidence needed to develop effective protections for spinner dolphins while helping balance marine tourism, cultural stewardship, and long-term ecosystem health in Hawaiʻi.”<\/span><\/p>\n

Future research and monitoring will depend on available funding, with scientists aiming to track long-term changes in age structure, reproduction, and population and further refine non-invasive drone-based methods.<\/p>\n","protected":false},"excerpt":{"rendered":"

Previous research has shown that this population of dolphins experiences the highest levels of disturbance exposure recorded for dolphins worldwide.<\/p>\n","protected":false},"author":16,"featured_media":237040,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[30],"tags":[53,1467,1363,936,937,158,9],"class_list":["post-237032","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research","tag-hawaii-institute-of-marine-biology","tag-manoa-excellence-in-research","tag-manoa-research","tag-marine-mammal-research-program","tag-marine-mammals","tag-publication","tag-uh-manoa","entry","has-media"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t