Boats are killing and injuring an endangered type of manatee at an alarming rate, a study has found.
The research, published in the journal Endangered Species Research, documented increasing mortality of the Antillean manatee in the waters of Belize—a small nation on the eastern coast of Central America—as a result of collisions with watercraft.
The study raises concerns about the survival of what had been considered a relatively healthy population of these endangered manatees, the researchers said.
Belize, which lies on the western edge of the Caribbean Sea, is home to the largest proportion of the Antillean manatee (Trichechus manatus manatus) in its range.
The creature is one of two subspecies of the West Indian manatee (Trichechus manatus)—also known as the North American manatee.
The other subspecies is the Florida manatee (Trichechus manatus latirostris), which is also considered to be endangered. Both subspecies are threatened by habitat loss, pollution, and other human activities.
Manatees are large, fully aquatic marine mammals that are sometimes referred to as sea cows.
The Antillean manatee population is thought to number around 1,000 individuals, but tourism and boat traffic have increased substantially over the past three decades, resulting in a spike in manatee deaths and injuries.
In the Endangered Species Research study, scientists wanted to assess the impacts of increasing boat traffic in the manatee population.
To do this, they examined 25 years of stranding data from Belize—involving both dead or injured animals—between the years 1995 and 2019.
The researchers also looked at six aerial surveys of the manatee population—conducted in 1997, 1999, 2000, 2001, 2002, 2014—as well as two decades of boat registration data.
They found that the number of watercraft collisions increased “significantly” over time from one to four per year in the late 1990s and early 2000s to 10 to 17 per year by the late 2010s.
Strandings occurred more frequently in areas where there was higher boat traffic, a high population density of humans, and mangrove habitats—particularly in Belize city, the country’s largest city, and the beach resort of Placencia.
“We knew that boat strikes were happening, but this study provides strong quantitative evidence of boat strikes as an increasing source of mortality for manatees in Belize, and it shows the areas where the risk is greatest,” study co-author Marm Kilpatrick, biologist and professor at the department of ecology and evolutionary biology at the University of California, Santa Cruz, said in a statement.
“These findings provide a basis for conservation measures that can be implemented to reduce the risk,” Kilpatrick said.
According to the authors, conservation efforts should focus on reducing the number of boats and the speed at which they can travel in areas with high numbers of manatees.
“This work has been shared with policymakers in Belize and will contribute directly to conservation planning, including protecting key areas for manatees such as the Belize River Mouth and the Placencia Lagoon,” said first author Celeshia Guy Galves in a statement. Galves is now affiliated the Clearwater Marine Aquarium Research Institute in Belize but led the study while studying as a graduate student at UC Santa Cruz.
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