Dolphins are bullying baby manatees
Dolphins are mysteriously attacking manatee calves, and this hostile behaviour may be a regular occurrence. In a recent study, researchers documented ten aggressive interactions by bottlenose dolphins towards Antillean manatee calves that targeted orphans as well as youngsters that were with their mothers. The attacks occurred near Belize over a 21-year timespan, from 1999 to 2020, with the majority of instances occurring between 2015 and 2020. “Dolphins don’t eat manatees, and why they act this way with another species is unclear,” said Eric Angel Ramos, a scientist at the Fundación Internacional para la Naturaleza y la Sustentabilidad. “It’s likely they are quite curious when they encounter manatees, and because dolphins are often aggressive with each other, they display this behaviour to other species like manatees.”
The researchers observed dolphins attempting to separate calves from their mothers and harassing, ramming and biting them. In each case, the dolphins initiated the interaction. Researchers believe the attacks were intentional. “I’m confident in saying that I think they want to inflict death,” said Jérémy Kiszka, a biological science professor at Florida International University. The researchers also found tooth rake marks with spacing that indicated dolphin teeth on orphaned calves during health checks, providing further evidence of these violent assaults. Although scientists don’t fully understand what’s going on, dolphins are known to display similar behaviours with their own young and calves from other species. They have previously been recorded biting other dolphins, and are known to attack and kill harbour porpoises.
Dolphins might act aggressively towards manatees and other marine animals because they perceive them as competitors for food, space or resources. And if these animals’ ecosystems degrade due to climate change and human activities, there’s a chance it could cause the species’ habitats to overlap further, resulting in an increase in these hostilities, Kiszka said. The aggressive interactions between manatees and dolphins took place over many years, so they’re likely more common than scientists previously thought and could impact the survival of the species. Antillean manatees are threatened across their range; this subspecies of the West Indian manatee can be found in marine, brackish and freshwater environments from southeastern Texas to northeastern Brazil. Even around Belize, which has a relatively healthy population, they’re threatened by vessel collisions. Understanding what’s going on could help conservationists protect calves and the wider manatee population, Kiszka said.