Dolphins have been observed harassing and attacking manatee calves in an aggressive act that has baffled scientists trying to understand why they would harm the most defenseless members of their cousin species.
The behavior was recorded ten times between 1999 and 2020 in the Caribbean Sea along the coast of Belize, with most interactions between adult bottlenose dolphins and manatee calves occurring in the last decade, according to a study published in early this month in peer magazine. -Revised scientific journal PLOS One.
Although many of the interactions left the manatees injured and, in at least one case, dead, the scientists did not make clear whether the highly sociable and intelligent “rough-playing” dolphins had any intention of harming them.
In one case captured on video, a pod of four dolphins were observed harassing a manatee calf and its mother, and separated them by “lifting the calf as they swam away.”
A lone dolphin then followed the calf for several minutes before “pulling the calf out of the water into the mangroves and biting it repeatedly,” forcing researchers to remove it from the water and send it for rehabilitation.
An Antillean manatee swimming with her baby photographed in her enclosure at Faunia Zoological Park, Spain, in 2019. LightRocket via Getty Images
In three of the cases, manatee calves were discovered with “clusters of rake teeth” and bite marks consistent with those of bottlenose dolphins, resulting in the death of one of the manatee calves.
In another incident, “large splashes and vigorous subsurface movements suggested” that a dolphin that had been stalking a manatee calf had become aggressive.
Drone footage from a separate incident recorded a single dolphin swimming in a counterclockwise circular path around a mother and calf manatee 11 times in four minutes as the pair tried to escape. The device ran out of battery before it could record how the interaction ended.
In several cases, dolphins were seen trying to push their calves to the surface, which could be interpreted as a playful or affectionate gesture.
“We don’t know if they are really trying to harm them or not. Dolphins play hard. They don’t have hands, so when they socialize, mate or play, they tend to bite and hit each other with their tails,” Eric Angel Ramos, author of the study and researcher at the International Foundation for Nature and Sustainability, told Newsweek.
Dolphins leap out of the water from the bow during a trip with Newport Coastal Adventure to view marine life along the coast of Orange County, California, in 2018. MediaNews Group via Getty Images
“They may be treating the manatees roughly, but they’re not really trying to harm them. However, bottlenose dolphins are also known to kill dolphin calves of their species, and probably others. “So the impulse to attack and kill the young could help explain how they treat the young of other species.”
Many of the attacked manatees were orphans, the researchers noted.
The dolphins’ unknown motives were evidenced by a case in which a group of orcas were reported to have adopted a pilot whale calf, a gesture that could also have been an abduction.
However, bottlenose dolphins can also turn against other marine mammals, including other dolphin species, in their fight for resources, Ramos warned.
“But it’s really difficult to understand these interactions because you don’t see them much and it’s difficult to determine who is involved and what the context of the interaction is,” Ramos told the outlet.
The researchers noted in their paper that “the dynamics and drivers of interspecies interactions in nature are not well understood, particularly those involving social animal species.”
“The bottom line is that dolphins display complex behaviors and sometimes interact with other species in ways similar to the way they interact with each other, and that can be aggressive and sometimes lead to injury,” Ramos said.
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Source: vtt.edu.vn