Brazilian scientists hope to continue this year the studies that try to clarify the reasons for a behavior that had not previously been registered in the pink dolphin (Inia geoffrensis) of the Amazons.
Researchers are waiting for funding to reactivate and the pandemic to end before resuming studies and understanding why older males are attacking cubs—and killing them. The behavior had not been observed before 2013, when the first case was observed.
The research that describes the strange behavior was published in Behavior magazine. According to the study, after 2013, other attacks were observed in 2014, 2016, 2017 and 2018.
The aggressive behavior shown by some porpoises is not part of this and other species of freshwater dolphins, said Brazilian scientist Vera Maria da Silva, a member of the Network of Specialists in Nature Conservation (RECN), of the Grupo Boticário Foundation.
According to Vera Maria, who has been monitoring porpoises for 26 years and leading the study on changing the species’ behavior, her research team was ‘surprised’ by the results of the observations since 2013.
how attacks happen
In research, scientists wrote that not all puppies attacked are killed.
The leader of the group of researchers said that, even observing these animals daily, the chances of noticing an attack of this size are small, since most of it occurs under water.
However, she highlights that an aggression event was registered by a team from the Federal Rural University of Rio de Janeiro (UFRRJ) with the dolphin, from Guanabara Bay. It was not possible to confirm whether the puppy died or not.
Researchers are still trying to figure out why so few records have been made, and why this behavior has only recently been observed.
According to Vera Maria, it may be that this type of behavior was already frequent, but it escaped the eyes of observers.
The hypothesis is contested, which is related to the deep observation that researchers have developed over the years of the region’s porpoises.
“There are females that we have followed for five generations: great-grandmother, grandmother, mother, daughter, granddaughter. There are several well-known animals,” Vera told Brazil Agency. Every year, expeditions are made to capture and mark the animals, before returning them to the rivers”, said the researcher.
why the attacks
The team of biologists believes that aggression against puppies can represent a socio-sexual display, which means that the dolphins use attacks to show strength in front of females.
The researcher believes that there is a possibility that there is a period with greater frequency of this behavior – which corresponds to the birth of the puppies, between September and October of each year, which would support the theory that the attacks have a sexual component.
Another possibility, according to the study, is that the violent exhibitions are the result of a social pathology, “which is found in other mammals that kill offspring”, they wrote.
The researchers estimate that the aggressive behavior of some dolphins cannot be paralleled by the behavior of lions, which kill offspring to pass their DNA on, because the boto does not have the behavior of keeping with the same female for a prolonged time.
“This aggression can be much more of a dysfunctional thing”, says the researcher.
*With information from Agência Brasil
Reference: CNN Brasil
