Dolphins are among the most intelligent and social animals on the planet. They form strong bonds with their mothers and stay with them for several years.
However, this close relationship may also have a dark side.
A new study has found that baby dolphins are receiving high doses of harmful chemicals from their mother's milk, which could affect their health and behavior for the rest of their lives.
The study sheds light on the plight of dolphins and other marine mammals that are exposed to persistent organic pollutants (POPs) in their habitats.
These pollutants are man-made substances that do not break down easily and can accumulate in the environment and in the bodies of animals.
The study also provides insights into how these pollutants move through the ocean and affect the food web.
The alarming discovery of persistent organic pollutants in dolphin calves
MORTEN STRICKER/Ritzau Scanpix/AFP via Getty Images
A new study has revealed that baby dolphins are being exposed to high doses of toxic chemicals through their mother's milk.
The researchers from the National Oceanic and Atmospheric Administration (NOAA) and the Naval Information Warfare Center Pacific (NIWC Pacific) analyzed the milk and blood samples of six mother-calf pairs of bottlenose dolphins from the U.S. Navy Marine Mammal Program in San Diego Bay.
They found that the milk contained high levels of persistent organic pollutants (POPs), such as PCBs, DDTs, CHLDs, HCHs, and PBDEs, which are known to disrupt the endocrine system and cause various health problems.
The study, published in the journal Science of The Total Environment, also showed that the calves had higher concentrations of POPs in their blood and blubber than their mothers by the time they were weaned.
This means that the calves were receiving more POPs from their mother's milk than from their environment or their food intake.
The researchers estimated that the calves ingested about 80% of their lifetime POP burden during the first year of their life.
They explained that the high transfer of POPs from the mothers to the calves was because the mothers continued to hunt and eat prey that had POPs in their bodies while they were lactating.
The POPs accumulated in the mothers' blubber and were mobilized into their milk when they needed energy to produce it.
The researchers also noted that the POP levels in the mother's milk and blood decreased over time, while the POP levels in the calves' blood increased, indicating a dynamic exchange of contaminants between the mother and the calf.
The study's lead author, Dawn Noren, a research fishery biologist at NOAA's Northwest Fisheries Science Center, said in a statement: "The newborns are getting the highest concentrations soon after birth, at the time when they are most vulnerable.
Mammals are still developing neurologically after birth, so high exposure early on is a huge concern."
The implications and recommendations for dolphin conservation
The study's findings have important implications for the conservation of dolphins and other marine mammals that are exposed to POPs in their habitats.
The researchers warned that the high levels of POPs in the calves could impair their growth, development, reproduction, and survival.
They also suggested that the POPs could affect the behavior and cognition of the dolphins, as some of the compounds have been linked to neurotoxicity and learning deficits.
The researchers recommended that more studies should be done to monitor the POP levels in dolphin populations and to assess the effects of POPs on their health and fitness.
They also urged for more efforts to reduce the sources and emissions of POPs into the environment, as these chemicals can persist for a long time and travel long distances through air, water, and food webs.
The potential risks of POPs for other marine mammals that feed at the top of the food chain, such as orcas, which also continue to hunt and eat prey while nursing their young, have also been highlighted.
According to the researchers, orcas could face similar or even worse scenarios of POP transfer from their mothers, as they have longer lactation periods and higher fat contents in their milk.
