In addition to deaths caused by boat impacts – widely known and reported –, parasitic and bacterial infections, as well as the effects of climate changeare among the main reasons why an increase in deaths has been observed. manatees in Puerto Rican waters.
This was reflected in a new study, published in the scientific journal Latin American Journal of Aquatic Mammalsin which researchers from the Caribbean Manatee Conservation Center detail the new natural threats that threaten the survival of the Antillean manatee (Trichechus manatus) on the island.
The investigation revealed that, In Puerto Rico, annually, between 10% and 15% of manatees die from emerging infections, such as leptospirosis and toxoplasma.diseases caused by Leptospira bacteria and the parasite Toxoplasma gondiirespectively.
According to the doctor Antonio Mignuccidirector of the Caribbean Manatee Conservation Center, These emerging infections are caused, in part, by “the parasites or bacteria present in the feces deposited by feral cats (without human contact since birth) or rats, respectively, which, due to rain and runoff, are reaching the sea, where they can infect other species such as the manatee.”.
“In the case of manatee deaths due to toxoplasmosis, this is due to possible overpopulation of cats, one of the main carriers of Toxoplasma gondii on the island,” highlighted Mignucci, author of the publication.
In 2012, researchers from Puerto Rico and the United States published a first report, in which they documented four manatees that died with toxoplasmosis. Since then, and until 2022, 17 deaths related to emerging infections and other diseases have been recorded..
For its part, Carla Rivera Perezdeputy director and researcher at the Caribbean Manatee Conservation Center, described the situation as a circle: the animals die infected and, because it is a zoonotic diseasecan then be transmitted to other animals and even spread to humans.
“Currently, we are analyzing samples from cases of manatees that have died, in recent years, to continue evaluating the causes and prevalence of parasitic and bacterial diseases or due to other factors”highlighted Rivera Pérez.
Meanwhile, Mignucci pointed out that “it is important to continue educating and be attentive to future news related to emerging diseases in Puerto Rico, which can also affect manatees. “We must continue studying these diseases, document them and, then, look for alternatives so that these pathogens do not affect marine animals.”
Climate change limits resources
Other threats facing the Antillean manatee in Puerto Rico include loss of habitat and seagrass meadows (their food) because of climate change.
“The rise in temperature, as part of climate change, can affect the presence of seagrasses, a very important food source for the manatee. For example“When temperatures rise, other organisms, such as seaweed, grow and block the penetration of sunlight into the seagrass, limiting this food resource in the manatee habitat.”Mignucci explained.
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We must continue studying these diseases, document them and, then, look for alternatives so that these pathogens do not affect marine animals. ”Antonio Mignucci
Although most of the deaths of the endangered mammal are associated with impacts from boats and jet skis, staff at the Caribbean Manatee Conservation Center – led by the Caribbean Stranding Network and the Interamerican University of Puerto Rico– urged citizens to be attentive to recent threats against the species.
In March, the Department of Natural and Environmental Resources (DRNA) reported that, between 2021 and the first three months of 2024, 13 manatee deaths were reported due to boat accidents. The figure does not include cases of manatees found in a state of decomposition, in which the cause of death is unknown.
According to the agency, the manatee mortality rate used to average 10 a year, but has increased to between 13 and 16.
In the last DNER census, about 300 manatees were identified in the waters of Puerto Rico. Specialists agree, however, that an ideal and stable population would be 3,000. The agency new manatee count underway for this year.
The author is a student of the Communicating Science course at the University of Puerto Rico in Humacao. Her professor, Dr. Kevin Alicea Torres, collaborated on this story.