Sloths as Sentinels of Ecosystem Health: Evaluation of Agricultural Pesticides in Plasma of Free-Ranging Hoffmann’s Two-Toed (Choloepus hoffmanni) and Brown-Throated Three-Toed (Bradypus variegatus) Sloths
Pesticide exposure is a well-documented risk factor in wildlife population declines, particularly in delicate and threatened tropical rainforests. Costa Rica supports 5% of the world’s total biodiversity, but uses the highest volumes, per unit area, of pesticides in the world. This combination suggests that animals living in Costa Rican agricultural plantations and in surrounding ecosystems are chronically exposed to significant levels of various insecticides, fungicides, and herbicides. Currently, there are no published reports of pesticide accumulation in sloths, which could serve as ideal sentinel species for ecosystem health in Costa Rica, as they are the most abundant mid-size mammal, share habitat with people, and in Limon Province (our study site) there is a high density of conventional banana and pineapple plantations on which pesticides are applied. Within this region, FINMAC, an organic cacao plantation, supports a stable population of sloths, many of which are radio-collared for behavioral ecology and genetic studies. Since fruit plantations border our study site, we hypothesized that sloths, living on the periphery of the cacao plantation, had higher circulating concentrations of pesticides than those living in either the center of the study site, or control animals (sloths living in U.S. zoos). To investigate this hypothesis, we collected blood samples from sloths in three groups: 1) peripheral study site, 2) central study site, and 3) a subset of U.S. zoo sloths. We quantified circulating pesticides, and their metabolites, via liquid chromatography and mass spectrometry and/or gas chromatograph equipped with an electron capture detector, including: 1) chlorothalonil and its metabolite, hydroxyl chlorothianil; 2) diazinon and its metabolite, 2-isopropyl-6-methyl-4-pyrimidinol; 3) thiabendazole; 4) chlorpyrifos; 5) ethyl phosphonic acid; and 6) ametryn. Information acquired from this study will direct future efforts to determine the impacts of pesticide exposure on sloths, the local ecosystem, and, eventually, human health in Limon Province of Costa Rica.
This project was supported by the American Association of Zoo Veterinarians Research Grants, Wild Animal Health Fund.