Environmental contaminants in blood, hair, and tissues of ocelots from the Lower Rio Grande Valley, Texas, 1986-1997

Abstract

The ocelot (Felis pardalis) is an endangered neotropical cat distributed within a small range in the Lower Rio Grande Valley (LRGV), in Texas, U.S.A. Studies of the impacts of environmental contaminants in wild cats are few. Approximately one fourth of the estimated population (about 100) of ocelots in the LRGV was sampled to evaluate the impacts of chlorinated pesticides, polychlorinated biphenyls, and trace elements on the population. Hair was collected from 32 ocelots trapped between 1986-1992, and blood was collected from 20 ocelots trapped between 1993-1997. A few blood samples were obtained from individuals recaptured two or three times. Tissue samples from 4 road-killed ocelots were also analyzed. DDE, PCBs, and Hg were some of the most common contaminants detected in hair and blood. Mean Hg levels in hair ranged from 0.5 to 1.25 μg g-1 dw, Se from 1.5 to 3.48 μg g-1 dw, and Pb from 0.56 to 26.8 μg g-1 dw. Mean DDE concentrations in plasma ranged from 0.005 μg g-1 ww to 0.153 μg g-1 ww, and PCBs ranged from 0.006 μg g-1 ww to 0.092 μg g-1 ww. Mean Hg levels in red blood cells ranged from 0.056 μg g-1 dw to 0.25 μg g-1 dw. Concentrations of DDE, PCBs, or Hg, did not increase significantly with age, although the highest concentrations of DDE and Hg were found in older animals. Overall, concentrations of DDE, PCBs, and Hg were low and at levels that currently do not pose any threat to health or survival of the ocelot. This is further supported by good reproduction of the ocelot in the LRGV, where adult females averaged about 1.5 kittens/litter. Thus, it seems that the current major threat to recovery of the ocelot in the LRGV may be habitat loss, although potential impacts of new generation pesticides, such as organophosphorus and carbamate insecticides need further study.