Atropine sulfate is a common anticholingeric drug that is used in human medicine and veterinary medicine, as well as in scientific research. At doses less than 0.1mg/kg, it is used to treat bradycardia, ptyalism, and as an antidote for organophosphate poisoning. Although the effects of atropine have not been thoroughly examined in reptiles, previous studies utilized atropine, 1‐5mg/kg doses, to abolish shunting in reptiles, including snakes, crocodilians, and chelonians . In the present study, we investigated the influence of intramuscular administered atropine on heart rate in freshwater turtles, Trachemys scripta. To achieve this objective, an untethered electrocardiogram device recorded continuously in healthy female adult turtles (n=5, m=1‐2kg) before, during, and after the injections of veterinary grade atropine (0.01‐5mg/kg I.M.) with minimal observer interference. Heart rate was then derived from these measurements. Turtles showed a rapid increase to the peak heart rate less than ten minutes after the injection of atropine, except after the 0.01mg/kg dose, then gradually returned to the resting heart rate. In all doses above 0.01mg/kg, the length of the peak elevated heart rate constitutes about 1/5 of the total time atropine has an effect on heart rate. As a result, the extent of the elevated heart rates in the turtles increased exponentially as the dose of atropine also increased. Thus, we conclude that the lasting consequence of atropine on elevated heart rate is dose‐related. These results suggest that scientists can effectively eliminate shunting in turtles at lower atropine doses without subjecting the animal to prolonged tachycardia and associated cardiovascular adjustments.Grant Funding Source: Supported by NSF (1121324‐IOS)