Efficacy of Rhodamine B as a Fecal Marker for White-Tailed Deer

Abstract

Rhodamine B has been used as a wildlife marker for microherbivores and meso­ predators, but has yet to be evaluated for ruminants. Our objective was to determine the efficacy of rhodamine B as a wildlife marker for white-tailed deer (Odocoileus virginianus). We tested the effect of rhodamine Bon the production of mold growth, the palatability, lag time, variable concentration effectiveness, and persistence of rhodamine Bas a fecal marker in penned white-tailed deer. Liquid rhodamine B was added to corn and alfalfa-based, pelleted deer feed in concentrations of 0.06-oz. and 0.13-oz. of rhodamine B/lb. of grain and either placed in metal containers immediately or allowed a 1-hr drying period before being placed in metal containers. Grain samples that were sprayed with rhodamine and not allowed to dry produced mold quicker than non-marked grain; however, if the dye was allowed a 1-hr drying peri­ od immediately after application, then rhodamine B did not enhance mold produc­ tion. Five deer (2 M, 3 F) were fed for two days a pelleted diet sprayed with a sur­ face coating of 0.00045 oz. of rhodamine B/lb. body weight, and five deer (3 M, 2 F) were fed the same diet but sprayed with a surface coating of 0.0009 oz.of rhodamine Bllb. body weight, then fed a pelleted diet ad libitum thereafter without rhodamine B. Seven deer (n = 10) had feces marked during the first 12 hours and all deer pro­ duced marked feces after 36 hours. Rhodamine B persisted as a fecal marker up to 60 hours post-ingestion. White-tailed deer selected against feed that was marked by rhodamine B, but would consume feed that contained the dye. Rhodamine B can be a useful marker of white-tailed deer, especially if one wishes a non-lethal and non­ capture method to determine animal movements.