A Field Evaluation of the Efficacy of Milorganite as a Repellent for Non-Venomous Rat Snakes (Elaphe obsolete)

The objective of this study was to evaluate the efficacy of Milorganite® as a repellent for rat snakes. Milorganite® is the bio solids by-product left from the activated sludge process from the Milwaukee Metropolitan Sewer District. During 3, 7-day release periods, 5-6 mature rat snakes were placed within a 0.1ha plastic fence enclosure intended to impede escape. The enclosure contained natural and artificial hides and water. Snakes were fitted with an externally attached radio transmitter with location of each snake determined 3 times per day by radio telemetry and visual confirmation. During the first 2, 7-day period, with no Milorganite® treatment, snakes were contained within the enclosure for a similar (p\u3e0.05) duration of 9.1h±1.8 and 9.4h±1.8 respectively, before escaping. Prior to release of snakes in period 3, a total of 907.2g of Milorganite® was applied by hand in a 20cm width strip along the interior perimeter of the enclosure fence. During period 3, 6 snakes were maintained within the enclosure longer (p\u3c 0.005) compared to periods 1 and 2, with an average containment time of 23.5h/day±0.5. Total snake-hours that animals were maintained in the enclosure was higher (p\u3c0.005) during the Milorganite® treatment (164.0h±1.4) compared to non-treated period 1 (64.0h±1.8) or period 2 (66.0h±9.0). All snakes remained within the enclosure throughout the 7-day treatment period. One snake died on day 6, posttreatment from unknown causes. Results of this study suggest Milorganite® was effective as a repellent for the rat snake under these experimental conditions