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We evaluated the efficacy of capsaicin as an aversive agent to captive and free-ranging gray squirrels (Sciurus carolinenssi). Capsaicin appeared more aversive in lipid-based formulations. Sunflower hearts treated with capsaicin oleoresins at 100,000 Scoville Heat Units (SHU's) demonstrated near-complete aversiveness to captive squirrels. These treatments were sampled by food-deprived captive squirrels, but were not consumed due to their extreme pungency. Additionally, capsaicin-treated suet was very effective at lower concentrations than was observed with seeds (24,000 SHU-suet versus 100,000 SHU-seed). Three ground-pepper treatments (A = 8,250 SHU's, B = 27,500 SHU's, and C = 82,500 SHU's) offered simultaneously with control seeds to free-ranging squirrels revealed a dose-dependent aversive response. These same three treatments (A, B, and C) on sunflower hearts with control hearts available were also avoided by free-ranging squirrels; however, there was no significant differences (P>0.05) in mean consumption between the capsaicin levels. Apparently, even low capsaicin concentrations (8,250 SHU's) are as aversive as higher concentrations (27,500 to 82,500 SHU's) when applied directly to sunflower hearts.