Diet and chemical defenses of the Sonoran Desert toads

The Sonoran Desert Toad is the only animal known to secrete the psychedelic compound 5-MeO-DMT as a chemical defense, but whether it produces this compound itself or acquires it from its diet was unclear. Analyzing toxin gland secretions and stomach contents from wild toads and other amphibians in and around Tucson, Arizona, showed that all Sonoran Desert Toads had high concentrations of 5-MeO-DMT, while other toad species did not. The diet of the Sonoran Desert Toad was similar to that of other amphibians, suggesting no special dietary source. Slight differences in diet between toads from native and urban habitats were observed. These findings indicate that diet is not directly linked to 5-MeO-DMT production, supporting the idea that the toads either synthesize the compound themselves or rely on a microbial partner.

Study at a glance

Abstract

Abstract The Sonoran Desert Toad ( Incilius alvarius ) is the only animal known to secrete the psychedelic compound 5-MeO-DMT as a chemical defense, but the source of 5-MeO-DMT in I. alvarius remains unknown. Some amphibians endogenously produce chemical defenses while others acquire them from specialized diets. In this study we analyzed toxin gland secretions and diet profiles from wild I. alvarius and sympatric anurans from native and urban habitats around Tucson, Arizona to explore possible links between diet and 5-MeO-DMT production. All I. alvarius secreted high concentrations of 5-MeO-DMT, whereas other sympatric toads did not. The diet of I. alvarius was similar to that of sympatric anurans, indicating that I. alvarius does not exhibit relative dietary specialization. Slight dietary differences between I. alvarius in native and urbanized habitats were observed. Taken together, these lines of evidence suggest that diet is not directly linked to 5-MeO-DMT production, and support the alternative hypotheses that Sonoran Desert toads synthesize 5-MeO-DMT endogenously or via a microbial symbiont.