Structure and Morphometrics of two Cane Toad (Rhinella marina) Populations in Coastal Jalisco, Mexico

An important goal in ecology is to understand what allows species to be successful invaders. The cane toad (Rhinella marina) is native to Mexico and South America but has successfully invaded 1/3 of Australia since being introduced in the early 1900s. To explore factors associated with why R. marina are such successful invaders, we investigated Cane Toads in a seasonally dry tropical forest (SDTF) in coastal Jalisco, Mexico, where they are native. We compared features of two cane toad populations: one from a relatively undisturbed forest (Chamela) and another, approximately 12 km away, in a village (Francisco Villa). Previous data suggested that toads from the forest were larger than those in the village and therefore might be more nomadic. Therefore, I predicted that forest toads would show differences from those of the village in size and population structure. I measured body and limb lengths of all captured toads and used the mark-recapture methods to estimate population sizes. Population sizes were similar in Chamela and Villa, toads in Chamela were significantly larger and heavier (with longer limbs). Both populations had sex ratios highly skewed towards females (which were also larger than males), traits that contribute to their potential to be invasive. Plausible reasons for size differences could be predators, levels of activity, and food availability. Continued investigation of these cane toads year after year will help better understand the dynamics of their populations and why Rhinella marina can become so invasive in habitats where they are not native