Effect of microhabitat and body size on toe pad size in arboreal, semi-arboreal, and torrential frogs

Abstract

Frogs can be classified into specialized microhabitats, and for our study, we chose to focus on arboreal (tree dwelling), semi-arboreal (tree and terrestrial dwelling), and torrential (freshwater stream dwelling) species. These species are characterized by their ability to adhere to substrates in their environments, and the adaptations that support these adhesive abilities are enlarged finger and toe pads on the distal tips of each digit and specialized ventral epithelia. A distinction between arboreal and torrential species is that arboreal and semi-arboreal species rely on finger/toe pads alone to adhere, whereas torrential species utilize pads and ventral surfaces. Previous studies have focused on the relationship between morphology and adhesive efficiency, but we sought to analyze the influence of microhabitat and body size on finger/toe pad size. We hypothesized that arboreal species would have the greatest toe pad size in relation to a given body size, followed by torrential and then semi-arboreal with the smallest toe pad area. We measured the body size and toe pad area of 230 specimens, and our results supported our hypothesis. We found that microhabitat and body size have a significant effect on toe pad size.