Does voluntary wheel running exist in Neotropical wild mammals?

Running wheels are frequently used to improve the welfare of captive animals, increase environmental enrichment, and, by doing so, reduce stereotypic behaviors. With the exception of a single investigation, all previous scientific literature investigating wheel running behavior has been based on animals in captive environments. This specific study reported that free-ranging animals in the Netherlands voluntary run in wheels placed in nature. Our study explores that same line of investigation, examining whether wild animals will voluntarily use running wheels in a natural area in Paraguay in comparison to the urban and semi-urban settings in the Netherlands. Of the 1857 small mammal visits we recorded, only two occasions showed evidence of what could be considered as wheel running behavior; over 100-fold fewer than previously reported. The potential reasons for the observed difference in wheel running activity, such as different species pool or seasonality, are discussed. The difference, however, is expected to be due to the much lower probability of Neotropical mammals in a remote natural site encountering man-made objects and experiencing urbanization-related behavioral patterns.