Activity patterns of many nocturnal mammals are synchronized to daily cycles of light and dark. Light intensity is an important cue for nocturnal mammals because of the interplay between illumination and risk from visual predators. Studies suggest that nocturnal rodents are at greater risk from visually oriented predators before full darkness than after full darkness. We examined onset of surface activity of Ord's kangaroo rat (Dipodomys ordii) over 3 seasons in central Nebraska. To determine surface activity, we used a nonobtrusive procedure—buried timers near burrows. Although initiation of aboveground activity was significantly correlated with sunset from season to season, mean onset of surface activity differed among seasons: 1 min before the start of full darkness in summer, 4 min before full darkness in autumn, and 15 min after full darkness in winter. Despite apparent costs of emerging before darkness, 61% of kangaroo rats in summer and 63% in autumn emerged before full darkness. In winter, however, only 19% of kangaroo rats began surface activity before full darkness. We suggest that emergence behaviors of nocturnal rodents from daytime shelters are plastic and probably linked to seasonal trade-offs between costs of predation and benefits of reproduction and food abundance.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.