The complete study of semiaquatic ectothermic animals is often limited by the researchers' ability to detect them in their nonbreeding habitat. This is particularly challenging for semiaquatic amphibians whose detectability is greatest during the breeding season as they engage in visual and or auditory reproductive behaviors within specific aquatic microhabitats. Our collective ability to obtain information on the nonbreeding terrestrial habitat use and occupancy of postmetamorphic hylid treefrogs is markedly difficult because they are typically highly cryptic and vertically mobile, and it is often unfeasible to outfit smaller individuals with radiotelemetry devices. Because amphibians represent one of the most at-risk group of vertebrates, there is a great urgency to better understand both the breeding and nonbreeding natural history parameters of postmetamorphic individuals to inform species-specific and ecosystem-level management and conservation strategies. Therefore, in this study, we attempted the nearly year-round detection and capture of postmetamorphic treefrogs and their distinct age–sex groups in a previously unstudied remnant swamp wetland complex in southern Illinois, USA. We used 70 artificial refugia made of polyvinyl chloride (PVC) pipes mounted to trees within the upland aquatic-terrestrial ecotone of a single pond site to examine the factors influencing their nonbreeding occupancy and detection. Our artificial refugia allowed us to detect and capture the various age–sex groups of three Hyla species over an 8-mo period from April to November 2022. Using single-season Bayesian occupancy models, we found that the overall probability of occupancy among Cope's Gray Treefrogs (Hyla chrysoscelis) was primarily influenced by the relative ratio of an occupied refugia being consecutively occupied (i.e., the probability of a refugium being occupied was influenced by its previous occupancy state) and the probability of their detection was most influenced by the survey temperature. Importantly, we found nontrivial variation in the influence of both site-and-survey–specific occupancy and detection covariates among the different H. chrysoscelis age–sex groups, indicating at least partial differentiation in nonbreeding refuge preferences and requirements. Overall, our findings validate the use of tree-mounted artificial PVC refugia to detect and gather otherwise unattainable, nearly year-round, population-level information on the various age–sex groups of terrestrial, postmetamorphic, nonbreeding treefrogs in a remnant southern Illinois swamp wetland complex.