Mudpuppy (Necturus maculosus) populations are apparently declining throughout the Great Lakes region, yet little is known about their natural history. Using minnow traps, I captured 120 individual mudpuppies in Wolf Lake, Chicago, Illinois, and recaptured 34 of those individuals. Trapping periods of ≥ 3 consecutive nights occurred at intervals during January to May 2015, and October 2015 to March 2016. I also caught 25 mudpuppies using hand nets, including 1 recapture, during ice-free periods. Overall trapping success differed among trapping periods (p = 0.01). Relatively high trapping success during trapping periods from early November through early April suggests that there is a fairly large window in which mudpuppies may be successfully captured. The number of captures was negatively correlated with water temperature and was marginally significant (r = - 0.23, p = 0.09). However, daily capture success declined precipitously above 14.1° C, as indicated by a nonparametric two-dimensional Kolomogorov-Smirnov (2DKS) test (p < 0.001). Analyses of size classes indicated potential gear biases, with mudpuppies in traps (mean 26.9 ± 0.5 cm) larger than those caught using hand nets (mean 14.7 ± 0.8 cm, p < 0.0001). These results suggest multiple capture methods may be necessary to accurately assess demographic profiles and levels of recruitment. Stomach contents obtained through gastric lavage, a non-lethal stomach flushing method, included mollusks, leeches, insects, isopods, amphipods, crayfish, fish, a frog, and a juvenile mudpuppy. Invasive species were present in guts, including rusty crayfish (Orconectes rusticus), round gobies (Neogobius melanostomus), and zebra/quagga mussels (Dreissena spp.), suggesting that mudpuppies may forage on invasives in changing aquatic communities. Small juvenile mudpuppies (< 20 cm) consumed fewer fish and no crayfish, but more leeches and amphipods, than adult size classes (p < 0.0167). Nonmetric multidimensional scaling ordinations showed overall different communities of prey among size classes. ANOSIM results confirmed observed differences in composition among size classes (Global R = 0.253 for abundance, 0.258 for volume, and 0.267 for % volume of gut contents, p = 0.001 for all). These results suggest that mudpuppies in lake ecosystems occupy a broad niche that changes over their development.