Completely aquatic and gilled throughout life. Among mudpuppies and waterdogs (genus Necturus), this species is medium-sized. All mudpuppies and waterdogs have bushy external gills, two gill slits, a laterally compressed tail, and four toes on front and hind feet. Necturus beyeri is brownish dorsally and lighter brown ventrally. Numerous dark brown to blacks spots can be seen on the dorsum, sides, and venter. Adults are 16-22 cm total length. Sexually mature males can be distinguished by the swollen cloaca and pair of enlarged cloacal papillae that project posteriorly. Hatchlings are mottled with a few light spots dorsally. Hatchling size is 13-16 mm snout to vent length (Shoop 1965). Juveniles are spotted and do not have stripes as seen in N. maculosus. Description primarily from Petranka (1998).
Sympatric with N. alabamensis in some localities, but these species differ in body shape (near cylindrical in N. beyeri vs. flattened in N. alabamensis), ventral coloration (presence vs. absence of spots), and microhabitat use (living in streambank burrows, and frequently active in the water column vs. shelter under rocks or debris, active on the bottom) (Neill. 1963; Bart et al. 1997).
The systematics of Necturus in general, and N. beyeri in particular have been problematic. Some authors have doubted that the Alabama waterdog (N. alabamensis) is a separate species from the Gulf Coast waterdog. Although they co-occur in some areas, these forms are apparently distinct in microhabitat preference, morphology, and with respect to genes (Neill 1963; Guttman et al. 1990; Bart et al. 1997). See Petranka (1998) for discussion.Necturus beyeri, N. alabamensis, and N. maculosus are relatively closely related (Guttman et al. 1990).
- Bart, H. L., Jr., Bailey, M. A., Ashton, R. E., Jr., and Moler, P. E. (1997). ''Taxonomic and nomenclatural status of the Upper Black Warrior River Waterdog.'' Journal of Herpetology, 31, 192-201.
- Guttman, S. I., Weigt, L. A., Moler, P. E., Ashton, R. E., Jr., Mansell, B. W. and Peavy, J. (1990). ''An electrophoretic analysis of Necturus form the southeastern United States.'' Journal of Herpetology, 24(2), 163-175.
- Neill, W. T. (1963). "Notes on the Alabama waterdog, Necturus alabamensis Viosca." Herpetologica, 19, 166-174.
- Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington and London.
- Sever, D. M., and Bart, H. L., Jr. (1996). ''Ultrastructure of the spermathecae of Necturus beyeri (Amphibia: Proteidae) in relation to its breeding season.'' Copeia, 1996(4), 927-937.
- Shoop, C. R. (1965). "Aspects of reproduction in Louisiana Necturus populations." American Midland Naturalist, 74, 357-367.