Courtship in Desmognathine Salamanders: The Southern Dusky Salamander, Desmognathus auriculatus

-The courtship of the southern dusky salamander, Desmognathus auriculatus (Plethodontidae), is described for the first time. Most of a male's effort is expended in orienting to and stimulating (or 'persuading') his partner. Much of the stimulation provided by the male is tactile (nudging and rubbing), although he also exhibits behavior patterns associated with the transfer of courtship pheromones (snapping and pulling). Movements of the male's forelimbs may stimulate the female visually. The consummatory act of courtship is indirect sperm transfer by means of a spermatophore, and this stage of courtship appears identical in all desmognathines yet described. Courtship behavior patterns in the subfamily Desmognathinae are an apparent mosaic of ancestral and derived characters, with some evidence for homoplasy. Formal analyses of behavioral evolution await a robust phylogenetic hypothesis and detailed ethograms for multiple populations of all recognized taxa. The absence of lungs is a character shared by all salamanders in the family Plethodontidae (Duellman and Trueb, 1986). Reliance on cutaneous gas exchange may be a major constraint on the geographic distribution of these animals. The majority of taxa are found in relatively cool and moist habitats, especially in the montane regions of the Pacific Northwest and Appalachian Mountains of North America, and the cloud forests of Central America. An exceptional, but not unique, taxon is the southern dusky salamander, Desmognathus auriculatus (subfamily Desmognathinae), populations of which occur throughout the Gulf and Atlantic Coastal Plains of the southeastern United States. Winters typically are mild and summers warm and humid in these physiographic provinces. Well away from the mountains, D. auriculatus can be found in the organic debris along the shady margins of small streams, hypoxic pools and swamps. Little has been published on the natural history of the southern dusky salamander (but see Robertson and Tyson, 1950, for some observations of this species in eastern North Carolina). Here I report the first laboratory observations of this species' courtship and mating behavior. I then compare these to descriptions for other desmognathine salamanders, in anticipation of a formal, phylogenetic analysis of the evolution of courtship in this subfamily. MATERIALS AND METHODS Sexually mature D. auriculatus were collected in the summer of 1994 from several sites near the Savannah River Site in Aiken and Barnwell Counties, South Carolina (see Gibbons and Semlitsch, 1991). Most were found by raking through the organic debris on the margins of small pools. Desmognathus auriculatus is the only desmognathine that has been recorded in this part of South Carolina, although the presence of D. fuscus is possible (see Gibbons and Semlitsch, 1991). Each of my specimens was identified as D. auriculatus on the basis of body size, the presence of pale lateral spots, and the speckled appearance of the belly. Animals were transported to the laboratory in cooled containers, where they were maintained at approximately 15 C on a natural (Pullman, Washington) photoperiod. Salamanders were housed individually in plastic boxes measuring 9 x 17 x 31 cm, with a damp paper towel as substratum and a crumpled damp paper towel as a refuge. An ad libitum diet of vitamin-mineral dusted waxworms (moth larvae) was provided. I staged a total of seven heterosexual encounters between pairs of single males and females drawn from a pool of four males and two females. No two individuals were paired together more than once. Encounters were staged in a plexiglass observation arena measuring 17 x 17 x 5 cm, floored with a damp paper towel; no refuge was made available. Animals were introduced at approximately 1500 h and left together until 0800 h the following morning. All behavioral interactions were recorded under dim red illumination on a time-lapse videotape recorder (Panasonic AG-6010) using a low-light video camera (Panasonic WV-BD400).