Southern Dusky Salamander
© 2010 Todd Pierson (1 of 7)
Desmognathus auriculatus (Holbrook, 1838b)
D. Bruce Means1
1. Historical versus Current Distribution. The geographic distribution of southern dusky salamanders (Desmognathus auriculatus) has been mapped according to museum records and the literature (Means, 1999a). This distribution includes the Coastal Plain of the southeastern United States from extreme southeastern Virginia to mid peninsular Florida, then west through the Florida Panhandle to the Escambia River and barely entering southern Alabama, except at Florala and Mobile Bay. There appears to be a hiatus in the range between the Escambia and Perdido rivers, but the species ranges westward from Mobile Bay into southern Mississippi, Louisiana, and eastern Texas to the Trinity River basin. Many areas should be further investigated, such as northeastern Florida east of the St. Johns River; Escambia and Santa Rosa counties, Florida; southern Alabama; southern Louisiana; and Texas. Because there has been an alarming decline in the number of historical localities throughout the range of the species (Dodd, 1998; Means, 2003d), it may not be possible now to find southern dusky salamanders where they once might have ranged.
2. Historical Versus Current Abundance. Chaney (1949) found southern dusky salamanders abundant in the Florida Parishes of Louisiana, but Dundee and Rossman (1989) and Jeff Boundy (in Means, 2003d) report that they have disappeared or severely declined in known sites there. In Florida, southern dusky salamanders were the most abundant salamander in their habitat, but Dodd (1998) and Means (2003d) have reported wholesale extinctions in > 50 sites that appear to be relatively undisturbed. Likewise, the species has declined dramatically in Georgia, South Carolina, and North Carolina and may have been extirpated entirely from Virginia (Means, 2003d).
3. Life History Features.
A. Breeding. Reproduction is semi-aquatic. Eggs are laid and incubated on land. Hatchlings move into water and larvae are aquatic.
i. Breeding migrations. Probably do not occur. In > 30 yr of road cruising on rainy nights at all seasons, only one specimen was ever found crossing a highway at a creek swamp inhabited by the species (personal observation).
ii. Breeding habitat. Same as adult habitat.
i. Egg deposition sites. Females lay eggs in grape-like clusters in cavities or small depressions. Nests also have been found in Sphagnum moss, in cypress logs, beneath logs and bark, and in stumps within 1–2 m from water (see Petranka, 1998).
Eggs with developing embryos were found in the field from 4 September–12 October in Alabama (Folkerts, 1968); from early September to late October in North Carolina (Robertson and Tyson, 1950; Eaton, 1953), and on 28 October in Florida (Goin, 1951). Chaney (1949) reported egg clutches in many stages of development on 26 September in Louisiana, indicating to him that the eggs were laid in late August or early September. The mid June record from near Augusta, Georgia, probably is for northern dusky salamanders (D. fuscus; Neill and Rose, 1949). Neill (1951c) reported a female guarding her eggs in late October in north-central Florida, and eggs were estimated to have been deposited in Devil’s Millhopper in north-central Florida from August–December (Dodd, 1998). Tiny hatchlings (9.2–10.1 mm SVL) were found on 7 October in Devil’s Millhopper and late October in North Carolina (Eaton, 1953).
ii. Clutch size. From 9–26 eggs (Robertson and Tyson, 1950; Goin, 1951; Wood and Clarke, 1955).
C. Larvae/Metamorphosis. Older larvae have been found in all months except March, July, and September at Devil’s Millhopper (Dodd, 1998), and close by at other localities in October, December, and January (Neill, 1951c). Metamorphosis was reported in January in Louisiana (Chaney, 1949) and January and February in North Carolina (Eaton, 1953).
D. Juvenile Habitat. Same as for adults.
E. Adult Habitat. Southern dusky salamanders have been collected in shallow water under logs along the edge of a creek in Texas (Dial, 1965); in swampy mucklands or ravines, especially around seepages, beneath logs and debris, and in shallow water or adjacent to the water in Louisiana (Dundee and Rossman, 1989); in muddy, bottomland swamps and sloughs in Mississippi (Valentine, 1963a); from under debris at the edge of mucky floodplain sloughs, at mucky edges of swampy lakes, and in other sites of muck or wet peat associated with black waters in Florida; when in steephead ravines, they were found only where organic debris had accumulated along seepages (Means, 1974, 2000). In Alabama, they have been found at the edges of cypress ponds and sloughs, swampy places, and along the edges of springs and spring-runs under leaf mold, logs, or mats of marginal aquatic vegetation (Folkerts, 1968; Means, 1986d). In Georgia, the species was common in mucky, swampy black-water streams of the Lower Coastal Plain (Means, 1974). Martof et al. (1980) reported southern dusky salamanders to be abundant under leaf litter and rotten logs in swamps and bottomland forests in the Carolinas and Virginia; Eaton (1953) found a female with unhatched eggs and hatchlings under a log in wet mud in a cypress swamp in North Carolina; and Wood and Clarke (1955) found a nest and attending female in a small crevice beneath a cypress limb embedded in the mud in a dense cypress forest in Virginia.
F. Home Range Size. Unknown.
G. Territories. Because some congeners are highly territorial and southern dusky salamanders do not migrate, it is possible that adult males, at least, defend territories or choice hiding places, but no studies have been conducted.
H. Aestivation/Avoiding Dessication. During droughts, which may occur at any time of the year, individuals may seek refuge by burrowing deeply into peat (personal observation). Whether any specific physiological changes take place during these times is unknown.
I. Seasonal Migrations. Unknown, but in swampy flatwoods and river floodplains during drought, individuals may burrow deep into peat or follow the edge of receding or rising water (personal observation).
J. Torpor (Hibernation). Neill (1948b) found this species to be active in air temperatures of -2–0 ˚C (28–32 ˚F) in Richmond County, Georgia. In northern Florida steepheads, in which the preferred microhabitats are kept constantly at the temperature of the seeping groundwater (19–21 ˚C; 67–70 ˚F), specimens normally were active when found throughout the winter; in swampy habitats subject to extremes of temperature, southern dusky salamanders were not so commonly found as in spring and fall and were cold and sluggish when handled (personal observations).
K. Interspecific Associations/Exclusions. Means (1975a) demonstrated through geographic and habitat distributional analysis that the southern dusky salamander is probably competitively excluded from first- and second-order ravine habitats by Apalachicola dusky salamanders (D. apalachicolae) and spotted dusky salamanders (D. conanti) in western Florida. Southern dusky salamanders are almost always associated with mud salamanders (Pseudotriton montanus), dwarf salamanders (Eurycea quadridigitata), three-lined salamanders (E. guttolineata), many-lined salamanders (Stereochilus marginatus), and one-toed amphiumas (Amphiuma pholeter) where they are sympatric with these species (Means, 1974, 2000).
L. Age/Size at Reproductive Maturity. In Louisiana, Chaney (1949) reported that males attain sexual maturity in their second or third year after hatching; the majority of females reach sexual maturity in their third year of growth, but some may do so in their second year. In Florida, one population of males reached sexual maturity by 44 mm SVL, and females were gravid by 39 mm SVL (Means, 1974).
M. Longevity. Wild-caught southern dusky salamanders have been maintained in captivity nearly 7 yr (Snider and Bowler, 1992).
N. Feeding Behavior. Carr (1940a) reported aquatic beetle larvae, lumbricid worms, beetles, tabanid larvae, lycosid spiders, and tipulid larvae. Folkerts (1968) found larval and adult insects, arachnids, and annelids in the stomachs of eight specimens.
O. Predators. Only the banded water snake (Nerodia fasciata) and the red-fin pickerel (Esox americanus) have been reported as predators, but Means (2003d) implicated feral pigs (Sus scrofa). Oophagy and cannibalism were reported by Chaney (1949), Rose (1966c), and Wood and Clarke (1955).
P. Anti-Predator Mechanisms. Individuals thrash about and dive into black, saturated organic soils when exposed, disappearing quickly down crayfish burrows or among masses of rootlets and wet peat (personal observations).
Q. Diseases. None known, except that the widespread and pervasive disappearance of southern dusky salamanders throughout their range since the mid 1970s may have been caused by some unknown pathogen (Means, 2003d).
R. Parasites. Chigger mites were found on southern dusky salamanders in Texas (Loomis, 1956).
4. Conservation. No detailed population surveys or studies of the ecology of southern dusky salamanders have been undertaken since the work of Cook and Brown (1974) and Means (1974, 1975a), until Dodd (1998) and Means (2003d) discovered that the species had experienced a widespread decline throughout its range beginning about the mid 1970s. Considering how widespread and severe this decline has been (Means, 2003d), it is imperative that studies be undertaken to determine the cause of the decline. Also, surveys are urgently needed to ascertain the population status in every state in the geographic distribution of the southern dusky salamander. Because the disappearance of many local populations has taken place in relatively undisturbed, and in some cases pristine, native habitat (Dodd, 1998; Means, 2003d), management recommendations must await determination of the cause(s) of the decline.
1D. Bruce Means
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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