Apalachicola Dusky Salamander
© 2017 Dr. Joachim Nerz (1 of 16)
Country distribution from AmphibiaWeb's database: United States
Desmognathus apalachicolae Means and Karlin, 1994
D. Bruce Means1
1. Historical versus Current Distribution. Apalachicola dusky salamanders (Desmognathus apalachicolae) have a relatively small geographic distribution in the Coastal Plain of the southeastern United States The entire range of the species is confined principally to tributaries of the Apalachicola and Chattahoochee rivers below the Fall Line at Columbus, Georgia, but populations are also known from the Chipola River basin in Florida, the Ochlockonee River basin in Georgia and Florida, and from the upper Choctawhatchee River drainage in Alabama (Means and Karlin, 1989; Means, 1993). So far as known, the species' current distribution is identical with its historical range.
2. Historical Versus Current Abundance. Currently abundant in two types of deep, moist ravines. One type is the classic gully eroded ravine in sandy clay "red hills" soils, which are common all along the Chattachoochee River from Columbus to Fort Gaines in Georgia and on the eastern side of the Apalachicola River from the town of Chattahoochee to Big Sweetwater Creek in Florida (Means and Karlin, 1989). The second type of ravine, called "steephead," is found in a wide band of deep Pleistocene sands in parts of the Chipola, Apalachicola, and Ochlockonee rivers (Means, 1991). Steepheads are unique in having permanent, copious, cold-water (20–21 ˚C) flow from numerous hillside seepages (Means, 1975a, 2000). Historical abundance is probably not much different from that of today because principal habitats are in high relief terrain and many are protected by state parks and The Nature Conservancy.
3. Life History Features.
A. Breeding. Reproduction is semi-aquatic. Adults lay eggs on land near water and brood them. Eggs hatch and larvae are aquatic.
i. Breeding migrations. Probably not present in this territorial species.
ii. Breeding habitat. Same as adult habitat.
i. Egg deposition sites. Beneath stones, small logs, and other cover, or in or along seeps. Eggs have been found in the field from the third week in May to the second week in November. Females presumably brood (Means and Karlin, 1989).
ii. Clutch size. Unknown.
C. Larvae/Metamorphosis. No specific studies of the larval development of Apalachicola dusky salamanders have been conducted.
i. Length of larval stage. From 9–10 mo. Larvae have been found from the second week in July to the second week in March (Means and Karlin, 1989).
ii. Larval requirements.
a. Food. Unknown, but larvae are undoubtedly carnivorous.
b. Cover. Larvae are found in organic litter such as twigs, leaf fragments, and pieces of bark lying on seepage slopes (personal observations).
iii. Larval polymorphisms. Unknown.
iv. Features of metamorphosis. Unknown.
v. Post-metamorphic migrations. Unknown.
vi. Neoteny. Not present. All larvae metamorphose into the fully terrestrial morphology (personal observations).
D. Juvenile Habitat. Similar to adult habitats in mesic ravines except that juveniles are excluded from the choice microhabitats by the aggressive, territorial adult males (personal observations). Juveniles are found under litter and other debris, rocks when they occur, and wet organic matter in mesic ravines in or adjacent to seepages and water (personal observations).
E. Adult Habitat. The principal habitats are first-order streams in highly relieved areas; these may be gully eroded ravine valley heads or a special type of ravine called a steephead (Means, 2000). Adults are found in daytime under suitable debris including logs, rocks when they occur, and leaf packs in mesic ravines. Individuals usually are situated at the ground/water/air interface lying under debris with their bodies immersed in water and their heads protruding into the air column. Debris at the edge of water is best. When suddenly exposed, Apalachicola dusky salamanders usually dive into water to escape. At night, adults are often found out foraging in leaf litter or over the moist soil at the edge of seepages and on the banks of small streams. Individuals are rarely found > 2 m from water.
F. Home Range Size. Not known.
G. Territories. Adult males are almost never found under debris with conspecifics, except for an occasional adult female (personal observations). Behavioral experiments indicate that adult males actively defend their daytime refugia from conspecific males by chasing and biting (unpublished data). This behavior suggests that the species is highly territorial.
H. Aestivation/Avoiding Dessication. Apalachicola dusky salamanders are found least commonly during daytime in mid summer, when air temperatures are hot, and especially during regional droughts. It is presumed that they retire to deeper recesses in the ground during these times, although individuals are active on warm summer nights, especially during and after rains.
I. Seasonal Migrations. Not known, but probably do not occur in this relatively sedentary, territorial species.
J. Torpor (Hibernation). Individuals are sluggish during winter when found in cold microhabitats, but become active immediately upon warming in one’s hand. In microhabitats bathed by seepage water, which is relatively warm in mid winter, individuals are as active as at other times of the year (personal observation).
K. Interspecific Associations/Exclusions. Means (1974), Karlin and Guttman (1986), and Verrell (1990c) demonstrated that Apalachicola dusky salamanders are most closely related to mountain dusky salamanders (D. ochrophaeus) of the southern Appalachian Mountains, but the two species are allopatric in the Chattahoochee River drainage in Georgia. Means (1975a) used parapatric distributional relationships to demonstrate that Apalachicola dusky salamanders probably competitively exclude southern dusky salamanders (D. auriculatus) from their habitats. Wherever the two species are sympatric geographically, Apalachicola dusky salamanders occupy first- and second-order ravines, while southern dusky salamanders live downstream in larger order, swampier reaches of drainages (Means, 1974, 1975a). Two other plethodontid salamanders, red salamanders (Pseudotriton ruber) and southern two-lined salamanders (Eurycea cirrigera), are always allotopic with Apalachicola dusky salamanders (Means, 2000).
L. Age/Size at Reproductive Maturity. The smallest males with two lobes/testis measured 40 mm SVL, but smaller males with one lobe/testis can be sexually mature; the smallest gravid female measured 33.0 mm SVL (Means, 1974, 1993). Age at sexual maturity may be 2 yr for males and 3 yr for females, but a definitive study has not been published.
M. Longevity. Males with three lobes/testis are common in populations, occupying the larger size classes of males. Allowing for 1 yr to metamorphosis and 1 yr for each lobe/testis, some males readily may reach 4 yr of age. There is no physiological/anatomical size-correlated marker for females, but there is no obvious reason why females do not live as long as males. These estimates are probably conservative.
N. Feeding Behavior. No food studies have been published.
O. Predators. Potential predators often found in the habitat of Apalachicola dusky salamanders are copperheads (Agkisrodon contortrix), cottonmouths (A. piscivorus), plainbelly water snakes (Nerodia erythrogaster), southern water snakes (N. fasciata), eastern ribbon snakes (Thamnophis sauritus), snapping turtles (Chelydra serpentina), red salamanders (Pseudotriton ruber), congo eels (Amphiuma means), and green frogs (Rana clamitans), and mammals including shrews (Soricidae), opossums (Didelphis virginiana), raccoons (Procyon lotor), gray fox (Urocyon cinereoargenteus), river otters (Lutra canadensis), and armadillos (Dasypus novemcinctus).
P. Anti-Predator Mechanisms. Apalachicola dusky salamanders use cryptic coloration to go unnoticed by their predators. There is a high degree of intraspecific variation and sexual dimorphism in color pattern (Means, 1974). Adult males become uniformly dark brown in color, but females retain the juvenile pattern of bright dorsal blotches. Color pattern varies with ontogeny, and individuals also exhibit metachrosis to effect background color matching (Means, 1974). As with other members of the genus, Apalachicola dusky salamanders can flip themselves out of a grasp by the action of strong trunk, leg, and tail muscles. The hind legs are twice the thickness of the front legs, allowing individuals to make impressive leaps.
Q. Disease. None recorded.
R. Parasites. None recorded.
4. Conservation. Apalachicola dusky salamander populations seem to be stable throughout their range. This is probably due, in part, to their proclivity for deep, shaded, wet ravines which are unsuitable for human development. Pollution from stormwater runoff, however, could be a threat to water quality and the integrity of streamside microhabitats, but few towns exist in the rugged topography in which their ravines are located. Apalachicola dusky salamanders are potentially protected in Torreya State Park and the Apalachicola Bluffs and Ravines Preserve of The Nature Conservancy in Florida, and in Kolomoki Mounds State Park in Georgia.
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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Citation: AmphibiaWeb. 2017. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 25 Sep 2017.
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