Dwarf Black-bellied Salamander, Dwarf Blackbelly Salamander
© 2016 Dr. Joachim Nerz (1 of 19)
Country distribution from AmphibiaWeb's database: United States
Desmognathus folkertsi Camp, Tilley, Austin and Marshall, 2002
Carlos D. Camp1
1. Historical versus Current Distribution. Dwarf black-bellied salamanders (Desmognathus folkertsi) are cryptic and syntopic with black-bellied salamanders (Desmognathus quadramaculatus). Animals are currently known from tributaries of two streams (Wolf Creek and Helton Creek) that independently flow into the Nottely River of Union County in the Blue Ridge Physiographic Province of Georgia (Camp et al., 2002). Black-bellied salamanders are commonly collected and sold as fish bait in Georgia (Jensen and Waters, 1999) and have been introduced into new areas as a result (Martof, 1953b). It is possible that collectors in the range of dwarf black-bellied salamanders have also collected and sold them, possibly having introduced them into other areas as well.
2. Historical versus Current Abundance. Dwarf black-bellied salamanders are abundant in the two streams where they occur. There seemed to be no discernible differences in abundance from collections made during 1998 versus those made a decade earlier (C.D.C., unpublished data).
3. Life History Features.
i. Breeding migrations. Unknown.
ii. Breeding habitat. Adult males and females are found throughout the year in and along high-gradient streams (C.D.C., unpublished data). They presumably use these habitats for mating as well as other activities (e.g., foraging).
i. Egg deposition sites. Unknown. Presumably similar to closely related black-bellied salamanders (D. quadramaculatus), syntopic congeners that share similar habitats. Females of the latter species have been found attending clutches beneath stones in the middle of creek channels at one of the streams where dwarf black-bellied salamanders occur (C.D.C., personal observations).
ii. Clutch size. Oviposited clutches have not been found. Clutches estimated from developing follicles of mature females range from 2–62 eggs/clutch, averaging 39 eggs/clutch. Clutch size is positively related to female body size (C.D.C., unpublished data), similar to other desmognathines (Tilley, 1968).
i. Length of larval stage. Larvae of dwarf black-bellied salamanders and black-bellied salamanders currently cannot be distinguished. Collections of larvae of presumably both species indicated the presence of four distinct size classes (Austin and Camp, 1992). The largest size class corresponds with sizes of newly metamorphosed black-bellied salamanders (Camp et al., 2000). Newly metamorphosed dwarf black-bellied salamanders appear to correspond to the second size class. The probable larval period, therefore, is 2 yr (Camp et al., 2002).
ii. Larval requirements.
a. Food. Unknown. Presumably aquatic invertebrates.
b. Cover. Larvae of (presumably) both dwarf black-bellied and black-bellied salamanders occur in the interstices of riffle areas in streams (Austin and Camp, 1992).
iii. Larval polymorphisms. No distinct larval polymorphisms are known.
iv. Features of metamorphosis. Newly metamorphosed individuals average 36 mm SVL (range = 34–37; Camp et al., 2000, 2002).
v. Post-metamorphic migrations. Unknown.
vi. Neoteny. Complete neoteny is unknown. As with black-bellied salamanders, adults exhibit the neotenic retention of lateral line pores (sensu Hilton, 1947; Camp et al., 2002).
D. Juvenile Habitat. Juveniles have been collected under cover objects within streams during the day and actively wandering within streams at night. Several juvenile specimens were collected while raking through wet leaves at the margins of streams (S.G.T., personal observation).
E. Adult Habitat. Adults have been collected in high-gradient, turbulent first- and second-order streams. They are most abundant in shallow areas of streams where they take cover under rocks. At night they occasionally are seen wandering away from cover; however, they usually remain with only their heads and/or anterior parts of their bodies protruding from cover sites. No differences in habitat have been noted between the sexes (C.D.C., personal observations).
F. Home Range Size. Unknown.
G. Territories. Unknown in nature, although it is probable that individuals defend cover sites in the way that other semi-aquatic desmognathines do (e.g., seal salamanders [D. monticola], Keen and Sharp, 1984; black-bellied salamanders, Camp and Lee, 1996). A study of bite-scar patterns (Camp, 1996) in presumed black-bellied salamanders included dwarf black-bellied salamanders as well. Several dwarf black-bellied salamanders had distinct wounds inflicted by bites of other salamanders. It is unknown whether these bites were inflicted by conspecific and/or heterospecific salamanders.
H. Aestivation/Avoiding Dessication. Unlikely. Individuals are active throughout the summer (C.D.C., personal observations).
I. Seasonal Migrations. Unknown, but unlikely.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. Dwarf black-bellied salamanders are syntopic with four congeneric species: seepage salamanders (D. aeneus), Ocoee salamanders (D. ocoee), seal salamanders, and black-bellied salamanders. The extent of potential competitive interactions is unknown. Dwarf black-bellied salamanders are similar in size to seal salamanders but are more aquatic. Dwarf black-bellied salamanders occupy habitats similar to larger black-bellied salamanders. Gut analyses of syntopic adult black-bellied salamanders provided no evidence of predation on dwarf black-bellied salamanders (Camp, 1997b).
Dwarf black-bellied salamanders exhibited avoidance of substrates with chemical cues of individual black-bellied salamanders from both sympatric and allopatric populations in laboratory-based experiments. Black-bellied salamanders were neutral to the cues of dwarf black-bellied salamanders (S. Myers, M. Rubo, and J.L. Marshall, unpublished data).
Martof (1962b) noted the enigmatic absence of shovel-nosed salamanders (D. marmoratus) in areas of apparently favorable habitat in the Nottely River. The presence of a similar-sized desmognathine of the quadramaculatus-marmoratus clade (sensu Titus and Larson, 1996) in streams of the Nottely River system may help explain this absence. Whether this potential parapatry is the result of ecological exclusion or evolutionary divergence, however, has yet to be investigated. Shovel-nosed salamanders are entirely aquatic, and dwarf black-bellied salamanders are semi-aquatic. Therefore, competitive exclusion, while possible, seems unlikely.
L. Age/Size at Reproductive Maturity. Adult males average 72 mm SVL (range = 58–81 mm), and adult females average 66 mm SVL (range = 57–75 mm; Camp et al., 2002).
M. Longevity. Unknown. Similar-sized desmognathines are known to live at least 11 yr (Castanet et al., 1996).
N. Feeding Behavior. The guts of 12 adult individuals contained adult water bugs (Hemiptera) and crane-fly larvae (Tipulidae; C.D.C., unpublished data). Individuals with heads protruding from refugia readily seize earthworms when offered as bait on a hook (sensu Camp and Lovell, 1989). This behavior and the observed tendency of most adult individuals to remain in refugia at night with only their heads (or anterior parts of bodies) exposed suggest an ambush foraging strategy similar to that of adult seal and black-bellied salamanders (Brandon and Huheey, 1971; Kleeberger, 1985; Camp and Lee, 1996).
O. Predators. Unknown. The streams where dwarf black-bellied salamanders occur are undoubtedly inhabited by predatory fish (e.g., sculpins, trout). Although no aquatic snakes have been observed at these sites, we presume that northern water snakes (Nerodia sipedon) occur, at least on lower stretches of the streams. Spring salamanders (Gyrinophilus porphyriticus) are natural predators of small salamanders (Bruce, 1979) and are relatively common in seepages that feed into streams containing dwarf black-bellied salamanders (Wharton, 1978; C.D.C., personal observations). Spring salamanders almost certainly prey on juvenile/larval dwarf black-bellied salamanders. Larvae are probably eaten by aquatic invertebrates, including insects.
P. Anti-Predator Mechanisms. Presumably the same as other desmognathines, i.e., flight, writhing, and biting. A number of specimens have missing or regrown tails (C.D.C., personal observations), a possible indication of failed attempts at predation.
Q. Diseases. Unknown.
R. Parasites. Leeches have been observed on specimens (C.D.C., personal observations). Goater (2000) noted the prevalence of leeches (Oligobdella biannulata) on black-bellied salamanders and their probable use as vectors for the transmission of blood trypanosomes.
4. Conservation. Dwarf black-bellied salamanders are not legally protected at present. Their known range is small, consisting of streams of the Nottely River system of Union County, Georgia. Whether dwarf black-bellied salamander populations extend beyond this range is unknown; they may occur in other stream systems such as the Ocoee and upper Hiwassee rivers of Georgia, North Carolina, and Tennessee. However, if they are restricted to the vicinity of the Nottely River system, dwarf black-bellied salamanders may be in need of legal protection.
Georgia does not require permits for the collection of desmognathine salamanders for fish bait, and local bait collectors are known to collect Desmognathus from streams inhabited by dwarf black-bellied salamanders (C.D.C., personal observations). Dwarf black-bellied salamanders, therefore, are undoubtedly exploited for this purpose. They remain abundant, however, at sites where they have been previously collected (C.D.C., unpublished data).
1Carlos D. Camp
2Stephen G. Tilley
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Dec 2019.
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