Southern Dwarf Siren, Narrow-stripped Dwarf Siren, Everglades Dwarf SIren
© 2010 Michael Graziano (1 of 9)
Pseudobranchus axanthus Netting and Goin, 1942(b)
Paul E. Moler1
1. Historical versus Current Distribution. Southern dwarf sirens (Pseudobranchus axanthus) are restricted to peninsular Florida; their northern boundary includes Alachua, Clay, Duval, Levy, and Putnam counties. Two subspecies, narrow-striped dwarf sirens (P. a. axanthus) and Everglades dwarf sirens (P. a. belli), are recognized (Moler and Kezer, 1993; Crother et al., 2000). The current distribution of southern dwarf sirens is undoubtedly reduced compared with their historical distribution, as wetlands in peninsular Florida have been reduced through drainage of surface waters associated with residential, agricultural, and silvicultural development.
2. Historical versus Current Abundance. Southern dwarf sirens are often common in suitable habitat. Current numbers are reduced relative to historical abundance due to the loss of wetland habitat.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Southern dwarf sirens do not migrate. They breed and permanently reside in the same aquatic habitats.
ii. Breeding habitat. Southern dwarf sirens live and breed in heavily vegetated marshes and shallow lakes.
i. Egg deposition sites. Eggs are laid singly or in small bunches among aquatic vegetation throughout the spring (Carr, 1940a; Netting and Goin, 1942b). According to Petranka (1998) the oviposition period lasts from early November to March. Newly laid eggs average 3 mm and are surrounded by the vitelline membrane and three jelly envelopes (Noble and Richards, 1932; see also Petranka, 1998).
ii. Clutch size. Unknown.
C. Larvae. Newly hatched larvae are between 10–11.5 mm SVL, colored brown dorsally with lighter stripes on the dorsal midline and lateral portions of the body and head (Goin, 1947c; see also Petranka, 1998). They have limb buds (Noble, 1927b). Ashton and Ashton (1988) indicate Pseudobranchus larvae make take 2 yr to reach sexual maturity.
D. Juvenile Habitat. Same as adult habitat.
E. Adult Habitat. Southern dwarf sirens are most abundant in heavily vegetated marshes and shallow lakes (Carr, 1940a). They may be abundant in floating mats of vegetation or in mucky shoreline deposits.
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Southern dwarf sirens burrow into bottom sediments and form a protective cocoon when wetlands dry. Individuals may remain buried for several months until their wetland refills (Freeman, 1958; Etheridge, 1990a).
I. Seasonal Migrations. None.
J. Torpor (Hibernation). Carr (1940a) reported that southern dwarf sirens "have been found hibernating in deep mud." Nevertheless, although they may become inactive during prolonged periods of cold weather, they may be collected throughout the winter, especially in southern Florida.
K. Interspecific Associations/Exclusions. Southern dwarf sirens occur sympatrically, but only occasionally syntopically, with northern dwarf sirens (P. striatus) in northern peninsular Florida. In areas of sympatry, northern dwarf sirens are typically found in more acidic habitats than are southern dwarf sirens, but they are known to occur syntopically at a few sites (Moler and Kezer, 1993).
L. Age/Size at Reproductive Maturity. Unknown.
M. Longevity. Unknown.
N. Feeding Behavior. Reported foods include amphipods, chironomid larvae, aquatic oligochaetes, and ostracods (Harper, 1935; Carr, 1940a; Duellman and Schwartz, 1958; Freeman, 1967).
O. Predators. Southern banded water snakes (Nerodia fasciata) have been observed preying on flood-displaced southern dwarf sirens (personal observations). Van Hyning (1932) reported predation by the striped crayfish snake (Regina alleni), and Carr (1940a) reported predation by the mud snake (Farancia abacura). Black swamp snakes (Seminatrix pygaea) are also common associates and likely prey on dwarf sirens. Other likely predators include predaceous fish and various species of wading birds, especially where dwarf sirens are concentrated by falling water levels.
P. Anti-Predator Mechanisms. Flight. Southern dwarf sirens are slippery and difficult to hold. Also, when seized, they may produce high-pitched squeaks, but the utility of these sounds as an anti-predator mechanism is unknown.
Q. Diseases. Unknown.
R. Parasites. Unknown.
4. Conservation. Southern dwarf sirens have a restricted distribution, although they are often common in suitable habitat. The current distribution and abundance of southern dwarf sirens is undoubtedly reduced compared with historical levels.
1Paul E. Moler
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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