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Minimum size at maturation in the mud snake, Farancia abacura (Serpentes: Colubridae) from the southeastern United States.

Article Excerpt
Abstract -- Museum specimens of 129 female mud snakes (Farancia abacura) were examined for body size and reproductive condition. Specimens from Texas, Oklahoma, Louisiana, Mississippi, Florida, Tennessee and South Carolina provided data on the minimal size at maturation. A small (42.0 cm snout vent length) reproductive female F. abacura with Class I follicles was observed in this investigation and is reported here with an analysis for the relationship between body size and mean follicle length. The theoretical significance of early reproduction with respect to increased fecundity and fitness is presented and may provide future researches with additional information for investigating the evolutionary ecology of this secretive snake species.

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The age and size at which a species becomes reproductive is one of its most important natural history traits. This trait is often more influential to a species' fitness than any other natural history trait (Sterns 1992). Species that become reproductive earlier in life have a greater probability of survival to reproductive age and the potential for greater fecundity. Although there are costs associated with this life history strategy, for many species the benefits of early reproduction are much greater than the potential costs.

Constraints on the age at maturation include phylogeny and body size. In squamates, researchers have demonstrated a positive correlation between adult body size and age at maturation (e.g., Dunham & Miles 1985). Although there may be exceptions, this relationship is conserved among most reptiles.

There is limited information on the reproductive life history of mud snakes, Farancia abacura (see Fitch 1970; Mitchell 1982). Quantifying the reproductive traits in this species is difficult due to its secretive habits. There are several reports of oviposition and subsequent hatching (Meade 1935; 1937; 1940a; 1940b; Goldstein 1941; Reynolds & Solberg 1942; Meade 1945), but little is known about the minimum body size at which this species becomes reproductive. More recently, Robinette & Trauth (1992) investigated both female (n = 22) and male (n = 22) reproductive cycles from F. abacura collected throughout Arkansas. The smallest female with follicles was approximately 56.0 cm snout-vent length (SVL). This female is only 29.0 to 40.1 cm larger than the reported 15.9 to 27.0 cm hatching size of F. abacura (Conant & Collins 1998).

METHODS AND MATERIALS

A total of 129 female F. abacura museum specimens from throughout their range were examined to determine the minimum body size...

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