Wood Frog Life History 39 



with vegetation, remained on the bottom of the pond. The freshly de- 

 posited R. sphenocephala egg mass (eggs had completely cleared the 

 cloacal opening) was resting on the posterior surface of the female and ob- 

 scured her hind limbs. Whether or not the male R. sylvatica had 

 extruded sperm over the eggs is not known. The cause of the apparent 

 breakdown in isolating mechanisms in this case is also unknown. Per- 

 haps a breakdown in habitat isolation is a partial explanation. Rana 

 sylvatica and R. sphenocephala were found as breeding associates only 

 in sites where the forest had been removed. In Alabama, R. sylvatica 

 usually breeds in woodland pools, whereas R. sphenocephala breeds in 

 a variety of open aquatic habitats, as well as in woodland pools. Eggs of 

 both species were found in only one woodland pool during this study. 

 Rana sphenocephala has often been seen breeding in woodland pools in 

 other areas of Alabama (R. H. Mount, pers. comm.). Some ecological 

 separation may occur in the part of the state where the two species are 

 sympatric. 



Nelson (1971) mentioned a female R. sylvatica that was clasped by 

 a male R. pipiens. None of the R. sylvatica eggs fertilized by the R. 

 pipiens developed beyond gastrulation. Moore (1955) found that devel- 

 opment did not proceed beyond gastrulation in experimental laboratory 

 reciprocal crosses of R. sylvatica and R. pipiens. Interspecific pairing of 

 male R. sylvatica with other amphibians in the laboratory was reported 

 by Wright (1914). 



OVIPOSITION 



The eggs of R. sylvatica in Alabama are laid as submerged globular 

 masses, usually attached to vegetation. Often, upper portions of the egg 

 mass become emergent. Moore (1949) pointed out that the deposition of 

 submerged egg masses by northern ranid species (those adapted to cool 

 climates) is an adaptation that helps protect the developing embryos 

 from freezing. The rapid drop in water level that often occurs in tem- 

 porary pools in Alabama may cause exposure of the egg masses in cer- 

 tain situations. Desiccation then becomes an added mortality factor. 

 The depth of water in which oviposition occurs is fairly consistent, 

 averaging 15 to 20 cm. 



Wood frogs characteristically have communal oviposition sites. The 

 advantages of this behavior have been discussed (Wells 1977, Howard 

 1980, Seale 1982, Waldman 1982, Waldman and Ryan 1983). Commu- 

 nal oviposition sites (COS) were encountered in this study only in breed- 

 ing ponds with larger populations. The largest such site was in a pond 

 south of Mt. Cheaha where 147 egg masses, arranged in two layers, 

 were found in an area 1.5 x 1 m square. Another COS (65 egg masses) 



