The oak toad (Anaxyrus quercicus) is a species of toad in the family Bufonidae. It is endemic to the coastal regions of southeastern United States. It is regarded as the smallest species of toad in North America, with a length of 19 to 33 mm (0.75 to 1.30 in).
The oak toad can be identified by its light mid-dorsal stripe, variable brown and black spots, and proportionally large parotoid glands. One of the most remarkable features of this species is its small adult size relative to other toads.
The male can be distinguished from the female by its clear white belly and a slightly distended, loose flap of skin beneath the mouth, which expands into the vocal sac. The female has a dark-spotted belly and lacks a vocal sac.
Habitat and distribution
The oak toad's natural habitat includes sandy pine flatwoods and oak scrub, open pine and pine-oak woods, pine or oak savanna with sandy soils, and maritime forests. They appear to favor open-canopied pine flatwoods with grassy ground cover.
The toad's range extends across the coastal plains of the southeastern United States from eastern Louisiana to southeast Virginia and south throughout Florida.
It is mostly diurnal and spends much of its time burrowed into the loose soil of its habitat. It may remain in its burrow during the winter, often in hibernation.
Breeding takes place in shallow pools that accumulate during heavy rains. The male expands his distinctive elongated vocal sac to produce a chirping call. The breeding season extends from April to October, peaking early on. Heavy, warm spring rains stimulate mating behavior.
An average of 300–500 eggs are laid in short strands of 3 to 8 eggs each, with each egg about a millimeter wide. The strands are attached to vegetation, usually submerged blades of grass 4 to 12 cm (1.6 to 4.7 in) beneath the surface. Energy investment in producing this quantity of eggs is significant, and many females are found dead during the mating season due to the rigors of the process. Fertilization takes place externally, with sperm being released in the vicinity of the eggs. As with other species of toad, the male oak toad has a Bidder's organ, which can become a functional ovary in the event of testicular malfunction.
Eggs develop quickly, hatching in a mere 24 to 36 hours. The tadpole reaches a maximum length of 18 to 19.4 mm (0.71 to 0.76 in). It is grayish olive or grape-green dorsally and purplish ventrally. The tail has 6 or 7 black saddle marks. The tadpole completes metamorphosis into a juvenile toadlet in 4 to 6 weeks, and it reaches adulthood and sexual maturity at 1.5 to 2.3 years of age.
As with many bufonids, the oak toad inflates its body in unkenreflex when confronted by a potential predator. It secretes toxins from its parotoid glands and urinates when threatened. The male may chirp as a response to predators. Eggs also appear to have some toxic properties.
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