Oak toad

Oak toad
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Bufonidae
Genus: Anaxyrus
Species: A. quercicus
Binomial name
Anaxyrus quercicus
(Holbrook, 1840)
Habitat range of A. quercicus
Synonyms

Bufo quercicus Holbrook, 1840

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.[2][3] 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).[3]

Description

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.

Adult male (left), female (right). Note the sharply contrasted ventral surface, the vocal sac on the male's throat, and the female's larger size.

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.[1]

The toad's range extends across the coastal plains of the southeastern United States from eastern Louisiana to southeast Virginia and south throughout Florida.[4]

Behavior

The oak toad eats mainly small insects and other arthropods. The adult has a strong preference for ants.[5]

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.[5]

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.[6][7] Heavy, warm spring rains stimulate mating behavior.[8]

Oak toad tadpole

An average of 300–500 eggs are laid in short strands of 3 to 8 eggs each, with each egg about a millimeter wide.[5] The strands are attached to vegetation, usually submerged blades of grass 4 to 12 cm (1.6 to 4.7 in) beneath the surface.[9][10] 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.[11][12]

Life cycle

Eggs develop quickly, hatching in a mere 24 to 36 hours.[5] 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.[11][12] 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.[5]

The length of the lifespan is unclear.[3] There are records of specimens living for four years in captivity,[9][11] and the reported average lifespan in captivity is 1.9 years.[13]

Predation

The primary predators of the oak toad are snakes, particularly hognosed snakes, which are specialized for eating toads. Other predators include garter snakes and gopher frogs.[11][14]

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.[5]

Size comparison. Adult male (left), female (right).
Smallest toad species in North America.

References

  1. 1 2 Geoffrey Hammerson (2004). "Anaxyrus quercicus". IUCN Red List of Threatened Species. IUCN. 2004: e.T54743A11197905. Retrieved 30 January 2016.
  2. ↑ Frost, Darrel R. (2016). "Anaxyrus quercicus (Holbrook, 1840)". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 30 January 2016.
  3. 1 2 3 University of Michigan Museum of Zoology. Retrieved on 21 October 2008.
  4. ↑ Oak Toad, Bufo quercicus. USGS, Northern Prairie Wildlife Research Center, Checklist of Amphibian Species and Identification Guide. Retrieved 30 March 2013.
  5. 1 2 3 4 5 6 Lannoo, M. Amphibian Declines: The Conservation Status of United States Species. University of California Press. 2000. 432-33.
  6. ↑ Harper, F. 1931. A dweller in the piney woods. Science Monthly 32 176–81.
  7. ↑ Einem, G. E. and L. D. Ober (1956). "The seasonal behavior of certain Floridian Salientia". Herpetologica. 12: 205–212. JSTOR 3889772.
  8. ↑ Wright, A. H. and A. A. Wright. 1949. Handbook of Frogs and Toads of the United States and Canada. Third edition. Comstock Publishing Associates, Ithaca, New York.
  9. 1 2 Ashton, R. E., Jr. and P. S. Ashton. 1988. Handbook of Reptiles and Amphibians of Florida: Part Three: The Amphibians. Windward Publishing, Miami, Florida.
  10. ↑ Hamilton, W. J. (1955). "Notes on the ecology of the oak toad in Florida". Herpetologica. 11: 205–210. JSTOR 3889360.
  11. 1 2 3 4 Wright, A. 1932. Life Histories of the Frogs of Okefinokee Swamp, Georgia: North American Salientia (Anura) No. 2. United States: Cornell University Press.
  12. 1 2 Bufo quercicus. Virginia Department of Game & Inland Fisheries. 2004. Retrieved on 20 October 2005.
  13. ↑ Bowler, J. K., 1975. Longevity of reptiles and amphibians in N. American collections as of 1 November 1975. Society for the Study of Amphibians and Reptiles, Miscellaneous Publications, Herpetological Circular 6 1-32.
  14. ↑ Behler, J. 1979. The Audubon Society Field Guide to North American Reptiles & Amphibians. New York: Chanticleer Press, Inc.

Further reading

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