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Anaxyrus quercicusOak Toad

By Ryan Buckley

Geographic Range

Oak toads are found in the coastal plains of the southeastern United States. They are found from the southern tip of Florida to the southern portion of Virginia and to parts of eastern Louisiana. ("The Pelican Post", 2004; Anonymous, 2000; Behler, 1979)

Habitat

Oak toads are generally found in moist, grassy areas near pine or oak savannahs with sandy soil. They are also found in vernal pools and freshwater wetlands. They breed in shallow pools, ditches, and ponds. (Behler, 1979; Knapp, 06/28/03; Wright, 1932)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools

Physical Description

Anaxyrus quercicus is the smallest toad species in North America, ranging from 1.9 to 3.3 cm. It is so small that adults found in the wild were commonly classified as “half-grown” or “juvenile” southern toads (Bufo lentiginosus). They have a short head with a pointed nose and the short, flat body is black or brown in color (color can change with temperature) with a long dorsal stripe that may be white, cream, yellow, or orange. There are 4 to 5 pairs of dark blotches found on the back. The back is finely tuberculate, with the fine bumps (red, orange or reddish-brown in color) giving it a rough texture. The underside is grayish white and has no blotches, but is covered in tubercles. Oak toads have elongated, teardrop-shaped paratoid glands that extend down either side. These glands house a poisonous fluid used deter predators. Males can be distinguished by their dark, dusky colored throats. (Anonymous, 2004; Dickerson, 1969; Knapp, 06/28/03; Wright, 1932)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    19 to 33 mm
    0.75 to 1.30 in

Development

In the span of two months, tadpoles hatch from their eggs and go through metamorphosis, becoming adult toads. Tadpoles have a grayish olive or grape green color to the body due to close set dots against a black background. The underside has a pale purplish color. the tail has 6-7 black saddles (coloration that wraps around the tail to a degree). Juvenile toads remain near the natal pond for a few days before moving to land, where they will spend the majority of their time. (Anonymous, 2004; Wright, 1932)

Reproduction

Males arrive before females at shallow, semi-permanent or temporary ponds, and roadside drainage ditches. At breeding ponds males establish territories and begin calling females with a high-pitched chirp. Approximately 100-250 eggs are laid at a time in long strings, held together by a gelatinous material, and either float or stick to surfaces. Fertilization takes place externally when the male frog releases his sperm in the vicinity of the eggs. In the case of a testicular malfunction, male oak toads have an ovary that will become functional, allowing them to breed as females. (Anonymous, 2000; Wright, 1932)

Male and female oak toads form a pair when the male grabs onto the female from behind in a position referred to as amplexus. The male stays attached to the female until she releases her eggs into the water. The female emits several eggs and then the male releases sperm into the water. The female will continue to release eggs. The eggs are released in bars containing 4-6 eggs apiece. Each female will lay about 700 eggs in total in a single season. These eggs will hatch within 3 to 3.5 days and develop into adult oak toads within 2 months. (Anonymous, 2000; Wright, 1932)

  • Breeding interval
    Oak toads are seasonal breeders and breeds once per year.
  • Breeding season
    Oak toads breed from April to September or October. The mating season often begins with the arrival of warmer temperatures and thunderstorms. The interval of ovulation is approximately late May-mid August.
  • Average number of offspring
    700
  • Range time to hatching
    72 to 80 hours
  • Average age at sexual or reproductive maturity (female)
    2 months
  • Average age at sexual or reproductive maturity (male)
    2 months

The extent of female energy investment is great during the ovulation and mating periods, as many females are found dead during these periods due to either the rigors of pair formation or energy investment in the laying of eggs. Once the eggs are fertilized and attached to a surface, there is no further parental care. (Wright, 1932)

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning

Lifespan/Longevity

Oak toad lifespans are not well known.

Behavior

Oak toads are active during the day, but occasionally they are found at night taking part in breeding choruses. Outside of the breeding season, oak toads are solitary. They spend most of the day buried in the sand or hiding under leaves or rocks. (Behler, 1979; Dickerson, 1969)

Communication and Perception

Male oak toads make a high-pitched, bird-like chirping calls to attract females. Oak toads perceive their environment through visual, auditory, tactile, and chemical senses. ("The Pelican Post", 2004; Behler, 1979; Dickerson, 1969; Wright, 1932)

Food Habits

Oak toads are predaceous and feed primarily on terrestrial insects and other small arthropods. (Knapp, 06/28/03; Wright, 1932)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods

Predation

The primary predators of oak toads are snakes, particularly hognosed snakes (Heterodon platirhinos), specialized for eating toads. Other predators of oak toads are garter snakes (Thamnophis sirtalis) and gopher frogs (Lithobates capito). (Behler, 1979; Wright, 1932)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Although smaller than other toads, the Oak Toad still plays a crucial role in insect population control. (Behler, 1979)

Economic Importance for Humans: Positive

Oak toads help control population levels of insects and other small arthropods.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known negative impacts of oak toads on humans.

Conservation Status

Oak toad populations are declining throughout many states. In Virginia it is listed as a species of special concern (one that is not yet threatened but is expected to be in the near future). Also, in North Carolina, it is on the watch list for species that may be facing problems in the near future. A possible cause for decreases in oak toad populations is the clearing of the savannah forest habitats they prefer. (Anonymous, 2000)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Ryan Buckley (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

2004. "The Pelican Post" (On-line). Nature's Calender. Accessed October 28, 2005 at http://www.weeksbay.org/newsletter/Win_2003/Pg6_2.htm.

Anonymous, 2000. "Georgia Wildlife Web" (On-line). Toads. Accessed October 20, 2005 at http://museum.nhm.uga.edu/gawildlife/amphibians/anura/bufonidae/bquercicus.html.

Anonymous, 2004. "Virginia Department of Game & Inland Fisheries" (On-line). Virginia Wildlife Information: Bufo Quercicus. Accessed October 20, 2005 at http://www.dgif.state.va.us/wildlife/species/display.asp?id=020063.

Behler, J. 1979. The Audubon Society Field Guide to North American Reptiles & Amphibians. New York: Chanticleer Press Inc..

Dickerson, M. 1969. The Frog Book: north american toads and frogs, with a study of the habits and life histories of those of the northern states. Canada: General Publishing Company.

Knapp, W. 06/28/03. "The Frogs & Toads of Georgia" (On-line). Oak Toad- Bufo Quercicus. Accessed October 20, 2005 at http://wwknapp.home.mindspring.com/docs/oak.toad.html.

Wright, A. 1932. Life Histories of the Frogs of Okefinokee Swamp, Geeorgia: North American Salientia (Anura) No. 2. United States: Cornell University Press.

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