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Anaxyrus terrestrisSouthern Toad

By Jeff Jenkins

Geographic Range

Southern toads are found in the southeastern United States, in the Atlantic and Gulf Coastal Plain regions. Their range extends as far west as Louisiana, and from southern Florida (including the Florida Keys) north through the Carolinas and into southeastern Virginia. Many populations are disjunct; for example, they are found in Georgia only below the Fall Line, but also in portions of the Blue Ridge and Piedmont regions of South Carolina. (Duellman, 2004; Elliott, et al., 2009; Hammerson, 2013; Jensen, et al., 2008; Jensen, 2013)

Habitat

Southern toads are generally restricted to sandy soil habitats around coastal plains. They are typically found in pinewoods, scrub oak, and mixed forest environments; they may also be found in agricultural fields or even in backyards. These toads bury into soft soil during the day and many also be found hidden under logs or other debris. They require fresh water for laying their eggs and during their initial larval life stages. (Edwards, et al., 2006; Elliott, et al., 2009; Hammerson, 2013; Jensen, et al., 2008; Jensen, 2013; Metts, et al., 2012)

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

Physical Description

Southern toads range in size from approximately 40 to 113 mm long, with an average mass of about 19 g. Size varies somewhat by population; for example, individuals found on Georgia's barrier islands tend to be larger than those found on the mainland. Coloration is usually brown, grey, or reddish, with several dorsal spots and warts. The belly is usually greyish in color, and the chest area is spotted. They have high cranial crests with pronounced knobs, located between and behind the large, protruding eyes. These knobs help distinguish Southern toads from American toads (Anaxyrus americanus) and Fowler's toads (Anaxyrus fowleri). Southern toads have wide mouths, large heads, and short bodies with no tail. Their muscular hind limbs are modified for jumping. These toads are sexually dimorphic: males have darker throats (possibly always, but at least during breeding season) and are smaller than females. Tadpoles are generally solid black with a diagonal gold line located behind the eye. (Duellman, 2004; Elliott, et al., 2009; Forster, 2013; Hammerson, 2013; Jensen, et al., 2008; Tacutu, et al., 2013)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Average mass
    19 g
    0.67 oz
  • Average mass
    19.267 g
    0.68 oz
    AnAge
  • Range length
    40 to 113 mm
    1.57 to 4.45 in
  • Range basal metabolic rate
    1.25 to 1.8 cm3.O2/g/hr
  • Average basal metabolic rate
    1.5 cm3.O2/g/hr

Development

Eggs, generally 1-1.4 mm in diameter, are deposited in long coils. Females lay their eggs in shallow freshwater, usually in vegetation. Eggs hatch within 2-4 days. Southern toads begin life as legless tadpoles that breathe through internal gills, have pronounced tails used for swimming, and exhibit a vegetarian diet (aquatic plant life and algae). The tadpole larval period lasts from 30 to 55 days; metamorphosis begins when individuals reach a length of 6.5-11 mm. Tadpoles are unpalatable, potentially even toxic, to potential predators, and can be seen swimming in open water, often in schools. As tadpoles metamorphose, they absorb their tails, grow limbs, develop lungs and begin to breathe air, finally moving onto land and switching to the carnivorous diet of adults. (Elliott, et al., 2009; Hammerson, 2013; Jensen, 2013; Metts, et al., 2012; Moseley, et al., 2004)

Reproduction

Males may either call to females and wait or move through a breeding area (shallow freshwater areas such as temporary or permanent pools and ponds) in search of potential mates. During breeding season, males issue a shrill, trilling advertising call, 4-8 seconds in length, to attract females. There may be several males in the same body of water and their combined calls can be quite loud. Competition can result in multiple matings with multiple partners for both sexes. During mating, a male climbs on a female's back, grasping her behind the forelimbs in a position called axillary amplexus, and releasing sperm as she releases eggs; fertilization is external. Males will produce a release vocalization after breeding, comprised of a series of chirps or notes, along with a low-pitched, soft hum and abdominal vibration. (Duellman, 2004; Elliott, et al., 2009; Jensen, et al., 2008)

Breeding season for southern toads is February through October, depending on location, though most breeding takes place during the earlier months of this range. These toads migrate from their sandy, upland habitats to breeding sites near freshwater; adults may return to the same body of water in which they hatched or migrate to a different water source. Breeding aggregations can be quite large. During breeding, females eject clutches of 2500-4000 eggs, which are encased in a jelly-like substance and are released into shallow freshwater. Southern toads reach sexual maturity within 2-3 years (42-82 mm snout-vent length for males, 44-92 mm snout-vent length for females). Southern toads are capable of hybridizing with Fowler's toads (Anaxyrus fowleri) and American toads (Anaxyrus americanus). (Duellman, 2004; Elliott, et al., 2009; Jensen, et al., 2008; Jensen, 2013; Metts, et al., 2012)

  • Breeding interval
    Southern toads may mate multiple times during the breeding season.
  • Breeding season
    Breeding season for this species is from February through October, with most breeding completed by mid-summer.
  • Range number of offspring
    2500 to 4000
  • Average number of offspring
    2750
    AnAge
  • Range time to hatching
    2 to 4 days
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Neither male nor female Southern toads exhibit parental investment beyond laying and fertilizing eggs. (Elliott, et al., 2009; Jensen, et al., 2008; Metts, et al., 2012; Moseley, et al., 2004)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

The lifespan of southern toads is not well documented, but there have been individuals held in captivity for as long as 10 years. American toads (Anaxyrus americanus), which are closely related, are said to have a lifespan of up to 10 years in the wild. (Elliott, et al., 2009; Hammerson, 2013; Jensen, 2013; Tacutu, et al., 2013)

  • Range lifespan
    Status: captivity
    10 (high) years
  • Typical lifespan
    Status: wild
    10 (high) hours
  • Average lifespan
    Status: captivity
    10 years
    AnAge

Behavior

Southern toads are mainly nocturnal, usually hiding in self-made burrows during the day and feeding at night. They are commonly seen near residential areas and other buildings, which may attract insects with their outdoor lights. Adults are mainly terrestrial until breeding season, when they migrate to nearby wetlands to breed. Males emit an advertising call to attract females during breeding season; they may also call during heavy rains at any time of the year, though this will not be accompanied by breeding. In hybridized individuals, calls will sound like a mix of the calls of both species. Southern toads have skin that is very water permeable, allowing potentially rapid evaporative water loss across the skin. To combat dehydration, southern toads are capable of storing large quantities of water in their bladders and reabsorbing it as needed. They are much less active during colder months, burrowing to depths of a foot or more. (Duellman, 2004; Elliott, et al., 2009; Forster, 2013; Hammerson, 2013; Jensen, et al., 2008; Jensen, 2013; Metts, et al., 2012)

  • Range territory size
    1.6 (high) km^2

Home Range

Adults inhabit home ranges that may extend up to 1.6 km^2. Adults migrate to wetlands during the breeding season. (Elliott, et al., 2009; Jensen, et al., 2008; Jensen, 2013; Metts, et al., 2012)

Communication and Perception

Southern toads rely mainly on their well-developed eyesight for detecting potential prey. During breeding season, they rely on sound production and processing in order to find mates. (Duellman, 2004; Duellman, 2004; Edwards, et al., 2006; Elliott, et al., 2009; Jensen, et al., 2008; Metts, et al., 2012)

Food Habits

Southern toad tadpoles have a mainly vegetarian diet, consisting of algae and other plant material; they may feed on material suspended in the water or scrape it from the substrate. They have also been observed consuming eggs from dead gravid adult females. Adult southern toads are carnivorous and feed mainly on invertebrates including spiders, beetles, ants, and other insects. Prey is captured using a quick flip of the tongue, which is coated in sticky secretions, and is swallowed whole. These toads may develop fat reserves in order to sustain them through winter months. (Duellman, 2004; Elliott, et al., 2009; Forster, 2013; Jensen, 2013; Moseley, et al., 2004; Schacht, 2009; Todd and Rothermel, 2006)

  • Animal Foods
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • algae

Predation

Southern toads rely heavily on camouflage to protect them from predators. If caught, they may inflate their lungs in order to appear larger. These toads secrete bufotoxin, a cardiotoxic substance, which makes them unpalatable or even toxic to predators. Southern toads have been observed attempting to escape from predators by charging, moving side-to-side, or kicking sand at them. Eggs and tadpoles may also be unpalatable or toxic to predators. Nonetheless, eggs, tadpoles, and adults are all prey items for many invertebrate and vertebrate predators. (Duellman, 2004; Elliott, et al., 2009; Hammerson, 2013; Jensen, 2013)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Some trematode larvae parasitize southern toad tadpoles, often using them as intermediate hosts. It has been shown that some trematodes may exhibit a preference for this species as a host. (Jensen, 2013; Sears, et al., 2012)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

There are no known positive economic impacts of this species for humans. In some areas, southern toads may consume insects that would be considered to be pests. (Duellman, 2004; Edwards, et al., 2006; Elliott, et al., 2009; Hammerson, 2013)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse affects of this species on humans. (Duellman, 2004; Edwards, et al., 2006; Elliott, et al., 2009; Hammerson, 2013; Moseley, et al., 2004)

Conservation Status

Southern toads are listed as a species of "least concern" by the International Union for the Conservation of Nature and Natural Resources. They are not currently considered to be threatened or endangered by any agency, although population numbers have decreased in areas where cane toads (Rhinella marina)have been introduced (in southern Florida, particularly). (Hammerson, 2004; Hammerson, 2013)

Other Comments

This species was previously known as Anaxyrus terrestris In 2006, the genus Bufo was split into multiple genera, including Anaxyrus. Nevertheless, some current researchers continue to use the original name for the species in publications, and it has been suggested that the original genus designation should be reinstated, with Anaxyrus considered a subgenus. (Frost, et al., 2006; Smith and Chiszar, 2006)

Contributors

Jeff Jenkins (author), Sierra College, Jennifer Skillen (editor), Sierra College, Jeremy Wright (editor), University of Michigan-Ann Arbor.

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

agricultural

living in landscapes dominated by human agriculture.

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

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.

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.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

freshwater

mainly lives in water that is not salty.

herbivore

An animal that eats mainly plants or parts of plants.

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.

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

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.

nocturnal

active during the night

oviparous

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

polygynandrous

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

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

scrub forest

scrub forests develop in areas that experience dry seasons.

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

suburban

living in residential areas on the outskirts of large cities or towns.

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.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Duellman, W. 2004. Anura (Frogs and Toads). Pp. 61-68 in M Hutchins, ed. Grzimek's Animal Life Encyclopedia, Vol. 6, 2 Edition. Detroit: Gale Virtual Reference Library. Accessed May 09, 2013 at http://go.galegroup.com/ps/i.do?id=GALE%7CCX3406700354&v=2.1&u=rock89639&it=r&p=GVRL&sw=w.

Edwards, T., K. McCoy, T. Barbeau, M. McCoy, J. Thro, L. Guillette Jr. 2006. Environmental context determines nitrate toxicity in Southern toad (Bufo terrestris) tadpoles. Aquatic Toxicology, 78/1: 50-58. Accessed March 14, 2013 at http://www.ncbi.nlm.nih.gov/pubmed/16569448.

Elliott, L., H. Gerhardt, C. Davidson. 2009. The Frogs and Toads of North America: A Comprehensive Guide to Their Identification, Behavior, and Calls. Boston, MA: Houghton Mifflin Harcourt. Accessed April 05, 2013 at http://books.google.com/books?id=rwmBpMs2Q-gC&printsec=frontcover#v=onepage&q&f=false.

Forster, C. 2013. Dehydration in Southern toads (Anaxyrus terrestris): Metabolic costs and effects of temperature selection. Scripps Senior Theses, Paper 161: 1-19. Accessed August 13, 2013 at http://scholarship.claremont.edu/scripps_theses/161.

Frost, D., T. Grant, J. Faivovich, R. Bain, A. Haas, C. Haddad, R. De Sa, A. Channing, M. Wilkinson, S. Donnellan, C. Raxworthy, J. Campbell, B. Blotto, P. Moler, R. Drewes, R. Nussbaum, J. Lynch, D. Green, W. Wheeler. 2006. The Amphibian Tree of Life. Bulletin of the American Museum of Natural History, 297: 1-371. Accessed June 09, 2013 at http://digitallibrary.amnh.org/dspace/handle/2246/5781.

Hammerson, G. 2013. "Anaxyrus terrestris" (On-line). NatureServe. Accessed May 11, 2013 at http://www.natureserve.org/explorer/servlet/NatureServe.

Hammerson, G. 2004. "Anaxyrus terrestris" (On-line). International Union for Conservation of Nature and Natural Resources. Accessed August 15, 2013 at http://www.iucnredlist.org/details/54777/0.

Jensen, J. 2013. "Anaxyrus terrestris" (On-line). Amphibiaweb. Accessed August 14, 2013 at http://amphibiaweb.org/cgi/amphib_query?where-genus=Anaxyrus&where-species=terrestris.

Jensen, J., M. Elliott, W. Gibbons, C. Camp. 2008. Amphibians and Reptiles of Georgia. Athens, GA: University of Georgia Press. Accessed April 06, 2013 at http://books.google.com/books?id=F4ffa47N9wwC&dq=Jensen,+J.B.,+2008.+Southern+toad+Bufo+(Anaxyrus)+terrestris.+In:+Jensen,+J.B.,&lr=&source=gbs_navlinks_s.

Metts, B., K. Buhlmann, D. Scott, T. Tuberville, W. Hopkins. 2012. Interactive effects of maternal and environmental exposure to coal combustion wastes decrease survival of larval southern toads (Bufo terrestris). Environmental Pollution, 164: 211-218. Accessed March 16, 2013 at http://www.srel.edu/research/projects/docs/DArea/metts_2012_bufo.pdf.

Moseley, K., S. Castleberry, J. Hanula, W. Ford. 2004. Diet of southern toads in Loblolly pine stands subject to coarse woody debris manipulations. The American Midland Naturalist, 153: 327-337. Accessed March 16, 2013 at http://naldc.nal.usda.gov/download/37904/PDF.

Schacht, M. 2009. Factors promoting variation in feeding morphology of larval southern toads (Bufo terrestris). Electronic Theses and Dissertations: Georgia Southern University: 1-96. Accessed August 13, 2013 at http://digitalcommons.georgiasouthern.edu/cgi/viewcontent.cgi?article=1700&context=etd.

Sears, B., A. Schlunk, J. Rohr. 2012. Do parasitic trematode cercariae demonstrate a preference for susceptible host species?. PLoS ONE, 7/12: e51012. Accessed May 11, 2013 at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0051012.

Smith, H., D. Chiszar. 2006. Dilemma of name recognition: Why and when to use new combinations of scientific names. Herpetological Conservation and Biology, 1/1: 6-8. Accessed June 09, 2013 at http://www.herpconbio.org/volume_1/issue_1/Smith_Chiszar_2006.pdf.

Tacutu, R., T. Craig, A. Budovsky, D. Wuttke, G. Lehmann, D. Taranukha, J. Costa, V. Fraifeld, J. de Magalhaes. 2013. "AnAge entry for Anaxyrus terrestris" (On-line). AnAge: The Animal Ageing and Longevity Database. Accessed May 11, 2013 at http://genomics.senescence.info/species/entry.php?species=Anaxyrus_terrestris.

Todd, B., B. Rothermel. 2006. Assessing quality of clearcut habitats for amphibians: Effects on abundances versus vital rates in the Southern toad (Bufo terrestris). Biological Conservation, 133/2: 178-185. Accessed March 16, 2013 at http://toddlab.ucdavis.edu/publications/todd%20and%20rothermel%202006.pdf.

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