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Scaphiopus holbrookiiEastern Spadefoot

By Tristan Smith

Geographic Range

The native geographic range of eastern spadefoot toads (Scaphiopus holbrookii) extends from as far north as Massachusetts to as far south as Florida and as far east as the Mississippi River. The species range does not extend into the higher elevations of the middle to northern Appalachian mountain range, and there are fewer populations in the colder regions north of Virginia. (Dodd Jr., 2013; ; Camp, et al., 2008; Moran and Button, 2011)

Habitat

Eastern spadefoot toad populations are mainly located in regions of loose, sandy soil with a moderate temperature and steady rainfalls. Because this species has such a vast geographic range, there has been no recorded elevation specific to this species. Eastern spadefoots are not located in the higher elevations of the Appalachian Mountain range and have less frequent populations as the range extends further northeast from Virginia to Massachusetts.

Eastern spadefoot toads primarily make burrows where the soil is easy for them dig with the spade-like protrusions on their hind legs. Areas of development do not hinder the species' ability to thrive. Burrows have been found in regions of grasslands, ravines, swamps, flatwoods, pastures, farmland, and suburban neighborhoods. They typically burrow 7-30cm below the surface, but there have been several cases of this species found in burrows several meters below the surface, mainly the in colder regions. When they have finished digging, the burrow is filled with leaf litter and twigs for insulation and protection. The location of their burrow depends on the location of a breeding ground, level of predation in the area, and access to food. Burrows are located a maximum distance of 915 m (range: 91-915m) from a breeding pond or body of water.

Breeding sites for the eastern spadefoot are rarely located in a pond that has a permanent or long lasting source of water. Spadefoots breed in temporary, still water areas such as roadside ditches, puddles in a field, or areas on a road that has flooded. (Cook, et al., 2014; Delis, et al., 2001; Dodd Jr., 2013; Greenberg and Tanner, 2004; Hildebrande, 2009; IUCN SSC Amphibian Specialist Group, 2015; Johnson, 2003; Jones and Jones, 2017; ; Moran and Button, 2011)

  • Aquatic Biomes
  • lakes and ponds
  • temporary pools
  • Range depth
    0.07 to 2 m
    0.23 to 6.56 ft

Physical Description

Eastern spadefoot toads are dark in color, ranging from black to olive, with a grey to white belly. There are two noticeable stripes that extend parallel from the eyes, along the back, and join in the posterior region, to form what can be described as an "hourglass" or "lyre" shape. The skin has small warts and small parotoid glands. This species excretes a strong musty or peppery smell, to which some people and animals may be allergic. Eastern spadefoots have large eyes with vertical pupils, whereas most other toad species have horizontal pupils. The large eyes are believed to be useful for nocturnal sight. On the inner hind legs, eastern spadefoots have a black, spade-like protrusion used for burrowing into the ground. Skin darkness and color depend on environmental factors on the population or individual.

Eastern spadefoot toads generally weigh between 1.0-23.0 grams, with an average adult weight of 6.6g. Their body length averages 60mm (range 45-78mm). There is no sexual dimorphism in this species but few cases report females being larger than males in populations. (Camp, et al., 2008; Dodd Jr., 2013; Hildebrande, 2009; Johnson, 2003; Moran and Button, 2011; Palis, 2016)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    1.0 to 23 g
    0.04 to 0.81 oz
  • Average mass
    6.6 g
    0.23 oz
  • Range length
    45 to 78 mm
    1.77 to 3.07 in
  • Average length
    60 mm
    2.36 in

Development

The length of time it takes eastern spadefoot eggs to hatch after fertilization depends on water temperature in which the eggs are laid. In water temperatures that are around 25.5 degrees Celsius, the eggs will hatch within 24 hours. For colder temperatures hatching took place 7-14 days after fertilization. If the temperature gets too low, close to or below freezing, many of the eggs will not hatch or the development of the tadpoles will be abnormal.

Once hatched, the tadpoles are free from the membranes. They attach to an object nearby and remain still for the first few days. During this period, the mouth is formed, gills become covered by the surrounding skin folds and the ventral sucker will be re-absorbed. The tadpoles’ tails will lengthen, and tail membrane will develop. Once formed, tadpoles will begin to constantly move through the water, feeding on algae and other phytoplankton. At this point, their mouth has not yet fully developed but will be fully developed in 3-6 days depending on water temperature. With a fully-developed jaw and mouth, tadpoles will begin consuming drowned earthworms, dead plants, or floating particles. When the change in feeding begins, so does their swimming style in the pond.

While the jaw is developing, and they are feeding on algae, tadpoles are evenly spread throughout the top 5 centimeters of water. After the development of the jaw, they gradually begin to swim in clusters. The school of tadpoles can swim separately from the movement of the water and in larger depths than before. The orientation of the school depends on the body of water and current strength of the water. Richmond (1947) reports that this collective group provides safety for the tadpoles.

In some cases, tadpoles will eat other eastern spadefoot eggs that are in the body of water that are already dead or developing. From experiments in labs, eastern spadefoot tadpoles are opportunistic feeders, consuming plant matter and microscopic larvae of insects and other anuran species in the water.

One month after hatching, tadpole metamorphosis begins; forelimbs begin to develop and their tail size decreases. Individuals willleave the school and spend more time around the water’s edge. Once their forelimbs have fully developed, they leave the water and finish their metamorphosis on land, hidden under objects. Full development after forelimbs appear takes one week. (Bragg, 1964; Cook, et al., 2014; Dayton, et al., 2005; Dodd Jr., 2013; Harris Jr., 2008; ; Richmond, 1947)

Reproduction

Breeding activity is stimulated by sufficient rain at minimum temperatures of 7.2–10 ˚C in a variety of temporary water bodies, including temporary ponds in uplands and bottomlands, flooded fields and roads, roadside ditches and borrow pits. Males float atop the water and call for their mates. Sexually active males will begin calling once they reach the breeding site, attracting the females towards the pond. The sound is a very distinct explosive grunt or long drawn-out languishing moans. A single call from a male can be heard several kilometers away but not all males will call during breeding but wait for a female to appear and grasp on to them. The process of grabbing onto a potential mate just anterior of the hind limbs is called amplexus. This form of amplexus is the more primitive form compared to other species that use amplexus during mating. A female can be grabbed by more than one male on the way to the breeding site, though the chosen male will issue warning calls or vigorously kick at any male that tries to mate with the female. Females choose where the eggs will be deposited while swimming with the chosen male holding onto them. (Black and Gosner, 1955; Cook, et al., 2014; Dodd Jr., 2013; Greenberg and Tanner, 2004; Johnson, 2003; ; Moran and Button, 2011; Palis, 2013)

Eastern spadefoot toads breed sporadically throughout the year, but individually breed 1-3 times per year. Variations in breeding are based on rainfall, temperature, and barometric pressure. Because the geographic range of this species covers such a wide area, there is no specific breeding season, however, they are capable of breeding during any month in the southern portion of their range, but only breed from March–August further north. Heavy rainfall is a primary indicator of a suitable time to breed. Because the breeding grounds of this species are temporary bodies of water, breeding occurs after this heavy rain, either during the night or day.

Eggs are deposited in vegetated areas of the water, and clutch size can range from 800 to 4500 eggs with a mean mass of 3.78 g per clutch. Across the season, this averages to 3838 offspring per individual (range 2332-5468). Eggs can hatch in as little as 12 hours or 14 days (average 7 days) depending on temperature of the water and air. Time to independence is immediate, as parents provide no care.

Toads reach sexual maturity at about 17 months (range 15-19 months). (Cook, et al., 2014; Greenberg and Tanner, 2004; Greenberg and Tanner, 2005; Johnson, 2003; Palis, 2013)

  • Breeding interval
    Eastern spadefoot toads can breed 1 to 3 times per year or can forego breeding for an entire year.
  • Breeding season
    Egg laying and fertilization of and eastern spadefoot toad happens in several different intervals throughout the gegraphic region. In southern states, breeding season typically takes place throughout the year. In more nothern regions, breeding takes place in the warmer summber months but have had instances of breeding iduring colder temperatures.
  • Range number of offspring
    2332 to 5468
  • Average number of offspring
    3838
  • Range time to hatching
    0.5 to 14 days
  • Average time to hatching
    7 days
  • Average time to independence
    0 minutes
  • Range age at sexual or reproductive maturity (female)
    15 to 19 months
  • Range age at sexual or reproductive maturity (male)
    15 to 19 months

Beyond the mating process, there is no parental investment. However, when mating, females choose the egg site that provides some cover or protection from the eggs. (Black and Gosner, 1955; Dodd Jr., 2013; Goodman, 1971; Greenberg and Tanner, 2004; Johnson, 2003; Palis, 2013; Palis, 2016)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

Eastern spadefoot toads have an average lifespan of five to nine years in the wild. Their average lifespan increases to seven to ten years in captivity. The oldest toad in captivity was twelve years. (Cook, et al., 2014; Dodd Jr., 2013; ; Richmond, 1947)

  • Range lifespan
    Status: captivity
    12 (high) years
  • Typical lifespan
    Status: wild
    5 to 9 years
  • Typical lifespan
    Status: captivity
    7 to 10 years

Behavior

Adult eastern spadefoot toads are solitary burrowers that will stay in a specific area unless they locate to a new area after a breeding season. Members of this species will spend most of their time inside their burrows. Although both nocturnal and diurnal, they typically forage during the day; less than 10% of foraging is completed at night. Eastern spadefoot toads have higher activity during more humid days. Even in an area of greater population sizes, individuals avoid one another and only become aggressive if an individual of the same sex is near their burrow. Individuals have been captured up to 914 meters away from the nearest source of water indicating that, after reproduction, individuals will return to their home sites, even to the same burrow. Populations located in the northern region of the range hibernate during the colder, winter months but remain active year-round in the southern region. Hibernation can be interrupted by surface activity during unusually warm weather. (Baughman and Todd, 2007; Cook, et al., 2014; Dodd Jr., 2013; Greenberg and Tanner, 2004; Greenberg and Tanner, 2005; Harris Jr., 2008; Johnson, 2003; ; Palis, 2013; Palis, 2016)

Home Range

Home range for an eastern spadfoot toad is 0.62m^2 to 82.1m^2, and averages 10.1m^2. Males tend to have a smaller average range than the females do. Members of the species are territorial of their burrow against same sex member of their species. Migrations is not common, but they have been known to build a burrow in a new location. The change in burrow location has no set pattern. (Baughman and Todd, 2007; Cook, et al., 2014; Johnson, 2003; ; Palis, 2013; Palis, 2016)

Communication and Perception

Eastern spadefoot toads are a nocturnal species that have large, protruding eyes used to visualize surroundings at night. The vertical pupil helps absorb as much light as possible to navigate through surroundings.

Eastern spadefoot toads have a distinct breeding call that can be heard for up to 1.6 km away. They are not a social species and tend to stay in burrows unless they need to feed or breed. The call of the eastern spadefoot toad is often described as nasal, medium tone that resembles an unhappy infant or the cry of a young cow. Warning calls during breeding season are also common between males. There is not much information on interspecific communication. (Camp, et al., 2008; Dodd Jr., 2013; Johnson, 2003)

Food Habits

Eastern spadefoot toads are nocturnal foragers with a diet of invertebrates, insects, arachnids, termites, worms, and larvae of several insect species. They forage near their burrow, only traveling a maximum distance of 2.04 m (range: 0.002-2.04m). A tactic that some individuals use is sitting at the opening of the burrow and waiting for prey to pass by. The diet of the male and female of the species is generally the same. Diet may change alongside seasonal or environmental factors. Smaller insects like ants are important in the diet of the species juveniles.

As tadpoles, they consume algae for the first few days post-hatching. Once their mouth is fully developed, they consuming drowned earthworms, dead plants, or floating particles. (Camp, et al., 2008; Dodd Jr., 2013; Johnson, 2003; ; Moran and Button, 2011)

  • Animal Foods
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • terrestrial worms

Predation

The dark coloration of eastern spadefoots toads makes it easier for them to blend in with the soil type of their habitat. To avoid predators, eastern spadefoot toads will bury themselves in the soil, posterior first. They can bury themselves in seconds. If unable to dig or surprised by a predator, their secondary defense is to tuck tightly into themselves, covering their ventral sections and keeping their eyes closed. They then expose their dorsal surface, which is covered in a secretion that is used to ward off predators by smell and taste. There have been instances of spadefoot toads giving warning calls when being irritated by a predator.

Common predators of eastern spadefoot toads are other toads like members of the same species Scaphiopus holbrookii, bullfrogs, Lithobates catesbeianus, and southern toads Anaxyrus terrestris. Snakes include cottonmouths Agkistrodon piscivorus, black racers Coluber constrictor, southern hognose snakes Heterodon simus, southern water snakes Nerodia fasciata, and northern water snakes Nerodia sipedon. Mammals include raccoons (Procyon lotor), Virginian opossums Didelphis virginiana, wild boar Sus scrofa, and northern short-tailed shrews Blarina brevicauda. Birds include cattle egrets Bubulcus ibis, gulls Larus, common grackles Quiscalus quiscula, and European starlings Sturnus vulgaris. Eastern newts Notophthalmus viridescens may also prey on these toads. (Black and Gosner, 1955; Dodd Jr., 2013; Goodman, 1971; Harris Jr., 2008; Johnson, 2003; Maier, 2005; Palis, 2016)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Eastern spadefoot toads have no environmental role in their community aside from soil aeration from digging their burrows.

Parasites include protozoans (Nyctotherus cordiformis, Octomitus intestinalis, Opalina ablanceolata, Opalina obtrigonoidea, Opalina carolinensis, Opalina triangulata, Trichomonas augusta). Cestodes include Distoichometra bufonis, Proteocephalus, and nematodes include Agamonema, Cosmocercoides dukae, Oswaldocruzia leidyi, Opalina pipiens, Physaloptera, and Rhabdias. (Dodd Jr., 2013)

Commensal/Parasitic Species
  • Cestode (Distoichometra bufonis)
  • Cestode (Proteocephalid cysts)
  • Nematode (Agamonema)
  • Nematode (Cosmocercoides dukae)
  • Nematode (Oswaldocruzia leidyi)
  • Nematode (Opalina pipiens)
  • Nematode (Physaloptera)
  • Nematode (Rhabdias)
  • Protozoan (Trichomonas augusta)
  • Protozoan (Nyctotherus cordiformis)
  • Protozoan (Octomitus intestinalis)
  • Protozoan (Opalina ablanceolata)
  • Protozoan (Opalina obtrigonoidea)
  • Protozoan (Opalina carolinensis)
  • Protozoan (Opalina triangulata)

Economic Importance for Humans: Positive

Eastern spadefoot toads are sold as pets through various pet stores and animal websites. (Cook, et al., 2014)

Economic Importance for Humans: Negative

There are no negative economic influences of eastern spadefoot toads on humans.

Conservation Status

Eastern spadefoot toads are listed as a species of "Least Concern" by the IUCN Red List, and have no special status listed on the US federal list, the Michigan state list, and the CITIES international in the United States or internationally. This species is not considered to be threatened due to its large distribution and predicted population in that range.

There are no major threats to the eastern spadefoot toads, but minor threats may include urbanization and agriculture where the ground disturbances effect hibernation and burrows or temporary pond sites are eliminated.

There are no direct conservation efforts for eastern spadefoot toads, though indirect conservation efforts include reducing the pesticides used in agriculture. (Dodd Jr., 2013; Harris Jr., 2008; IUCN SSC Amphibian Specialist Group, 2015; ; Palis, 2016; Richmond, 1947)

Contributors

Tristan Smith (author), Radford University, Alex Atwood (editor), Radford University, Lindsey Lee (editor), Radford University, Karen Powers (editor), Radford University, Joshua Turner (editor), Radford University, Tanya Dewey (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.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

choruses

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

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.

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

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.

fossorial

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

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.

natatorial

specialized for swimming

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.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

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.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

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.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

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

Baughman, B., B. Todd. 2007. Role of substrate cues in habitat selection by recently metamorphosed Bufo terrestris and Scaphiopus holbrookii. Journal of Herpetology, 51/4: 154-157.

Black, I., K. Gosner. 1955. The effects of temperature and moisture on the reproductive cycle of Scaphiopus h. holbrooki. The American Midland Naturalist, 54/1: 192-203.

Blackwater Reptiles, 2017. "Eastern spadefoot toad for sale" (On-line). Accessed April 15, 2018 at www.blackwaterreptiles.com/toads/eastern-spadefoot-toad-for-sale.html.

Bragg, A. 1964. Further study of predation and cannibalism in spadefoot tadpoles. Herpetologica, 20/1: 17-24.

Camp, C., M. Elliot, J. Jensen, W. Gibbons. 2008. Amphibians and Reptiles of Georgia. Athens, Georgia: University of Georgia Press.

Cook, R., K. McGarigal, B. Timm. 2014. Upland movement patterns and habitat selection of adult eastern spadefoots (Scaphiopus holbrookii) at Cape Cod National Seashore. Journal of Herpetology, 51/4: 84-97.

Dayton, G., D. Saenz, K. Baum, R. Langerhans, T. DeWitt. 2005. Body shape, burst speed, and escape behavior of larval anurans. Oikos, 111/3: 582-591.

Delis, P., K. Jansen, A. Summers. 2001. Spadefoot toads (Scaphiopus holbrookii holbrookii) in an urban landscape: Effects of nonnatural substrates on burrowing in adults and juveniles. Journal of Herpetology, 35/1: 141-145.

Dodd Jr., C. 2013. Frogs of the United States and Canada: Volume 2. Baltimore, Maryland: Johns Hopkins University Press.

Goodman, D. 1971. Territorial behavior in a Neotropical frog, Dendrobates granuliferus. Copeia, 1/2: 365-370.

Greenberg, C., G. Tanner. 2004. Breeding pond selection and movement patterns by eastern spadefoot toads (Scaphiopus holbrookii) in relation to weather and edaphic conditions. Journal of Herpetology, 38/4: 569-577.

Greenberg, C., G. Tanner. 2005. Spatial and temporal ecology of eastern spadefoot toads on a Florida landscape. Herpetologica, 73/4: 20-28.

Harris Jr., H. 2008. The eastern spadefoot toad, Scaphiopus holbrookii in Maryland. Bulletin of the Maryland Herpetological Society, 44/3: 107-110.

Hildebrande, W. 2009. Eastern Spadefoot, Scaphiopus holbrookii. Bulletin of the Maryland Herpetological Society, 45/2: 47-50.

IUCN SSC Amphibian Specialist Group, 2015. "Scaphiopus holbrookii" (On-line). The IUCN Red List of Threatened Species 2015: e.T59042A64981907. Accessed February 01, 2018 at http://dx.doi.org/10.2305/IUCN.UK.2015-2.RLTS.T59042A64981907.en.

Johnson, K. 2003. Abiotic Factors Influencing the Breeding, Movement, and Foraging of the Eastern Spadefoot (Scaphiopus holbrookii) in West Virginia (Master's Thesis). Huntington, West Virginia: Marshall University.

Jones, K., G. Jones. 2017. Scaphiopus holbrookii (eastern spadefoot). Herpetological Review, 48/1: 171-172.

Lannoo, M. 2005. Amphibian Declines: The Conservation Status of United States Species. Berkeley, California: University of California Press.

Maier, T. 2005. Predatory behaviors of Blarina brevicauda toward a fossorial eastern spadefoot toad (Scaphiopus holbrookii). Special Publication of the International Society of Shrew Biologists, 1/1: 361-366.

Moran, K., C. Button. 2011. A GIS model for identifying eastern spadefoot toad (Scaphiopus holbrookii) habitat in eastern Connecticut. Applied Geography, 31/3: 980-989.

Palis, J. 2016. The eastern spadefoot, Illinois' storm frog. Illinois Audubon, 335: 19-21.

Palis, J. 2013. Breeding frequency and success of eastern spadefoots, Scaphiopus holbrookii, in southern Illinois. Proceedings of the Indiana Academy of Science, 121/2: 158-162.

Richmond, N. 1947. Life history of Scaphiopus holbrookii holbrookii (Harlan). Part I: Larval development and behavior. Ecology, 28/1: 53-67.

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