Plains Spadefoot

The European, American, or Plains Spadefoot Toad is a small but rotund toad-like frog, generally resembling true toads (Bufonidae) in body form. Spea bombifrons can grow up to 2¼" in snout-vent length (Colorado Herpetological Society 2002). Its skin, which is relatively smooth, can range from gray to brown, sometimes with a greenish hue, and is scattered with darker spots or blotches. The skin is also smoother and thinner than that of Bufonidae. Along the dorsal and lateral surfaces run four vague light stripes, the middle two of which occasionally resemble an hourglass. There are many small tubercles on the otherwise smooth skin. The ventral surface is white and has no markings, although the throat of the male is bluish or grayish on the sides (USGS 2002). There is a raised, bony lump (boss) between the large eyes. The eye has an elliptical, vertical, cat-like pupil, and thus differs from the true toads, whose pupils are round. S. bombifrons also differs from Bufo in that it has no parotid glands (or, when present, they are indistinct) (USGS 2002). Like the other members of the family Pelobatidae, or the spadefoots, S. bombifrons is named for its large, well-developed, wedge-shaped, sharp-edged, black tubercle or metatarsal "spade" on the bottom of each hind foot. This bony element, which is capped with a keratinous cover, is used to burrow rear-first (USGS 2002).Substantial population declines observed during extended droughts are more likely a result of non-breeding during suboptimal environmental conditions than true population declines (Cottonwood 1986).

Spea bombifrons is native to the more arid Plains region of western North America: the plains east of the Rocky Mountains from southern Alberta, Manitoba, and Saskatchewan to northwest Texas and Chihuahua, Mexico, east to Missouri and eastern Oklahoma and into eastern Arizona, with isolated populations in south Texas and Mexico (Stebbins 1985). Throughout the majority of its range, the distribution S. bombifrons is highly correlated with sandy, gravelly, or sandy loam soils, but it ranges from deserts in the American Southwest to aspen parkland in the Canadian prairies(Bragg 1944; Cook 1960; Black 1970; Huggins 1971; Femmer 1978; Collins 1982; Cook and Hatch 1964; Cottonwood Consultants 1986). S. bombifrons has been found in unvegetated sand dunes, sand dunes with willow and cottonwood, upland prairie, desert, short and mixedgrass prairie, mixed shrubland, fescue grassland, floodplains, and sagebrush (Bragg 1944; Black 1970; Huggins 1971; Stebbins 1985; Axys 1996 and 1997). East of the Rockies, S. bombifrons is found in shortgrass prairie and desert grasslands, where the soil is loose (USGS 2002).

There is no evidence to suggest that the range is contracting (Lauzon 1999). The spadefoot toads as a group do not include any declining species (Corn 1994). This amphibian is not included on any list of rare, endangered, threatened, or sensitive species (Nature Conservancy 1999; RedList). The Nature Conservancy assigns S. bombifrons a global rank of G5, indicating that the species is “demonstrably secure” across its global range (Nature Conservancy 1999). The Province of Alberta places S. bombifrons on its Blue List of species that may be at risk of declining to non-viable levels within the Province’s boundaries (Alberta Wildlife Management Division 1996). This species’ highly variable population size, the result of annual variability in the availability of breeding wetlands, is responsible for this designation. The population there is considered stable but moderately threatened due to current land use practices (Lauzon 1999).

The habitat, breeding season, and breeding location are highly related. S. bombifrons is nocturnal, and spends most of its time underground, emerging only to breed in favorable moist conditions, or to feed (Lauzon 1999). During extended droughts, the frog does not remain underground indefinitely but emerges, especially during humid weather, to forage during the evening (Bragg 1965; Ruibal 1969). S. bombifrons burrows deeper into the soil and emerges less frequently as the summer progresses and the soil dries (Bragg 1965). It prefers loose soil, where it can easily burrow with the aid of its “spades” up to depths of almost 1 m (Baxter & Stone 1980; Russell & Bauer 1993; USGS 2002). They will most often burrow along the edge of a solid object or near a plant that provides security or shade (Bragg 1944). During the winter, it burrows deeply to avoid freezing and desiccation, as S. bombifrons does not tolerate freezing and must burrow below the frost line (Baxter & Stone 1980). This spadefoot toad surfaces quickly from its burrow and opportunistically migrates to breeding wetlands during periods of heavy rainfall and warm temperatures (Bragg 1965; Klassen 1998; Lauzon & Balagus 1998). The measured amount of rainfall required for emergence varies from 2.5 to 10.4 cm (Black 1970; Femmer 1978; Farrar & Hey 1995). Large choruses of these frogs have been associated with heavy rainfall, but the temporary wetlands that result from light rain or snow melt are known to attract small choruses as well (Lauzon 1999). S. bombifrons has been observed calling when daily maximum temperatures were 12.5°C to 23.5° and daily minimum temperatures were 7°C to 10.5°C (Klassen 1998), although breeding frogs have been observed in the southeastern extreme of their range at temperatures as low as 9°C (Bragg 1965). S. bombifrons has been observed calling at water temperatures of 10.5°C to 16°C (Lauzon 1999). No studies have been conducted on the home range of S. bombifrons, but the related Eastern Spadefoot (Spea holbrooki holbrooki) has an average home range of 10.1 m2, with male home ranges generally larger than those of the female (Pearson 1955). S. bombifrons is known to be capable of migrating at least 1.6 km to breeding sites, and juveniles have been found more than 2 km from known breeding wetlands within weeks of metamorphosis (Landreth & Christensen 1971; Klassen 1998). This frog forages above ground, and its prey are a variety of insects (Lauzon 1999). In Oklahoma, this included flies, hymenopterans, moths, beetles, pentatomids, and various spiders (Bragg 1944). S. bombifrons is generally active from the start of its breeding season until the fall (Lauzon 1999). The breeding season is generally correlated with annual peaks in precipitation. In the center of its range, S. bombifrons breeds from May to August. In the southern end of its range, S. bombifrons breeds in July, after the summer rains. In the northern part, breeding may take place in late May at the earliest. If appropriate environmental conditions do not occur during the active season, breeding may not occur at all; conversely, S. bombifrons may breed more than once in a single year if conditions are particularly conducive (Bragg 1944 & 1965; Klassen 1998). Spea bombifrons lays its eggs in a variety of wetlands, but prefers flooded areas and temporary pools (USGS 2002). Its preference for sandy soils leaves S. bombifrons with limited breeding opportunities, since the soil drains rapidly and precludes the development of breeding wetlands. As a result, this spadefoot relies on fine-textured, less permeable soils within sandier habitats where temporary wetlands form and it is able to breed (Lauzon 1999). Breeding pond depths vary from 10 cm to more than 1 m. It tolerates varying amounts of vegetation, and native as well as tame habitats (Bragg 1965; Farrar & Hey 1995; Klassen 1998). Spawning S. bombifrons have been observed in partially flooded fields, roadside ditches, flooded dugouts, shallow temporary wetlands in fallow fields, temporary ponds in uplands, along streams, semi-permanent pools, oxbow lakes, stream meander channels, unvegetated sloughs, marshy depressions, flooded cultivated fields, temporary wetlands in pastures, river backwaters, and ditches (Cook 1965; Cottonwood 1986; Preston & Hatch 1986). These frogs have been observed breeding in non-native habitats such as a construction site (Femmer 1978), flooded soybean fields and cornfields (Farrar & Hey 1995), a flooded wheat field, and even driveways and bicycle paths (Didiuk). This spadefoot breeds quickly to take advantage of its typically ephemeral wetland, and to allow the eggs and larvae as much time as possible to develop. The largest numbers have been observed during or the first night after heavy rains, with counts falling off dramatically thereafter (Bragg 1965). Generally, males migrate to the breeding wetlands before females, and generally outnumber them in a given time and place (Bragg 1945; Baxter & Stone 1980). The call of the male is loud, harsh, and may be heard at distances of up to 3 km (Lauzon 1999). The male spadefoot call greatly stimulates both sexes, and larger choruses attract more individuals of both sexes (Bragg 1945). Females lay up to 2000 eggs in clutches of 10 to 250 each (Bragg 1965; Collins 1982). Whereas true toads lay their eggs in strings, S. bombifrons females lay eggs in spherical masses, attached to submerged vegetation (Baxter & Stone 1980). Suspended soil particles and other debris adhere to the sticky surface of the egg mass to help camouflage them from predators (Bragg 1965). The rate of egg development is temperature dependent, and under normal conditions spadefoot eggs will hatch in about two days (Bragg 1965). The lethal temperature limits for eggs are 34°C (Justus 1977). Spadefoot toads (family Pelobatidae) as a group have the fastest development rate among amphibians (Bragg 1961). Larval development is also temperature dependent and thus allows the tadpoles to develop faster in conditions that evaporate the temporary breeding wetlands (Buchholz & Hayes 1996). In southern regions (in this study, Oklahoma), the time from hatching to metamorphosis may be as little as 14 days (Bragg 1967), with a range of 17 to 20 (in Missouri) days being more common (Femmer 1978); in the north (Alberta), metamorphosis has been observed 21 to 34 days after hatching, with some tadpoles requiring 60 days (Klassen 1998).

Alteration and destruction of habitat are considered the only possible risk to habitats suitable for S. bombifrons. Availability of wintering and breeding habitats are the likely limiting factors of this amphibian; agriculture is primarily responsible for the loss of prairie land and is probably the most significant threat (Lauzon 1999). Cultivation and drainage of wetlands, as for cattle, as well as flood control, have also been identified as potential threats (Cottonwood 1986). The extent to which fragmentation of prairie land and other habitats has affected toad movements between populations or the re-colonization of populations sinks is unknown (Didiuk 1997). Other human activities, such as the widespread use of herbicides and pesticides, oil and gas exploration and development, and road kills have been implicated in the decline of related amphibians and those with similar ranges as S. bombifrons, but none has been studied specifically with regard to this species (Lauzon 1999).

The maximum lifespan of plains spadefoot toads is estimated at 13 years.

Typical lifespan
Status: wild: 13 (high) years.

The cryptic coloration and burrowing habits of Spea bombifrons may protect many individuals from predation. They also have noxious skin secretions that may deter predators. Tadpoles gather in large feeding aggregations when they detect a predator, which may protect some individuals.

Hydrophilid beetle larvae (Hyrus triangularis), crustaceans (Apus), and other spadefoot toad tadpoles prey on tadpoles. Adults may be preyed on by barn owls (Tyto alba), Swainson's hawks (Buteo swainsoni), prairie rattlesnakes (Crotalus viridis), and burrowing rodents.

Known Predators:

• Hydrophilid beetle larvae (Hyrus triangularis)
• crustaceans (Apus)
• barn owls (Tyto alba)
• prairie rattlesnakes (Crotalus viridis)
• burrowing rodents (Rodentia)

Anti-predator Adaptations: cryptic

Plains spadefoot toads measure 38.1 to 63.5 mm (2 to 2.5 inches) in length, and weigh approximately 30 grams. Females tend to be slightly larger. They are brown or gray, sometimes with hints of green, and dark splotches or warts. On their dorsal and lateral surfaces are 4 vague stripes, with the middle two stripes sometimes forming an hourglass-like shape. Some have red or orange spots as well. Plains spadefoot toads are called "spadefoot" because of a welll-developed, sharp, spade-shaped and black tubercle on each of their rear feet. This is a bony extension of the metatarsal, covered with keratin that is used to burrow with the rear feet. There is a raised bone (or "boss") between their eyes, and their pupils are vertical, like those of cats. Adult, breeding males have a keratinous "nuptial pad" on their thumbs.

Plains spadefoot toads are not true toads (Bufonidae). They are members of a small, frog family, Pelobatidae.

Average mass: 30 g.

Range length: 38.1 to 63.5 mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: female larger; sexes shaped differently

Plains spadefoot toads are found mainly in the arid grasslands of western North America. They are restricted to areas with loose soils for burrowing. They can also be found in savannas, loess hills, sandhills, and semi-desert and desert scrub. They are found in shallower summer burrows and deeper winter burrows throughout the year. Larvae require small, ephemeral ponds for development, such as cattle ponds, vernal pools, playa lakes, and flooded agricultural fields. Suitable ponds are difficult to find in habitats that plains spadefoot toads prefer. The soft, sandy soils they prefer for burrowing are also usually permeable to water. Because of this they also require proximity to areas where soils are less permeable and permit formation of temporary breeding pools. Juveniles burrow into soft mud along the ponds in which they developed or crawl into crevices in dried mud or under plant litter.

Range elevation: 700 to 7500-8000 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral ; scrub forest

Aquatic Biomes: lakes and ponds; temporary pools

Other Habitat Features: agricultural

Plains spadefoot toads, Spea bombifrons, are native to the Nearctic region. Their North American range stretches from southern Alberta and Saskatchewan, Canada south to the panhandle and lower tip of Texas, and into northern Mexico. They range as far west as southeastern Arizona and east to Nebraska, western Missouri, and western Oklahoma. Their range seems to be expanding along the Missouri River floodplain and in southern Alberta and Saskatchewan. There are disjunct populations in southern Colorado, northeastern Mexico, southernmost Texas, and along the Arkansas River in Arkansas.

Biogeographic Regions: nearctic (Native )

Plains spadefoot toad tadpoles can develop into carnivorous "trophic morphs" or omnivorous "trophic morphs." Carnivorous tadpoles develop faster than omnivorous tadpoles and eat other spadefoot toad tadpoles and invertebrates. Cannibalism in breeding ponds is common. Omnivorous tadpoles eat organic matter, especially algae.

Adult plains spadefoot toads eat small invertebrates, such as hymenopterans, flies, moths, beetles, spiders, and stink bugs.

Animal Foods: amphibians; insects; terrestrial non-insect arthropods; terrestrial worms

Plant Foods: algae

Other Foods: detritus

Primary Diet: carnivore (Insectivore , Eats non-insect arthropods)

Plains spadefoot toads are important members of the healthy ecosystems in which they live.

There is no known negative economic importance for humans.

Plains spadefoot toad eggs usually hatch within two days of being laid. At 30 degrees Celsius eggs hatch in 20 hours. Tadpole development (time to metamorphosis) usually lasts 13 to 20 days, depending on ambient temperatures. In northern parts of the range, time to metamorphosis may be up to 60 days, with average times in Alberta being 21 to 34 days. Tadpoles reach up to 7 cm in length and have a dark olive/yellow color with irridescent highlights. Plains spadefoot toad larvae develop primarily in small, temporary ponds and larvae are tolerant of widely fluctuating and high water temperatures. They metamorphose rapidly, before breeding ponds evaporate. As members of the family Pelobatidae, plains spadefoot toads have one of the fastest development rates among amphibians.

Development - Life Cycle: metamorphosis

Plains spadefoot toad populations seem to be healthy, for the most part. Local population declines are often the result of lack of breeding during drought years. In Alberta they are on the "blue list" of species at risk of decline because of non-viable population levels in the province. Plains spadefoot toads may be expanding their range in North America but local populations may be threatened by development that endangers breeding ponds, such as wetland draining and conversion of land to agriculture. The use of pesticides, herbicides, and the presence of other pollutants in water may also be a threat to these frogs.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Plains spadefoot toads affect populations of their invertebrate prey. They also share breeding ponds with other spadefoot toad species (Spea) and with Great Plains toads (Anaxyrus cognatus). Plains spadefoot toad tadpoles will eat Anaxyrus cognatus tadpoles where they share breeding ponds. They also share breeding ponds with Woodhouse's toads, Anaxyrus woodhousii woodhousii.

Plains spadefoot toads will outcompete Mexican spadefoot toads (Spea multiplicata) for fairy shrimp (Anostraca) where they co-occur.

Tadpoles are sometimes infected with Saprolegnia fungus. Adults have been found with intradermal mites (Acari) and may carry a monogean parasite, Pseudodiplorchis americanus.

Commensal/Parasitic Species:

• intradermal mites (Acari)
• monogean parasite, Pseudodiplorchis americanus

Plains spadefoot toads have a mating call that is approximately 0.5 - 1.0 second in length and sounds similar to that of a mallard. This call, and another low, rough call, both act as mating calls. A male's mating call can be heard as far as 3 km away.

Communication Channels: tactile ; acoustic

Perception Channels: visual ; tactile ; acoustic ; chemical

After heavy rains, males travel to breeding ponds and begin to call. Calls attract both males and females, with louder choruses attracting the most individuals. Calls are loud and harsh and can be heard up to 3 km away. In some areas of the southwest Spea bombifrons uses the same breeding ponds as other Spea species and hybridization has been documented in the laboratory. Mating calls act as reproductive isolating mechanisms in these circumstances. Two mating call types have been identified in plains spadefoot toads. Spea bombifrons has been observed calling at mating ponds at temperatures as low as 10.5°C.

Mating System: polygynandrous (promiscuous)

Plains spadefoot toads mate during or after heavy rains (from 2.5 to 10.4 cm). Times of rainfall vary with latitude, but in the center of the range of S. bombifrons, this is from May to August. Plains spadefoot toads live primarily on land, traveling to breeding ponds only to mate. They lay their eggs in temporary ponds created by the rain. These ponds are generally up to 1 meter in depth. They have been observed breeding in natural ponds, oxbow areas of rivers, and sloughs as well as irrigation and roadside ditches, flooded areas of playgrounds and constructions sites, and in flooded agricultural fields. Females lay up to 2,000 eggs, in masses of 10 to 250. Eggs fall to the pond bottom or are attached to vegetation or other submerged objects. Sexual maturity is reached in the second year after hatching.

Breeding interval: Plains spadefoot toads may breed multiple times during a season, if conditions are good, or they may not breed in a year if conditions are poor.

Breeding season: Plains spadefoot toads will breed after periods of sufficient rain between the months of May and August.

Range number of offspring: 2000 (high) .

Range time to hatching: 2 to 3 days.

Average age at sexual or reproductive maturity (female): 2 years.

Average age at sexual or reproductive maturity (male): 2 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous

After the eggs are deposited in a temporary pond, there is no further parental care.

Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female)

The plains spadefoot toad (Spea bombifrons) is a species of American spadefoot toad which ranges from southwestern Canada, throughout the Great Plains of the western United States, and into northern Mexico. Like other species of spadefoot toads, they get their name from a spade-like projection on their hind legs which allows them to dig into sandy soils. Their name, in part, comes from their keratinized metatarsals, which are wide instead of "sickle shaped". The species name translates as buzzing leaf shaped. This refers to the species' distinguishing features; its buzzing mating call, and its leaf-shaped digging metatarsals. It was first described by Cope in 1863.

Spea bombifrons​ es una especie de anfibio anuro de la familia Scaphiopodidae.

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Spea bombifrons Spea generoko animalia da. Anfibioen barruko Scaphiopodidae familian sailkatuta dago, Anura ordenan.

Le Crapaud des Plaines, Spea bombifrons, est une espèce d'amphibiens de la famille des Scaphiopodidae.

Опис

Загальна довжина досягає 3—4 см. Спостерігається статевий диморфізм: самиці більші за самців. Голова й тулуб доволі широкі й масивні. Очі з вертикальними зіницями. Має ороговілі вирости з гострими краями на задніх лапах — «лопати», яким може швидко рити землю, зариваючись у м'який ґрунт за кілька секунд. Паратідні гландули відсутні, слухової мембрани (тімпанальної перетинки) не помітно. Шкіра відносно суха, з бородавками. На чолі між очей розташований кістяний горбок, розміром 3-5 см.

Забарвлення коливається від коричневого до сірого з крапочками зеленого кольору. Уздовж спинки і з боків проходять 4 розмиті смужки. На черевці шкіра біла, без плям. У самців горло з боків синюватого або сіруватого відтінку.

Спосіб життя

Полюбляє посушливі, напівпустельні місцини. Доволі потайлива амфібія. активна виключно вночі або після дощу. Велику частину часу проводить зарившись у землю. Живиться комахами, іншими безхребетними.

Розмножуються у травні-серпні, після дощів, у тимчасових водоймах. Крики самців короткі, нагадують крики качок. Самиця відкладає у кладку від 10 до 250 ікринок, прикріплюючи її до водних рослин в декількох сантиметрах від поверхні. Пуголовки завдовжки до 7 см з'являються з ікри через 48 годин і розвиваються протягом 21—40 днів. Пуголовки хижі, можуть поїдати пуголовок інших видів або навіть молодих жаб. Їх ротовий апарат влаштований так, що вони мають дзьобоподібний виступ на верхній щелепі та виїмку на нижній.

Розповсюдження

Мешкає у провінціях Альберта, Саскачеван (Канада), штатах Аризона, Арканзас, Колорадо, Айова, Міссурі, Монтана, Техас (США), Чіуауа і Тамауліпас (Мексика).

Джерела

• http://amphibiaweb.org/cgi/amphib_query?query_src=aw_lists_genera_&where-genus=Spea&where-species=bombifrons

Равнинный лопатоног (лат. Spea bombifrons) — вид бесхвостых земноводных (Anura).

Общая длина достигает 3—4 см. Наблюдается половой диморфизм — самки крупнее самцов. Голова и туловище довольно широкие и массивные. Глаза с вертикальными зрачками. Имеет ороговевшие выросты с острыми краями на задних лапах — «лопаты», которыми может быстро рыть землю, зарываясь в мягкий грунт за несколько секунд. Кожа относительно сухая, с бородавками. На лбу между глаз расположен костяной бугорок, размером 3—5 см.

Окраска колеблется от коричневого до серого с точечками зелёного цвета. Вдоль спины и по бокам проходят 4 размытые полоски. На брюшке кожа белая, без пятен. У самцов горло по бокам синеватого или сероватого оттенка.

Любит засушливые, полупустынные места. Довольно скрытное земноводное. Активен исключительно ночью или после дождя. Большую часть времени проводит зарывшись в землю. Питается насекомыми, другими беспозвоночными.

Специальным устройством для всасывания воды из чуть влажной почвы (водозаборником) является так называемое «тазовое пятно», пронизанное кровеносными сосудами. У юных норных лопатоногов, американских родственников наших чесночниц, такое тазовое пятно совсем маленькое и занимает всего 5 % всей поверхности тела. Однако его всасывающая способность в 18 раз выше, чем у остальной кожи. Благодаря такому «водозаборному устройству» лопатоноги способны охотиться днем во время летней жары. Сидя на чуть влажной земле, они всасывают такое же количество воды, какое испаряет остальная часть их тела.

Размножаются в мае-августе, после дождей, во временных водоёмах. Крики самцов короткие, напоминают крики уток. Самка откладывает в кладку от 10 до 250 икринок, прикрепляя её к водным растениям в нескольких сантиметрах от поверхности. Головастики длиной до 7 см появляются из икры через 48 часов и развиваются в течение 21—40 дней. Головастики хищные, могут поедать головастиков других видов или даже молодых лягушек. Их ротовой аппарат имеет клювовидный выступ на верхней челюсти и выемку на нижней.

Вид распространён в Канаде (провинции Альберта, Саскачеван), США (штаты Аризона, Арканзас, Колорадо, Айова, Миссури, Монтана, Техас) и Мексике (Чиуауа и Тамаулипас).