The Plains Spadefoot Toad (Spea bombifrons) is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of spadefoot toad

Spadefoot Toad

Spadefoot refers to the following toads:* Scaphiopodidae - American spadefoot toads* Pelobates - European spadefoot toads* Notaden - genus that includes Australian spadefoot...

 which ranges from southwestern Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, throughout the Great Plains

Great Plains

The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...

 of the western United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, and into northern Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

. Like other species of spadefoot toad, they get their name from a spade

Spade

A spade is a tool designed primarily for the purpose of digging or removing earth. Early spades were made of riven wood. After the art of metalworking was discovered, spades were made with sharper tips of metal. Before the advent of metal spades manual labor was less efficient at moving earth,...

-like projection on their hind legs which allows them to dig into sandy soils.

Description

The Plains Spadefoot Toad generally grows from 1.5 to 2.5 inches in length, has a round body, with relatively short legs. These toads are usually a tanish to dark brownish color with visible orange spots. They are one of the easiest toads to recognize in their region because of their appearance looking more like a frog. Sometimes they have light striping on their back.

Behavior

Plains Spadefoot Toads are nocturnal

Nocturnal animal

Nocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....

, and secretive. They spend most of the dryer seasons buried in the soil in estivation

Estivation

Aestivation is a state of animal dormancy, characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions...

, typically only emerging during spring and fall rains. Breeding takes place in temporary pools of water left by rainfall, which requires the tadpole

Tadpole

A tadpole or polliwog is the wholly aquatic larval stage in the life cycle of an amphibian, particularly that of a frog or toad.- Appellation :...

s to metamorphose quickly, before the water dries up. Eggs

Egg (biology)

An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

, laid in clutches numbering from 10-250, often hatch within 48 hours of being laid, and the larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e can change into toadlets in as little as two weeks. The tadpoles exhibit phenotypic plasticity

Phenotypic plasticity

Phenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. Such plasticity in some cases expresses as several highly morphologically distinct results; in other cases, a continuous norm of reaction describes the functional interrelationship...

, with some tadpoles changing from an omnivorous morphology into a cannibalistic carnivorous morph with oversized jaw muscles and a pronged beak. A recent study has shown that in some cases female spadefoot toads will choose to mate with Spea multiplicata

Spea multiplicata

The New Mexico Spadefoot Toad is a species of American spadefoot toad found in the southwestern United States and Mexico. Like other species of spadefoot toad, they get their name from a distinctive spade-like projections on their hind legs which enable them to dig in sandy soils...

rather than with males of their own species, if the resulting hybrid tadpole would have higher chances of survival. Character displacement

Character displacement

Character displacement refers to the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur but are minimized or lost where the species’ distributions do not overlap. This pattern results from evolutionary...

has also been examined in ponds where Spea bombifrons and Spea multiplicata occur together. Researchers found that reproductive and ecological competition between the two species likely causes selection for smaller and less reproductively successful individuals of Spea multiplicata.