Couch's Spadefoot Toad

Couch's Spadefoot Toad
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Amphibia
Order:	Anura
Suborder:	Mesobatrachia
Family:	Scaphiopodidae
Genus:	Scaphiopus
Species:	S. couchii
Binomial name
Scaphiopus couchii Baird, 1854

Couch's Spadefoot Toad (Scaphiopus couchii) is a species of North American spadefoot toad. The epithet couchii is in honor of American naturalist Darius Nash Couch, who collected the first specimen while on a personal expedition to northern Mexico to collect plant, mineral and animal specimens for the Smithsonian Institution.^[1]

Distribution

Couch's Spadefoot Toad is native to the southwestern United States, northern Mexico, and the Baja peninsula. They can be found throughout the Sonoran Desert, which includes parts of southern Arizona and California.

Physical description

Unlike other toads which have horizontal pupils, spadefoot toads have vertical pupils. On the underside of the hind foot, there is a hard, dark "spade" that gives spadefoot toads their name. These creatures can get to be 24" in length. These "spades" are used by the toads to burrow into the ground to prevent water loss and hide from predators. There are two spadefoot species in the Sonoran Desert of Arizona and California. Couch's Spadefoot toad (Scaphiopus couchi) has a sickleshaped "spade", whereas the Western spadefoot toad (Spea hammondii) has a rounded "spade". Spadefoots are not true toads and should therefore simply be called spadefoots.^[2]

Mating and reproduction

Water is a necessary medium for the fertilization of spadefoot eggs, and once the eggs hatch, water also provides a place for tadpoles to mature to the adult stage. Because of the importance of water, spadefoots are active during the wet season (spring and summer in the northern hemisphere), and remain underground during the dry season (fall and winter). When a summer thunderstorm arrives, the male toads emerge from underground and look for pools of rainwater. When they find water, the males produce a mating call that attracts female toads. Because the pools of water may be short-lived, mating occurs the first night after rainfall begins.

During reproduction, the male mounts the female and releases sperm to fertilize the eggs, which are deposited in the pools of water in the form of a floating mass. The eggs hatch into tadpoles, which quickly mature into adult toadlets. They must reach the toadlet stage before the pool of water evaporates, and thus they sometimes mature in as little as nine days after the eggs are laid. Western spadefoot toads take longer to mature (at least three weeks).

The small pools of water are warmed by the sun, which speeds up the growth of the tadpoles. Tadpoles will eat a variety of foods, such as small insects nearby the pool and algae, which they scrape off rocks. They also filter microorganisms from the water as it is passed over their gills. Tadpoles gather in wriggling masses, stir up the muck on the bottom of the pool, and filter out the organic nutrients. Unlike most tadpoles, which are exclusively herbivores and filter feeders, spadefoot tadpoles are omnivores. They also eat dead insects and tadpoles, as well as fairy shrimp.

Western spadefoots are known for more aggressive cannibalism. If the pool is crowded and prey is abundant, a few of the tadpoles change into oversized, voracious carnivores which will eat other tadpoles. They prefer different species, but will eat their own if necessary for survival.

References

1. ^ Ellin Beltz: Scientific and Common Names of the Reptiles and Amphibians of North America - Explained, http://ebeltz.net/herps/biogappx.html, January 15, 2007.
2. ^ Arizona-Sonora Desert Museum: Couch’s spadefoot (Scaphiopus couchi), http://www.desertmuseum.org/books/nhsd_spadefoot.php, 2006-2010.

Offsite Links

• Santos-Barrera & Hammerson (2004). Scaphiopus couchii. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 09 May 2006. Database entry includes a range map and justification for why this species is of least concern
• Animal Diversity Web: Scaphiopus couchii