Couch’s Spadefoot Toad, Scaphiopus Couchii

The Couch’s Spadefoot Toad, Scaphiopus couchii, is a species of North American spade foot toad. The specific nickname couchii honors an American naturalist Darius Nash Couch, who gathered the first specimen while on a personal expedition to northern Mexico to collect mineral, plant, and animal specimens for the Smithsonian Institution.

It is endemic to the southwestern United States, the Baja Peninsula, and northern Mexico. They can be found throughout the Sonoran Desert, which consists of parts of southern Arizona and California.

Unlike other toads which have horizontal pupils, spade foot toads have pupils that are vertical. On the underside of the hind foot is a hard and dark “spade” that provides spade foot toads their name. These creatures have the potential to grow to be about 3.5 inches long. These toads utilize these “spades” to burrow into the ground to avoid loss of water and to hide from predators. Currently, there are two spade foot species within the Sonoran Desert of Arizona and California. Couch’s Spadefoot Toad has a sickle-shaped “spade”, whereas the western Spadefoot Toad, Spea hammondii, has a rounded “spade”. These spade foots aren’t true toads and should therefore, merely be called spade foots.

Water is an essential medium for the fertilization of spade foot eggs, and as soon as the eggs hatch, water also offers a place for the tadpoles to mature to the adult stage. Due to the significance of water, spade foots are active during the wet season, which is the spring and summer in the Northern Hemisphere, and stay underground during the dry season, which is the fall and the winter. When a thunderstorm arrives, the male toads come up from underground and search for rainwater pools. When they do find water, the male toads produce a mating call that attracts the female toads. Due to the pools of water possibly being short-lived, the mating process occurs the first night after the rainfall begins.

During reproduction, the male mounts the female and releases his sperm to fertilize her eggs, which are deposited into the pools of water in the form of a floating mass. The eggs hatch into tadpoles, which rapidly mature into adults. They need to reach this stage before the pool of water evaporates and, therefore, sometimes mature in as little as nine days after the eggs are laid. The western spade foot toad takes at least three weeks to mature.

The minute pools of water get warmed by the sun, which hurries the growth of the tadpoles. These tadpoles will consume a variety of foods, such as small insects found near the pool and algae, which they scrape off of the rocks. They filter microorganisms from the water as it passes over their gills as well. They gather in wriggling conglomerations, stir up the muck located on the bottom of the pool, and filter out the organic nutrients. Unlike the majority of tadpoles, which are entirely herbivores and filter feeders, the spade foot tadpoles are omnivores. Additionally, they consume dead insects and tadpoles along with fairy shrimp.

Image Caption: Couch’s Spadefoot Toad (Scaphiopus couchii), Amistad National Recreational Area, Del Rio, Texas, USA. Credit: Clinton & Charles Robertson/Wikipedia (CC BY-SA 2.0)