Monday, August 19, 2013
Sonoran Desert Toad
The monsoon is in full swing and one of the interesting creatures who makes an appearance during this season is the Sonoran Desert Toad.. If you live in the Sonoran Desert, you may be hearing them, especially on rainy nights. The Sonoran Desert toad is Arizona’s largest toad, growing to 7.5” or more in length and is a common, nocturnal visitor to yards near water or natural desert vegetation. They emerge after the summer rains to feed and breed in large, temporary rain pools. During the rest of the year, the toads hibernate underground.
Sonoran Desert Toads are olive green to brown in color and have lumpy skin, large glandular lumps on their hind legs, golden eyes with horizontally elliptical pupils, large, poison-filled parotoid glands behind their eye and tympanum, and one or more distinctive white tubercles at the corners of their mouth. The diet consists of just about anything that moves and will fit into their mouths, including insects, centipedes, spiders, lizards, mice and other amphibians.
Occurring across southern Arizona, this toad is absent from the higher mountains and from the arid, western desert valleys. Although also known as the Colorado River Toad, its populations are declining around the Colorado River, and it is believed that they no longer exist on the California side of the river. The habitat of the Sonoran Desert toad includes semi-desert grasslands, oak woodlands, creosote bush desertscrub, valley bottoms and lower elevations hills. In the western portion of its range, the species becomes increasingly tied to permanent water, such as rivers or the edges of agriculture.
Most Sonoran Desert toads are found at night during the monsoon season, but they may emerge a month or more before the summer rains begin, particularly in areas of permanent water (such as the mountain lion enclosure!). Breeding generally occurs on one night within a couple of days of a rainfall event of more than one inch. At permanent water areas, breeding may be independent of rainfall. They may breed in cattle tanks, reservoirs, backwaters and ponds. Males may call for females from the water or actively search for females. Sonoran Desert Toad (Incilius alvarius) Call Females deposit long stringers of up to 8000 eggs in shallow water. Tadpoles typically metamorphose in a month or two. The toads live at least 10 years, and possibly as long as 20 years.
The defensive toxins released from several glands in the skin are extremely potent. Animals that harass the toad are intoxicated through the mouth, nose or eyes. The toxin is strong enough to kill full-grown dogs that pick or mouth the toads. Symptoms include excessive salivation, head shaking, irregular heartbeat and gait, and pawing at the mouth. The toxins are also hallucinogenic and poisonous to humans.