Desert Toads and How They Live - New Hampshire Public Television
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Desert Toads and How They Live Synopsis The scenic beauty of Arizona's Sonoran Desert is the setting for this look at life cycle of the spadefoot toad. Here, in midsummer, the daytime temperature can reach 113 degrees Fahrenheit in the shade; the surface of the ground can become as hot as 140 degrees F. The heat and lack of water make it difficult for humans to live in this harsh environment, but many animals are well adapted to life in the Sonoran Desert. Among them is the spadefoot toad. For 10 months of the year the spadefoot toad hibernates a foot or so beneath the desert surface. When the summer rains begin, the toad digs its way out of the ground to start its two months of active life. In this short period of time, desert toads must mate, then constantly eat to prepare for their next hibernation. The toads' develop- ing young also must race against time because the pools of water where they grow, will evap- orate quickly under the fierce desert sun. Tadpole eggs hatch within a day and metamor- phosize into young adults within a week. These and other unique behaviors of the spadefoot toad are explored in this fascinating program. Questions to Ask Before Viewing • Have you ever visited a desert in the southwestern United States? What types of plants and animals can be found in the desert? • Because of the lack of cloud cover, the desert is very hot during the day and cold at night. How do you think these variations in temperature affect animals that live in the desert? • How often does it rain in the desert? • In what ways do you think infrequent rain might affect the plants and animals that make the desert their home? Questions to Ask After Viewing 1. Desert toads are amphibians. What is an amphibian? (Amphibians are a class of vertebrates that spend part of their life in water and part on land. The word amphibian literally means "double life.") 2. Toads like other amphibians, are ectothermic. What does that term mean? (It means they are cold-blooded -- their body temperature stays about the same as the temperature of their surroundings.) 3. Spadefoot toads are also nocturnal-they come out only at night. What is the reason for this? (They need to avoid the searing heat of the desert sun so they can keep cool and retain water.) 4. How much of the year does the desert toad spend hibernating in its burrow? (Ten months.) 5. When does the desert toad surface? (For two months during the summer rains.) 6. How are the toads awakened from their hibernation? By the vibrations of the rain pounding on the soil. Their biological clocks allow them to be awakened by summer rains, but sleep right through winter storms.) 7. What adaptation allows the spadefoot to dig its way through the soil to the surface of the desert? (The toad has a small, hard, crescent-shaped growth on the side of each hind foot, which gives it its name.) 8. The spadefoot toads emerging from hibernation must immediately do two things. What are they? (They must find a mate and they must regain their energy by eating.) 9. Male toads immediately head for the shallow pools of water formed by rain. How do the makes attract their mates? (they begin to call as soon as they reach the water. The sound can be heard for miles.) 10. Where do the spadefoot toads mate and the female toad lay their eggs? (They mate underwater and the eggs are laid in small clusters on a rock, twig, or vegetation submerged under the water. The male toad immediately fertilizes the eggs.) 11. How many eggs does the female lay? (Approximately 4,000.) 12. When does the mating take place? (During the first night after the toads emerge from hibernation. After mating, the adult toads leave the water and begin to search for food.) 13. Review the definition of "metamorphosis." (Metamorphosis is the transformation of body structure as some animals develop from egg to adult.) 14. What type of metamorphosis do toads experience? (An incomplete metamorphosis consisting of egg, tadpole, and adult stages.) 15. The spadefoot toad's survival depends on rapid development. How long does it take the eggs to hatch in the warm water? (Less than 24 hours.) 16. How much time does it take the tadpoles to become young adults? (About seven days.) 17. Why does the program call the spadefoot toads' mating process a "race against time?" (Because there is a very brief period-about ten days before the water pools evaporate-for the adults to mate and lay eggs, for the eggs to hatch into tadpoles, and for the tadpoles to develop into young adults able to live on land.) 18. The program refers to tadpoles as "eating machines." How are their bodies adapted to carry on so much eating? (Their mouths have several rows of fine, comb-like teeth that filter out tiny particles of food from the water.) 19. What do tadpoles eat? (They eat mostly algae.)
Transcript of Desert Toads and How They Live - New Hampshire Public Television
Desert Toads and How They Live
Synopsis The scenic beauty of Arizona's Sonoran Desert is the setting for this look at life cycle of the spadefoot toad. Here, in midsummer, the daytime temperature can reach 113 degrees Fahrenheit in the shade; the surface of the ground can become as hot as 140 degrees F.The heat and lack of water make it difficult for humans to live in this harsh environment, but many animals are well adapted to life in the Sonoran Desert. Among them is the spadefoot toad. For 10 months of the year the spadefoot toad hibernates a foot or so beneath the desert surface. When the summer rains begin, the toad digs its way out of the ground to start its two months of active life. In this short period of time, deserttoads must mate, then constantly eat to prepare for their next hibernation. The toads' develop-ing young also must race against time because the pools of water where they grow, will evap-orate quickly under the fierce desert sun. Tadpole eggs hatch within a day and metamor-phosize into young adults within a week. These and other unique behaviors of the spadefoot toad are explored in this fascinating program.
Questions to Ask Before Viewing • Have you ever visited a desert in the
southwestern United States? What types of plants and animals can be found in the desert?
• Because of the lack of cloud cover, the desert is very hot during the day and cold at night. How do you think these variations in temperature affect animals that live in the desert?
• How often does it rain in the desert? • In what ways do you think infrequent rain
might affect the plants and animals that make the desert their home?
Questions to Ask After Viewing 1. Desert toads are amphibians. What is
an amphibian? (Amphibians are a class of vertebrates that spend part of their life in water and part on land. The word amphibian literally means "double life.")
2. Toads like other amphibians, are ectothermic. What does that term mean? (It means they are cold-blooded -- their body temperature stays about the same as the temperature of their surroundings.)
3. Spadefoot toads are also nocturnal-they come out only at night. What is the reason for this? (They need to avoid the searing heat of the desert sun so they can keep cool and retain water.)
4. How much of the year does the desert toad spend hibernating in its burrow? (Ten months.)
5. When does the desert toad surface? (For two months during the summer rains.)
6. How are the toads awakened from their hibernation? By the vibrations of the rain pounding on the soil. Their biological clocks allow them to be awakened by summer rains, but sleep right through winter storms.)
7. What adaptation allows the spadefoot to dig its way through the soil to the surface of the desert? (The toad has a small, hard, crescent-shaped growth on the side of each hind foot, which gives it its name.)
8. The spadefoot toads emerging from hibernation must immediately do two things. What are they? (They must find a mate and they must regain their energy by eating.)
9. Male toads immediately head for the shallow pools of water formed by rain. How do the makes attract their mates? (they begin to call as soon as they reach the water. The sound can be heard for miles.)
10. Where do the spadefoot toads mate and the female toad lay their eggs? (They mate underwater and the eggs are laid in small clusters on a rock, twig, or vegetation submerged under the water. The male toad immediately fertilizes the eggs.)
11. How many eggs does the female lay? (Approximately 4,000.)
12. When does the mating take place? (During the first night after the toads emerge from hibernation. After mating, the adult toads leave the water and begin to search for food.)
13. Review the definition of "metamorphosis." (Metamorphosis is the transformation of body structure as some animals develop from egg to adult.)
14. What type of metamorphosis do toads experience? (An incomplete metamorphosis consisting of egg, tadpole, and adult stages.)
15. The spadefoot toad's survival depends on rapid development. How long does it take the eggs to hatch in the warm water? (Less than 24 hours.)
16. How much time does it take the tadpoles to become young adults? (About seven days.)
17. Why does the program call the spadefoot toads' mating process a "race against time?" (Because there is a very brief period-about ten days before the water pools evaporate-for the adults to mate and lay eggs, for the eggs to hatch into tadpoles, and for the tadpoles to develop into young adults able to live on land.)
18. The program refers to tadpoles as "eating machines." How are their bodies adapted to carry on so much eating? (Their mouths have several rows of fine, comb-like teeth that filter out tiny particles of food from the water.)
19. What do tadpoles eat? (They eat mostly algae.)
20. How do they breathe? (Through gills.) 21. What other animals can be found in the
pools of water formed by the rain? (Tiny freshwater shrimp and beetles.)
22. What predator is a danger to the developing tadpoles? (Beetle larvae, which eat both shrimp and tadpoles.)
23. As the puddles begin to evaporate, there may be too many tadpoles for the amounts of water, oxygen and food that is left. In what way do tadpoles ensure their survival? (Some tadpoles-particularly those that feed on freshwater shrimp-develop much larger heads and mouths than the others. They survive through cannibalism, by eating smaller tadpoles.)
24. Not all tadpoles are able to complete their metamorphosis before the water dries up completely. What happens to them? (Exposes to the sun, they die. Their bodies will form a sort of fertilizer for the algae that appear during the next rainy season.)
25. Why must adult toads eat constantly during their two months of active life? (Because when the rainy season is over, they must be able to survive on their reserve of body fat. During hibernation, a toad loses up to 50 percent of its body weight.)
26. Desert toads are carnivores, or meat eaters. What to toads prey on? (Beetles, insect larvae, grasshoppers and crickets.)
27. What are the adult toads' enemies? (Anything larger than themselves-snakes, lizards, birds.)
28. Of the 4,000 eggs laid by the female toad, how many will survive to adulthood? (About four. Of those, only two or three will reach sexual maturity in four years time.)
Related Titles in the AIMS Collection 9984 Frogs and How They Live 8270 Newts and How They Live Length • 16 minutes Subject Area • Life Science Audience Levels • Intermediate-Adult Catalog Number • 8478 Annotation A look at the life cycle and behaviors of thespadefoot toad and the ways it has adapted to life in Arizona's Sonoran Desert. Produced by Telepool.
AIMS Multimedia
9710 De Soto Avenue Chatsworth, CA 91311
(818) 773-4300 www.aimsmultimedia.com
Discussion Guide _____________________________________ Desert Toads and How They Live
Objectives • To explore he life cycle and behaviors
of the spadefoot toad of the American Southwest.
• To explain the ways that desert toads have adapted to their environment.
• To present other forms of plant and animal life that thrive in the Sonoran Desert.
