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Daily Classroom Special
Critter Corner: Meet the Cane Toad  
About this Daily Classroom Special
Critter Corner allows teachers and students to learn and share experiences about organisms that can be kept in the classroom. Critter Corner is maintained by Judith Jones, teacher at East Chapel Hill High School (NC) and Teachers Network web mentor. E-mail Judith. Make sure to visit Judy's other Daily Classroom Special, The Time Travel Interviews with Famous Scientists

To the Critter Corner Directory.

Introduction

Cane Toad Several years ago, I received an odd little catalog in my mail, and in a moment of curiosity, I browsed through it. I came across an advertisement for a video called "CANE TOADS: An Unnatural History." The video was touted as the "Monty Python of Nature Videos." Always on the alert for anything that would excite my students' interest, I sent off for it. In previewing the video at home, I was charmed and found myself laughing often at the wonderful humanity of my own species as well as realizing that there was a true biological message about the hazards of introducing species into non-native environments. It seems that Australian officials decided to introduce Cane Toads (Bufo marinus ) into Queensland and the eastern part of their country island, hoping that the amphibians would eat the larvae of the cane beetle that was threatening the sugar cane crops. Of course, the toads never did much damage to the larvae but have adapted beautifully to the eastern Australia environment, eating anything else that they can snap up, including "Whiskas" cat food that devoted human followers put out for them! The video highlights the biological problem as well as the personalities of the delightful people who interact with the giant toad.

A couple of years later, I discovered the Carolina Biological Supply Company in Burlington, NC, sells Cane Toads and I ordered some for my classroom zoo so that my students can actually observe and touch these fascinating creatures. It makes the video even more interesting to have the actual "stars" on site. Over the years, the video has become so beloved by our biology students that their younger brothers and sisters enter our classes asking when they will see it. Two years ago, a clip even appeared in our famous yearbook slide show at the end of the year. The students were laughing hard while the non-science teachers were befuddled!

Since that first encounter with a crazy little catalog and my purchase of the video, I have discovered much about Bufo marinus. I have talked to people from Australia at conferences and I have received information from as far away as Hawaii. The Cane Toads were brought from Hawaii to Australia, but a friend of mine, who teaches in Hawaii, said that they are not native to Hawaii, either - hence a mystery. Where the heck are they from?

Scientific Name

Bufo marinus is the scientific name of the Cane, Marine, or Giant Neotropical Toad. These toads belong to the family Bufonidae. The genus Bufo includes the "true toads." In Hawaii the toad is called "Poloka."

General Physical Description

Cane Toads can reach nearly ten inches in length (snout to vent) and weigh almost three and a half pounds. However, on the average they range from four to sevem inches and only reach record sizes in the most tropical environments. Females tend to be larger than males! Cane Toads are big, brown toads with deeply pitted glands extending down the sides of the body. Cane Toads are very fat-bodied with thick skin and the typical "warts" of true toads. Their legs are relatively short.

Behavior

Toads in general give off gland secretions that can be very irritating to mucous membranes and Cane Toads are no exception. Bufo marinus gives off a chemical called bufotenine that is highly toxic. In Australia, this toxic has killed many a predator that has tried to eat the Cane Toad. This chemical is highly toxic to humans. Consult the appropriate emergency medical professionals if you cme in contact with this secretion. However, in general, very few people have died from Cane Toads. They can be handled gently. If they are highly disturbed, they can actually shoot their venom and it will cause great pain and temporary blindness if it gets into one's eyes. Generally, humans are quite safe unless they try to eat a Cane Toad. (I have personally never been tempted!) In the wild, they are nocturnal. They will avoid the sun since it dries out their skin, although they can successfully "collapse" their bodies when they are deprived of water. The male has a loud flute-like call. In many parts of the world where they have been introduced, they have been adopted as pets and will eat cat and dog food out of dishes; they will even eat out of people's hands. They will also eat live mice and some have even attempted to eat ping-pong balls as they go bouncing by (although this is not a recommended dietary addition!). Cane Toads will even eat each other on occasion.

Reproduction

These amazing toads will breed all year long in the tropical climates that they prefer. They plant long black strings of eggs in still water (irrigation ditches, canals, streams, ponds, reservoirs, and fishponds). In one year, a single pair of Cane Toads can plant 60,000 eggs. Fortunately, very few of these will reach adulthood. However, they have been very successful in northeastern Australia and it is estimated that there is at least one Cane Toad per square yard in that region! In 1932 about 150 toads were introduced into two small areas of Hawaii. The toads were so successful that in a little over two years, there were about 100,000 toads available for distributing into other parts of Hawaii. To reproduce, the males will enter the still water in the early evening and begin their "diesel engine" trilling to attract females. Apparently, it works. When the female appears the male will grasp her in what is called "amplexus." He grasps her from behind around the chest. She will then release into the water thousands of eggs attached to each other in a string. The male externally fertilizes the eggs as they are released. The eggs hatch after a few days into tiny dark tadpoles. The tadpoles eat algae and other small plant life. After about a month, the tadpoles go through metamorphosis; they develop hind legs, then fore legs; the mouth enlarges and goes from a mouth that can scrape algae to a mouth that can grab insects. Gills change into lungs and the tail is reabsorbed. Only a few of the small toads will survive to adulthood.

Classroom Habitat and Food

I keep my Cane Toads in a large aquarium that has bark on the bottom that they can burrow into. I put a large shallow dish full of water at one end of the aquarium. The Carolina Biological Supply Company recommends using an inclined tank with water in one end or a "semiaquatic terrarium." I add plants for the toads to hide under - and because it makes the terrarium look nice! The water will need to be changed frequently! I feed my toads crickets and mealworms. I buy the large mealworms - they are big and squishy; the toads love 'em. They can certainly eat other soft bodied insects. I even give my Cane Toads "pinkie" or new born mice on occasion. You can "dust" the food with pet vitamins to keep your Cane Toads in tip top shape. I usually feed them about three times a week, but I give my two toads a few dozen large crickets or meal worms each time.

Native Habitat and Role in the Environment and Folklore

Cane Toads are actually native to Mexico and Central and South America. They have been introduced into Puerto Rico, Hawaii, Australia, and Florida to name a few places. They can also be found in areas around the Rio Grande. In most cases they were introduced by farmers to eat the sugar cane beetle and its larvae. They prefer to live in land areas with lots of hiding places that are close to still water for breeding. Generally, they only enter the water after dark. They will actually range over fairly large areas eating insects, larvae, worms, spiders, slugs, and even small mammals. They like to live in well-watered gardens and have adapted very well to human encroachment!

Handling Tips

The Cane Toads can be safely handled if you are gentle. You have to be careful not to drop them. I always make sure that students wash their hands afterwards. If the toads secrete too much of their toxin it could cause a burning sensation. In Australia, children play with them out in gardens and there have not been serious effects. However, dogs that grab them and chew on them can die! The message here is "touch but don't bite!"

 

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