DESERT TORTOISE 3 rd Grade

Transcription

1 TIME/AIDS INTRODUCTION 5 minutes General Background Map Flip chart 10 minutes Tortoise Background 5 minutes Description of Life Cycle Ping pong ball Pokey-Mon ball 10 minutes Become a Tortoise Activity 15 minutes CONTENT Introduce yourself and welcome students to the Desert Discovery Center. Give some background on the partnership and the Jr. Naturalist program. Show them the coyote sign for being quiet. Explain what the BLM is and their role. Introduce the Mojave Desert conditions dry, little rain fall, windy, intense sunlight. Tortoises are a type of reptile. Other reptiles include lizards and snakes. Reptiles have scaly skin; most lay eggs, and are cold blooded. The tortoise life began when his mother used her hind legs to dig a hole (nest) in the ground and lay several eggs (1-14). The egg is the size of a ping pong ball. Two to four months go by while the tortoise grows big and strong. Finally, they hatch and are the size of a silver dollar. They have to be careful since their shell is still soft and the mother is not around to protect them. Ask for a volunteer to come up and become the tortoise. Begin with the shell what is an advantage/disadvantage of a shell to the tortoise? Explain the shape, each of the three parts, number of large scutes on the carapace, the color of the shell, and the use of the gular horn. (revised Aug. 2007) 1

2 Tortoise Temperature Activity (step 1) Colored dots Clip board w/ pencil Instruction chart Paper tortoise w/thermometer (15 minutes) Needs of a Tortoise 10 minutes Seasonal Behavior Traits 15 minutes Tortoise Temperature Activity (step 2) White board 15 minutes Tortoise Etiquette Tortoise Trouble Game Tortoise pledge cards 20 minutes Children will separate into 6 groups each color coordinated. They will be given a clip board and a paper tortoise. Instruct the students to record the present temperature on the instruction chart and place the tortoise outside according to their given location. After the tortoises are in place students will return to their carpets for the following topics. Discuss the needs of a tortoise such as their food, water conservation, and burrows. Describe the following: brumation--one way the tortoise escapes the cool temperatures and survives the winter with little or no food; aestivation the tortoise goes underground to conserve energy and water during the hottest and driest part of the season; emergence when the above temperatures permit the tortoise to move, they will walk out of their burrows. Take kids outside to show them the burrows and have them collect their paper tortoises and record temperature. Record results on white board so students can see the various temperatures Explain what to do if you find a tortoise in the wild and what to do if you find a tortoise in the city. Explain some of the hazards that tortoise face concerning ravens, OHVs, and released domestic tortoises. (revised Aug. 2007) 2

3 General Background DESERT TORTOISE 1. How many of you know what the BLM stands for? The BLM (Bureau of Land Management) is an agency of the US Department of the Interior that was established in 1946 and is responsible for 270 million acres of public land nationwide nearly one-eighth of all the land in the United States. 2. What is public land? Public land: undeveloped land with no improvements, mostly land that has never been in private ownership. Back in the early 19 th century, during the western expansion, the Federal government assumed responsibility for the protection and use of public lands. (This can be compared to a playground supervisor, also think about what the playground would be like without supervision!!) The mission of the BLM is to sustain the health, diversity, and productivity of the public lands for the use and enjoyment of present and future generations. Some of the things we manage are: Wild Horse and Burro Minerals Range Recreation Cultural Fire Management Soil, Water, and Air Lands and Realty Wilderness Wildlife Today we are going to talk about the land the Barstow Field Office manages. 3. Who can tell me what desert we live in? We live in the Mojave Desert--one of 4 deserts in North America. The Mojave Desert is the smallest and driest of the 4 only 25,000 square miles. 4. Why do they call the Mojave Desert dry? The rain that occurs is irregular, usually less than 5 inches per year. Some areas of the Mojave have gone 767 days (almost 2 ½ years) without rainfall! In the (revised Aug. 2007) 3

4 summer temperatures can exceed 120 degrees Fahrenheit and in the winter we may have freezing temperatures with frost and snow. That is called extreme temperatures. The wind and intense sunlight also contribute to the dry desert conditions. One of the animals, which made the Mojave Desert its home for thousands of years, is the desert tortoise. Some scientists say that the tortoise is the oldest living creature on earth. According to fossils (remains or evidence of prehistoric plant and animal life), the Desert tortoise is one of four tortoise species that have remained virtually unchanged for 30 million years. Scientists say that turtles survived the mass extinction of dinosaurs and its present form has thrived for approximately 150 million years. This is three times longer than modern mammals and 3000 times longer than modern man. Tortoise Background 5. What type of animal is a desert tortoise? Tortoises are a type of reptile. Other reptiles include lizards and snakes like the kind you see in our display case. Reptiles have scaly skin; most lay eggs, and are cold blooded. 6. What is the difference between a cold-blooded animal and a warmblooded animal? Cold-blooded, or ectothermic animals depend on heat from outside their bodies (unlike mammals and birds that generate their own heat), so they must rely on an external energy source (the sun) to keep them warm to survive. When you see reptiles in the sun they are not trying to get a suntan but warming their bodies. The tortoise is most comfortable when its body temperature is between approximately 85 and 95 degrees. 7. Is a tortoise a turtle? Yes, but not all turtles are tortoises. When we think of turtles, the first thing that comes to mind is a turtle spending its time sun bathing next to a pond. But, there aren t many ponds in the desert and the tortoise doesn t know how to swim. The tortoise is a land dwelling turtle and only goes to the water to drink. The desert tortoise is not green, like so many cartoons depict turtles, but vary in colors ranging from light tan to yellow-brown to black all of which blend in to the desert environment. (revised Aug. 2007) 4

5 Description of Life Cycle 8. Where do tortoises come from? Life for a tortoise begins when his mother uses her hind legs to dig a hole (nest) in the ground and lays several eggs (1-14) in early spring. The eggs are the size of a ping pong ball (show tortoise egg & ping pong ball). Two to four months go by and the tortoise grows big and strong inside the egg. Finally, the tortoise is ready to face the outside world (in late summer). The size of a silver dollar, the tortoise has to be careful since his shell is still soft (like a baby s head after birth) and his mother is not around to protect him. Once a tortoise emerges from the shell they are independent and live solitary lives except during mating season. Maturity does not occur until around age 15 or older in the wild. 9. How can a tortoise fit inside of a small, round shell? Show Pokey-Mon toy and explain how the hatchling folds into the shell. Because of the soft flexibility of the shell, it can grow and fit into a circular shape even though it begins to harden once it emerges. 10. What do you think some of the dangers of having a soft-shell are? A soft-shelled tortoise makes a great lunch for ravens, coyotes, bobcats, and badgers. It is known in the tortoise world that only one to five out of every 100 hatchlings will survive to be an adult. If they make it, a tortoise may live to be about 60 to 100 years old. Eventually, when they are about 5 years old, their shells harden as more and more bone is formed underneath the scutes and his shell can be a defense against predators while outside his burrow. Become a Tortoise Activity 11. What is an advantage/disadvantage of a shell to the Desert Tortoise? The shell is composed of living bone tissue covered with nonliving horny plates called scutes (much like our finger nails). The shell has three basic parts: the plastron on the underside, the carapace covering the back with 13 large scutes arranged in a pattern on the top of the carapace; and the bony bridges that connect the plastron and carapace. Smaller scutes rim the perimeter of the carapace. Advantages of the shell are that it provides protection from predators. A disadvantage is that it slows the tortoise down and is sometimes difficult to maneuver. (revised Aug. 2007) 5

6 12. Do tortoises have teeth? DESERT TORTOISE Tortoises only have one tooth in the embryo-state and a horny beak like a bird eventually replaces it. The egg tooth is used to break out of the shell. 13. How can you tell the difference between a male and a female tortoise? Both the male and female have a gular horn located on the front of the plastron. The horn is longer in the male and often upturned. Males use these in fighting with other males throughout the year and many times can flip the other male on its back. The opponent attempts to stand as high as possible to prevent this from happening. You can also tell a male tortoise by the concave shape of the plastron. 14. How do the tortoise s flat scales on the forelegs serve the tortoise? The scales help reduce injury. Share a dog story. 15. What do you suppose the tortoise uses his long nails for? The long toenails act as tiny shovels for digging. Strong hind legs with their long nails facilitate the tortoise in digging nests and burrows in the dry, sandy soil. (Tortoise Temperature Activity) Needs of a Tortoise 16. What are some of the things a tortoise needs to survive? Tortoises are herbivores plant eaters. They eat grasses, blossoms, and succulent cactus flesh. Their metabolism allows them to go months without eating and drinking. They get almost all of their water from consuming plants. As the spring plants dry out, the tortoise will eat some of the drying flowers and grasses. Tortoises will eat the plants that are readily available, but they have food that they prefer. As weeds become more widespread tortoises may lose native forage. 17. How are tortoises able to go so long without drinking water? A tortoise s bladder is capable of storing over a cup of water, to be reabsorbed by the body as needed. Much of the water intake comes from moisture in the (revised Aug. 2007) 6

7 grasses and wildflowers they eat in the spring. Tortoises will also drink from rain puddles, even constructing their own puddles by scrapping shallow depressions in the soil to catch rain. A wild tortoise will lose its water when startled or picked up. Although the tortoise can withstand considerable dehydration, to replace this water requires additional rainfall and/or moist food. This may not be available. Therefore, it is important NOT to disturb a wild tortoise UNLESS it is in imminent, life-threatening danger. 18. Where do the tortoises live? Tortoises dig numerous burrows some are shallow and some extend up to 30 feet. The decline may vary anywhere between 4 and 40 degrees. Temperature regulation is the main function of a burrow. Although temperatures range greatly within the burrow throughout the year it still acts as a temperature buffer against the extreme above ground temperatures overhead. In the summer the protection provided by being under the surface prevents continued heating of the body to lethal temperatures. Tortoises use burrows to prevent freezing during the dormant season as well. The tortoise can have a dozen or more burrows scattered throughout its home range, which is about one square mile. Seasonal Behavioral Traits 19. What does the tortoise do in the cold winter months? In the fall the temperatures begin to drop in the Mojave Desert. One way to escape the cool temperatures and to survive the winter with little or no food is to brumate. They typically enter long burrows, many of which have a characteristic half-moon shape entrance and can be more than 30 feet long. The burrow channel can conform to the shape and girth of the tortoise and may not even allow the tortoise to turn around except after reaching the end. This snugness is efficient for temperature regulation and helps maintain a slightly higher humidity in the burrow. During the dormant time, several tortoises may occupy the same burrow. While brumating the tortoise is in an extended period of inactivity. The body slowly loses heat and stabilizes to the air temperature found in the burrow, about degrees Fahrenheit. All body processes are slowed including the heart rate and respiration rate. Tortoises are not asleep like antelope, ground squirrels, which hibernate, but their body metabolism does slow and they re just waiting for warm weather again. (revised Aug. 2007) 7

8 20. What does the tortoise do to cool down in the summer? Burrows also provide protection from the intense heat of the desert. The ground in the Mojave Desert can reach up to 140 degrees and since the tortoise cannot control its internal temperature it must find ways to keep from overheating. A tortoise might only be active above ground in the early mornings and late afternoons or evenings. The rest of the day a tortoise will retreat to the burrow. During aestivation, the tortoise is underground conserving energy and water during the hottest and driest part of the season. 21. When does the tortoise know when to wake up in the spring? It is impossible to predict exactly when the tortoise will come out of its burrow in the spring. There are three factors that may influence the tortoise to emerge. The outside temperature is the first factor. Since tortoises are reptiles, they respond quite quickly to temperature change. As winter retreats, the sun s rays become more direct, the ground begins to heat gradually and eventually the warmth reaches the depth of the burrow. As the weather gets warmer, so do their bodies, allowing them to begin to move. When the above ground temperatures permit the tortoise to move, some will walk out of their burrows. The amount of daylight each day is another factor. As spring approaches each day gets longer. The third and most important factor is the tortoise s internal clock. It seems that sometimes tortoises have an unexplained behavior or instinct, regardless of the temperature or amount of daylight to just emerge one day. Tortoise Etiquette & activity 22. What can you do to protect the habitat of the desert tortoise? Stay on the roads and trails when traveling through the desert. If you pack it in, pack it out. Litter is harmful to desert plants and animals. Leave soil, rocks, plants and animals undisturbed. 23. What would you do if you saw a tortoise in the wild? LEAVE IT ALONE! If it is injured or in the middle of a busy highway, stop safely, approaching from the front. Move the tortoise gently, several steps to the side of the road in the direction it is heading and if possible place it under a shrub/shade keeping the plastron level to the ground. (revised Aug. 2007) 8

9 24. What would you do if you see a tortoise in the city? DON T RETURN IT TO THE WILD! Collect if safely, take it home, and put it in a cool place where it cannot be harmed by dogs or other animals. A cardboard box with a ventilated lid is suitable. Call the: Bureau of Land Management Barstow Field Office (760) The Turtle & Tortoise Club--Judy Roger (760) California Dept. of Fish & Game (909) If you want to keep the tortoise you will need to get a free permit from the Department of fish and Game. The tortoise is protected under the Endangered Species Act. During recent decades, desert tortoise populations have declined dramatically. The intent of the federal listing is to ensure that the species listed and their natural habitats receive the protection needed for recovery. (revised Aug. 2007) 9