Durango Nature Studies Habitat Assessment
Executive Summary
The Durango Nature Studies property is used as a community place to learn about habitats, animals and how humans interact with nature. DNS works with the Association of Nature to help educate young kids, families and adults about animals and nature. Founded in 1994, the 140 acre property serves as place to interact with nature by offering workshops, training, research opportunities and much more. Though it is a home to many native species, the property is still threatened by some invasive species, such as the bullfrog.
Bullfrogs (Rana catesbeina) began to be spotted in 2010 at DNS and have been a growing concern. Invasive species are harmful to the environment they are introduced into because they fight native species for resources. Leopard frogs (Rana pipiens) are native to the Southwest and bullfrogs are fighting them for resources, potentially damaging the leopard frog population significantly.
Durango Nature Studies recruited the 10th Grade class of Animas High School to conduct several studies that included water quality tests, vegetation surveys and visual encounter surveys. This will help DNS estimate population growth of bullfrogs and the cost of removal for the frog, if needed.
The annual budget for Durango Nature Studies was estimated to be around $140,000 in 2007 and will be making management and monitoring efforts concerning bullfrogs with this budget in mind. It is a non-profit organization which has served as an important resource in teaching families the relevance of nature. By helping DNS, Animas High School students have contributed to the well-being of the Durango Nature Studies organization for years to come.
Species Overview
Rana pipiens
The northern leopard frog, or Rana pipiens, is a native species to the Central Plains but, because of a recent decline in population, the species is now mostly found in lower Midwestern states. Recognizable from a prominent dorsolateral ridge, these frogs usually only grow to a size of 5.1-9.0 cm. After breeding in the spring, females are known to lay up to 2,000-6,000 eggs. In the winter, leopard frogs usually hibernate in deep water, hiding under debris or building shallow pits in ponds. Unfortunately, the native Rana pipiens has been under consideration for the Endangered Species Act due to an invasive species of Rana catesbeina, or bullfrog.
Rana catesbeina
The Rana catesbeina was native to the eastern part of North America, but has been a widely growing population reaching from the whole of North America to China and other parts of the world. Bullfrogs can grow up to 10-18cm, with the females typically being larger and these frogs have a prominent ear drum ridge. After breeding in June and July, females can lay up to 20,000 eggs. Bullfrogs are extremely aggressive and territorial, and have been classified as generalist predators, usually eating everything they can fit into their mouths. In the summer, these frogs usually migrate to higher land, while in the winter they hibernate in water. But bullfrogs carry a disease known as chytridiomycosis which can harm native species of frogs. This disease, as well as the bullfrogs’ natural competitive instinct, has been a growing concern in Colorado as leopard frog populations are dwindling. Due to this, bullfrogs are classified as an invasive species.
Results
The 10th grade class of Animas High School was recruited to test and evaluate the health of the DNS property. The phosphate levels in both the pond and river were high: 5ppm and 4ppm respectively. High levels of phosphates can contribute to the growth of algal blooms, which lead to decreased oxygen levels in the water. In the pond, dissolved oxygen levels were concluded to be 7.5mg/L, a level good for amphibians. The dissolved oxygen levels in the river were inconclusive because of recent rainstorms mudding the water. The pH levels in both the river and the pond were 8, which is alkaline. The nitrate tests concluded that the river and pond are both unpolluted. Coliform is known to cause deformities in the growth of amphibians, and the river and pond tested positive for it. The Shannon-Weiner Diversity Index calculated for both the pond and river macroinvertebrates were over 1, suggesting that it is a stable and healthy environment. Also the average diversity calculated from eight different veg plots was over 1.
Discussion & Recommendations
The Shannon-Wiener Diversity Index calculated for the DNS pond and river were both one, concluding that the property is stable and diverse but not highly pristine. The diversity index average for eight veg plots on the land also concluded to be one. There were no stoneflies found in the pond and the river. Stoneflies are macroinvertebrates that only live in very pristine, unpolluted water. With these facts in mind, it can be concluded that while the pond and river at DNS is not totally pristine, but it is has a fairly stable diversity index.
The water quality data taken from the Florida River and the pond at DNS showed high levels of phosphates; chemicals mostly caused by the breakdown of feces. There are many grazing pastures upstream for livestock on the Florida River, which may account for the elevated levels of phosphates in the water.
High levels of phosphates can increase the growth of algal blooms, plants which can significantly lower oxygen levels in the water. While amphibians thrive on higher dissolved oxygen levels, it is good to have a healthy balance of low and high dissolved oxygen levels in water.
The Animas class used two methods for estimating the leopard frog population. First was the visual encounter survey. This was conducted throughout the course of two days, the first dedicated to students capturing and marking frogs, while the second day was for capturing and recording the amount of frogs which were already marked from the previous day. The second method, mark-recapture data, used the following equation M*C/R to estimate population. M being the amount of frogs marked, C number of frogs caught on the second day, while R was frogs which were caught but had already been marked. Out of these two methods it is reasonable to assume mark-recapture data would be more reliable, due the factor of having a much more diverse amount of frogs, since it was conducted over two days instead of one, even if the time between the two visits might not have given dependable data.
To better monitor the population of leopard frogs, Durango Nature Studies could install “frog loggers”. This is a device that can capture a frog’s call and record the data to determine any population changes. Though frog loggers are susceptible to weather, wildlife and other forms of disruption, it can be a good way to monitor frogs (Corn, Paul Stephen; Muths, Erin; Iko, Willam M. 2000). Frog loggers are pretty inexpensive, around $350 each, and are simple to install.
The Animas class did not find any bullfrogs on the DNS property, but the employees there have reported seeing bullfrogs on several occasions. Young bullfrogs are known to be quick travelers, moving at least 6 miles in several weeks, according to a report by Dennis Suhre, a graduate student from the University of Arizona. Because of this, it makes them hard to find and capture. There are several ways DNS could control the increasing bullfrog population on its property. Chemicals and toxins could be used to kill unwanted tadpoles, but it would also harm native species already facing endangerment. Another tactic, which is used by the Buenos Aires National Wildlife Refuge, suggests that in the dry season they drain ponds in which bullfrog tadpoles are located to eradicate the species. Then native leopard frogs could be reintroduced to those areas. But this would most likely have to be done on a big scale, about all the ponds in a similar area, since bullfrogs are such fast travelers (National Geographic 2004).
Bibliography
"Aldo Leopold Wilderness Research Institute Publications." Aldo Leopold Wilderness Research Institute Publications. N.p., n.d. Web. 16 Oct. 2013.
“Invading Bullfrogs Appear Nearly Unstoppable." National Geographic. National Geographic Society, 28 Oct. 2010. Web. 16 Oct. 2013.
The Durango Nature Studies property is used as a community place to learn about habitats, animals and how humans interact with nature. DNS works with the Association of Nature to help educate young kids, families and adults about animals and nature. Founded in 1994, the 140 acre property serves as place to interact with nature by offering workshops, training, research opportunities and much more. Though it is a home to many native species, the property is still threatened by some invasive species, such as the bullfrog.
Bullfrogs (Rana catesbeina) began to be spotted in 2010 at DNS and have been a growing concern. Invasive species are harmful to the environment they are introduced into because they fight native species for resources. Leopard frogs (Rana pipiens) are native to the Southwest and bullfrogs are fighting them for resources, potentially damaging the leopard frog population significantly.
Durango Nature Studies recruited the 10th Grade class of Animas High School to conduct several studies that included water quality tests, vegetation surveys and visual encounter surveys. This will help DNS estimate population growth of bullfrogs and the cost of removal for the frog, if needed.
The annual budget for Durango Nature Studies was estimated to be around $140,000 in 2007 and will be making management and monitoring efforts concerning bullfrogs with this budget in mind. It is a non-profit organization which has served as an important resource in teaching families the relevance of nature. By helping DNS, Animas High School students have contributed to the well-being of the Durango Nature Studies organization for years to come.
Species Overview
Rana pipiens
The northern leopard frog, or Rana pipiens, is a native species to the Central Plains but, because of a recent decline in population, the species is now mostly found in lower Midwestern states. Recognizable from a prominent dorsolateral ridge, these frogs usually only grow to a size of 5.1-9.0 cm. After breeding in the spring, females are known to lay up to 2,000-6,000 eggs. In the winter, leopard frogs usually hibernate in deep water, hiding under debris or building shallow pits in ponds. Unfortunately, the native Rana pipiens has been under consideration for the Endangered Species Act due to an invasive species of Rana catesbeina, or bullfrog.
Rana catesbeina
The Rana catesbeina was native to the eastern part of North America, but has been a widely growing population reaching from the whole of North America to China and other parts of the world. Bullfrogs can grow up to 10-18cm, with the females typically being larger and these frogs have a prominent ear drum ridge. After breeding in June and July, females can lay up to 20,000 eggs. Bullfrogs are extremely aggressive and territorial, and have been classified as generalist predators, usually eating everything they can fit into their mouths. In the summer, these frogs usually migrate to higher land, while in the winter they hibernate in water. But bullfrogs carry a disease known as chytridiomycosis which can harm native species of frogs. This disease, as well as the bullfrogs’ natural competitive instinct, has been a growing concern in Colorado as leopard frog populations are dwindling. Due to this, bullfrogs are classified as an invasive species.
Results
The 10th grade class of Animas High School was recruited to test and evaluate the health of the DNS property. The phosphate levels in both the pond and river were high: 5ppm and 4ppm respectively. High levels of phosphates can contribute to the growth of algal blooms, which lead to decreased oxygen levels in the water. In the pond, dissolved oxygen levels were concluded to be 7.5mg/L, a level good for amphibians. The dissolved oxygen levels in the river were inconclusive because of recent rainstorms mudding the water. The pH levels in both the river and the pond were 8, which is alkaline. The nitrate tests concluded that the river and pond are both unpolluted. Coliform is known to cause deformities in the growth of amphibians, and the river and pond tested positive for it. The Shannon-Weiner Diversity Index calculated for both the pond and river macroinvertebrates were over 1, suggesting that it is a stable and healthy environment. Also the average diversity calculated from eight different veg plots was over 1.
Discussion & Recommendations
The Shannon-Wiener Diversity Index calculated for the DNS pond and river were both one, concluding that the property is stable and diverse but not highly pristine. The diversity index average for eight veg plots on the land also concluded to be one. There were no stoneflies found in the pond and the river. Stoneflies are macroinvertebrates that only live in very pristine, unpolluted water. With these facts in mind, it can be concluded that while the pond and river at DNS is not totally pristine, but it is has a fairly stable diversity index.
The water quality data taken from the Florida River and the pond at DNS showed high levels of phosphates; chemicals mostly caused by the breakdown of feces. There are many grazing pastures upstream for livestock on the Florida River, which may account for the elevated levels of phosphates in the water.
High levels of phosphates can increase the growth of algal blooms, plants which can significantly lower oxygen levels in the water. While amphibians thrive on higher dissolved oxygen levels, it is good to have a healthy balance of low and high dissolved oxygen levels in water.
The Animas class used two methods for estimating the leopard frog population. First was the visual encounter survey. This was conducted throughout the course of two days, the first dedicated to students capturing and marking frogs, while the second day was for capturing and recording the amount of frogs which were already marked from the previous day. The second method, mark-recapture data, used the following equation M*C/R to estimate population. M being the amount of frogs marked, C number of frogs caught on the second day, while R was frogs which were caught but had already been marked. Out of these two methods it is reasonable to assume mark-recapture data would be more reliable, due the factor of having a much more diverse amount of frogs, since it was conducted over two days instead of one, even if the time between the two visits might not have given dependable data.
To better monitor the population of leopard frogs, Durango Nature Studies could install “frog loggers”. This is a device that can capture a frog’s call and record the data to determine any population changes. Though frog loggers are susceptible to weather, wildlife and other forms of disruption, it can be a good way to monitor frogs (Corn, Paul Stephen; Muths, Erin; Iko, Willam M. 2000). Frog loggers are pretty inexpensive, around $350 each, and are simple to install.
The Animas class did not find any bullfrogs on the DNS property, but the employees there have reported seeing bullfrogs on several occasions. Young bullfrogs are known to be quick travelers, moving at least 6 miles in several weeks, according to a report by Dennis Suhre, a graduate student from the University of Arizona. Because of this, it makes them hard to find and capture. There are several ways DNS could control the increasing bullfrog population on its property. Chemicals and toxins could be used to kill unwanted tadpoles, but it would also harm native species already facing endangerment. Another tactic, which is used by the Buenos Aires National Wildlife Refuge, suggests that in the dry season they drain ponds in which bullfrog tadpoles are located to eradicate the species. Then native leopard frogs could be reintroduced to those areas. But this would most likely have to be done on a big scale, about all the ponds in a similar area, since bullfrogs are such fast travelers (National Geographic 2004).
Bibliography
"Aldo Leopold Wilderness Research Institute Publications." Aldo Leopold Wilderness Research Institute Publications. N.p., n.d. Web. 16 Oct. 2013.
“Invading Bullfrogs Appear Nearly Unstoppable." National Geographic. National Geographic Society, 28 Oct. 2010. Web. 16 Oct. 2013.