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Amphibian population estimates and ecosystem assessment on the Durango Nature Studies property
Introduction:
Durango Nature Studies (DNS) is a non-profit educational organization that owns a plot of land in Durango, Colorado. The DNS land is just on the other side of Farmington Hill and is on the right if driven to from Durango as if going to Farmington. The DNS property was obtained in June of 1998 and since then the purpose of the program has been to educate and protect the many habitats encompassed in the 140 acres of land. The land contains areas of ponderosa pines, xeri-scaped land, sage-rabbit rush, riparian habitats, meadows, oak brush clumps, woodlands, pinoñ-juniper forests and desert arroyos. The DNS land also has the Florida River flowing through the property. Close to the river is a small pond averaging about 200 ft². Individuals and groups of all ages are permitted research and learn about the environment. Research groups including Animas High School, Fort Lewis College, and numerous local elementary and middle schools are allowed access to the property for various educational purposes.
A concern that the program faces is the relationship between Rana catesbeiana (bullfrog) and the Rana pipiens (leopard frog). Bull frogs currently are listed as an invasive species in Colorado and they are causing the status of the leopard frogs to be a concern. An invasive species is a group of animals that is not native and is harming the health of the native animals. Some species are non-native, but can live in harmony with the native animals. Invasive species, however, are concerning because they threaten the existence of the native animals by depleting the resources and outcompeting the native species. On the DNS land, the native leopard frogs are at risk due to the relationship between the bluegill fish in the pond and the bull frogs. The bull frogs are larger and more aggressive and they push the leopard frogs out from the prime habitat on the banks of the pond and into the middle of the water. The bluegill fish are then able to easily prey upon the leopard frogs. Clearly the leopards frogs’ safety is seen as a concern.
Natural History
Leopard frogs can breed anywhere in between late April and early June. The females lay their eggs, up to 5,000, in pond or streams on sticks or plant life submerged in the water. Within 5 to 7 days the eggs hatch and turn into tadpoles. The tadpoles can then change into froglets in between July and August after they have been a tadpole for about 60 days or they can spend the winter as a tadpole and change into a froglet the next summer. In order to survive the leopard frogs need a safe environment for the tadpoles to hatch and change into froglets. Also, they need plenty of insects and small macro-invertebrates to nourish them in their multiple stages of life.
Female bullfrogs lay an average of 25,000 eggs, but the eggs float on the surface of the water making them vulnerable and many of the eggs don’t progress to the tadpole stage. For a bull frog to turn into a fully mature frog, it may take 2 to 3 years of development. Bullfrogs’ life expectancy ranges from 7 to 9 years. For bullfrogs, survival comes easy because the frogs are large, strong and aggressive. They need to have some source of food, but this is simple because a bull frog will eat almost anything, from birds, other frogs and fish to insects. Based on what each frog needs for survival, we see that the bullfrog is an intimidating factor in the life of a leopard frog. Not only can leopard frogs become a meal for the blue gill fish in the pond, they may also fall victim to a bull frog. Even then if the leopard frog doesn’t get eaten, their food source of insects is also being exhausted by their potential predator, the bull frog.
Methods and Materials:
In order to estimate amphibian population size three methods were used, pitfalls, visual encounters and marked and recapture. Pitfalls were put in place in an attempt to capture amphibians. Two five-gallon buckets were placed next to the pond and two five-gallon buckets were also assembled near the river. All of these buckets were checked daily for a four day period to examine specimens that may have been captured. Along with the pitfalls, visual encounter surveys were conducted daily over a four day period. On the second day of research the frogs were captured and marked with pink elastomer. The specimens were marked on their inner right hind leg. After the marking, an hour of a recapture session ensued.
When researching a species, it is important to understand the other species, as well as the elements of the environment and the impact that a change in habitat may cause on the species in question. In the river, the kick method was used to collect macro-invertebrate samples. Similar to the river, the pond was also sown for macro-invertebrates, but a dip net was used in the pond instead of the kick method. The kick method is a sampling process where one person stands up stream and kicks the rocks around to dislodge the insects from their homes. Downstream, the second person stands with a net ready to capture the liberated creatures. Using a dip net is reaping the same results in the pond, but the process is essential to dip a net into the water and scoop from the bottom of the pond to collect the specimens. Water samples were taken from the river and the pond and tested for nitrates, phosphates, dissolved oxygen, pH, coliform and temperature to determine water quality.
Results:
Through the collection of macro-invertebrates and the use of the Shannon-Weiner index, the diversity index for the DNS pond was calculated to be 1.21. This number is considerably elevated compared to the results of 2011 where the diversity index was 0.99. In the river in 2011, the diversity index of the river was 1.03 but in 2012 the rivers diversity totaled out to be 0.88. When testing water quality we tested for nitrates, phosphates, pH, dissolved oxygen and coliform. In the pond, nitrates were found to be at a normal level, the phosphates were high and the dissolved oxygen levels were low. Also in the river we found that the pH level was alkaline, meaning that pH level was higher than 7, and the pond tested positive in the coliform test. The river also tested positive for coliform and the pH level was alkaline as well. However, the river had high levels of nitrates and phosphates and a normal level of dissolved oxygen. As far as macro-invertebrates go, the river contained many more insects than the pond. To determine the population of the leopard frogs, marking and recapture as well as visual encounters were used. In the marking and recapture, the population of the Rana pipiens (leopard frog) can be estimated to be fifteen. Using the results of the visual encounter the population of the leopard frogs was about eleven and the population of the Rana catesbieana (bullfrogs) was estimated to be one. From this we can average the population of the leopard frogs and estimate that the total is thirteen frogs.
Conclusion:
Through our data we have found that the biodiversity of the pond has increased and the biodiversity of the river has decreased. The increase in diversity may be due to the fact that the pond may contain more plant life which in turn could have resulted in a population rise in macro-invertebrates in the pond. However, it is mysterious that the diversity of the pond increased because the year was hot, the pond lost water and the nitrates and phosphate levels increased. These same things affected the river and acted in the way that is expected. The diversity of the river decreased from last year to this year due to the factors previously mentioned. The water quality may also contribute to the rise and fall of the diversity in both the river and the pond. From what we see in the diversity index in the pond and the river compared to last year, we can conclude that the water quality in the pond has improved so more species may exist in the pond. Conversely, the river water quality has become worse and so that may contribute to the fall in biodiversity. Also regarding the water quality, in the pond the nitrate and phosphate levels are high. This puts the pond at risk for an algal bloom. An algal bloom is when the water is rich with nutrients and so more plant life begins to grow. While this may seem nonthreatening to the environment of the pond, in reality algal blooms are dangerous. When the plant life becomes untamed and dense the plants begin deplete the oxygen levels and the creatures living in the pond don’t get enough oxygen and suffocate. An algal bloom results in all life forms in the pond dying off eventually. Coliform in the water indicates that feces from warm blooded animals are in the water. This may be caused by the animals, such as livestock, that live near Lemon Reservoir. Livestock, like cows, graze near the reservoir and dispose their waste into the dam. This then flows into the Florida River and causes the coliform tests to be positive in the river.
The bullfrog population was estimated to be two frogs last year but over the summer the property management captured one frog and removed it from the property. Based on the data the conclusion can be reached that although the bullfrogs are an invasive species, they are not creating a large drop in the population of the leopard frogs. Some may view this situation as something that needs to be acted on and investigated so precautions can be put into place in case the bullfrogs begin to further disrupt the life cycle of the leopard frogs. Nonetheless nature is something so far beyond humans we can’t even to pretend we control it. There is the argument that humans have messed up nature so much it is up to us to fix it. The fact that humans have messed up nature is something that cannot be denied and there are many pieces of evidence to prove this. However, many times by trying to solve something, the outcome is far worse than before. An example of this is indeed the bullfrogs. This animal was introduced into an environment where it didn’t belong to help control pests but instead the frog began to take over. So by trying to fix something that might not have even needed fixing, a larger problem was created that now needs to be fixed as well. Maybe the reason for this roundabout way of thinking is to put biologists into jobs, but in the end nature is our master and we should stop messing with it. The earth has its own agenda that we can never be truly aware of because we are such a short piece of it. In fact, the global issue of global warming is just part of nature’s plan. “Though climate change can be caused by fluctuations in Earth’s cycles and temperature due to “natural” flux in solar radiation, seasonality, or atmospheric concentration…” (123helpme!com) This article is saying that the changes in the temperature are natural and part of how the earth is changing, so slowly that it takes millions and millions of years for the transition to really show. Research has been done on the atmosphere and scientists have found that the earth goes through an ebb and flow pattern of global warming and cold streaks. To think that humans have control over the grander plan of nature seems like a foolish thing to believe in. The issue about bullfrogs and leopard frogs is simple part of nature’s way of evolving and changing. It is meant to be the way it is happening, even if it is painful or sad, nature knows what’s best and nature knows the plan even when humans fail to see it.
Durango Nature Studies (DNS) is a non-profit educational organization that owns a plot of land in Durango, Colorado. The DNS land is just on the other side of Farmington Hill and is on the right if driven to from Durango as if going to Farmington. The DNS property was obtained in June of 1998 and since then the purpose of the program has been to educate and protect the many habitats encompassed in the 140 acres of land. The land contains areas of ponderosa pines, xeri-scaped land, sage-rabbit rush, riparian habitats, meadows, oak brush clumps, woodlands, pinoñ-juniper forests and desert arroyos. The DNS land also has the Florida River flowing through the property. Close to the river is a small pond averaging about 200 ft². Individuals and groups of all ages are permitted research and learn about the environment. Research groups including Animas High School, Fort Lewis College, and numerous local elementary and middle schools are allowed access to the property for various educational purposes.
A concern that the program faces is the relationship between Rana catesbeiana (bullfrog) and the Rana pipiens (leopard frog). Bull frogs currently are listed as an invasive species in Colorado and they are causing the status of the leopard frogs to be a concern. An invasive species is a group of animals that is not native and is harming the health of the native animals. Some species are non-native, but can live in harmony with the native animals. Invasive species, however, are concerning because they threaten the existence of the native animals by depleting the resources and outcompeting the native species. On the DNS land, the native leopard frogs are at risk due to the relationship between the bluegill fish in the pond and the bull frogs. The bull frogs are larger and more aggressive and they push the leopard frogs out from the prime habitat on the banks of the pond and into the middle of the water. The bluegill fish are then able to easily prey upon the leopard frogs. Clearly the leopards frogs’ safety is seen as a concern.
Natural History
Leopard frogs can breed anywhere in between late April and early June. The females lay their eggs, up to 5,000, in pond or streams on sticks or plant life submerged in the water. Within 5 to 7 days the eggs hatch and turn into tadpoles. The tadpoles can then change into froglets in between July and August after they have been a tadpole for about 60 days or they can spend the winter as a tadpole and change into a froglet the next summer. In order to survive the leopard frogs need a safe environment for the tadpoles to hatch and change into froglets. Also, they need plenty of insects and small macro-invertebrates to nourish them in their multiple stages of life.
Female bullfrogs lay an average of 25,000 eggs, but the eggs float on the surface of the water making them vulnerable and many of the eggs don’t progress to the tadpole stage. For a bull frog to turn into a fully mature frog, it may take 2 to 3 years of development. Bullfrogs’ life expectancy ranges from 7 to 9 years. For bullfrogs, survival comes easy because the frogs are large, strong and aggressive. They need to have some source of food, but this is simple because a bull frog will eat almost anything, from birds, other frogs and fish to insects. Based on what each frog needs for survival, we see that the bullfrog is an intimidating factor in the life of a leopard frog. Not only can leopard frogs become a meal for the blue gill fish in the pond, they may also fall victim to a bull frog. Even then if the leopard frog doesn’t get eaten, their food source of insects is also being exhausted by their potential predator, the bull frog.
Methods and Materials:
In order to estimate amphibian population size three methods were used, pitfalls, visual encounters and marked and recapture. Pitfalls were put in place in an attempt to capture amphibians. Two five-gallon buckets were placed next to the pond and two five-gallon buckets were also assembled near the river. All of these buckets were checked daily for a four day period to examine specimens that may have been captured. Along with the pitfalls, visual encounter surveys were conducted daily over a four day period. On the second day of research the frogs were captured and marked with pink elastomer. The specimens were marked on their inner right hind leg. After the marking, an hour of a recapture session ensued.
When researching a species, it is important to understand the other species, as well as the elements of the environment and the impact that a change in habitat may cause on the species in question. In the river, the kick method was used to collect macro-invertebrate samples. Similar to the river, the pond was also sown for macro-invertebrates, but a dip net was used in the pond instead of the kick method. The kick method is a sampling process where one person stands up stream and kicks the rocks around to dislodge the insects from their homes. Downstream, the second person stands with a net ready to capture the liberated creatures. Using a dip net is reaping the same results in the pond, but the process is essential to dip a net into the water and scoop from the bottom of the pond to collect the specimens. Water samples were taken from the river and the pond and tested for nitrates, phosphates, dissolved oxygen, pH, coliform and temperature to determine water quality.
Results:
Through the collection of macro-invertebrates and the use of the Shannon-Weiner index, the diversity index for the DNS pond was calculated to be 1.21. This number is considerably elevated compared to the results of 2011 where the diversity index was 0.99. In the river in 2011, the diversity index of the river was 1.03 but in 2012 the rivers diversity totaled out to be 0.88. When testing water quality we tested for nitrates, phosphates, pH, dissolved oxygen and coliform. In the pond, nitrates were found to be at a normal level, the phosphates were high and the dissolved oxygen levels were low. Also in the river we found that the pH level was alkaline, meaning that pH level was higher than 7, and the pond tested positive in the coliform test. The river also tested positive for coliform and the pH level was alkaline as well. However, the river had high levels of nitrates and phosphates and a normal level of dissolved oxygen. As far as macro-invertebrates go, the river contained many more insects than the pond. To determine the population of the leopard frogs, marking and recapture as well as visual encounters were used. In the marking and recapture, the population of the Rana pipiens (leopard frog) can be estimated to be fifteen. Using the results of the visual encounter the population of the leopard frogs was about eleven and the population of the Rana catesbieana (bullfrogs) was estimated to be one. From this we can average the population of the leopard frogs and estimate that the total is thirteen frogs.
Conclusion:
Through our data we have found that the biodiversity of the pond has increased and the biodiversity of the river has decreased. The increase in diversity may be due to the fact that the pond may contain more plant life which in turn could have resulted in a population rise in macro-invertebrates in the pond. However, it is mysterious that the diversity of the pond increased because the year was hot, the pond lost water and the nitrates and phosphate levels increased. These same things affected the river and acted in the way that is expected. The diversity of the river decreased from last year to this year due to the factors previously mentioned. The water quality may also contribute to the rise and fall of the diversity in both the river and the pond. From what we see in the diversity index in the pond and the river compared to last year, we can conclude that the water quality in the pond has improved so more species may exist in the pond. Conversely, the river water quality has become worse and so that may contribute to the fall in biodiversity. Also regarding the water quality, in the pond the nitrate and phosphate levels are high. This puts the pond at risk for an algal bloom. An algal bloom is when the water is rich with nutrients and so more plant life begins to grow. While this may seem nonthreatening to the environment of the pond, in reality algal blooms are dangerous. When the plant life becomes untamed and dense the plants begin deplete the oxygen levels and the creatures living in the pond don’t get enough oxygen and suffocate. An algal bloom results in all life forms in the pond dying off eventually. Coliform in the water indicates that feces from warm blooded animals are in the water. This may be caused by the animals, such as livestock, that live near Lemon Reservoir. Livestock, like cows, graze near the reservoir and dispose their waste into the dam. This then flows into the Florida River and causes the coliform tests to be positive in the river.
The bullfrog population was estimated to be two frogs last year but over the summer the property management captured one frog and removed it from the property. Based on the data the conclusion can be reached that although the bullfrogs are an invasive species, they are not creating a large drop in the population of the leopard frogs. Some may view this situation as something that needs to be acted on and investigated so precautions can be put into place in case the bullfrogs begin to further disrupt the life cycle of the leopard frogs. Nonetheless nature is something so far beyond humans we can’t even to pretend we control it. There is the argument that humans have messed up nature so much it is up to us to fix it. The fact that humans have messed up nature is something that cannot be denied and there are many pieces of evidence to prove this. However, many times by trying to solve something, the outcome is far worse than before. An example of this is indeed the bullfrogs. This animal was introduced into an environment where it didn’t belong to help control pests but instead the frog began to take over. So by trying to fix something that might not have even needed fixing, a larger problem was created that now needs to be fixed as well. Maybe the reason for this roundabout way of thinking is to put biologists into jobs, but in the end nature is our master and we should stop messing with it. The earth has its own agenda that we can never be truly aware of because we are such a short piece of it. In fact, the global issue of global warming is just part of nature’s plan. “Though climate change can be caused by fluctuations in Earth’s cycles and temperature due to “natural” flux in solar radiation, seasonality, or atmospheric concentration…” (123helpme!com) This article is saying that the changes in the temperature are natural and part of how the earth is changing, so slowly that it takes millions and millions of years for the transition to really show. Research has been done on the atmosphere and scientists have found that the earth goes through an ebb and flow pattern of global warming and cold streaks. To think that humans have control over the grander plan of nature seems like a foolish thing to believe in. The issue about bullfrogs and leopard frogs is simple part of nature’s way of evolving and changing. It is meant to be the way it is happening, even if it is painful or sad, nature knows what’s best and nature knows the plan even when humans fail to see it.
Works Cited
123helpme!com. 123HelpMe.com, n.d. Web. 10 Oct. 2012. <http://www.123helpme.com/view.asp?id=38899>. This site aided my conclusions individuality.
Answers. Answers Corporation, n.d. Web. 10 Oct. 2012. <http://wiki.answers.com/Q/Where_did_bullfrogs_come_from>. I used this to aid my conclusion, even though I know wiki.answers can be unreliable.
Bullfrogs.com. www.Bullfrogs.com, n.d. Web. 4 Oct. 2012. <http://www.bullfrogs.com/Bullfrog-Life-Cycle.html>. This site assisted me with Bullfrog information.
Lee and Rose Warner Nature Center. Science Museum of Minnesota, n.d. Web. 4 Oct. 2012. <http://www.smm.org/warnernaturecenter/animals/leopardfrog>. I used this site for Leopard frog information.
Nature North. N.p., n.d. Web. 4 Oct. 2012. <http://www.naturenorth.com/1np/Species/amphibian/1Ffrle.html>. I used this site to learn about the cycles of Leopard frogs.
VDH. Virgina Department of Health, n.d. Web. 10 Oct. 2012. <http://www.vdh.virginia.gov/epidemiology/DEE/Waterborne/HABS/>. I used this site for information on algal blooms.
Wikipedia. Wikimedia Foundation, n.d. Web. 10 Oct. 2012. <http://en.wikipedia.org/wiki/Algal_bloom>. I used this site to refresh my memory on algal blooms.
Answers. Answers Corporation, n.d. Web. 10 Oct. 2012. <http://wiki.answers.com/Q/Where_did_bullfrogs_come_from>. I used this to aid my conclusion, even though I know wiki.answers can be unreliable.
Bullfrogs.com. www.Bullfrogs.com, n.d. Web. 4 Oct. 2012. <http://www.bullfrogs.com/Bullfrog-Life-Cycle.html>. This site assisted me with Bullfrog information.
Lee and Rose Warner Nature Center. Science Museum of Minnesota, n.d. Web. 4 Oct. 2012. <http://www.smm.org/warnernaturecenter/animals/leopardfrog>. I used this site for Leopard frog information.
Nature North. N.p., n.d. Web. 4 Oct. 2012. <http://www.naturenorth.com/1np/Species/amphibian/1Ffrle.html>. I used this site to learn about the cycles of Leopard frogs.
VDH. Virgina Department of Health, n.d. Web. 10 Oct. 2012. <http://www.vdh.virginia.gov/epidemiology/DEE/Waterborne/HABS/>. I used this site for information on algal blooms.
Wikipedia. Wikimedia Foundation, n.d. Web. 10 Oct. 2012. <http://en.wikipedia.org/wiki/Algal_bloom>. I used this site to refresh my memory on algal blooms.
Animas High School 3206 North Main Avenue Durango, CO 81301 (970) 247-2474
My Contact Information: [email protected]
Updated on: 12.15.12
My Contact Information: [email protected]
Updated on: 12.15.12