California Tiger
Ambystoma tigrinum
Salamander
The California Tiger Salamander一Direly Threatened by Humans Before They Even Hatch
A salamander’s life begins as a three and a half millimeter long fragile egg dropped by its mother in clusters along with one to four other siblings. The eggs, secured by their mother to vegetation, rocks or debris, will remain there for two weeks. They are left vulnerable to the elements, predators一and the salamander's biggest threat一humans. Habitat destruction, specifically deforestation, is the salamander’s biggest threat during its developmental stage (Hammerson, 2004). Below are listed all the threats salamanders face during the most helpless time of their life. It is important to remember that all of these impacts are caused by anthropogenic changes to the environment.
Introduction of Nonnative Species
This is a natural result of the salamanders
being an R-strategist species, but because of
longer rains in some regions and damming
leaving a permanently water covered habitat,
it allows more permanent predators to
establish themselves in Salamander
breeding ponds, which are supposed to only
remain full until the Salamanders are big
enough to survive on their own. Introduction
of non-native predators also increases the
frequencies of these predator related deaths.
This Bullfrog is an example of an invasive species now inhabiting many California vernal pools and wetlands. This frog eats many of the California Tiger Salamander eggs and larvae, causing a dramatic decline in the salamander's population.
Danger Prone Salamanders
Certain aspects of the salamanders niche also makes it more susceptible to being killed in this initial stage. Since the eggs are aggregated, it is much easier for predators to find and kill highly concentrated patches of eggs (Hammerson, 2004). The group of eggs the mother lays will remain on the vegetation for fourteen days. A single individual in a pond can lay up to 1,410 eggs.
Deforestation
Deforestation and the resulting habitat destruction is a salamanders largest foe. Much of the deforestation occurring in the salamander habitat is due to urbanization. This is occurring due to financial prospects taken by developers to turn pristine, unused land into residential homes. This loss of tree cover, especially along a pond, can easily kill salamander embryos. Vegetation and tree cover provide shade and block radiation from entering the water where the mother salamander laid its eggs. When the vegetation is gone, the eggs are exposed to lethal amounts of UV radiation. Radiation at this level can purge hundreds of
salamander eggs.
Acid Deposition
Industrialization and combustion which release sulfuric acid into the atmosphere is also a major threat to salamanders. Acid deposition occurs as result of emissions from coal fired power plants, which is a cheap and abundant energy source. These emissions cause acid deposition, which lowers the pH of water, increasing the acidity of a pond to a level that kills amphibian embryos. Acidic water can also increase the toxicity of other contaminants, such as metals, pesticides, and petroleum products. Even what you put on your lawn can affect salamanders; some widely used, commercially available herbicides contain a chemical that is directly toxic to amphibians (Worldwide Amphibian Declines, 2010).
Pollution
Acid deposition and pollution are even of higher threat to wetland ecosystems. Because wetlands are low-lying areas where contaminants in stormwater runoff can accumulate, causing the salamander to not even be safe in its own habitat. Chemical run-off from vehicles contaminates roadside ditches and pools. According to Steven P. Brady, salamander survival in roadside pools averaged just 56%, as compared to 87% in woodland pools. Thus, an average of 36% fewer individual salamanders embryos survived to hatching in roadside versus woodland pools (Threats to Salamanders, 2013).
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Agricultural Development
Due to drought and development, many vernal pools suffer from desiccation year round. Farmers have converted these pools into drinking holes for their livestock instead. Sediment from topsoil erosion can accumulate in ponds, and while some mud is needed to keep the eggs hidden from predators, too much mud can easily kill a salamander from oxygen depletion. This causes cultural eutrophication, and a salamander embryo cannot survive in these conditions (Worldwide Amphibian Declines, 2010).
