California Tiger
Ambystoma tigrinum
Salamander
As soon as California Tiger Salamanders wriggle out of their eggs, they are faced with another array of threats. During larval stages, the wetland ecosystem becomes crucial to the animal’s survival. These wetlands must to retain water until May or June for successful metamorphosis to occur, as the salamander babies can only survive in aquatic conditions. These salamanders have gills, and are completely dependent on water. Several factors are contributing to the loss of juvenile salamanders.
The metamorphsis of the California Tiger Salamander is trigged by the drying out the vernal pool which the larvae are living in. If the pools dry out early or have low water levels, the California Tiger Salamander is unable to fully develop and is at a much higher risk of death.
Threats to Salamander During Larval Stage
Since the salamanders at this stage are fully aquatic, the loss of vernal ponds is an imminent threat to the survivorship of California Tiger Salamander. Today, 55-58% of historic breeding sites, and reportedly about 75% of the historical vernal pool-breeding habitat has been lost. The critical habitat designation for the central California population—made in 2005 under political influence—illegally slashed critical habitat in half, and in the same year, the Sonoma County population’s critical habitat was completely eliminated. (California Tiger Salamander, 2012).
There is a very small portion of area which can accommodate the diverse needs of the California Tiger Salamanders. The specific range of the California Tiger Salamander spans from the eastern foothills of the Sierra Nevada, West to the outer coast range in Southern San Mateo County to central San Luis Obispo, and also in the vicinity of northwestern Santa Barbara County. In the North, the Tiger Salamanders can be found from Sonoma and Yolo counties. The southernmost of their range is to northwestern Kern County and northern Tulare County (Boyd, 2012).
To further reduce the amount of area California Tiger Salamanders can colonize, this salamander can only live in grasslands and foothills limited to elevations of 1,500 feet. If even a small portion of the fraction of space these salamanders can inhabitant is developed; it will seriously impair the Tiger Salamander’s chance of survival (Boyd, 2012).
What are the specific habitat requirements for the California Tiger Salamander?
Agricultural Development
Hundreds of thousands of acres of wetlands have also been drained for agriculture. Globally, agriculture accounts for 65% of the total water withdrawal on Earth (Threats to wetlands, 2014). The conversion of land into agricultural area has reduced the frequency of these ponds. Industrial farmers and farm pose some of the most lethal threats to California Tiger Salamanders by draining vernal ponds to plot more fertile soil. Development and agriculture near habitats put salamanders at serious risk from industrial contaminants, sedimentation, sewage run off, pesticides, oils, and other chemicals and toxic substances.
Pollution
Amphibians are believed to be sensitive to pollutants because of they’re highly permeable skins, and their varied lives. Furthermore, because salamanders dwell on land and water and eat both plants and animals at various stages of their life cycles, they are affected by pollution from many different areas. There is a direct link between abundance of pollutants and survival of California Tiger Salamanders. In areas with higher pollution, the populations are not as successful. Hundreds of thousands of acres of wetlands have also been drained for agriculture. Agriculture is one of the main causes of the salamander's habitat destruction (Boyd, 2009).
Ecosystem Dependency
For a wetland habitat to exist, the ecosystem of the wetland must be in balance to provide enough food and ecosystems services to keep the Salamander population healthy. Salamanders generally feed on snails, earthworms, and slugs. There must be healthy populations of these animals to support the juveniles. Wetlands have been extensively degraded in the United States. Anything that is a threat to wetlands are also a threat to California Tiger Salamanders. These threats include chemical contamination, excess nutrients, and sediment from air and water. Global climate change could affect wetlands through increased air temperature; shifts in precipitation; increased frequency of storms, droughts, and floods; increased atmospheric carbon dioxide concentration; and sea level rise. All of these impacts could affect species composition and wetland functions. It is quite unfortunate that wetlands are becoming so degraded because they are biological hotspots and have a very high net primary productivity (California Tiger Salamander, 2012).
Nonnative Species
Juvenile salamanders are endangered as prey for nonnative species such as bullfrogs, crayfish, and mosquito fish. In an ideal and healthy California Tiger Salamander habitat, the seasonal pond water will be available to the eggs during the reproductive period but will dry up in the late summer. This ensures that no populations of the salamanders predators have the time to develop in theses pools. But because of damming, few seasonal ponds are available and more predator populations feed on the salamanders when they are in a juvenile stage. Although the Tiger Salamanders may be in terrestrial from, they are not fully-grown for 4-6 years, and remain vulnerable in their juvenile life (California Tiger Salamander, 2012).
Food Source Depletion
Salamanders are secondary consumers in the wetland ecosystem, instantly predators from the moment they hatch. During the first six weeks of their lives, the salamander young consumes zooplankton, such as cladocerans and copepods, small crustaceans midge larvae, water boatmen, and pond snails. As they develop, they then switch to larger prey such as the small tadpoles of Pacific treefrogs and California red-legged frogs. The salamanders are dependent on a predator-prey relationship with another California endangered amphibian: the red legged frog. The Salamanders food source is threatened in many ways. The use of pesticides for mosquito abatement reduces this food resources for salamanders, as well as other insects the Salamanders
depend on (Threats to Salamanders, 2012).
Vernal Pool Habitat Destruction - The California Tiger Salamander's Biggest Threat
Healthy Vernal Pool Ecosystem
Clean Water
No Unnatural Predators
Food Sources (worms, small insects)
Optimal Elevation (1,500 ft)
Shade Cover
Close to Mates
It is estimated that during the life of an average female California Tiger Salamander, just 11 of her 200 offspring will reach metamorphosis. (United States Environmental Protection Agency, 2010)
Causes of Vernal Pool Destruction
Deforestation
Deforestation is extremely harmful to salamanders in this stage because it reduces available pond space, shade cover, and habitat space. When the amount of shade that covers the forest floor is reduced, the increased sunlight can allow for higher temperatures to reach the forest floor. This causes the desiccation of vernal pools and any salamanders dwelling in them. When the pond dries up at the right time, it triggers the Salamander’s metamorphosis into a terrestrial adult, so if the pond dries up too early the salamander cannot grow to the proper size before moving to the next stage (Leon, 2012).
Climate Change
One of the most prominent threats to California Tiger Salamanders is drought. In California, drought has become more common due to climate change. Climate change is also threatening the California Tiger Salamanders because it causes climate and weather patterns to shift. and Some of these weather changes, particularly in stronger El Niño years, cause heavy early rain, triggering early migration and reproduction for the California Tiger Salamander (Leon, 2012). Then little or no rain falls mid-to late-season, inhabiting the salamander larvae’s ability to metamorphosize successful. The California Tiger Salamander breed in vernal pools during the months of Febuary and June.In the below graph, you’ll notice a direct correlation between the worst times of drought and breeding season for the California Tiger Salamanders.
Urbanization
Human activities and modifications to natural areas often cause alterations in water tables, wetlands, ponds, and lakes. These alterations of water flows from natural areas for human usage can prevent flows that supply salamander habitats from creating important pools, ponds, and flooded areas (Leon, 2012).