Arizona Amphibians Disappearing

Arizona Amphibian Conservation

Fresh water, the essential habitat of Arizona’s amphibians, is declining in both quality and quantity.  Frogs, toads, and salamanders are dependent on open water habitats.  Like many other places in the world, Arizona’s human population has exceeded the state’s carrying capacity.  Water resources in most areas of the state can no longer support the state’s human population.  In their unconscious drive to become the only species left, Arizona’s humans have depleted and polluted their water resources.  As the human population continues to grow, water and amphibians will continue to disappear.

Rocky Mountain Toad

Rocky Mountain Toad

The photograph shows a palm-sized Rocky Mountain Toad.  In spring, it cries its nasal “waaah” mating call from the banks of Arizona’s streams, lakes, and temporary rain pools.  On warm moist nights, one or more of these small predators will often sit beneath outdoor lights and windows where insects congregate.

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The International Union for the Conservation of Nature (IUCN.org) has this to say about amphibians:

  • Amphibians are among the oldest organisms on earth, having survived the last five mass extinctions.
  • They play a tremendous role in ecological studies due to their ability to act as bio-indicators, representing climate change and environmental stress.
  • They are a tremendous ecological asset due to their ability to act as both predator and prey, thereby maintaining a balance of nature.
  • Amphibians are found to be very useful for agricultural purposes due to their ability to act as a biological pest controlling agents.
  • They can help control the spread of diseases, such a malaria, by controlling the population of vectors such as mosquitos. 
  • Compounds derived from amphibian skin offers a promising pathway towards new medicinal discoveries.
  • Amphibians have played an important role in human culture, from religion to fables and traditional medicine.

The numbers

  • 122 amphibian species have become extinct in the last 25 years.
  • The current rate of amphibian extinction is 211 times the background amphibian extinction rate.
  • One-third of the world’s 6,000 amphibian species are under threat of extinction.
  • 427 of the world’s amphibian species are listed as Critically Endangered by The IUCN Red List of Threatened Species.
  • 38 species that are classified as Extinct in the most recent Red List are indigenous to Asia.
  • 21 of these species are native to Sri Lanka.”

68% of Arizona Amphibians Imperiled

(From Amphibiaweb and AZGFD):
World:  6,400
United States:  230
Arizona natives:  34
Arizona native amphibians imperiled:  23

Why Are Arizona Amphibians Disappearing?

Arizona amphibians are declining because of habitat loss, water pollution, disease, UV-B radiation, and competition from introduced exotic species.

Amphibians prefer small streams and pools of open water with lots of shoreline.  These habitats are declining across the state.  I have three spring-fed stock-watering ponds near my house.  An upstream farm and nearby small city depend on water pumped from the aquifer that supplies my ponds.  The city’s population of around 30,000 people uses about five million gallons of water per day.  During summer, the farm probably uses more.  Added to these users, are more than 1,000 private residential wells using the aquifer, each with the right to use up to 50,000 gallons of water per day.  The State of Arizona Department of Water Resources has determined that human water consumption in this area exceeds the amount provided by precipitation.  Not surprising, the water level in my ponds is sinking.

Pollutants are building up in the water that remains.  Farms, mines, and urban areas are contributing toxic minerals such as mercury and arsenic, and a long list of toxic chemicals ranging from herbicides to hormones.  The pollutants are harmful in many ways, but perhaps the most visible are the malformations they cause.  Extra limbs, crooked or missing limbs, and facial disfigurements are common.  These and internal malformations make feeding difficult, and can prevent reproduction.

A one-eyed Rocky Mountain Toad comes in July to sit by my back door.  The toad sometimes misses stationary targets as he shoots out his tongue.  I suppose it’s because he can’t adjust to his one-dimensional view of things.  The toad is smaller than other Rocky Mountain Toads in my yard, but otherwise seems normal.  I can’t be sure the missing eye is a birth defect, but it is the kind of defect caused by water pollutants.

Adding to other problems, a fungal disease is attacking and killing amphibians.  The fungus is causing even greater devastation than the white-nose syndrome that is killing bats in the eastern United States.  The fungus attacking the amphibians is Batrachochytrium dendrobatidis (Bd).  Surveys described on the Internet (www.amphibia-web.org and http://www.bdmaps.net), found Bd in more than half the amphibians tested in several watersheds in the central and southeastern portions of Arizona.

Chytridiomycosis has become so bad in some places that most amphibians are extinct.  The Golden Frog, Panama’s national emblem, is now extinct outside of the quarantine arcs that protect it while researchers hunt for a cure for the disease.

Another problem for amphibians is the increasing levels of ultraviolet radiation reaching the earth’s surface.  The radiation has been increasing for decades due to gradual depletion of atmospheric ozone, and possibly some other factors.  Amphibians are vulnerable to the radiation because they have thin skin, and their eggs have no shells.  Researchers have found that the radiation slows amphibian growth rates, causes immune dysfunction, and multiplies the effects of contaminants, pathogens, and elevated temperature.  The Amphibiaweb website provides a review of the ultra-violet radiation problem.

The invasive species that people have accidentally introduced are also eliminating amphibians.  AZGFD includes the American Bullfrog on its list of the state’s ten most unwanted invasive species.  Bullfrogs are a problem because they eat other frogs and their food.  Bullfrogs themselves are susceptible to Bd and toxic human wastes.  Bellowing bullfrogs in my stock watering ponds have always announced the arrival of summer.  The bellows began declining in 2009, and in 2012, there have been gaps of several weeks between bellows.

Bullfrog decline in my ponds might be due to factors other than pollution.  The raccoons that fish from the banks of the ponds might be becoming more numerous.  A Double Crested Cormorant began fishing the ponds in 2007, and Great Blue Herons raised three chicks in a nest over one of the ponds in 2011.  Herons have always been present around the ponds, but the needs of nestlings might have increased the herons’ interest in frogs.  The cormorant did not return in 2012, but herons built a second nest and produced four chicks.

Chemical pollution is a possible cause of the decline of the bullfrogs.  The ponds are downstream from the active farm and a small city described above.  Water tests show that the ponds contain toxic levels of nitrogen.  I do not know the levels of herbicides, insecticides, antibiotics, hormones, and other organic wastes in the ponds.  The added nitrogen is probably responsible for the growth of algae that has twice covered the entire surface of two of the ponds.  On one occasion, the algae began dying, probably because it had used all the oxygen in the water.  As the algae died, all the fish in the pond died, too.

The combination of decreasing habitat, increasing toxic pollutants, increasing harmful radiation, disease, and exotic invaders is rapidly driving amphibians toward extinction.

Arizona Amphibian References

Field guides for identifying frogs, toads, and salamanders are available online (Arizona Herpetological Association, Brennan, 2008), and in print (Bishop, 1962, Stebbins, 1966).  The online Naturalist’s Bookstore has field guides and other references.  Go to:  http://bit.ly/RKW2bC.

Arizona Amphibian Conservation Status

  • E = Species endangered in all or part of its range according to the U. S. Endangered Species Act.
  • I = Introduced and Invasive species from various sources.
  • S = Species recognized as candidates for listing as E or T according to ESA, and species of concern to the Arizona Game and Fish Department, U. S. Bureau of Land Management, U. S. Forest Service, Navajo Tribe, and Mexican government (includes Arizona species that are endangered, threatened, or of concern in Mexico).
  • T = Species threatened in all or part of its range according to the ESA.

Arizona Amphibians Checklist

Go here for general checklist information.

S….Ambystoma mavortium mavortium  /  Barred Tiger Salamander

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S….Ambystoma mavortium nebulosum  /  Arizona Tiger Salamander

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E….Ambystoma mavortium stebbinsi  /  Sonora Tiger Salamander

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E….Ambystoma tigrinum  /  Tiger Salamander

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……Anaxyrus cognatus  /  Great Plains Toad

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S….Anaxyrus debilis  /  Green Toad

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S….Anaxyrus debilis insidior  /  Western Green Toad

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S….Anaxyrus microscaphus  /  Arizona Toad

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……Anaxyrus punctatus  /  Red-spotted Toad

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S….Anaxyrus retiformis  /  Sonoran Green Toad

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……Anaxyrus woodhousii  /  Woodhouse’s Toad

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……Anaxyrus woodhousii australis  /  SW Woodhouse’s Toad

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……Anaxyrus woodhousii woodhousii  /  Rocky Mountain Toad

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S….Craugastor augusti  /  Barking Frog

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S….Craugastor augusti cactorum  /  Western Barking Frog

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S….Gastrophryne olivacea  /  Western Narrow-mouthed Toad

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……Hyla arenicolor  /  Canyon Treefrog

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S….Hyla wrightorum  /  Arizona Treefrog

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S….Hyla wrightorum (Huachuca/Canelo Pop.)  /  Arizona Treefrog

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……Hyla wrightorum (Mogollon Rim Pop.)  /  Mogollon Rim Treefrog

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S….Lithobates (Rana) onca  /  Relict Leopard Frog

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T….Lithobates chiricahuensis  /  Chiricahua Leopard Frog

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S….Ollotis alvaria  /  Sonoran Desert Toad

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S….Pseudacris hypochondriaca  /  Baja California Treefrog

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……Pseudacris triseriata  /  Western Chorus Frog

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I….Rana berlandieri  /  Rio Grande Leopard Frog

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S….Rana blairi  /  Plains Leopard Frog

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I….Rana catesbeiana  /  American Bullfrog

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S….Rana pipiens  /  Northern Leopard Frog

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S….Rana tarahumarae  /  Tarahumara Frog

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S….Rana yavapaiensis  /  Lowland Leopard Frog

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……Scaphiopus couchii  /  Couch’s Spadefoot

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S….Smilisca fodiens  /  Lowland Burrowing Treefrog

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……Spea bombifrons  /  Plains Spadefoot

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S….Spea intermontana  /  Great Basin Spadefoot

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……Spea multiplicata  /  Mexican Spadefoot

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I….Xenopus laevis  /  African Clawed Frog

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Please contact me with your observations, notes, and corrections.  [contact_form lang=en]

2 thoughts on “Arizona Amphibians Disappearing

  1. Pingback: Arizona Amphibian Update–October 2013 | The Blog Farm

  2. Pingback: National Lakes Assessment 2012 Key Findings | National Aquatic Resource Surveys | US EPA | GarryRogers Nature Conservation

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