The Spread, Effect and Mitigation of The Spread, Effect and Mitigation of Bullfrogs in the Western United Bullfrogs in the Western United

StatesStates

Jennifer SpawnJennifer SpawnSWES 474SWES 474

28 November 200628 November 2006

The Origin of BullfrogsThe Origin of Bullfrogs

Bullfrogs are originally native to EuropeBullfrogs are originally native to Europe

They were introduced to the Eastern U.S.They were introduced to the Eastern U.S. They are now considered “naturalized” They are now considered “naturalized”

West of the Rocky Mountains they are still West of the Rocky Mountains they are still considered non-nativeconsidered non-native

Where art thou, Bullfrog?Where art thou, Bullfrog?

highly aquatic, but will use the landhighly aquatic, but will use the land migrationmigration

Found in both lentic and lotic freshwater Found in both lentic and lotic freshwater environmentsenvironments

Mainly temperate and subtropical species Mainly temperate and subtropical species Like vegetation to hide in and lay eggs onLike vegetation to hide in and lay eggs on

Ya’ll might make me act A’frog up Ya’ll might make me act A’frog up in herein here

mostly nocturnal but are somewhat active mostly nocturnal but are somewhat active during the dayduring the day

Males are territorialMales are territorial They will eat anything will fit in their They will eat anything will fit in their

mouths…including small children and pets mouths…including small children and pets breathe through their skinbreathe through their skin

The Big, Bad BullfrogThe Big, Bad Bullfrog

Bullfrogs have been in the West since the 1890’sBullfrogs have been in the West since the 1890’s They were introduced as a sport animalThey were introduced as a sport animal Because of their voracious appetite bullfrogs Because of their voracious appetite bullfrogs

have been labeled a nuisance have been labeled a nuisance They are out-They are out-competing the nativecompeting the nativeanuran populationsanuran populations With a decline in With a decline in anuran populations anuran populations already, natives are inalready, natives are inmuch greater dangermuch greater danger

Are bullfrogs really Are bullfrogs really thatthat bad? bad? A study by Hecnar and M’Closkey A study by Hecnar and M’Closkey

found a change in community found a change in community composition in SE Canadacomposition in SE Canada

As bullfrogs declined the native As bullfrogs declined the native species flourishedspecies flourished

Interspecies competition was a Interspecies competition was a factorfactor

A release of predation was found A release of predation was found to be the leading cause of native to be the leading cause of native species revivalspecies revival

This study is the general This study is the general consensus among biologists: consensus among biologists: bullfrogs are a negative keystone bullfrogs are a negative keystone species in an ecosystemspecies in an ecosystem

A study done by Hayes and A study done by Hayes and Jennings indicates bullfrogs may Jennings indicates bullfrogs may not be the causenot be the cause

Habitat loss, fragmentation and Habitat loss, fragmentation and pollution may also be factorspollution may also be factors

Other predators may also be to Other predators may also be to blameblame

Disease is also a major playerDisease is also a major player Bottom line we really don’t have a Bottom line we really don’t have a

clear answer…interspecific clear answer…interspecific relationships are complex relationships are complex

So what’s the deal here?So what’s the deal here?(Arizona)(Arizona)

The native Ranid species in Arizona are all The native Ranid species in Arizona are all either threatened or are of special concerneither threatened or are of special concern

In many areas native species are in direct In many areas native species are in direct competition with and predation by bullfrogscompetition with and predation by bullfrogs

However to say bullfrogs are the sole However to say bullfrogs are the sole cause is irresponsiblecause is irresponsible Bullfrog populations are out of control in some Bullfrog populations are out of control in some

areasareas

What’s the government doing?What’s the government doing?

The U.S. Fish and Wildlife The U.S. Fish and Wildlife Service is the main agency Service is the main agency dealing with bullfrog effectsdealing with bullfrog effects ESA ESA

The Arizona Game and Fish The Arizona Game and Fish Department also helps out Department also helps out You can hunt bullfrogs if you You can hunt bullfrogs if you

want!want! www.azgfd.govwww.azgfd.gov

Specific MitigationSpecific Mitigation

BiologicalBiological

ChemicalChemical

MechanicalMechanical

Integrated Pest ManagementIntegrated Pest Management

Biological ControlBiological Control

As of yet there is no really great biological As of yet there is no really great biological control of bullfrogscontrol of bullfrogs

Large Mouth Bass, Diving beetles, Large Mouth Bass, Diving beetles, Dragonfly larvae and water nymphs like to Dragonfly larvae and water nymphs like to eat themeat them None species specific None species specific

But still, the bullfrog population is growing But still, the bullfrog population is growing rapidly in some areas of the staterapidly in some areas of the state

Chemical ControlChemical ControlRotenoneRotenone

Rotenone is a chemical used primarily by Rotenone is a chemical used primarily by fisheriesfisheries

It does not allow cellular respirationIt does not allow cellular respiration The electron transport chain is interruptedThe electron transport chain is interrupted Oxygen builds up in the blood and slows Oxygen builds up in the blood and slows

breathing until the animal diesbreathing until the animal dies Adult bullfrogs do not have gills but diffuse Adult bullfrogs do not have gills but diffuse

oxygen across their skin…thus Rotenone oxygen across their skin…thus Rotenone should have an affect on adult bullfrogsshould have an affect on adult bullfrogs

HOWEVER…it HOWEVER…it doesn’t !doesn’t !

Lessons from the San Rafael Lessons from the San Rafael ValleyValley

Rotenone was Rotenone was applied to kill bullfrogsapplied to kill bullfrogs

People were People were positioned around the positioned around the tank to gig bullfrogs tank to gig bullfrogs as they left the water as they left the water

People were also People were also positioned to rescue positioned to rescue salamanderssalamanders

Lessons from the San Rafael Lessons from the San Rafael ValleyValley

Rotenone although it breaks down by itself in Rotenone although it breaks down by itself in about a week, must be neutralized with about a week, must be neutralized with Potassium permanganate Potassium permanganate

Lessons from the San Rafael Lessons from the San Rafael ValleyValley

No bullfrogs were killed by RotenoneNo bullfrogs were killed by Rotenone We seined and put out traps and no bullfrogs were We seined and put out traps and no bullfrogs were

found deadfound dead Frogs can also breathe using their mouths and lungsFrogs can also breathe using their mouths and lungs However, if tadpoles were present they were certainly However, if tadpoles were present they were certainly

killedkilled

The salamanders were harmedThe salamanders were harmed It was expensive, smelly and inefficient It was expensive, smelly and inefficient

compared to other methodscompared to other methods

Mechanical or Physical ControlMechanical or Physical Control

ShootingShooting

SeiningSeining

Hand Capture/GiggingHand Capture/Gigging

TrappingTrapping

SeiningSeining

Hand Capture and GiggingHand Capture and Gigging

Frogs are pretty hard to catch during the day Frogs are pretty hard to catch during the day unless you have “frog eyes” and can sneak up unless you have “frog eyes” and can sneak up on themon them Hand capture at night with a flashlight is easierHand capture at night with a flashlight is easier

The best way is to seine The best way is to seine

the frogs out of the tank the frogs out of the tank

or stream and either gig or stream and either gig

or smash them against or smash them against

a rocka rock

TrappingTrapping

You can also use minnow traps to try and You can also use minnow traps to try and lure in frogs with some bait…lure in frogs with some bait…

Integrated Pest ManagementIntegrated Pest Management

A combination of chemical and physical A combination of chemical and physical controls is the best solution controls is the best solution

New technologies and solutions need to New technologies and solutions need to be pursuedbe pursued

More research about bullfrogs and their More research about bullfrogs and their effects need to be doneeffects need to be done

In Conclusion…In Conclusion…

Bullfrogs are a typical invasive speciesBullfrogs are a typical invasive species

They should not be made into this terrible They should not be made into this terrible monstermonster

There needs to be a better way to control the There needs to be a better way to control the populationpopulation

Get a hunting license and go eat some frogs…Get a hunting license and go eat some frogs…you’ll help out wildlife all over AZ!you’ll help out wildlife all over AZ!

SourcesSources Clarkson, R.W., DeVos Jr, J.C. The bullfrog, Clarkson, R.W., DeVos Jr, J.C. The bullfrog, Rana catesbeianaRana catesbeiana Shaw, in the Shaw, in the

Lower Colorado River, Arizona-California. Journal of Herpetology (20)1: 42-Lower Colorado River, Arizona-California. Journal of Herpetology (20)1: 42-49. 198649. 1986

Hayes, M.P., Jennings, M.R. Decine of ranid frog species in Western North Hayes, M.P., Jennings, M.R. Decine of ranid frog species in Western North America: are bullfrogs, America: are bullfrogs, Rana catesbeianaRana catesbeiana, responsible? Journal of , responsible? Journal of Herpetology (20)4: 490-509. 1986Herpetology (20)4: 490-509. 1986

Hecnar, S.J., M’Closkey, R.T. Changes in the composition of a ranid frog Hecnar, S.J., M’Closkey, R.T. Changes in the composition of a ranid frog community following bullfrog extinction. American Midland Naturalist community following bullfrog extinction. American Midland Naturalist (137)1: 145-150. 1997.(137)1: 145-150. 1997.

Moyle, P.B. Effects of introduced bullfrogs, Moyle, P.B. Effects of introduced bullfrogs, Rana catesbeianaRana catesbeiana, on the native , on the native frogs of the San Joaquin Valley, California. Copeia (1973)1: 18-22. 1973.frogs of the San Joaquin Valley, California. Copeia (1973)1: 18-22. 1973.

Roach, John. “Invading Bullfrogs Appear Nearly Unstoppable.” National Roach, John. “Invading Bullfrogs Appear Nearly Unstoppable.” National Geographic News. 28 September 2004. <Geographic News. 28 September 2004. <http://news.nationalgeographic.com/new/2004/09/0928_040928_bullfrog.hthttp://news.nationalgeographic.com/new/2004/09/0928_040928_bullfrog.htmlml> 20 November 2006.> 20 November 2006.

Ryan, M.J. The reproductive behavior of the bullfrog (Ryan, M.J. The reproductive behavior of the bullfrog (Rana catesbeianaRana catesbeiana). ). Copeia 1: 108-114. 1980.Copeia 1: 108-114. 1980.

Spawn, J. Personal field notes pp.24-26. 18 July 2006.Spawn, J. Personal field notes pp.24-26. 18 July 2006.