dragonforce 65 rc sailboat

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RC Sailboat/ Yacht Joysway DragonForce 65 Version 7 RTR DF65

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Product Description

Joysway DragonForce 65 Version 7 Sailboat RTR 8815

The Joysway DragonForce is the one of the best selling RC yacht/ sailboats in the world, and with the new Version 7, it just got better!!

New features on the DF65 Version 7 Include:

• 50 Micron Mylar " A" Sails, ships flat in box, with corner reinforcement, battens, eyelets and improved jib luff
• Boom Vang redesigned  to be easier to adjust, better connection to boom
• Redesigned "no flex" Servo tray, featuring improved control arm geometry , and larger opening to accept larger servo
• New Jib forestay fitting for easier more consistent jib rigging
• Upgraded digital  metal gear rudder servo
• New Pre-installed Upgraded High torque Sailwinch for fast, more precise control
• New Boat Stand Laydown Kit  to substantially reduce risk of high winds blowing over your boat
• New Keel Bolt main sheet guide fitting, to stabilize main sheet ring
• Upgraded Joysway radio, with improved adjustment
• Redesigned rudder post, to improve fit and stability
• Recessed deck track for eyelets, and improved under deck plastic insert to keep eyelets waterproof without extra glue
• Retooled mold designed to make boat more durable / thicker

The Joysway DragonForce 65 V7, or DF65 for short, is currently the best-selling RC sailboat in the world. The reasons are as simple as the concept and design itself, which was developed in collaboration between Joysway and  top RC performance yacht designers throughout the world . Sleek lines and competition-developed sails make the DragonForce 65 race, perform and compete against even those sailboats that would be 10 times the price! The boat is based on the ICE design with an ABS hull, profiled aluminum fin and molded plastic rudder. The A rig is a full sized, fractional low aspect rig with carbon spars and a ball raced gooseneck help make the DF65 a top performer. The DragonForce 65 is a recognized competition RC yacht that can be sailed in the restricted DF65 Class which is recognized by the American Model Yachting Association, with well-defined rules and RC associations that are located worldwide. 

With DF65 clubs all over North America, chances are there is a group near you sailing one! This is the perfect boat to start your own group sailing as well.

The DF65 V7 RTR Version is shipped  with everything necessary to get started . Preinstalled Servo's, Preassembled booms, sails, fittings, 2.4G controller and receiver, etc. All you need to do is assemble the spars , Mast, hang the sails, and go race!

Specifications and Features

• Length: 650 mm
• Beam: 116.5 mm
• Rig Height: 915mm
• Overall Height: 1388mm
• Sail area (Mainsail): 1460 square cm
• Sail Area: (Jib): 766 square cm
• Sail Area (overall) 2226 square cm
• 50 micron Mylar Film racing sails with printed Flow stripes and Logo -- - ships flat in box, with corner reinforcement, battens, eyelets and improved jib luff
• RTR Total Weight: 1200g (not including batteries)
• ABS Molded and Painted Hull with decal stickers
• Rubber bow bumper
• Counterweighted Jib
• 2.4GHz Joysway 4 Channel Digital Radio Included
• Extruded Aluminum Keel with Zinc Alloy Ballast Bulb
• Extruded Carbon Fiber Mast and Boom Tubes
• Metal Geared Digital Rudder Servo
• Display stand – Molded Plastic and Fiberglass Tubes
• New Boat Stand Laydown Kit to substantially reduce risk of high winds blowing over your boat

With DF65 clubs all over North America, chances are there may be a group near you sailing these! This is also the  perfect boat to start you own group sailing as well.

Having a Joysway DragonForce 65 means that, should you like to, you can often find a location local to you to learn sailing tips and how to configure sails or rigging, compare (and hone) your sailing skills against others, participate in local, state, national or even international 

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Dragonforce 65 purchase.

Posted by peter clarke on 7th Oct 2022

lots of fun rigging her and getting her ready and the first sail yesterday removed any doubt of the wisdom of this purchase. I actually felt like I was on board this perfect little vessel as she tacked about the small lake in a perfect fall breeze. I will upgrade my radio eventually, however, so that I can monitor the battery strength on the boat itself while sailing. That will merely be icing on the cake..thanks for the prompt service and delivery. This is a big thanks from a very happy crew on the West Coast.

Dragonforce 65

Posted by Paul Blackmore on 16th May 2022

Very good product. Exceeded my expectations in every way. Assembly tip. Cut all shorter lengths of rigging line at least 10mm longer than what the manual says. It will make the knot tying so much easier particularly on the shorter pieces of line. Lastly, for the final rigging of the gybe sail, which happens to be the last line to tie into place, follow the letter designations only and match them to the picture provided. The numbering system differs on the last two eyelets from what is shown on the initial parts labeling diagram and the printed instructions which follow. Follow the placement shown in the picture and the letter designations and all will be well. Happy sailing.

Great value - Fun to build & sail

Posted by AndyH on 7th Jul 2021

This quality RC sailboat is significantly cheaper than equivalents on the market. I found it great fun to assemble/build and have been impressed by the range & reliability of the RC components. Hours of fun on the water!

The product arrived in a relatively short period of time and in extremely good condition. I have been most impressed by the quality of the individual components and the overall product now completed and ready for "sea trials". Threading the "Bowsie

Posted by Dan Johnson on 4th Jul 2021

This is a great product and the company providing it has been easy to deal with, and responded rapidly to my order placement. I will buy from them again.

Posted by John simmonds on 28th Dec 2020

Very good quality construction. Took quite a while to put together as instructions very typical Chinese translations. Good value for the money

Joysway Dragon Force 65 RC Sailboat

Posted by Peter King on 17th Aug 2020

Took a little time to set up carefully. Well worth the investment. It sails beautifully.

Posted by rob on 16th Aug 2020

Biggest bang for the $$ I've seen in a long time. Unit is in spectacular condition in a sophisticated packing box, Assembly instructions appear to have been written in non-translated English and are terrific. Parts and finish are excellent and first sailings are fantastic. Why kids waste time playing games with their thumbs when such amazing toys are available is beyond me. Kudos to rchobbiesoutlet for fast service and response to an inquiry also.

Dragon force 65

Posted by Ross Griffin on 9th Feb 2020

Arrived promptly in good shape, It took a while to tie all knots and thread bowsies. After waiting a week for the pond to thaw, everything went well, and second time there were other df65's there. Everthing works well and is a speedy boat

DF65 RC Sailboat

Posted by Andy on 29th Jan 2020

Great value! At under $300 this RC model yacht beats the competition. Build quality is excellent and it comes with everything you need to start rc sailing. I was also impressed with the transmitter-receiver range (at least 100m). There is quite a bit of assembly required but this was fun with the clear instruction manual. What you are left with is a serious model racing yacht with full range of adjustments for sail trimming to suit various wind conditions. Full marks Joysway!

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Joysway DragonForce 65 V7 655mm (25.7") Racing Sailboat - PNP

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Bancroft DragonForce 65 V7 655mm (25.7") Racing Sailboat from Joysway - PNP - BNC1048-002

There are few R/C modeling activities more peaceful than sailing a yacht on a summer’s evening enjoying a gentle, constant breeze on your preferred pond. Likewise, few activities can be more exciting than racing like a captain in the America’s Cup, using a model yacht against similarly-equipped competitors that places your sailing skills to the test!

Bancroft is pleased to offer the world-renown DragonForce 65 sailing yacht, a model perfectly suited to either activity. Manufactured by Joysway Model Co., it’s now available for sale through Motion RC!

Available in both PNP (no transmitter or receiver) and RTR (includes transmitter and receiver) versions, these models arrive highly prefabricated and ready for final assembly and rigging.

V7 improvements include a new, improved sail winch servo and a revised boat stand that allows either vertical or horizontal securement of the model for convenient storage, transport, or maintenance.

With active chapters in eight countries, DF racing has become an economical and enjoyable portal into the sport of RC sailing. Visit www.dfracing.world for information, rules, competition chapters, and events.

Stainless steel fittings and hardware, many with reliability-enhancing rubber seals ensure years of trouble-free performance and reliability from your DragonForce 65.

Thanks to its mylar racing jib and mainsail, the DragonForce 65 is a capable performer in both light and heavy wind conditions, providing the versatility to delight both expert and new sailors!

• PNP-Includes rudder servo and sail winch, requires minimum 2-channel stick transmitter and receiver
• Fully painted and decorated hull and sails
• Extruded carbon fiber masts and boom tubes
• Extruded aluminum keel with zinc alloy ballast bulb
• Display stand included
• Bancroft DragonForce 65 V7 655mm (25.7") Racing Sailboat - PNP
• Rudder and sail winch servos preinstalled
• 2 Channel radio - select a minimum 2 channel stick radio from our Radio Collection
• 2 Channel receiver - select a minimum 2 channel receiver from our Receiver Collection
• Eight (8) AA-sized 1.5V dry cell batteries, Alkaline or NiMH - we recommend Admiral AA NiMH 2600mAh rechargeable batteries or or suitable LiFe, NiMH, or LiPo battery

Product Specifications:

	N/A
	650mm / 25.7in
	116.5mm / 4.6in
	1338mm / 52.7in
	ABS Plastic
	AA Battery
	8
	JST
	N/A
	N/A
	N/A
	N/A
	N/A
	Splash-Proof
	N/A
	4 Channel
	5

Spare Parts

Product spare parts.

SKU: BNC6026-001

SKU: BNC7009-004

SKU: BNC1042-118

SKU: BNC5072-003

SKU: BNC1047-103

SKU: BNC1047-126

SKU: BNC1047-127

SKU: BNC1047-130

SKU: BNC1048-125

SKU: BNC1048-126

SKU: BNC1048-129

SKU: BNC1048-130

SKU: BNC1048-131

SKU: BNC1048-132

SKU: BNC1048-133

SKU: BNC1048-134

SKU: BNC1048-135

SKU: BNC1048-137

SKU: BNC1048-143

SKU: BNC1048-144

SKU: BNC1048-145

SKU: BNC1048-146

SKU: BNC1048-147

SKU: BNC1048-148

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Product support

Product manuals:.

• Joysway DragonForce 65 V7 655mm Racing Sailboat Instruction Manual
• Dragonforce 65 Restricted Class Rules
• Dragonforce 65 Tuning Guide

If you need any additional assistance, please visit the  Motion RC Help Center

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Dragon Force 65 V7  Racing  RC  Sail boat

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• Dragon Force RG65

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  Product Description

Meet the Joyway Dragon Force RG65 a complete Ready to Race Rg65 that is taking the RC sailing community by storm. This reasonably priced  RC sailboat comes with every thing necessary to have you on the water in an hours time. This kit requires minimal assembly and is the perfect starter boat for the individual or club that wants to build a competitive racing fleet. This boat was designed by a crack team of hard core RC sailors looking to mass produce an entry level boat that would be fun to sail in a variety of conditions.

This boat can be campaigned in the RG65 open class or the RG65DF restricted class. The Rg65DF restricted class has strict rules limiting modifications- but the open class allows for a variety of sail types and rig types that can be readily adapted to this hull.

• Length:  655mm / 25.8in
• Height:  1338 mm / 52.7 in
• Width / Diameter:  116 mm / 4.6 in
• Version: 2014 V2

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Great entry-level boat

Posted by Shawn Prigmore on 14th Nov 2016

Very happy with this boat so far, it sails well right out of the box. Very easy assembly, all you have to do is rig the mast, booms, and sails. Instructions can be a little vague, but there are numerous guides on the net to help. The radio leaves ssomthing to be desired, but you can't expect a spektrum system at this price. Highly recommended first boat.

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Dragon Force 65 V6 8815ARTS Sailboat

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Product information

Item Weight	4.4 pounds
ASIN	B0B7R69NDZ
Manufacturer	Josway

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Product Description

The new RG65 class Dragon Force version 6 undergoes profound changes. This major transformation does not affect its qualities and competitiveness compared to the previous model, quite the contrary: the hull comes from a new complete mould that allows to increase its resistance while keeping the same weight and profile, the mast fittings, booms and sails have been redesigned for maximum efficiency and strength, the sails are now made of film > of 5 0 microns, the Digital rudder servo sees its power increased by 10%, and the electronics has been further improved. The new Dragon Force RG65 V6 from Joysway benefits from 2.4GHz technology that guarantees precise handling, fast transmission and protection against interference, and immediate response times even at great distances. Join the next generation of RG65 class competition with the revolutionary Dragon Force 65 V6 racing yacht! Features:

• Very high quality RC sailboat delivered ready to sail
• Excellent performance
• ABS moulded painted shell
• Carbon fiber pole and fiber booms
• Aluminium keel with zinc ballast
• 50 micron Mylar foil sails with printed logos and stripes
• Digital steering servo with metal sprockets
• Powerful and fast winch servo
• Moulded plastic display stand with fiberglass tubes included
• Length: 650 mm
• Width: 116.5 mm
• Mast height: 915 mm
• Total height: 1338 mm
• Total weight: 1200g (batteries not included)
• Mainsail surface: 1500 cm²
• Jib sail surface: 1000 cm²
• Total sail area: 2500 cm²

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• Sail Numbering Diagrams
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• DF65 Boat / Sail Registration

Building and Tuning Guides and Tips

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Check out the links below, plus all the online resources available in our links page!

Tuning tips, the following link is a very nice video on tuning the df65. make by patrick rynne of the miami rc sailing squadron it will be a big help to all df65 skippers..

Here is a PDF created by Zach Kelchner to summarize the video above:

Df65-tuning.

———————————————————————————————————————————-

Tuning Your DragonForce 65  – DF65 Sail Tuning Guide by Soch Sails with measurements and procedure for getting your DF65 going fast!

———————————————————————————————————————————–

Next is a very handy printable Tuning Guide provided by Phil Burgess the President of the Australia DF Radio Sailing Assn.

=================================================================================

Sail Making

The files that follow are pdf’s of df65 a, a+, b, c sails that can be printed full size. the drawings are made from data in the class rules and mainsail luff curve reflects measurements from production sails., df65a+ templ, df65a templ , df65 b templ, df65 c templ, class rules sail numbering diagram pdf below, sail number diagram, if you need the proper sized numbers for putting numbers on your sails per the above diagram, the pdf below prints out accurately on most printers to comply with the rules v1.8, sail#temp v1.8.

——————————————————————————————–

Assembly Guides

Df65 v6 rigging instructions v1., chucks_df65 a+ assembly guide_rev_1, df65 rig kit assembly guide  – nice instructions  df65 rig building guide, bought a b or c rig and need some helpful tips on building it up correctly, then look no further, ———————————————————————-, other useful hints and tips.

• DF65 USA Club Registry Form
• DF65 USCOA Member Registration & Sail # Form
• International Class Assn.
• Regatta Schedule/NOR’s

© 2024 DragonForce 65 USA Class Owners Association

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JOS8815RTRFS – DF65 R/C Sailboat Kit – Ready to Run (With FlySky FS-i6 Radio)

$ 329.99

55 in stock

This version of the DragonForce 65 comes with the upgrade FlySky FS-i6 radio system.

Radio Specifications:

Channels – 6 Model Memory – 20 Models RF Range – 2.408-2.475 Bandwidth – 500 KHz RF Channel – 135 RF Power – Less than 20 dBm 2.4GHz system – AFHDS 2A Modulation Type – GFSK Stick Resolution – 4096 Low Voltage Alarm – Less than 4.2V Power Input – None PS2/USB Port – PS/2 Port PPM Antenna Length – 26mm Dual Antenna Size: – 174mm x 89mm x 190mm Battery Power – 6V DC (1.5V AA X 4) Weight – 392g

This is the Dragon Force 65 V6 by Joysway.  The DF65 is a hugely popular RC Sailboat Kit.  Inexpensive to buy, easy to build and really fun to sail.  Whether you are a seasoned racer or just want to have fun at the cottage this is the boat for you!!

Features on the DF65 Version 6 Include:

50 Micron Mylar ” A” Sails, ships flat in box, with corner reinforcement, battens, eyelets and improved jib luff Boom Vang redesigned to be easy to adjust, better connection to boom Redesigned “no flex” Servo tray, featuring improved control arm geometry New Jib forestay fitting for easier more consistent jib rigging Upgraded digital rudder servo New Keel Bolt main sheet guide fitting, to stabilize main sheet ring Upgraded radio, with improved adjustment redesigned rudder post, to improve fit and stability Recessed deck track for eyelets, and improved under deck plastic insert to keep eyelets waterproof with out extra glue Retooled mould designed to make boat more durable / thicker

This is the RTR version so it will include a FlySky FS-i6 Radio and Receiver

The DF65 is straightforward to build.  It will require a good pair of scissors or exacto knife to cut the dyneema sheeting.  Another thing that is very helpful is some Cyanacrylate Glue (Crazy Glue) to add to your knots.  We really like the Gel CA from Bob Smith.  It can be ordered through our site at – BSI116

I would also suggest checking online for build, set-up and tuning tips from the experts!  We have a list on our Links page of helpful sites.  I strongly recommend the blog by Mr. Klaus Harris!

FS-i6 instructions

JOS8815RTRFS - DF65 R/C Sailboat Kit - Ready to Run (With FlySky FS-i6 Radio)

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Sailboat Dragon Force 65 V7 PNP w/o Radio Equipment

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• Brand: Joysway
• Boat type: Sailboat
• Hull type: V-form
• Material: ABS Plastic
• Hull length: 650 mm
• Total length: 650 mm
• Width: 116,5 mm
• Height: 1338 mm
• Weight: 1200 g
• Transmitter: Not Included
• Also includes: Winschservo
• Need to be completed with: Transmitter & Receiver
• Brand Joysway

Description

Article no.: MC_JW8815AV7

Dragon Force 65 Version 7 (New Winsch Servo) - ARTR (no radio gear)

• Length: 650 mm
• Beam: 116.5 mm
• Rig Height: 915 mm
• Overal Height: 1338 mm
• RTR weight (no batteries): 1200 g
• Sail Area (main sail): 1460 cm2
• Sail Area (Jib): 766 cm2
• Sail Area (Total): 2226 cm2
• Hull material: Molded ABS with painted white finish and attached stickers
• ARTR: No radio gear included
• Fully painted blow molded ABS hull
• 50 micron Mylar film racing sails with printed flow stripes and logos
• Extruded carbon fibre mast and boom tubes
• Extruded aluminium keel with zinc alloy ballast bulb
• Metal geared digital rudder servo and fast powerful sail winch
• Display stand
• 4 channel transmitter & receiver (and batteries for those)

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【Item No.: 8815V7】DF65 V7 RTR(J4C05 Radio)

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Dragon Force 65 V7 Racing RC Sail boat

Model No.: 8815V7 (DF65V7)

SPECIFICATIONS:

Length: 650 mm Beam: 116.5 mm Rig Height: 915 mm Overall Height: 1338 mm RTR Total weight: 1200g (Batteries not included) Sail Area (Mainsail): 1460 cm 2 Sail Area (Jib): 766 cm 2 Sail Area (Overall): 2226 cm 2 Hull Material: Molded ABS with painted finish and logo sticker Supplied in two versions: (1) RTR version(8815) with transmitter & receiver (2) PNP version(8815A) with no radio gear RTR version with radio gear (8815) requires 4pcs AA batteries for transmitter & 4 pcs AA batteries for receiver

WHAT'S INCLUDED:

Fully Painted, Moulded ABS Hull 50 micron mylar film racing sails with painted flow stripes and logo Extruded carbonfibre mast and boom tubes Extruded aluminum keel with zinc alloy ballast bulb Metal geared digital rudder servo New Digital DF Racing sailwinch servo for more accurate sail control 2.4G 4CH digital proportional transmitter (RTR version 8815 only) 2.4G 4CH receiver (RTR version 8815 only) Display stand with laydown function (Moulded plastic and glassfibre tubes)

MEASUREMENT:

Boat Box dimention: 91.2 x 30.4 x 11.6 cm Carton size: 38 x 32 x 93 cm Gross/Net weight: 11.7/10.7 kg One Carton: 3 pcs 20' container: 774pcs/258 ctns 40' container: 1572pcs/524 ctns

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Joysway Dragon Force 65 Radio Controlled Yacht RTR Very Special Price

£ 299.99 Original price was: £299.99. £ 199.99 Current price is: £199.99.

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Joysway dragon force 65  version rtr sailing yacht.

SPECIFICATIONS

Length:  650 mm Beam:  116.5 mm Rig Height:  915 mm Overall Height:  1338 mm Total weight:  1200g (Batteries not included) Sail Area (Mainsail):  1460 cm2 Sail Area (Jib):  766 cm2 Sail Area (Overall):  2226 cm2 Hull Material:  Molded ABS with painted finish and logo sticker

WHAT’S INCLUDED

Fully Painted, Moulded ABS Hull 50 micron mylar film racing sails with painted flow stripes and logo Extruded carbonfibre mast and boom tubes Extruded aluminum keel with zinc alloy ballast bulb Metal geared rudder servo and fast, powerful sail winch 2.4G 4CH digital proportional transmitter (RTR version only) 2.4G 4CH receiver (RTR version only) Display stand with laydown function (Moulded plastic and glassfibre tubes)

REQUIRED TO COMPLETE

• 4 AA batteries for transmitter
• 4 AA batteries for receiver

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case study bullfrogs answers

The Biology Corner

Biology Teaching Resources

Case Study – Are Invading Bullfrogs Harmful?

Students follow a story about an ecologist and a student who are studying the population size of bullfrogs in California.   These amphibians are considered an invasive species in that area and have been causing the decline of native species.  

Students learn concepts related to community interactions and learn one species can cause the decline of another species as described by the competitive exclusion principle.

Students also construct a predator-prey graph that shows the relationship between the number of bullfrogs and the number of bass fish in lakes.  Bass were introduced to help control the bullfrog population because they are known to eat juveniles and tadpoles.  

Students must make a judgement about whether it is appropriate to introduce another non-native species to control bullfrogs.

Students also compare other methods of population control, such as toxicants and trapping.  Finally, students must write a recommendation which suggests the best way to control the frogs.

Grade Level:  11-12  |  Time Required  2-3 hours

HS-LS2-1 Use mathematical and/or computational representations to support explanations of factors that affect carrying capacity of ecosystems at different scales. HS-LS2-2 Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and populations in ecosystems of different scales.

HS-LS2-6 Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem HS-LS2-7 Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.*

Shannan Muskopf

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Open Access

Peer-reviewed

Research Article

Climate Change and American Bullfrog Invasion: What Could We Expect in South America?

* E-mail: [email protected]

Affiliation Centro de Zoología Aplicada, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina

Affiliation Departamento de Ecología y Territorio, Facultad de Estudios Ambientales y Rurales, Pontificia Universidad Javeriana, Bogota, Colombia

Affiliation Departamento de Ecologia, Universidade Federal de Goiás, Goiás, Brazil

Affiliations Centro de Zoología Aplicada, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina, CONICET, Buenos Aires, Argentina

• Javier Nori, 
• J. Nicolás Urbina-Cardona, 
• Rafael D. Loyola, 
• Julián N. Lescano, 
• Gerardo C. Leynaud

• Published: October 3, 2011
• https://doi.org/10.1371/journal.pone.0025718
• Reader Comments

Biological invasion and climate change pose challenges to biodiversity conservation in the 21 st century. Invasive species modify ecosystem structure and functioning and climatic changes are likely to produce invasive species' range shifts pushing some populations into protected areas. The American Bullfrog ( Lithobates catesbeianus ) is one of the hundred worst invasive species in the world. Native from the southeast of USA, it has colonized more than 75% of South America where it has been reported as a highly effective predator, competitor and vector of amphibian diseases.

Methodology/Principal Findings

We modeled the potential distribution of the bullfrog in its native range based on different climate models and green-house gases emission scenarios, and projected the results onto South America for the years of 2050 and 2080. We also overlaid projected models onto the South American network of protected areas. Our results indicate a slight decrease in potential suitable area for bullfrog invasion, although protected areas will become more climatically suitable. Therefore, invasion of these sites is forecasted.

Conclusion/Significance

We provide new evidence supporting the vulnerability of the Atlantic Forest Biodiversity Hotspot to bullfrog invasion and call attention to optimal future climatic conditions of the Andean-Patagonian forest, eastern Paraguay, and northwestern Bolivia, where invasive populations have not been found yet. We recommend several management and policy strategies to control bullfrog invasion and argue that these would be possible if based on appropriate articulation among government agencies, NGOs, research institutions and civil society.

Citation: Nori J, Urbina-Cardona JN, Loyola RD, Lescano JN, Leynaud GC (2011) Climate Change and American Bullfrog Invasion: What Could We Expect in South America? PLoS ONE 6(10): e25718. https://doi.org/10.1371/journal.pone.0025718

Editor: Adam Stow, Macquarie University, Australia

Received: July 21, 2011; Accepted: September 8, 2011; Published: October 3, 2011

Copyright: © 2011 Nori et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: JN, JNL and GCL research is supported by MINCyT – PID 2010 (project #000113/2011). RDL research is supported by CNPq (project #475886/2009-7), CAPES-FCT Program (project #12/2009) and the Brazilian Research Network on Global Climate Change. JNL has a doctoral fellowship from Consejo Nacional de Investigaciones Científicas y Técnicas. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Climate changes are likely to affect the distributional ranges of invasive species [1] – [4] , which are one of the most serious global threats for biodiversity [5] , [1] . Invasive species can modify ecosystem processes and affect ecosystem structure and functioning [6] – [9] , with economic impacts reaching billions of dollars [10] . Worldwide, many invasive species have colonized protected areas altering their ecological integrity [7] , [11] . However, management actions established within protected areas or along buffer zones that try to control invasive species are usually ineffective given that many threats come from outside the area itself [12] .

The American Bullfrog ( Lithobates catesbeianus ) is endemic to eastern North America and has been introduced in approximately 40 countries in four continents via aquaculture and the aquarium trade [13] . It has been considered one of the hundred worst invasive species in the world [14] . The negative effects of the American Bullfrog invasion on native species arise from competition, amphibian and fish predation, as well as the spread of ranavirus and the fungus Batrachochytrium dendrobatidis, which is systematically killing amphibians in pristine environments and protected areas [15] , [16] . Specifically in South America, L. catesbeianus has been reported in ten countries [17] – [19] .

In recent years, species distribution models (SDMs) have been widely used to predict ecologically suitable areas for the establishment of invasive species under current and future climate projections with the goal of pinpointing regions in which urgent preventive actions must be taken (see Franklin [20] for a comprehensive revision of SDM theory and applications). SDMs combine presence data of individuals within their known distribution range with climatic data from those same areas to generate models usually describing the Grinnelian niche of the organism [21] , estimate their current distribution and predict areas exhibiting the same or similar environmental space.

Several authors have already developed predictive models for the American Bullfrog distribution across the globe or South America. Ficetolla et al. [22] proposed a global potential distribution (at current conditions) mostly aimed at predicting the potential distribution of L. catesbeianus in Europe. Giovanelli et al. [23] and Nori et al. [24] modeled potential distributions of the species in Brazil and Argentina, respectively (at current conditions), concluding that the presence of this species in the Atlantic Forest Biodiversity Hotspot is of special concern in the continent. Urbina-Cardona and Castro [25] modeled bullfrog distribution in Colombia at present as well as in a future scenario (2050) and determined that the species tends to slightly reduce its suitable range in the future. However, these results contrast with the climate change models proposed by Urbina-Cardona et al. [26] which identify vulnerable areas of massive future expansion in the Caribbean, Amazon and Orinoquia regions. Finally, Loyola et al. [27] evaluated the impact of a L. catesbeianus invasion in the Brazilian Atlantic Forest protected areas using ensembles of forecasts based on different modeling algorithms and future climatic models. They suggest that protected areas are more likely to be invaded by the species in the future due to the climatic changes expected for the region.

Here, we modeled the potential distribution of L. catesbeianus in its native range based on different climatic models and projected the result onto all of continental South America under different time slices (present time, 2050, and 2080). We then overlapped all of the projected models onto the IUCN layers of terrestrial protected areas. Our main goals were to determine: (a) the potential distribution of the American Bullfrog in South America applying recent suggested approaches for modeling invasive species ranges, (b) the pattern of change in the potential suitable habitats of L. catesbeianus during different time slices of climate change scenarios, (c) changes in the potential suitable surface of L. catesbeianus under different climatic models during the same time period, and (d) the surface of environmentally suitable IUCN protected areas for L. catesbeianus in different time slices and under different climate models. Lastly, we compared our results with previous related research.

Materials and Methods

Study area and species occurrence data.

We focused our analyses in all of South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, Uruguay and Venezuela) spanning a total area of 17.825.184 km 2 .

We began our study with a dataset of 1431 individual records from the native range of L. catesbeianus , obtained from HerpNet ( http://www.herpnet.org ), CONABIO ( http://www.conabio.gob.mx/remib/doctos/remib_esp.html ) and GBIF ( http://data.gbif.org ), including occurrences in Mexico, USA and Canada ( Fig. S1 ). Additionally, we used 210 individual records of the American Bullfrog in South America, obtained from I3N IABIN ( http://i3n.iabin.net ), Species Link ( http://splink.cria.org.br ), herpetological collections (Instituto Hórus, Universidad de Antioquia, Centro de Zoología Aplicada of the Universidad Nacional de Córdoba), and relevant literature [22] , [23] , [24] , [28] , [29] and from the “spatial download data” section of the IUCN Red List of Threatened Species web site [30] . Georeferencing was conducted when necessary using the Alexandria Digital Library Gazetteer ( http://middleware.alexandria.ucsb.edu/client/gaz/adl/index.jsp ). Duplicate records were discarded via ENMTools 1.3 [31] .

Climatic data

We did a pairwise Pearson correlation between 19 bioclimatic and one topographic variable at a spatial resolution of 30 seconds. We selected ten variables that did not showed colinearity with other variables (r<0.75): Mean Diurnal Range, Isothermality, Maximum Temperature of Warmest Month, Temperature Annual Range, Mean Temperature of Wettest Quarter, Mean Temperature of Warmest Quarter, Precipitation of Wettest Month, Precipitation Seasonality, Precipitation of Driest Quarter and Altitude ( Table S1 ). To estimate the influence of global climate change on the potential distribution of L. catesbeianus , we modeled the distribution of the species for three different time slices: present, 2050, and 2080. Due to the large effect of different Atmosphere-Ocean Global Circulation Models (AOGCMs) in species range projections [32] , [33] , we selected three different AOGCMs (CCCMA-CGCM31, CSIRO_MK30 and IPSL_CM4) for each time slice. The selected AOGCMs for this research, are widely used in the literature, additionally they have different equilibrium climate sensitivity values ranging from 3.1°C to 4.4°C. Equilibrium climate sensitivity is the annual mean surface air temperature change experienced by the climate system after it has attained a new equilibrium in response to a doubling of CO 2 concentration, and are within the range of all AOGCMs available from IPCC [34] . We compiled current and future climatic data from the Worldclim database ( www.worldclim.com ) [35] . Future scenarios were developed by IPCC's Fourth Assessment Report (AR4). All climatic layers were clipped to (a) 13 countries of continental South America, and (b) the native range of L. catesbeianus ( Fig. S1 ).

Modeling Method

We modeled the potential distribution of L. catesbeianus in its native range. We separated the 1431 individual records into two groups, one for training the models (1074 records) and one for testing them (357 records). The resulting models were projected for all of South America, in both current and potential future environments for the three different AOGCMs. We used MaxEnt 3.3.3e [36] since it has been shown to be a robust method for presence-only datasets [37] , [38] . We ran the MaxEnt models using the default setting, except for when selecting regularization values. This parameter was determined by the application of the small sample corrected variant of Akaike's Information Criterion (AIC) implemented in ENMTools 1.3 (for details see [31] ).

The resulting outputs of MaxEnt were continuous maps, which allowed us to make fine distinctions between the modeled suitability of different areas. A “minimum training presence” value was used to discriminate suitable from non-suitable habitat, which minimized both the training and test omission rates without resulting in an overly general model. This value has been proposed in recent papers for modeling the range of invasive species (e.g. [38] , [39] ). We assessed model performance using 25% of the records as “test data” in order to calculate the area under the receiver operating characteristic curve (AUC/ROC) [40] .

We projected the resulting models of the species' native range, defined as a minimum convex polygon ( Fig. S1 ). To avoid spurious projections (or to search for novel climate conditions), we used the “clamping analysis” (implemented in MaxEnt). This analysis treats variables outside the training range as if they were at the limit of the training range. This allows the identification of locations where predictions are uncertain because of the method of extrapolation by showing where clamping substantially affects the predicted value [36] , [41] . We validated our results by plotting the actual reported populations for South America onto the predicted distribution map (for present conditions). Finally, we evaluated the similarity between the modeled results for different AOGCMs during the same period by applying I statics and Relative Rank (RR) with the latest version of ENMTools [31] .

Protected areas analysis

The shape files of the protected areas of continental South America were obtained from the World Database of Protected Areas ( http://protectedplanet.net/ ). We only considered “designated” protected areas in any of the six IUCN categories. We overlapped the resulting models onto the current network of South American protected areas to determine the potential surface of protected areas that are environmentally suitable for L. catesbeianus . We also did this for different time slices and AOGCMs. Finally, we also calculated the surfaces of the different IUCN categories using ArcGIS 9.3.1 [42] .

The predictive models had high AUC values (0.842+/−0.009 for test and 0.86+/−0.011 for training). The “minimum training presence” value was low (0.094) and the better regularization value (lower value of AICc) was 1. Both the I statics and the Relative Rank (RR) [31] reflected the highest values of similarity between results of different AOGCMs for the same time slice. The I statics index varied from 0.88 to 0.91 in the 2050 results and from 0.79 to 0.86 in the 2080 results. The RR varied between 0.84 and 0.91 (2050) and between 0.79 and 0.85 (2080).

The geographic projection of the model in current conditions was in remarkable concordance with the reported feral populations of the American Bullfrog in South America. The results of the analyses reflected a slight decrease in the potential suitable areas for this invasive species in the future ( Fig. 1 , 2 , 3 ). At current conditions, the species is predicted to be absent from a major portion of northwestern and central eastern parts of the continent as well as in the southeastern portion of Argentina. Additionally, in the future, the invasion could retract in central western Brazil as well as in a big portion of Argentina, Paraguay and Bolivia, but increase in northern Brazil, southeastern Colombia, eastern Peru and southern Venezuela ( Fig. 3 ).

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

Each map shows potential suitable areas for Lithobates catesbeianus at one of the three different analyzed AOGCMs, classified in: Retraction (suitable areas at present but not at 2080), Expansion (suitable areas at 2080 but not at present conditions) and suitable areas at present and at 2080.

https://doi.org/10.1371/journal.pone.0025718.g001

Each map shows potential suitable areas for Lithobates catesbeianus at one of the three different analyzed AOGCMs, classified in: Retraction (suitable areas at present but not at 2050), Expansion (suitable areas at 2050 but not at present conditions) and suitable areas at present and at 2050.

https://doi.org/10.1371/journal.pone.0025718.g002

Percentage of suitable surface of the entire continent for Lithobates catesbeianus at the three analyzed time slices and AOGCMs.

https://doi.org/10.1371/journal.pone.0025718.g003

Areas with highest values of suitability for L. catesbeianus were located in the southern portions of Brazil and Uruguay, and in north and central eastern Argentina. Figure 4 shows the suitability values of one of the AOGMs scenarios (CCCMA_CGCM31) at all of the studied time slices, however, all scenarios showed the same suitability pattern. The geographic projections of future scenarios showed an increase in the suitability values of the southern portion of Brazil and Uruguay and central eastern Argentina.

Each map shows suitability values (red gradient) and novel conditions (gray) at one of the three analyzed time slices.

https://doi.org/10.1371/journal.pone.0025718.g004

The histogram in Fig. 5 shows the percentage of surfaces of the IUCN protected areas that are environmentally suitable for L. catesbeianus , which according to this analysis, would slightly increase towards the future.

Percentage of suitable surface of all the IUCN protected areas in the continent for Lithobates catesbeianus at the three analyzed time slices and AOGCMs.

https://doi.org/10.1371/journal.pone.0025718.g005

Current suitable areas for invasion

The southern portion of Brazil and northeastern Argentina (Atlantic Forest), central eastern Argentina and all of Uruguay ( Fig. 1 – 2 ) show the highest values of suitability. Big portions of territories in these countries are also environmentally suitable for this alien species. This is in concordance with the fact that Brazil and Argentina are the countries with the most geographically extended biological invasion of the American Bullfrog in South America [24] , [28] . It is not a coincidence, however, that they are the main producers of bullfrog culture in the continent [43] . Giovanelli et al. [23] , Loyola et al. [27] and Nori et al. [24] mentioned that the presence of L. catesbeianus in this area is of special concern and here we provide new evidence supporting the vulnerability of this imperiled region.

Although reported populations in the northern and central western countries of the continent (Colombia, Peru, Ecuador and Venezuela) are located in suitable areas ( Fig. 1 – 2 ), their suitability values were very low ( Fig. 4 ), reflecting the great tolerance range of this alien species.

Potential changes in the future

Although projections in different AOGCMs showed slight differences, all the scenarios can be characterized by the same pattern of change (see results of I and RR ). In agreement with the hypothesis of Urbina-Cardona and Castro [25] , we found a slight reduction in suitable surfaces for L. catesbeainus in South America towards the future ( Fig. 1 , 2 , 3 ). However, areas that will continue to be highly suitable for this species are those where most populations have been reported and those that are of special concern in the continent (southern Brazil and northeastern of Argentina; Fig. 4 ) [23] , [24] , [27] .

The greater retraction of suitable surfaces figures in the central portion of Brazil, however, more than 95% of alien populations in this country were reported in regions which, according to our analyses, will continue to be environmentally suitable [23] . On the other hand, the larger expansion of suitable surfaces for this invasive species is located in the northern portion of the continent, specifically in Colombia, northern Brazil, Ecuador and Peru ( Fig. 1 – 2 ). We consider that this fact is of special concern because invasive populations of the bullfrog are currently restricted to reduced suitable surfaces, which means that an expansion would lead to an increase in their distributional range.

The Andean-Patagonian forest (southwestern Argentina and southeastern Chile), eastern Paraguay, and northwestern Bolivia have not been mentioned as a concern because invasive populations have not yet been found in those regions. But, according to our results, these areas would be optimal for the establishment of the species because they hold big extensions of suitable potential habitat for both current and futures conditions (see Fig. 1 ).

Invasion of protected areas

Although we did find a slight reduction in suitable surfaces for L. catesbeianus towards the future, the surfaces of protected areas that are environmentally suitable for the species increased ( Fig. 5 ). The reason for this result lies in the pattern of change of suitable surfaces; areas with the highest increase in suitable surfaces were those with a large percentage of IUCN protected areas, including most of Venezuela, western Colombia and Peru, and north central Brazil. In contrast, areas that showed the greatest retraction hold a considerably lower percentage of protected area surfaces. Additionally, our results showed considerable differences between different AOGCMs: while two of these climate models (IPSL_CM4 and CSIRO_MK30) reflected similar patterns of change (slight increase with respect to the present), the CCCMA-CGCM31 model showed a considerable increase in the last period (2080), probably because it included larger surfaces of reserves in southern Colombia and Venezuela and northern Brazil ( Fig. 1 ).

We provide further evidence into what Loyola et al. [27] pinpointed: a retraction in suitable surfaces for L. catesbeianus in the western portion of Brazil could drive the alien species into protected areas currently established in the Atlantic Forest. Although our analysis did not show a robust pattern of change, we can assert that beyond a hypothetical retraction in potential at risk surface in the continent, this invasive alien species will continue to be an important threat to the network of protected areas established in South America.

Methodological comments

Currently, SDMs are widely used to quantify the potential distribution of alien species [20] . These tools correlate environmental and topographic variables with observed distribution without taking into account physiological aspects of species, adopting the general assumption that the best indicator of a species' climatic requirements is its current distribution, and therefore resulting in estimations of the realized niche of the species [44] , [45] . However, because invasive species in non-native areas are concern of several (and sometimes geographical independent) case studies [39] , the application of this type of methodological protocol must take into account several important aspects for each particular case study.

Here we used the native range of the species for model calibration. Some studies have suggested that for the estimation of risk areas, models should be calibrated based on the “entire range” of the species (data of native plus invasive range) [3] , [46] – [48] . Nevertheless, others authors have demonstrated that when using only data from the native range, one can make very accurate predictions of areas at risk [23] – [27] , [39] , [49] , [50] . Particularly in alien amphibians, a recent paper pinpointed that invader establishment success is higher in areas with abiotic conditions similar to the native range [51] . In addition, the use of the distributional data from the invasive range of the species in model calibration implicitly makes an important assumption: all of the records used for model calibration represent viable populations (that survive and growth) that have colonized, established and are currently spreading along the landscape ( sensu Hellmann et al. [52] ). In this regard, alien populations are ecologically unknown and most of what is known has been published in the last five years [23] , [24] . In practical terms, this means that we cannot assume the viability of the populations of the invaded range and the inclusion of these records for model calibration would probably bias our results. Finally, the great concordance between our results and invasive records of the species reported by field researchers are evidence that the selection of the calibration records was correct.

We also applied a minimum convex polygon to search for the novel conditions ( Fig. S1 ). In contrast, Giovanelli et al. [23] and Nori et al. [24] used a large inset to calibrate their models, and generated a likely biased estimation of novel conditions, which could lead to mistakes in their final predictions. Further, we selected the “minimum training presence” value as a threshold for the model. In Giovanelli et al. [23] and Nori et al. [24] , the authors used other threshold criteria and, as a consequence, they converted to null values a big portion of the at risk area. For example, in Giovanelli et al. [23] , the major portion of the central east of Brazil (including a big part of the Cerrado and Atlantic Forest) appear converted to null values, even though invasive populations have been documented. Our analysis reflects that most of these sites, at current conditions, represent at risk areas ( Fig. 1 – 2 ) .

Management and policy recommendations

In order to control the spread of bullfrogs, the development of management policies should be based on sound science that characterizes the interactions between the species and climate change [53] . In this regard, SDMs are a cost-effective, early warning system that allows the identification of the most suitable areas of a potential invasion, thus giving the opportunity to prioritize and focalize actions as well as investments for certain regions. In order to control the spread of the existing L. catesbeianus populations, and to prevent further invasions in South America, we consider that the results of this study should be taken into account when identifying vulnerable areas and making management decisions.

Some management recommendations regarding the spread of L. catesbeianus in South America have been made in recent studies [23] , [24] , [26] , [27] . We agree with the authors and consider that urgent measures should be taken in the Atlantic Forest. It is essential for governments to make additional efforts in collaborating with universities, research institutes, environmental government and non-government agencies, as well as environmental corporations. Continuous monitoring of the native biodiversity in this biome should be a priority since L. catesbeianus is likely to colonize reserves more efficiently under climate changes [27] .

Prevention is the cheapest, most effective method for combating invasive species when compared with eradication or control [53] – [55] . Our results show that the Andean-Patagonian forest, eastern Paraguay and northwestern Bolivia, where L. catesbeianus has not yet been reported, are optimal places for the species to thrive. Therefore, we consider that importing, breeding and/or having individuals in captivity in these areas must be urgently forbidden and strictly regulated.

The most effective eradication programs could take place in Colombia, Venezuela, Ecuador and Peru, where the invasion of L. catesbeianus is restricted to “small areas” in poorly suitable environments. However, proper programs should begin in the near future because climate change could enable a considerable expansion of the species in these areas.

It is prioritary to generate a regional agenda to identify and isolate some wetlands and other natural ecosystems in which to conduct long-term monitoring of bullfrog populations and conduct experimental and ecological studies that allow us to better understand their behavior, reproductive biology, diet, competition with native species (at larval and adult stages), among other aspects. All of the above will allow the control of the dispersal of the species along permanent natural and artificial bodies of water such as irrigation districts for productive systems.

In the most vulnerable regions it is imperative to broad the population targets within the society so as to avoid the transport of bullfrogs used as pets or for food. Massive environmental campaigns must help local people identify the species, differentiate it from other native species, and be aware of the extreme damage that this species causes to ecosystem functions and services. Once the local people can identify the species and its preferred habitats, local government could begin an aggressive campaign to stimulate controlled hunting for bullfrog individuals which can be used as a source of food or in biomedical experiments in most (current and future) vulnerable regions.

This study provides more evidence highlighting the complexity of the L. catesbeianus problem in South America, as well as being useful for determining certain urgencies. However, we are aware that this type of research alone is not enough to resolve the problem. On one hand, a hard research line that answers some management-related questions is still needed [27] . On the other hand, a successful management to an imminent L. catesbeianus invasion in South America will only be possible if government agencies and related entities begin to play bigger role.

Supporting Information

Individual records of Lithobares catesbeianus from its native range used to perfom MaxEnt models and the minimum convex polygon used to calibrate the projections.

https://doi.org/10.1371/journal.pone.0025718.s001

Results of the Pearson correlation between the 20 variables.

https://doi.org/10.1371/journal.pone.0025718.s002

Acknowledgments

We are grateful to Dan Warren for advice with an essential part of the methodology, and Maria Eugenia Periago and Cecilia Garcia Martinelli who improved the English style. JN and JNL are grateful to to the Doctorado en Ciencias Biológicas, Universidad Nacional de Córdoba.

Author Contributions

Conceived and designed the experiments: JN JNU-C RDL. Performed the experiments: JN. Analyzed the data: JN JNU-C RDL JNL GCL. Contributed reagents/materials/analysis tools: JN JNU-C RDL JNL GCL. Wrote the paper: JN JNU-C RDL JNL GCL.

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Invading Bullfrogs Appear Nearly Unstoppable

A booming population of North American bullfrogs has been hopping outside places that aren't their native habitats.

The North American bullfrog population is booming. That may sound like good news, but it isn't—not when the frog has leaped far beyond its native habitat.

"They are one of the most successful amphibians in the world, and they are causing trouble in several countries," said Cecil Schwalbe, a biologist with the U.S. Geological Survey at the University of Arizona in Tucson.

Native to North America east of the Rocky Mountains, bullfrogs are now found throughout the world. In many areas outside their native range, the frogs are outcompeting—and eating—just about everything in their path.

On wildlife refuges in Arizona where Schwalbe studies the amphibian, bullfrogs have nearly eliminated the Mexican garter snake and the Chiricahua leopard frog. Even during a recent trip to Japan, Schwalbe said he heard the frog's familiar croak everywhere he went.

Recent research suggests the amphibians may be carriers of—but mostly immune to—the chytrid fungus, Schwalbe said. The fungus has been implicated as a major culprit behind dwindling frog populations around the world, according to the biologist.

"That could explain the spread of the chytrid fungus in some areas such as the American Southwest. They carry it to the frog populations they are interacting with," Schwalbe said.

According to biologists, bullfrogs began their leap around the world in 1898, when they were imported to California to satiate a consumer appetite for frog legs. Similar importations spread the croakers to Asia, Europe, and South America.

In their native habitat, predators such as large water snakes, alligators, and snapping turtles keep adult bullfrogs in check, while fish slurp tadpoles. But in western North America and other regions of the world, effective bullfrog predators are absent.

In the absence of predators, the bullfrogs' prolific nature allows them to flourish. "A bullfrog may lay, in a single clutch, 20,000 eggs. Our native [Arizona] frogs are laying 2,000 to 3,000," Schwalbe said. "Bullfrogs have an order of magnitude advantage from the get-go."

Bullfrog tadpoles are also less palatable to [Arizona's] native and most non-native fish than the native tadpoles, according to Phil Rosen. A biologist at the University of Arizona, Rosen studies what insects and fish prey on bullfrog tadpoles.

"The tadpoles are so successful that our [Arizona] ecosystem is completely overrun with small and large bullfrogs," Rosen said. "Most native predatory fish will eat leopard frog tadpoles but not [the] bullfrogs'."

More tadpoles mean more bullfrogs with voracious appetites.

Studies of bullfrog intestines reveal the amphibians eat just about anything they can fit into their mouths: birds, rats, snakes, lizards, turtles, fish, other frogs, and especially each other. In southern Arizona the most common vertebrates found in bullfrogs are other bullfrogs, Schwalbe said.

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Other frog species are also cannibalistic. But adult bullfrogs are acutely so, Schwalbe said. As long as tadpoles and young bullfrogs have enough algae and insects to eat, adult bullfrogs can subsist on the younger frogs. With such a reliable food source, the adult populations can grow well above what would normally be possible, putting additional pressure on the ecosystem.

Dennis Suhre is a graduate student who works with Schwalbe and Rosen at the University of Arizona. Surhe said this cannibalism, combined with competition for other food resources, gives younger bullfrogs incentive to leap far away from their hungry elders. And leap they do.

By marking and recapturing bullfrogs on and near the Buenos Aires National Wildlife Refuge in Arizona, Suhre has found that the young amphibians can move at least 6 miles (9.6 kilometers) in a few weeks.

To travel from one big pond to the next, the bullfrogs hop between small ponds interspersed throughout the arid landscape covered in grass and mesquite. "The wetter the year, the farther they will go," Suhre said.

Bullfrog Control

Their lack of predators, prolific nature, and incentive to relocate make bullfrogs a difficult invasive species to eradicate. No single method has proved effective in eliminating them, according to Schwalbe.

Rotenone and other toxic chemicals can be applied to ponds to effectively kill fish and frog tadpoles. But bullfrogs have a simple defense to the tactic: They hop out of the water. Schwalbe also noted that such toxins kill indiscriminately and, thus, are a problematic approach for areas with endangered native species.

Researchers have had some success controlling bullfrogs at Buenos Aires National Wildlife Refuge, however. They have drained bullfrog-infested ponds during the dry season, killing bullfrog tadpoles and enabling researchers to capture and dispose of adult bullfrogs that attempt to escape.

The drained ponds fill back up when the monsoon rains arrive. Biologists can then reintroduce native leopard frogs.

The problem, Suhre said, is that the bullfrogs travel great distances. Unless eradication programs are done on a large enough scale to encompass whole landscapes, the bullfrogs return.

"All you need is two bullfrogs, a male and a female," Suhre said. "A female lays about 20,000 eggs. … Once that happens, it's very difficult to get the frogs out."

Predatory insects, such as dragonfly nymphs and diving beetles, may help mitigate bullfrog populations, according to Rosen, the biologist who studies bullfrog-prey relationships. However, to date, the fish found to be most effective at killing bullfrog tadpoles is the largemouth bass, a non-native species in Arizona.

"No conservationist wants to hear that, because bass are a significant problem in their own right," Rosen said.

Regardless, the biologist said that effective control of bullfrogs may require redesigned ecosystems that incorporate some level of non-native species to control invasive populations of bullfrogs and crayfish. (In the Southwest, according to Rosen, non-native crayfish are just as much a problem as bullfrogs.)

"At this stage we have no hope of completely eradicating bullfrogs or crayfish" in the complex stream systems in central Arizona and New Mexico, Rosen said. "And if we don't completely eradicate them, we don't eradicate them at all, unless we come up with a biocontrol mechanism," he said. (Biocontrol, or biological control, describes the process of controlling pest species by interfering with their ecology.)

Schwalbe added that control measures in the isolated waters of the arid, mountainous terrain of southeastern Arizona may prove more effective than in the more complex stream systems farther west.

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Laura returned to the cabin where her and the other grad students were staying while they collected data. As the sun was going down she could hear the familiar call of bullfrogs from the nearby pond and lake. Questions: 1. The map shows the native range of the bullfrog and the areas where the bullfrog has been introduced.

Case Study - Are Invading Bullfrogs Harmful? Students follow a story about an ecologist and a student who are studying the population size of bullfrogs in California. These amphibians are considered an invasive species in that area and have been causing the decline of native species. Students learn concepts related to community interactions ...

This case study aims to shed light on the harmful nature of invasive bullfrogs and provide an answer key to the question of whether they are harmful or not. Case Study: Invasive Bullfrogs and Their Harmful Impact. The introduction of invasive species can have significant ecological and environmental consequences.

Download Bio bullfrog case study and more Biology Assignments in PDF only on Docsity! AP Case Study-Are Invading Bullfrogs Harmful? Name ___________ Part 1: What's in the Pond? Laura scooped a water sample from a pond near Clear Lake in California. The sample contained several larval forms of insects and a few tadpoles.

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a27a23a6-930f-4e27-bf50-a79355ca1a48 - Free download as PDF File (.pdf), Text File (.txt) or read online for free. Laura is studying invasive American bullfrogs in California ponds and finds they have displaced native species. Experiments show bass can control bullfrog populations but are not fully effective. Toxicants and trapping are also being explored as control methods, but there are ...

Could a population of 50 bullfrogs alone be the cause of the massive population decline of the California Red-legged frog? Use the numbers below to find out. Bullfrog weighs 1.1 lbs California Red-legged frog weighs 0.25 lbs Bullfrog needs 1500 calories/lb of body weight/day California Red-legged frog offers 1600 calories/lb of body weight

50 years, few specific case studies on its transmission and localized impacts in the San Francisco Bay Area have been conducted. During my study, I counted a total of 9 bullfrogs over the course of my study in the Botanical Garden Pond, Junior Ranger Pond, and Environmental Education Center Ponds.

Background Biological invasion and climate change pose challenges to biodiversity conservation in the 21st century. Invasive species modify ecosystem structure and functioning and climatic changes are likely to produce invasive species' range shifts pushing some populations into protected areas. The American Bullfrog (Lithobates catesbeianus) is one of the hundred worst invasive species in the ...

familiar call of bullfrogs from the nearby pond and lake. Questions: (Answer in your own complete academic sentences) 1. The map shows the native range of the bullfrog and the areas where the bullfrog has been introduced. Are there any natural barriers between the east side of the map and the west side? 2.

In addition to the toxicant experiments, Professor Roberts was also exploring ways to trap the frogs, based on experiments done in Australia to control the Cane toad. The research report also included data on bullfrogs that were trapped from the north side of Clear Lake (table 2). 8.

Find step-by-step Biology solutions and your answer to the following textbook question: A case study of how to control bullfrog population without adversely affecting its native species is being done. One artificial pond of interest contained largemouth bass. While the bass are not a native species to California, in places where they do live, they have been known to eat bullfrog tadpoles and ...

Final answer: Invasive bullfrogs can be harmful due to their role as reservoirs for the fungus Batrachochytrium dendrobatidis, which causes the disease chytridiomycosis, largely responsible for the global decline in amphibian species. Moreover, as voracious predators, they can cause ecological disruptions in non-native habitats. Explanation: The invasion of bullfrogs can indeed be harmful for ...

Study with Quizlet and memorize flashcards containing terms like The map shows the native range of the bullfrog and the areas where the bullfrog has been introduced. Are there any natural barriers between the east side of the map and the west side? do you think the frog would have naturally expanded its range?, 3. Use google to search from an image of a bullfrog. One unique feature is the ...

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