The Invasive Green Iguana Iguana iguana – What can …€¦ · Iguana iguana – What can be done...
Transcript of The Invasive Green Iguana Iguana iguana – What can …€¦ · Iguana iguana – What can be done...
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Iguana iguana – What can be done to reduce the threat?
The Invasive Green Iguana
Chloé Rodrigues – ONCFS – May 2014
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Green iguanas
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What are the main issues?
HYBRIDIZATION with the endangered Iguana delicatissima (Statia, Dominica, Petite Terre, Désirade, Chancel!!!)
Competition with native species Crops destruction Structure damages (Forts of the
caribbean… Historical Heritage) Human health? (Salmonella spp.,
Escherichia coli, Staph strains…) Aggressive individuals
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Hybridization with I. delicatissima
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Some traits of its biology to remember Highly opportunistic Herbivorous, mainly arboreal, adapted to
the different habitats of LA (same ecological niche like I. delicatissima)
High density supported by habitat Highly Cryptic Highly prolific (hatchling success, survival) Swims well - dispersal Live up to 20 y
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40 eggsYear 1
+ 2-3 yearsYear 3-4
10*40 œufs
+ 2-3 ans
200 - 400 iguanasYear 5
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Hybridization and expansion
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Status and Geographic range
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Status and Geographic range
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How to tackle the threats it poses?
NO INVASIVE REPTILE POPULATION HAS EVER BEEN
ERADICATED. NO MATTER WHAT EFFORTS HAVE BEEN
PROVIDED!
(Ex. Brown tree snake – Guam)
THE ONLY SOLUTION IS TO PREVENT INVASION.
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How to tackle the threats it poses? – Now it’s here Identify the threats: Specific answer
Crops destruction: Protect the crops (nets)Human vs Iguana issues: Raise public
awareness, basic hygiene, never feed iguanas, make the environment unsuitable
Competition/hybridization with I. delicatissima: isolate I. delicatissima
Competition with other native species: low density
AND Control the population
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How to regulate the population? Step by step…
Step 1: Define goal and success StrategyStep 2: Assess the populationStep 3: Estimate the means to achieve your
goal and schedule actionsStep 4: Define a METHODOLOGYStep 5: Assess your methodology
MONITORINGStep 6: adjust if needed
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Define goals and success
Control objective has to be clearly identified (Why?)
Define Time scales as you define goal(s) Define success Possible side effects?
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Assess the target population
Knowing your enemy will ensure your success:
How big is the population? Estimate its viability? Estimate its carrying capacity?
Behavior and basic biology If possible…
Estimate recruitmentSex ratioAge ratio
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Estimate the means to achieve your goal and schedule actions MANPOWER and COMMITMENT!!!!! Statutory designation Target a zone or a population! Prioritize zones Choose strategy (eradication, control,
containment, mitigation, prevention) Choose control Methods and combine them
(cost-effectiveness, relevance, Public opinion…)
Secure funding for the ENTIRE process Schedule actions efficiency +++
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Define a methodology
To be done with step 3 Chosen methods MUST be cost-
effective, highly specific, efficient ○ Mechanical control (recommended)○ Chemical control○ Biological control
Avoid SIDE EFFECTS, Hazard to non-target species, public opposition
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Monitoring…
Allows for correction The only way to know if you achieved
your goal
mass culling leading to population explosionRe-estimate costsAdjust scheduleRe-estimate effort to provide…
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The management of green iguana population in Martinique
What can we learn from Martinique?
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In Martinique…
Iguana iguana since 60’s Widespread = Well established Threats:
HYBRIDIZATION with I. delicatissimaDamages Fort Saint-Louis
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What went wrong?
Objective defined: eradication Unrealistic No initial assessment of the population No will to know its biology lack of commitment Popular beliefs never questioned (ex. “Out of FDF green
iguanas are scarce cause almost never spotted”…)
No evaluation of the needs Not enough manpower No definition of time scales No monitoring of the actions Lack of consideration of public opinion
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What went right?
Iguana iguana has never been protected Prefectural decree allowed its
destruction since 2005 Prefectural decree classified it as an
invasive species and allowed any mean to regulate it respecting basic ethic rules on animal welfare (July 2013)
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A new start… what do we do? Raising public and stakeholder
awarenessIt needs to be done properlyHand capture is not efficientNot enough commitment
Fort St Louis as “field-lab”Several hundreds of iguanasCarrying capacity seems not reachedPopulation is healthy and expanding
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Chosen methods in 2011-2012 For 2 years hand captures by ONCFS
officers only (shooting not allowed)-FDF Females Necropsies Results:
+/- 200 iguanas removed in FDFNecropsies of females:
○ eggs production starts as soon as 22cm SVL is reached
○ SVL [22-24] 18 to 28 eggs!!!!!○ Egg laying period seems: feb-April
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Hand capture - in the field…
Autotomy Noose poles branches, weigh>3Kg Behavioral adaptation Arborial… Good swimmer escape… On average: 1 caught out of 10 to 20
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Chosen methods in 2011-2012 Conclusion:
Not efficient at allNot enough commitment from stakeholders:
doing applied research, use of airguns refused
What are the real effects? Lowing the density might lead to increase of reproductive success…
Changes in the behavior harder to catch
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What has been proposed in 2012? Population survey – demography Neuter the male iguanas (Bilateral
Hemipenectomy) Find the nesting sites or create some! PREVENT the green iguana to enter
free territories exhaustive control of what enters free zones, raise public awareness, law enforcement,…)
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Iguanas shooting
Airgun head shot Easy with bigger individual Quick and efficient Can remove large quantity in short time Arboreal species Small individual ↓ efficiency Context of use (social…)
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Neutering the male iguanas
Males only (for now) Alpha males 90% offspring Testicles are not removed
testosterone produced Dominant behavior
Carrying capacity reduce the population? Life span 20 years
Public opinion Florida? Doug Madder, DVM
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Neutering the male iguanas Bilateral hemipenectomy Results:
○ healthy, and « territorial »○ Transmitters still in place○ Rubber band gone○ Behavior seems unchanged○ « Beta » males have been captured
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Questions arising
Recreational hunting?
Identification!
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Questions arising
Hunting for meat export?
Example of PR Trapping?
What bait?
Wheat/oatmeal bran + Critical care (Oxbow®) herbivore (2 to 4/1)
Fruits?
What kind of trap?
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Questions arising
How to euthanize the captured iguanas?
AVMA recommendation guide for euthanasia (costs?)
Used in Mq: Sodium Pentobarbital
Freezing: 2.8Kg >30min to die!
500g >3 min. to die!
When no vet available? Special authorization or Painkiller + anesthetic + freezing
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Thank you for your attention