Iguana iguana – What can be done to reduce the threat?

The Invasive Green Iguana

Chloé Rodrigues – ONCFS – May 2014

Green iguanas

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

Hybridization with I. delicatissima

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

40 eggsYear 1

+ 2-3 yearsYear 3-4

10*40 œufs

+ 2-3 ans

200 - 400 iguanasYear 5

Hybridization and expansion

Status and Geographic range

Status and Geographic range

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.

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

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

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?

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

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 +++

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

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…

The management of green iguana population in Martinique

What can we learn from Martinique?

In Martinique…

Iguana iguana since 60’s Widespread = Well established Threats:

HYBRIDIZATION with I. delicatissimaDamages Fort Saint-Louis

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

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)

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

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

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

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

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,…)

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…)

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

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

Questions arising

Recreational hunting?

Identification!

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?

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

Thank you for your attention