pe klug, km brindock, rn reed, aa yackel adams, mj mazurek, wc pitt, ca stricker
DESCRIPTION
Protection of Caves Important to the Endangered Mariana Swiftlet through Effective Deployment of Control Tools Based on Brown Treesnake Behavior. PE Klug, KM Brindock, RN Reed, AA Yackel Adams, MJ Mazurek, WC Pitt, CA Stricker National Military Fish and Wildlife Association March 2014 - PowerPoint PPT PresentationTRANSCRIPT
PE Klug, KM Brindock, RN Reed, AA Yackel Adams, MJ Mazurek, WC Pitt, CA StrickerNational Military Fish and Wildlife Association
March 2014 E-mail: [email protected]
Protection of Caves Important to the Endangered Mariana Swiftlet through Effective Deployment of Control Tools
Based on Brown Treesnake Behavior
Prior to the introduction of the invasive brown treesnake (BTS) the island of Guam had a sustainable avian community
Native species still on Guam
Native species extinct or extirpated from Guam
Non-endemic bird species extirpated from Guam
Native forest species still breeding on
Guam
The Mariana swiftlet is the last sustainable breeding population of native forest bird on Guam
Native species still on Guam
Native species extinct or extirpated from Guam
Non-endemic bird species extirpated from Guam
Native forest species still breeding on
Guam
The Mariana swiftlet currently occupies 3 caves on Guam
Population estimate = 1224 ± 164 birdsMahlac: 1031 ± 201Maemong: 97 ± 44
Fachi: 49 ± 35
Ring of BTS traps and toxic-bait tubes around caves and visual surveys within caves are current control measures
• Perimeter trapping with mouse-baited trapsMahlac = 40, Maemong = 29, Fachi = 25 traps
• Bait tubes added to perimeter trap lineMahlac = 36, Maemong = 29, Fachi = 25
• In-cave visual surveys 12 per quarter in each cave (48 surveys/year) 60 min searches with night vision goggles
* Mahlac: 5 bait tubes inside and 2 traps at cave mouth
Objectives of Brown treesnake (BTS) Research at Mariana swiftlet Caves on Guam1. Assess rate & characteristics of BTS in caves2. Assess residency (stable isotope diet analysis)3. Assess current operational control of BTS at caves4. Assess control tool deployment design5. Assess if BTS mouse-baited traps are beneficial in caves
Photo by Jack Jeffrey
Brown treesnakes may currently be limiting Mariana swiftlet recovery and thus it is necessary to reduce BTS
numbers in areas of conservation concern
Objectives of Brown treesnake (BTS) Research at Mariana swiftlet Caves on Guam1. Assess rate & characteristics of BTS in caves2. Assess residency (stable isotope diet analysis)3. Assess current operational control of BTS at caves4. Assess control tool deployment design5. Assess if BTS mouse-baited traps are beneficial in caves
Photo by Jack Jeffrey
Brown treesnakes may currently be limiting Mariana swiftlet recovery and thus it is necessary to reduce BTS
numbers in areas of conservation concern
After initial suppression of BTS in Mahlac the peak in activity is in the 3rd quarter (July-Sept)
(80)
(1)
(4)
Male BTS (n = 15)
** Initial 21 BTS caught in Mahlac not included
Female BTS (n = 48)
Visual Interior Cave Search
Of the 14 brown treesnakes that had stomach contents, 8 contained swiftlet carcasses
swiftlet remains
prey bulgeswiftlet remains
Relative to other populations of BTS on Guam the size distribution at caves is skewed toward larger, female
snakes
ectothermic prey
ectothermic prey
*
*
Objectives of Brown treesnake (BTS) Research at Mariana swiftlet Caves on Guam1. Assess rate & characteristics of BTS in caves2. Assess residency (stable isotope diet analysis)3. Assess current operational control of BTS at caves4. Assess control tool deployment design5. Assess if BTS traps are beneficial in caves
Photo by Jack Jeffrey
Brown treesnakes may currently be limiting Mariana swiftlet recovery and thus it is necessary to reduce BTS
numbers in areas of conservation concern
Assessment of whether BTS traps are beneficial in caves or are potentially attracting BTS and increasing predation risk
Bird-Alone Trt
Mouse-Alone Trt
Mouse-Paired Trt
Bird-Paired Trt
mouse-baited trap
bird-baited trap
Paire
d St
ation
Mou
se-A
lone
St
ation
Bird
-Alo
ne
Stati
on
Does the presence of mouse-baited traps result in an increase in catch-per-unit- effort (CPUE) of BTS in bird-baited traps?
Bird-Alone Trt
Mouse-Alone Trt
Mouse-Paired Trt
Bird-Paired Trt
Paire
d St
ation
Mou
se-A
lone
St
ation
Bird
-Alo
ne
Stati
on
*mouse-baited traps do NOT
increase risk of BTS contacting
birds
Are mouse-baited traps effective at removing BTS when paired with bird-baited traps?
Bird-Alone Trt
Mouse-Alone Trt
Mouse-Paired Trt
Bird-Paired Trt
Paire
d St
ation
Mou
se-A
lone
St
ation
Bird
-Alo
ne
Stati
on
*mouse-baited traps are
effective at removing BTS in the presence of
birds
Are mouse-baited traps drawing in more BTS to the focal area compared to bird-baited traps alone?
Bird-Alone Trt
Mouse-Alone Trt
Mouse-Paired Trt
Bird-Paired Trt
Paire
d St
ation
Mou
se-A
lone
St
ation
Bird
-Alo
ne
Stati
on
*additional prey odor does not attract more
snakes to an area
bird-alone CPUE surpasses all other treatments
The BTS population is not as suppressed at stations with only bird-baited traps compared
to stations with mouse-baited traps
Time (week)
Catc
h pe
r uni
t effo
rt (C
PUE)
1. Multiple factors may have contributed to the decline of Mariana Swiftlets, but it appears BTS may be limiting recovery with larger, female snakes found in caves.
2. Deploying mouse-baited traps in focal areas may not increase predation risk on prey of concern and may
alleviate risk by suppressing the BTS population
Questions?
Funding Sources
Additional Partners
Additional Assistance:
DoD NavyStephen Mosher
Project ManagementLea’ Bonewell
Colorado State UniversityBjörn Lardner
Shane SiersJulie Savidge
Guam-Based BiologistsThomas HinkleMatthew Cook
Meredith CampbellElden Holldorf
McKayla SpencerKevin DonmoyerJustine KasemanMarijoy Viernes
Charlotte RobinsonPatrick Barnhart
Co-authors: Kevin Brindock, Robert Reed, Amy Yackel Adams, MJ Mazurek, Will Pitt, Craig Stricker