Trapping strategies for deterring the spread of Brown Tree Snakes from Guam

The accidental introduction of the Brown Tree Snake Boiga irregularis to Guam has resulted in the extirpation of most of the island's native terrestrial vertebrates, has presented a health hazard to infants and children, and also has produced an economic problem. Prevention of its dispersal through Guam's cargo traffic to other Pacific islands has become a high environmental priority. Trapping around ports and other cargo staging areas is central to an integrated pest management programme designed to deter dispersal of the species. In this study, perimeter trapping of forested plots characteristic of those found in port areas was found to be the most effective trap placement strategy, although trap lines cut through the plot interior or placed along a single plot boundary were also effective. Snake removal potentially can be modelled using an exponential decay over time, providing the manager with a planning tool. Population recovery of Brown Tree Snakes in trapped plots was found to be slow in the fragmented forested habitats found around ports.

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Effectiveness of the detector dogs used for deterring the dispersal of Brown Tree Snakes

Pacific Conservation Biology ◽

10.1071/pc980256 ◽

1998 ◽

Vol 4 (3) ◽

pp. 256 ◽

Cited By ~ 13

Author(s):

Richard M. Engeman ◽

Daniel S. Vice ◽

Danny V. Rodriguez ◽

Kenneth S. Gruver ◽

William S. Santos ◽

...

Keyword(s):

Health Hazard ◽

Infants And Children ◽

Search Pattern ◽

Economic Losses ◽

Boiga Irregularis ◽

Routine Procedure ◽

Terrestrial Vertebrates ◽

Brown Tree Snake ◽

Brown Tree Snakes ◽

Accidental Introduction

The accidental introduction of the Brown Tree Snake Boiga irregularis to Guam has resulted in the extirpation of most of the island's native terrestrial vertebrates, has created a health hazard to infants and children, and has resulted in economic losses. Cargo inspections using teams of handlers and their detector dogs form a last line of defense for preventing Brown Tree Snake dispersal from Guam. To assess the efficacy of the teams of handlers and their dogs for locating stowed Brown Tree Snakes, we planted Brown Tree Snakes (in escape-proof containers) in cargo without the knowledge of the handlers inspecting the cargo. We found that when an observer attended the inspection to monitor procedures, 80% of the planted snakes were located. Without an attending observer present, 70% of the planted snakes were discovered, but only after such plantings had become a routine procedure. Prior to the routine planting of snakes, efficacy was nearly 50% less (38%). The reasons some planted snakes were missed by the dog teams were split between: an insufficient search pattern by the handler, or the dog giving no discernable indication that a snake was present.

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Morphology of the brown tree snake, Boiga irregularis, with a comparison of native and extralimital populations

Australian Journal of Zoology ◽

10.1071/zo99025 ◽

2000 ◽

Vol 48 (4) ◽

pp. 357 ◽

Cited By ~ 5

Author(s):

Joan Whittier ◽

Conrad Macrokanis ◽

Robert T. Mason

Keyword(s):

Solomon Islands ◽

Natural Populations ◽

Single Species ◽

Morphological Characters ◽

Nonparametric Analysis ◽

Native Range ◽

Boiga Irregularis ◽

Brown Tree Snake ◽

The Mean ◽

Brown Tree Snakes

We conducted an analysis of the morphology of specimens of the brown tree snake, Boiga irregularis, from the native range of eastern and northern Australia, Papua New Guinea and the Solomon Islands. First, a cluster analysis was conducted to determine natural groupings in the data; however, no groupings based on morphological characters were found. Then the importance of additional factors such as geographical groupings and coloration was analysed in a nonparametric analysis of variance. Significant differences were found in the mean rankings of key characters such as dorsal mid-body, ventral and subcaudal scale counts. However, the amount of variation and the degree of overlap among populations and groupings precluded separating animals on the basis of these features. Our data support the recognition of a single species with two subspecies based on colour variation. We also compared the morphology of a sample of brown tree snakes from an extralimital population on Guam to that of this species in the areas of the native range. Our data supported suggestions of alliances of the Guam population with northern Papuan populations. However, the Guam population of the brown tree snake was found to be less variable than were localised natural populations. Morphologically, the Guam population is distinctive, suggesting that it has undergone significant morphological change since its introduction.

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Stimulus control of predatory attack in the brown tree snake (Boiga irregularis)

Amphibia-Reptilia ◽

10.1163/156853888x00224 ◽

1988 ◽

Vol 9 (1) ◽

pp. 77-88 ◽

Cited By ~ 6

Author(s):

Hobart M. Smith ◽

Karl Kandler ◽

Robert Lee ◽

David Chiszar

Keyword(s):

Stimulus Control ◽

Chemical Cues ◽

Boiga Irregularis ◽

Choice Behaviour ◽

Volatile Chemicals ◽

Brown Tree Snake ◽

Predatory Attack ◽

Brown Tree Snakes

AbstractThree experiments studied predation upon neonatal rodents by brown tree snakes (Boiga irregularis). Experiment 1 showed that chemical cues arising from prey were used in foraging tests that could not be completed on the basis of vision alone. Experiment 2 provided only airborne chemical cues, and snakes performed at chance levels in selecting among odoriferous (baited) and non-odoriferous (unbaited) nests. Snakes performed above chance, however, when a chemical trail led to the baited nest (Experiment 3), suggesting that non-volatile chemicals are most important in guiding choice behaviour.

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Seasonal Testicular Development and Sperm Storage in Tropical and Subtropical Populations of the Brown Tree Snake (Boiga irregularis)

Australian Journal of Zoology ◽

10.1071/zo97027 ◽

1997 ◽

Vol 45 (5) ◽

pp. 479 ◽

Cited By ~ 17

Author(s):

Karina H. Bull ◽

Robert T. Mason ◽

Joan Whittier

Keyword(s):

Seasonal Pattern ◽

Sperm Storage ◽

Early Summer ◽

Testicular Development ◽

Boiga Irregularis ◽

Ductus Deferens ◽

South Eastern ◽

Brown Tree Snake ◽

Brown Tree Snakes ◽

Reproductive Cycles

The seasonal pattern of testicular development of tropical and subtropical brown tree snakes, Boiga irregularis, was investigated. We also examined sperm storage in the reproductive tracts of both sexes. Males in south-eastern Queensland had a testicular cycle that was strongly seasonal, with testicular regression during the wet summer. Males from Papua New Guinea had a continuous testicular cycle, in which sperm was present in some animals every month. Females from south-eastern Queensland had no stored sperm or sperm storage receptacles in their oviducts. Sperm was found in only one of 28 female reproductive tracts. The sperm was located in the lumen, suggesting recent insemination. In contrast, the presence of sperm in the ductus deferens of most males in both populations indicated that males store sperm. This facilitates the apparent dissociation between the male and female reproductive cycles that has been reported previously in south-eastern Queensland populations. Male B. irregularis must store sperm for at least six months, from the time of maximal testicular development in autumn, until ovulation occurs in spring and early summer. This pattern of reproduction in B. irregularis fits neither a postnuptial nor a prenuptial pattern, as has been observed in a few other tropical snakes.

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Implications of brown tree snake captures from fences

Wildlife Research ◽

10.1071/wr97110 ◽

1999 ◽

Vol 26 (1) ◽

pp. 111 ◽

Cited By ~ 5

Author(s):

Richard M. Engeman ◽

Michael A. Linnell ◽

Phillip Aguon ◽

Anthony Manibusan ◽

Steven Sayama ◽

...

Keyword(s):

Integrated Approach ◽

Horizontal Position ◽

Boiga Irregularis ◽

Steel Cable ◽

Management Implications ◽

Brown Tree Snake ◽

Chain Link ◽

Sea Ports ◽

The Difference ◽

Brown Tree Snakes

The capture of brown tree snakes (Boiga irregularis) from fence lines in the vicinities of air and sea ports is an important component of the integrated approach used for curtailing the dispersal of the species from Guam. Use of fences by brown tree snakes was characterised from over 600 captures of snakes during spotlight searches. Two construction designs of chain-link fences were searched, the difference being whether a horizontal bar or a steel cable was used to support the chain link on top. Both fence designs had snakes concentrated at the fence tops – fences having top bars produced 92% of captures on the top third of the chain link, the top bar, or the parallel barbed-wire strands above the fence; fences without top bars produced 82% of captures from the top third of the chain link or the wires above it. Most snakes were found in a horizontal position and no general trends were found through the night for when snakes ascend or descend the fences. To help concentrate snakes at the tops of fences for facilitating control efforts, we recommend the use of a horizontal bar to support the chain link on top, as well as the use of parallel barbed- wire strands above the fence. We discuss management implications for using searches of fences to control brown tree snakes and to detect new brown tree snake populations in other locales.

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Ssssneaky, Pesssky, Ssspeciess!

EDIS ◽

10.32473/edis-fa142-2007 ◽

2007 ◽

Vol 2007 (7) ◽

Author(s):

Charles Jacoby ◽

Nanette Holland ◽

Debbi Berger

Keyword(s):

Boiga Irregularis ◽

Brown Tree Snake

This 11-page activity illustrates how the brown tree snake, Boiga irregularis, has invaded Guam.

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A direct comparison of trapping and spotlight searches for capturing Brown Tree Snakes on Guam

Pacific Conservation Biology ◽

10.1071/pc010004 ◽

2001 ◽

Vol 7 (1) ◽

pp. 4 ◽

Cited By ~ 3

Author(s):

R. M. Engeman ◽

D. S. Vice

Keyword(s):

Forest Edge ◽

Management Programme ◽

Night Time ◽

Brown Tree Snake ◽

Population Reduction ◽

Reduction Methods ◽

Capture Method ◽

Standard Practices ◽

Brown Tree Snakes ◽

Over Time

Brown Tree Snake populations on Guam are controlled in the vicinities of cargo staging and transport areas to prevent their dispersal from Guam, and their populations are controlled in areas where endangered species are to be reintroduced. Trapping and night-time spotlight searches of fences are the two primary Brown Tree Snake population reduction methods used on Guam. We conducted a three month study comparing Brown Tree Snake captures by spotlighting fences to captures by trapping. Traps were placed either on the edge of the forest paralleling the fences, or they were hung on the fences. Applications of each capture method followed the standard practices used within the operational programme charged with deterring the spread of Brown Tree Snakes from Guam. We found captures by trapping to exceed those by spotlighting each month, but the captures by trapping decreased substantially over time, while those by spotlighting did not. We detected no differences statistically between numbers of captures taken by traps hung on the forest edge versus those hung on the fences. We found no differences in sizes of Brown Tree Snakes captured by spotlighting and trapping, based on average snout-vent length (SVL) or the distribution of SVLs. We feel that the two capture methods complement each other in an integrated pest management programme.

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