Augon, C. F., E. W. Campbell, III, and J. M. Morton. Under review. Efficiency of electrical

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1 Augon, C. F., E. W. Campbell, III, and J. M. Morton. Under review. Efficiency of electrical barriers used to protect Mariana crow nests. Wildlife Society Bulletin 30: Abstract: The initial success of an electrical barrier in protecting Mariana crow (Corvus kubaryi) nests and continued field use on Guam since 1990 prompted a more complete test of the barrier s effectiveness against intrusion by the brown treesnake (Boiga irregularis). We tested the efficiency of electrical barriers in preventing brown treesnake intrusion at Mariana crow nests on Guam during 2 14-day trials in June-July Barriers prevented all snake intrusions in treatment trees, while 49 snakes were caught in control trees. We found no evidence for a difference in capture rates in control trees during the first and second trial (overall mean= [SE] snakes caught per trap night). Based on these study results, electrical barriers could be used to protect active nest trees from snakes on Guam. Campbell, E. W., III, G. H. Rodda and T. H. Fritts. 1993a. Elimination of the Brown Tree Snake (Boiga irregularis) in small plots. Pages in Second World Congress of Herpetology, Adelaide, Australia. Abstract: While it is presently not practical to eliminate introduced populations of the Brown Tree Snake on Guam, it may be possible to control this species on a smaller scale. Snake densities in an area can be lowered if resident snakes are removed and dispersal into the site is eliminated. Recent developments in trap and barrier technology have made this practical in small-forested areas on Guam. Record advances in capture technology have yielded capture rates that have exceeded 10% of the population per night (in one case a sustained rate of 28%). Eighteen months were spent testing 18 different fencing designs and a 1.1 m high, five wire alternately charged electrical netting fence was found to have no snake escapes. We have constructed two 1 ha snake exclosures using electrical fencing designed to exclude Brown Tree Snakes. Snakes are being eradicated from these exclosures using a combination of hand capture, trap capture, and natural emigration over the barrier (which snakes can climb from the inside only). Lizard, bird, rat and snake populations are being monitored in two control plots and the two snake exclosures and to evaluate the effect of predator removal on prey populations. If practical, snake-free and snake-reduced sites could be used to reduce the extralimital spread of the Brown Tree Snake and provide habitat for endemic wildlife on Guam, which has declined or disappeared as a result of predation by the Brown Tree Snake.

2 Clark, C. S., G. H. Rodda and T. H. Fritts Practical aspects of using rodents as live bait. Page 41. in Society for the Study of Amphibians and Reptiles. 35 th Annual Meeting, El Paso, Texas, USA. Abstract: During trapping experiments targeting the Brown Tree Snake, Boiga irregularis, on Guam, live rodents have captured nine times as many snakes as other practical baits tested in matched comparisons. To protect and contain the bait mice, their housing must: 1) be durable, 2) protect the rodent from ingestion, 3) be escape proof, 4) be easily transferred in and out o the snake trap, 5) protect the rodent s from unwanted intruders, and 6) allow the bait s sensory cues to be detectable to the snake. A 65 x 65 x 205 mm chamber of 1/8-inch hardware cloth with folded end flaps met the above criteria when placed in a shaded trap. To provide for the comfort and wall being of the rodents, mice were repatriated to the airconditioned lab after five days, for a few day s rest before being returned to the field. Of 3,321 micenights used in a recent trap experiment, attrition was 0.2%, none of the rodents was ingested, and there were no escapes. A new design has recently been envisioned, which should improve convenience without comprising other design objectives. Clark, L., P. J. Savarie, J. A. Shivik, and S. Breck. submitted. Efficacy, effort and cost comparisons of trapping and acetaminophen-baiting control of brown treesnakes on Guam. Journal of Wildlife Management. Abstract: The brown treesnake (Boiga irregularis) is an invasive species to the island of Guam. Because it has extirpated the native forest avifauna on Guam and is a threat to other Pacific islands, the development of efficient and cost effective control methods if required. We compared the efficacy, and effort required to remove snakes on 6 ha plots in forest scrub on Guam using two methods: trapping and poison baiting. Toxic baits were made by inserting 80 mg of acetaminophen into dead neonatal mice and these mouse baits were used to treat plots. To assess efficacy, we used mark-recapture methods (program MARK) to estimate snake abundance on plots before treatment (12 days), monitoring bait-take or trap success during treatment (20 days), and used mark-recapture to estimate snake populations post-treatment (12 days). From 6,304 trap-nights we recorded 801 captures of 504 snakes on 6,6 ha plots during a 51 day period. Snake populations on plots ranged from prior to treatment. Using trapping to gauge survivorship of marked snake, the two methods (trapping and baiting) had similar efficacies (10%). Based on trapping, post-treatment population estimates ranged from 26-40, yielding reductions in standing estimated populations of 7-68% for both types of snake removal treatments (i.e., trapping and baiting). If post-treatment bait-take of unadulterated mice is used as an index of efficacy, poisoned baiting appears to be twice as effective as trapping in diminishing snake activity. Trapped plots had post-treatment bait-take rates similar to reference plots (75%) whereas poison-baited plots had bait-take rates of 38%, suggesting that some snakes cannot be trapped and that baiting affects a wider range of the snake population. Because of the potential for baiting to impact more snakes this method is about 59% more cost effective than trapping. If baiting were to occur via aerial drop rather than via bait stations, the economic incentive for using baiting as a control strategy would be even greater.

3 Engeman, R. M. and M. A. Linnell Trapping strategies for deterring the spread of Brown Tree Snakes from Guam. Pac. Conserv. Biol. 4: Abstract: 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 program designated to deter dispersal of the species. In this study, perimeter trapping of forested plots characteristic to 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 modeled 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 habits found around ports. Engeman, R. M. and M. A. Linnell. in press. The effect of trap spacing on the capture of brown treesnakes (Boiga irregularis) on Guam. Journal of Wildlife Restoration. Abstract: Inter-trap spacings of 20, 30 and 40 m along perimeter trap lines were compared using recaptures of tagged snakes and new captures. No differences were found among the different spacing distances for the distribution of recapture times or for numbers of new captures. The results indicate that for some situations, trapping efforts may be extended or made more efficient through increasing the distance between traps. Fritts, T.H., N.J. Scott, Jr., and B.E. Smith Trapping Boiga irregularis on Guam using bird odors. Journal of Herpetology 23(2): Abstract: The brown treesnake (Boiga irregularis) is native to islands in Papua New Guinea, and along the northern Australian coast. Funnel traps in conjunction with drift fences have been used to capture terrestrial snakes. Some funnel traps were suspended in trees and bated with live quail (Coturnix coturnix) to capture brown treesnakes in Guam. We wanted simple trap designs, avoid the use of drift fences, and eliminate the need for live baits. We investigated the suitability of two trap designs and the ability of bird odors to attract snakes to traps suspended above the ground in tress and shrubs.

4 Lindberg, A. C., J. A. Shivik, and L. Clark Mechanical mouse lure for Brown Tree Snakes. Copeia 2000: Abstract: The importance of prey movement for stimulating feeding behavior of Brown Treesnakes was tested by using a mechanical mouse model in combination with and without prey odor. Prey movement was found to be important in stimulating brown treesnake feeding behavior. Prey movement combined with prey odor was not significantly different than prey movement alone. In the development of simple artificial lures based on the stimulus of live mice, visual lures lacking movement are likely to be ineffective. Lures that combine a visual moving stimulus with prey odor are likely to be the most effective artificial lure for trapping brown treesnakes. Linnell, M. A., R. M. Engeman, M. E. Pitzler, M. O. Watten, G. F. Whitehead, and R. C. Miller An evaluation of two designs of stamped metal trap flaps for use in operational trapping of Brown Tree Snakes (Boiga irregularis). The Snake 28: Abstract: Two designs for stamped metal flaps used in traps to capture brown tree snakes were compared in separate studies to standard traps with wire mesh flaps. No difference in capture rates were detected between traps with the wire mesh flap on either of the stamped metal flaps. The second study included information on escape rates and numbers of jammed flaps. In that study, the stamped metal flap designed, using a set screw to insure one-way passage and a metal band on the exterior of the entrance to keep the hinge pin from jamming, produced proportionally fewer jammed doors and snake escapes than the wire mesh flap. Rodda, G. H., R. J. Rondeau, T. H. Fritts, and O. E. Maughan. 1992b. Trapping the arboreal snake Boiga irregularis. Amphibia-Reptilia 13: Abstract: The snake Boiga irregularis, an exotic on Guam, has eliminated the majority of the native vertebrates there. We tested traps designed to control this arboreal snake during three periods of days in 1988 and The relative trapping success with different baits and trap configurations indicated that this snake will not readily push through a visually obstructed entrance. However, under some conditions, 80% of the snakes escaped from traps lacking a physical blockage at the entrance. Live bait was more successful than odoriferous bait alone, and odoriferous guide ropes that led to trap entrances did not enhance capture rates. These findings corroborate laboratory experiments indicating an unusually strong dependence on visual cues in this highly successful nocturnal predator.

5 Vice, D Trapping the Brown Tree Snake. Koko s Call 16:2. Abstract: Most residents of Guam are familiar with the brown treesnake (Boiga irregularis) and the problems associated with its introduction to the island. Since their arrival in the early 1950 s, brown treesnakes have colonized the entire island, reaching extremely high densities in most forested areas. The snakes are also abundant in many urban and residential areas. As part of the brown treesnake control efforts on Guam, specially built snake traps are used to capture snakes from locations all around the island. The traps, which are modified crawfish or minnow traps, can be seen on fence lines and jungle edges at Won Pat International Airport, the Commercial Port, Anderson Air Force Base, and COMNAVMAR. Several agencies are involved in snake trapping or trap research, including the United States Department of Agriculture, the Guam Department of Agriculture, the United States Fish and Wildlife Service, and the Biological Resources Division of the United States Geological Survey.