Brown Tree Snake Boiga Irregularis Research Articles

Global economic costs of herpetofauna invasions

Biological invasions by amphibian and reptile species (i.e. herpetofauna) are numerous and widespread, having caused severe impacts on ecosystems, the economy and human health. However, there remains no synthesised assessment of the economic costs of these invasions. Therefore, using the most comprehensive database on the economic costs of invasive alien species worldwide (InvaCost), we analyse the costs caused by invasive alien herpetofauna according to taxonomic, geographic, sectoral and temporal dimensions, as well as the types of these costs. The cost of invasive herpetofauna totaled at 17.0 billion US$ between 1986 and 2020, divided split into 6.3 billion US$ for amphibians, 10.4 billion US$ for reptiles and 334 million US$ for mixed classes. However, these costs were associated predominantly with only two species (brown tree snake Boiga irregularis and American bullfrog Lithobates catesbeianus), with 10.3 and 6.0 billion US$ in costs, respectively. Costs for the remaining 19 reported species were relatively minor (< 0.6 billion US$), and they were entirely unavailable for over 94% of known invasive herpetofauna worldwide. Also, costs were positively correlated with research effort, suggesting research biases towards well-known taxa. So far, costs have been dominated by predictions and extrapolations (79%), and thus empirical observations for impact were relatively scarce. The activity sector most affected by amphibians was authorities-stakeholders through management (> 99%), while for reptiles, impacts were reported mostly through damages to mixed sectors (65%). Geographically, Oceania and Pacific Islands recorded 63% of total costs, followed by Europe (35%) and North America (2%). Cost reports have generally increased over time but peaked between 2011 and 2015 for amphibians and 2006 to 2010 for reptiles. A greater effort in studying the costs of invasive herpetofauna is necessary for a more complete understanding of invasion impacts of these species. We emphasise the need for greater control and prevention policies concerning the spread of current and future invasive herpetofauna.

Space use and activity of Boiga cyanea – A major songbird nest predator in a seasonal tropical forest in Thailand

Predator-prey interactions are fundamental drivers of population dynamics. Studying both predator and prey species simultaneously yields particularly useful insights into these complex interactions. Despite being significant, widespread avian nest predators, Southeast Asian snakes are rarely simultaneously studied in relation to avian prey. The Green Cat Snake Boiga cyanea is a primary nest predator, estimated to be responsible for 17–33% of forest songbird nest depredations in Northeast Thailand. We explored both diurnal and nocturnal movements of 14 (5 male, 9 female) adult B. cyanea with radio-telemetry for an average of 68 ± 16 days per individual, between 21 October 2017 and 8 June 2019 in the dry evergreen forest of the Sakaerat Biosphere Reserve (SBR). We quantified horizontal movements (m) and area of space use (ha) and activity through motion variance (Ϭ m 2 ) during the study period using dynamic Brownian Bridge Movement Models (dBBMMs) and reported our findings within the context of a simultaneously run avian nest monitoring study initiated in 2013 within the same forest. On average, adult B. cyanea moved 56.4 ± 10.4 m/day and used areas of 9.4 ± 3.4 ha, while their activity averaged 2.8 ± 0.8 Ϭ m 2 . Males moved 51.4 m/day farther than females, and in general, adult B. cyanea moved 50.3 m/day farther during the avian nesting season than the avian non-nesting season. We refrain from inferring statistical differences with the dBBMM outputs between sexes and seasons within our sample because of the unequal samples and sampling effort during the study period. Only two individuals (one male and one female) were sufficiently radio-tracked across both seasons (the avian nesting and non-nesting seasons), and these two displayed a clear increase in their respective movements, space use and activity during the avian nesting season. This could suggest that movements, space use and activity likely differ between the avian nesting and non-nesting seasons for male and female B. cyanea , however it is only two individuals. All individuals were exclusively nocturnal, moving throughout the night, and often descending from higher diurnal refugia (> 2 m) to forage closer to the ground after sunset. Our openly available data may yield further insight when combined with other major avian nest predator species like the congeneric invasive Brown Tree Snake Boiga irregularis on the island of Guam.

Recent recovery and expansion of Guam’s locally endangered Såli (Micronesian Starling) Aplonis opaca population in the presence of the invasive brown treesnake

SummaryAssessing the impacts of invasive predators on the demography and distribution of native species is critical for understanding mechanisms of species persistence and informing the design of recovery programmes. On the oceanic island of Guam, the introduction of the predatory brown treesnake Boiga irregularis after World War II caused the near-total loss of the native forest avifauna. Localised snake control measures have been implemented since the early 1990s, yet it remains poorly understood how they have impacted Guam’s remaining native bird populations. To address this question, we combined intensive area searches of Andersen Air Force Base (AAFB) with island-wide transect surveys and opportunistic sightings to provide a comprehensive update on the distribution and abundance of Såli (Micronesian Starling, Aplonis opaca) – one of Guam’s last extant native bird species. Area searches of AAFB, where the largest remnant of the Såli population persists, revealed a 15-fold population increase since the last survey in the early 1990s, and transect surveys and opportunistic sightings indicate incipient recolonisation of other urbanised areas of northern and central Guam. We estimate the current island-wide population size at ~1,400 individuals. The population increase can likely be attributed to a combination of snake control measures and the Såli’s ability to exploit urban refugia for nesting and roosting. Although these trends demonstrate some population recovery, a skewed age ratio (&gt;90% adults and subadults) at AAFB and a highly urbanised distribution and low abundance outside AAFB indicate that snake predation continues to strongly impact the population. More intensive snake suppression efforts, particularly in forested areas, may allow for the Såli population to attain its former distribution and abundance on Guam. More broadly, our findings reinforce the importance of urban areas as refugia for some threatened species.

Amphibian conservation: clarifications to comments from Andreone

We appreciate the comments from Andreone (2016) regarding our proposed alternative strategy for addressing the amphibian crisis. Andreone recognizes the utility of an Incident Command System approach but doubts the feasibility of implementation at an international level. We stated in our original article, however, that ‘the feasibility of our suggestion is debatable, but our point is that radically different approaches are necessary to effectively manage the largest extinction event in modern history’ (Muths &amp; Fisher, 2015). There are examples of where such top-down strategies are being applied; e.g. for the brown tree snake Boiga irregularis (Stanford &amp; Rodda, 2007), and biosecurity planning for Micronesia and Hawaii (NAVFAC Pacific, 2016). Another example is presented by Andreone. In Madagascar a community-wide conservation plan has been developed complete with prioritization of specific actions (Andreone, 2016). As with any top-down strategy, challenges will surface, especially when making decisions that affect economics. We note this caveat in our article, and Andreone points out such issues in Madagascar, where there are mismatches in priorities between biodiversity conservation and civil needs. Our suggestion is that a new paradigm needs to be considered given the gravity of amphibian decline, and one option may be to take a global approach focusing on specific, major threats. Application of an Incident Command System would not necessitate competition with, or emasculation of, local conservation priorities or actions.

Development and characterization of 33 novel polymorphic microsatellite markers for the brown tree snake Boiga irregularis.

BackgroundBoiga irregularis is a widespread invasive species on Guam and has led to extirpation of most of the island’s native avifauna. There are presently no microsatellite markers for this invasive species, hence we developed highly polymorphic microsatellite markers to allow for robust population genetic studies on Guam.FindingsWe isolated and characterized 33 microsatellite loci for the brown tree snake, B. irregularis. The loci were screened across 32 individuals from Guam. The number of alleles per locus ranged from three to ten, with an average of 4.62. The expected (He) and observed heterozygosity (Ho) ranged from 0.294 to 0.856 and from 0.031 to 0.813, with an average of 0.648 and 0.524, respectively. Significant deviations from Hardy–Weinberg equilibrium were detected at seven loci after Bonferoni correction. Probability of identity values ranged from 0.043 to 0.539.ConclusionsThese genetic markers are useful for understanding a suite of post-invasion population genetic parameters, sources of invasions, and effectiveness of management strategies for this invasive species.Electronic supplementary materialThe online version of this article (doi:10.1186/s13104-015-1620-z) contains supplementary material, which is available to authorized users.

The influence of time-dependent delay on behavior of stochastic population model with the Allee effect

This paper presents the analysis of behavior of stochastic time-dependent delay population model with the Allee effect. We prove the existence-and-uniqueness of positive solution of considered model. Then, we find the sufficient conditions under which the population will become extinct. We also show that if the initial population size exceeds environmental carrying capacity and time delay is sufficiently long, considered population is non-persistent in mean. The sufficient conditions for asymptotical mean square stability and stability in probability of the positive equilibrium states of the model, in terms of Lyapunov functional method, are obtained. Finally, as an illustration, we apply our mathematical results and predict time which a population of the African wild dog Lycaon pictus needs to reach it is equilibrium states, and also confirm that population of brown tree snake Boiga irregularis is non-persistent in mean if the initial population size is greater than carrying capacity and time delay is long enough.

Ecosystem services: do we need birds?

Ecosystem services: do we need birds?

Invasive reptiles and amphibians: global perspectives and local solutions

In the annals of invasive species biology, higher taxa such as mammals, plants and insects have received the lion’s share of research attention, largely because many of these invaders have demonstrated a remarkable ability to degrade ecosystems and cause economic harm. Interest in invasive reptiles and amphibians (collectively ‘herpetofauna’, colloquially ‘herps’) has historically lagged but is now garnering increased scrutiny as a result of their escalating pace of invasion. A few herpetofaunal invaders have received considerable attention in scientific and popular accounts, including the brown treesnake Boiga irregularis on Guam, Burmese python Python molurus in Florida, Coqui Eleutherodactylus coqui in Hawaii and cane toad Bufo marinus in Australia. However, relatively few are aware of many emerging and potentially injurious herpetofaunal invaders, such as Nile monitors Varanus niloticus in Florida, common kingsnakes Lampropeltis getula in the Canary Islands, boa constrictors Boa constrictor on Aruba and Cozumel, or a variety of giant constrictor snakes in Puerto Rico. For the vast majority of the most commonly introduced species, real or potential impacts to native ecosystems or human economic interests are poorly understood and incompletely explored; major pathways of introduction have only recently been elucidated, and effective management interventions have been limited (Kraus, 2009). The goal of this symposium was to bring together an international community of biologists working on invasive reptiles and amphibians so as to facilitate better communication of findings and sharing of ideas among this relatively small and geographically dispersed group of researchers. To date, those studying invasive herpetofauna have often been unaware of relevant research and control efforts in other countries and have lacked a working network for sharing data, ideas and potential control tools. The international trade in live reptiles and amphibians, valued in the billions of dollars, virtually ensures that establishment of alien herps will continue until the scale of the problem is more widely known and intervention is organized across multiple countries. The symposium consisted of 20 oral presentations over 2 days, with a total of 27 authors from countries including Australia, Canada, Japan, Portugal, South Africa, UK and USA. Among the many outstanding presentations were examination of links between invasive amphibians and the spread of Batrachochytrium, economic analysis of early detection and rapid response, education and outreach initiatives, an exploration of means of reducing intentional or accidental release of herps from the pet trade and case studies of control of bullfrogs, clawed frogs and viperine snakes. Evening discussions and subsequent email correspondence have enabled many of the participants to keep abreast of ongoing research findings and regulatory approaches that have been proposed or implemented to mitigate the effects of invasive herpetofauna. The three symposium contributions featured in this section (Kikillus, Hare & Hartley, 2010; Shanmuganathan et al., 2010; van Wilgen et al., 2010) address different topics directly relevant to improving management of invasive herpetofauna. We feel it is timely to emphasize this particular aspect of invasive-species biology because it is often neglected by the academic community, which more often treats biological invasions as a strictly (or primarily) biological phenomena. But they are not. The recent explosion of biological invasions, including the exponential growth in herpetofaunal introductions (Kraus, 2009) is primarily driven by cultural or social imperatives, not biological ones. Hence, solutions to the widespread transport and release of these organisms must also be cultural, social and political. For those social, cultural and political solutions to be attempted requires more detailed knowledge of what solutions might look like – we need improved knowledge of how and why species are transported, which species will establish and prove invasive and which methods might be used to mitigate the worst impacts of invaders. The symposium presentations featured here address factors driving the importation of live reptiles, develop models predicting invasion success and assess the potential utility of biocontrol against a notorious invader. Thus, they move us toward developing the knowledge required to mitigate and stop this global conservation problem.

Modelling detection probabilities to evaluate management and control tools for an invasive species

Summary 1. For most ecologists, detection probability (p) is a nuisance variable that must be modelled to estimate the state variable of interest (i.e. survival, abundance, or occupancy). However, in the realm of invasive species control, the rate of detection and removal is the rate‐limiting step for management of this pervasive environmental problem. 2. For strategic planning of an eradication (removal of every individual), one must identify the least likely individual to be removed, and determine the probability of removing it. 3. To evaluate visual searching as a control tool for populations of the invasive brown treesnake Boiga irregularis, we designed a mark–recapture study to evaluate detection probability as a function of time, gender, size, body condition, recent detection history, residency status, searcher team and environmental covariates. 4. We evaluated these factors using 654 captures resulting from visual detections of 117 snakes residing in a 5‐ha semi‐forested enclosure on Guam, fenced to prevent immigration and emigration of snakes but not their prey. Visual detection probability was low overall ( = 0·07 per occasion) but reached 0·18 under optimal circumstances. 5. Our results supported sex‐specific differences in detectability that were a quadratic function of size, with both small and large females having lower detection probabilities than males of those sizes. There was strong evidence for individual periodic changes in detectability of a few days duration, roughly doubling detection probability (comparing peak to non‐elevated detections). Snakes in poor body condition had estimated mean detection probabilities greater than snakes with high body condition. Search teams with high average detection rates exhibited detection probabilities about twice that of search teams with low average detection rates. Surveys conducted with bright moonlight and strong wind gusts exhibited moderately decreased probabilities of detecting snakes. 6. Synthesis and applications. By emphasizing and modelling detection probabilities, we now know: (i) that eradication of this species by searching is possible, (ii) how much searching effort would be required, (iii) under what environmental conditions searching would be most efficient, and (iv) several factors that are likely to modulate this quantification when searching is applied to new areas. The same approach can be use for evaluation of any control technology or population monitoring programme.

Recent status and trends of the land bird avifauna on Saipan, Mariana Islands, with emphasis on the endangered Nightingale Reed-warbler Acrocephalus luscinia

The avifauna of the Mariana Islands, an archipelago in the western Pacific, faces the threats of rapid economic development and the spread of non-native species, particularly a devastating predator, Brown Tree Snake Boiga irregularis. In this paper, we examine the status and trends of the land bird fauna of Saipan Island based on three island-wide surveys conducted in 1982, 1997, and 2007. During this period, the human population on Saipan increased more than four-fold and much of the island has been developed. The surveys employed standard point-transect methods based on Distance Sampling. Remarkably, we found nearly all species of land birds - 11 native species and three introduced species - to be common or abundant. The exception was the Micronesian Megapode Megapodius laperouse, a historically rare species that was not observed on the 2007 survey, although it does persist on Saipan and other Mariana islands. A comparison of species densities among the three surveys showed that seven species, mainly fruit and seed-eaters, had increased and three species of insectivorous birds had decreased - Rufous Fantail Rhipidura rufifrons, Nightingale Reed-warbler Acrocephalus luscinia, and Golden White-eye Cleptornis marchei. Of these three, Nightingale Reed-warbler is listed as ‘Endangered’ on the IUCN Red List and as an Endangered Species by the U.S. Fish and Wildlife Service. Reed-warbler densities on Saipan decreased by more than half between 1982 and 2007. Although point transect sampling worked well for this species, density estimates and trends assessment could be improved by reallocating sampling stations among habitats and by more frequent sampling.

Evaluation of trap capture in a geographically closed population of brown treesnakes on Guam

SummaryOpen population mark–recapture analysis of unbounded populations accommodates some types of closure violations (e.g. emigration, immigration). In contrast, closed population analysis of such populations readily allows estimation of capture heterogeneity and behavioural response, but requires crucial assumptions about closure (e.g. no permanent emigration) that are suspect and rarely tested empirically.In 2003, we erected a double‐sided barrier to prevent movement of snakes in or out of a 5‐ha semi‐forested study site in northern Guam. This geographically closed population of &gt;100 snakes was monitored using a series of transects for visual searches and a 13 × 13 trapping array, with the aim of marking all snakes within the site. Forty‐five marked snakes were also supplemented into the resident population to quantify the efficacy of our sampling methods. We used the programmarkto analyse trap captures (101 occasions), referenced to census data from visual surveys, and quantified heterogeneity, behavioural response, and size bias in trappability. Analytical inclusion of untrapped individuals greatly improved precision in the estimation of some covariate effects.A novel discovery was that trap captures for individual snakes consisted of asynchronous bouts of high capture probability lasting about 7 days (ephemeral behavioural effect). There was modest behavioural response (trap happiness) and significant latent (unexplained) heterogeneity, with small influences on capture success of date, gender, residency status (translocated or not), and body condition.Trapping was shown to be an effective tool for eradicating large brown treesnakesBoiga irregularis(&gt;900 mm snout‐vent length, SVL).Synthesis and applications.Mark–recapture modelling is commonly used by ecological managers to estimate populations. However, existing models involve making assumptions about either closure violations or response to capture. Physical closure of our population on a landscape scale allowed us to determine the relative importance of covariates influencing capture probability (body size, trappability periods, and latent heterogeneity). This information was used to develop models in which different segments of the population could be assigned different probabilities of capture, and suggests that modelling of open populations should incorporate easily measured, but potentially overlooked, parameters such as body size or condition.

Irditoxin, a novel covalently linked heterodimeric three‐finger toxin with high taxon‐specific neurotoxicity

A novel heterodimeric three-finger neurotoxin, irditoxin, was isolated from venom of the brown treesnake Boiga irregularis (Colubridae). Irditoxin subunit amino acid sequences were determined by Edman degradation and cDNA sequencing. The crystal structure revealed two subunits with a three-finger protein fold, typical for "nonconventional" toxins such as denmotoxin, bucandin, and candoxin. This is the first colubrid three-finger toxin dimer, covalently connected via an interchain disulfide bond. Irditoxin showed taxon-specific lethality toward birds and lizards and was nontoxic toward mice. It produced a potent neuromuscular blockade at the avian neuromuscular junction (IC(50)=10 nM), comparable to alpha-bungarotoxin, but was three orders of magnitude less effective at the mammalian neuromuscular junction. Covalently linked heterodimeric three-finger toxins found in colubrid venoms constitute a new class of venom peptides, which may be a useful source of new neurobiology probes and therapeutic leads.

Extinction of island endemics: it is not inbreeding depression

Extinction of island endemics: it is not inbreeding depression

Population trends of Mariana Crow Corvus kubaryi on Rota, Commonwealth of the Northern Mariana Islands

Endemic to the islands of Guam and Rota in the Mariana Islands, Mariana Crow Corvus kubaryi is the only corvid in Micronesia. Currently, it survives on Guam only because of translocation of individuals from Rota (1999–2003). Island-wide surveys in 1982 and 1995 on Rota yielded population estimates of 1,348 and 592 respectively, indicating a 56% decrease in only 13 years. A sharp decline in the only viable Mariana Crow population has serious implications for conservation efforts on Rota and for efforts to re-establish the Guam population. However, the validity of the apparent decline has been debated among scientists and government management agencies. We augmented the 1982 and 1995 island-wide VCP surveys with (1) an additional island-wide survey conducted in 1998, and (2) roadside surveys conducted during 1991–1993 and again during 1999–2002. We also outline historical changes in Rota's limestone forest based on aerial photographs and historical information. Data from all surveys indicate a significant decline in the Mariana Crow population. Declines occurred especially along the north-central coast and in the area east of the airport known as As Dudo in the 1990s, but the data indicate an island-wide decline over the entire span of the surveys. Introduced predators, human persecution, and habitat loss and degradation by anthropogenic and natural causes have all contributed to the decline. Long-term preservation of this species will require effective brown treesnake Boiga irregularis control, habitat protection, continued monitoring and research, and increased public education and awareness of Rota's rare and endangered species.

Characteristics of Brown Treesnakes Boiga irregularis removed from Guam's transportation network

The accidental introduction of the Brown Treesnake Boiga irregularis to Guam led to catastrophic ecological and economic consequences, including the extirpation of most native forest birds and millions of dollars in damages to the island's power distribution system. Since colonizing the island in the late 1940s, Brown Treesnakes associated with cargo from Guam have arrived at numerous locations throughout the world. Concerns for the potential establishment of other populations have led to intensive control efforts, aimed at the prevention of snake dispersal from the island. Information regarding snakes entering the outbound cargo flow is critical in the development and implementation of both operational control strategies and research necessary to improve available control technologies. Data collected from 31 snakes removed from the outbound cargo network on Guam reveal the typical snake in cargo is smaller in snout-vent length than the average snake captured using traps or hand capture in support of operational control. Potential reasons for small snakes in cargo include the presence of a snake cohort refractory to capture methods, and/or the nomadic behaviour of sub-adults. Additionally, snakes have been found in nearly every location that handles or processes cargo, indicating the need for containment efforts throughout the outbound shipping process. Intensive containment, coupled with the continued development of techniques that effectively capture small snakes, is necessary for successful interdiction efforts.

Exotic snakes in São Paulo City, southeastern Brazil: why xenophobia?

Introduced exotic species cause environmental changes and threat public health in target sites. Illegal trade has enhanced this problem. To first report these risks in Brazil, exotic snakes found in Sao Paulo City (SPC) (23 ◦ 32 � S, 46 ◦ 38 � W), southeastern Brazil, and sent to Instituto Butantan between 1995 and 2000, were listed and characterized by their biological attributes. Seventy-six individuals of sixteen alien species were collected. Euriecians snakes, mainly booids, were predominant. Using multivariate tech- niques, their ecological niches were compared to those of 26 native species, as a way to point out the resource's availability. To evaluate the potential of successful implantation, two species absent in SPC and considered as problem snakes are included in these analyses: the brown treesnake Boiga irregularis and the habu Trimeresurus flavoviridis. There were niche similarities between these pest snakes, exotic booids and native viperids largely due to the similarities in the chosen prey (mammals), diel activity (nocturnal), color pattern (variegated) and body size (medium to large). To avoid predictable undesirable effects of implanted pest snakes, traffic control and punishment should be improved, as well as parallel environmental education programs.

Sustained evaluation of the effectiveness of detector dogs for locating brown tree snakes in cargo outbound 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 created a health hazard to infants and children, and has resulted in economic losses. The high brown tree snake population densities on Guam, the species’ adaptations for successful dispersal, and Guam's position as a focal point for commercial and military cargo shipments have created a high level of concern that brown tree snakes could spread from Guam to colonize other vulnerable locations. Cargo inspections using teams of handlers and their detector dogs form the last line of defense for preventing brown tree snake dispersal from Guam. We assessed the efficacy of the teams of handlers and their dogs during 1998 and 1999 for locating stowed brown tree snakes by planting live brown tree snakes (in escape-proof containers) in cargo without the knowledge of the handlers inspecting the cargo. Many of these inspections were monitored by a concealed observer to determine the reason if a planted snake was not located by the dog teams. For 1998 and 1999, we found similar efficacies of 61% and 64%, respectively. When the snakes were not located by the dogs, we found that twice as many were missed because the dog did not change its behavior in response to the snake rather than because the handler did not conduct an adequate search pattern. During daytime inspections we found a greater efficacy for outdoor inspections than for indoor inspections. We found that the average efficacy of 62% for the 1998–99 period was lower than the baseline efficacy of 70% established in 1997.

Determination of the presence of Mycobacterium avium on Guam as a precursor to reintroduction of indigenous bird species

Eight of 11 native forest bird species on Guam were extirpated by the introduction of the Brown Tree Snake Boiga irregularis. Emergency measures necessary to rescue the Guam subspecies of Micronesian Kingfisher Halcyon cinnamomina cinnamomina from extinction involved translocation and captive breeding in American mainland zoos. Soon after the establishment of a captive breeding population, the kingfisher demonstrated a high degree of susceptibility to avian tuberculosis (ATB), a disease that proved to be a major threat to the preservation of the species. The cause of ATB is Mycobacterium avium which produces a prolonged course of infection in kingfishers and other birds. Kingfishers infected with M. avium are difficult to detect until late in the course of the disease, thereby potentially posing a risk of transmitting ATB to the Guam captive population of Guam Rails Gallirallus owstoni, if kingfishers are repatriated. M. avium is considered to be ubiquitous in nature. However, there are no reported mortalities due to ATB in any bird species on Guam. In this study, six of twenty-one cultures yielded Mycobacterium spp., two of which were further identified as M. avium. Since this study demonstrates that M. avium already exists on Guam, repatriating kingfishers to Guam poses no threat of introducing a new pathological agent to the island's ecosystem. Strict quarantine procedures along with rigorous animal husbandry protocols should minimize risks of repatriating infected kingfishers to Guam, and prevent transmission of ATB to the captive population of Guam Rails and other bird populations on Guam.

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.

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

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.