Bait Boxes Research Articles

Tick control bait box use by Peromyscus spp. influenced by habitat placement but raises questions on disease ecology

AbstractWhite‐footed mice, Peromyscus leucopus (Rafinesque), and deer mice, Peromyscus maniculatus Gloger, are considered important reservoir hosts for Borrelia burgdorferi sensu stricto, the causative agent of Lyme disease. Host‐targeted and nonlethal Select TCS bait boxes have been shown to be effective at killing ticks by delivering small doses of fipronil to wild Peromyscus spp., attracted to the provided bait. This results in reductions in the tick Ixodes scapularis, the vector of Borrelia burgdorferi, in the environment. However, habitat influences on bait box use, interactions with bait boxes, and overall use of bait by small mammals have not been evaluated. These factors may influence the use of this tick control measure. In the current study, bait box use by small mammals was evaluated at five field sites in Maryland, USA, during a two‐year study period. Bait consumption in relation to specific described habitats evaluated at each site was recorded, and bait nutrition was compared to nutrition from common northeastern acorn species. Rodent behavior around bait boxes was analyzed using camera traps as well. Bait boxes were used more frequently in herbaceous and shrub habitats than those placed in areas with bare ground or canopy cover alone. Significant amounts of bait were consumed throughout the study, but in some habitat types bait boxes were not used. The bait was found to be similar to native acorns in energy content, suggesting that it may serve as a supplement for natural foods which may have population dynamic implications. Behavioral analysis suggested that Peromyscus spp. foraged around bait boxes regardless of bait presence, but they did not forage in unbaited boxes as frequently. This may suggest the use of odors alone could be enough for attracting rodents to bait boxes potentially reducing the negative effects of baiting while maintaining protective tick control measures.

Testing the potential of 50 kHz rat calls as a species-specific rat attractant.

The control of mammalian pests relies heavily on the use of pesticides that are often avoided and are not species-specific. These problems are particularly acute for pesticides used to control rats (Rattus spp.). The efficacy and targeting of control could be improved by attracting animals to control measures using species-specific cues. One cue that has the potential to attract rats is the 50 kHz calls they emit in positive social situations. Here we test the potential of these rat calls as a species-specific attractant by examining the response of laboratory rats (Rattus norvegicus; n = 48) and non-target bank voles (Myodes glareolus; n = 16) to 50 kHz calls from either sex in a compartmentalised laboratory arena. Sounds of rat movement and white noise acted as control treatments, with each sound tested against a silent control in the opposite side of the arena. When sound cues were played above an empty bait box, rats were attracted to spend time close to 50 kHz rat calls, climbing on top of boxes, regardless of the sex of subject or caller. When either 50 kHz rat calls or rat movement sounds were played inside an empty bait box, rats of both sexes spent 3–4 fold more time inside boxes and visited more frequently. Rats were not attracted by intermittent white noise. Bank voles were neither attracted to, nor avoided, 50 kHz rat calls played inside empty bait boxes. Our findings show that 50 kHz rat calls are an effective attractant for rats of both sexes under laboratory conditions, while not attracting non-target bank voles. These calls are strong candidates for providing a species-specific lure that may be attractive even in the absence of food bait, but further trials will be needed to assess their efficacy under field conditions.

Exposure of non-target small mammals to anticoagulant rodenticide during chemical rodent control operations.

The extensive use of anticoagulant rodenticides (ARs) results in widespread unintentional exposure of non-target rodents and secondary poisoning of predators despite regulatory measures to manage and reduce exposure risk. To elucidate on the potential vectoring of ARs into surrounding habitats by non-target small mammals, we determined bromadiolone prevalence and concentrations in rodents and shrews near bait boxes during an experimental application of the poison for 2weeks. Overall, bromadiolone was detected in 12.6% of all small rodents and insectivores. Less than 20m from bait boxes, 48.6% of small mammals had detectable levels of bromadiolone. The prevalence of poisoned small mammals decreased with distance to bait boxes, but bromadiolone concentration in the rodenticide positive individuals did not. Poisoned small mammals were trapped up to 89m from bait boxes. Bromadiolone concentrations in yellow-necked mice (Apodemus flavicollis) were higher than concentrations in bank vole (Myodes glareolus), field vole (Microtus agrestis), harvest mouse (Micromys minutus), and common shrew (Sorex araneus). Our field trials documents that chemical rodent control results in widespread exposure of non-target small mammals and that AR poisoned small mammals disperse away from bating sites to become available to predators and scavengers in large areas of the landscape. The results suggest that the unintentional secondary exposure of predators and scavengers is an unavoidable consequence of chemical rodent control outside buildings and infrastructures.

Integrated control of juvenile Ixodes scapularis parasitizing Peromyscus leucopus in residential settings in Connecticut, United States

Lyme disease continues to be the most common vector-borne disease in the United States with an estimated 330,000 human cases annually. In the eastern United States, the blacklegged tick, Ixodes scapularis, is the primary vector of the Lyme disease spirochete, Borrelia burgdorferi, and the white-footed mouse, Peromyscus leucopus, is a primary reservoir host. In four residential neighborhoods in Connecticut over three years, we tested the effectiveness of different low-toxicity integrated tick management approaches to control larval and nymphal I. scapularis parasitizing P. leucopus. Combinations of white-tailed deer, Odocoileus virginianus, reduction, broadcast application of the entomopathogenic fungus Metarhizium anisopliae, and distribution of fipronil-based rodent-targeted bait boxes were evaluated against an experimental control. Deer reduction with no other intervention likely forced juvenile I. scapularis to obtain blood meals from available reservoir hosts, resulting in increased exposure of P. leucopus to B. burgdorferi compared to control sites. The M. anisopliae/bait box and the deer reduction/M. anisopliae/bait box treatment combinations resulted in 94% and 85% reductions in larvae parasitizing P. leucopus that tested positive for B. burgdorferi, respectively, compared to control. Deer reduction alone resulted in only a 3% reduction, likely because parasitizing juvenile I. scapularis were not targeted by bait box-delivered fipronil. Unless there is community support to reduce and maintain deer at very low densities (<5 deer/km2), it is clear that a combination of M. anisopliae/fipronil-based bait boxes offers an effective, localized, low-toxicity option for reducing I. scapularis parasitizing P. leucopus without complications from host switching.

Integrated Control of Nymphal Ixodes scapularis: Effectiveness of White-Tailed Deer Reduction, the Entomopathogenic Fungus Metarhizium anisopliae, and Fipronil-Based Rodent Bait Boxes.

Pathogens transmitted by ticks are the leading cause of arthropod-associated human diseases in the United States and managing the risk of exposure to potentially infected ticks is of vital public health importance. A 3-year integrated tick management program to control blacklegged ticks, Ixodes scapularis, the primary vector for the pathogenic agents of Lyme disease, human anaplasmosis, and babesiosis, was implemented in the town of Redding in southwestern Connecticut beginning in 2013. Combinations of white-tailed deer, Odocoileus virginianus, reduction, area application of the entomopathogenic fungus Metarhizium anisopliae, and fipronil-based rodent bait boxes were evaluated for their ability to reduce nymphal I. scapularis over 3 years. Interference from local hunters prevented sufficient, sustained deer removal previously reported to negatively impact I. scapularis abundances (i.e., <5 deer/km2). The combination of fipronil-based bait boxes and broadcast application of M. anisopliae had the most impact of any treatment combination; questing nymphs were reduced 78-95% within each year and Borrelia burgdorferi-infected questing nymphal I. scapularis encounter potential was reduced by 66% as compared with no treatment in the third year of the study. A combination of the broadcast application of M. anisopliae and small rodent-targeted fipronil-based bait boxes is an effective low-toxicity integrated approach that significantly reduced encounters with B. burgdorferi-infected questing nymphal I. scapularis on individual properties.

Trade of live bait in Portugal and risks of introduction of non-indigenous species associated to importation

Different invertebrate groups are often exploited on sediment shores and mudflats, including polychaetes, sipunculids, bivalves and crustaceans. The commercial importance of polychaetes and sipunculids, that has increased in the early 2000's because of its use as a food source for the aquaculture sector and a growing demand of worms for use as sea angling bait, seems to be declining nowadays. In Portugal bait harvesting from natural populations became insufficient to meet market demands and as a result, polychaetes and sipunculids have been imported in recent years. Due to this it was important to know the ways of the live bait import to Portugal, and to assess the risk of introduction of non-indigenous species associated to that live bait trade. The origin and quantities of imported live bait were determined by examining the landing's records at Lisbon airport, from two periods: 2002–2003 and 2012–2015. Live worms imported to Portugal arrived almost exclusively from China, USA and Vietnam. Monthly import data and bait registers at fish auction landings were significantly correlated, showing that bait captures and imports are directly related to higher bait demand. In addition, the risk of live bait's importation as an introduction vector for non-indigenous species was evaluated by examining the bait boxes content. Five worm species were identified in bait boxes with foreign species: Glycera dibranchiata, Namalycastis rhodochorde, Perinereis cultrifera, Perinereis linea, and Sipunculus (Sipunculus) nudus. The examination of bait boxes in Portugal suggested that there is a low risk of associated hitchhiker species introduction and dissemination, mostly because of packaging procedures, which should be advised. The same is not true to the non-indigenous live bait species.

Evaluation of the SELECT Tick Control System (TCS), a Host-Targeted Bait Box, to Reduce Exposure to Ixodes scapularis (Acari: Ixodidae) in a Lyme Disease Endemic Area of New Jersey

We describe a 2-yr trial to evaluate the ability of SELECT Tick Control System (TCS) host-targeted bait boxes to reduce numbers of host-seeking Ixodes scapularis nymphs in a residential neighborhood. After four successive 9-wk deployments, nymphal and larval I. scapularis infestation prevalence and intensity were significantly reduced on target small mammals. In addition, these deployments resulted in 87.9% and 97.3% control of host-seeking nymphs in treatment sites at 1 yr and 2 yr postintervention, respectively. Installation of a protective metal cover around the SELECT TCS bait boxes eliminated nontarget wildlife damage to bait boxes that resulted in failure of previous bait box types. The results are discussed in the context of the residential environment and future research needs.

Feeding Behavior of Subadult Sixgill Sharks (Hexanchus griseus) at a Bait Station

This is the first in-situ study of feeding behaviors exhibited by bluntnose sixgill sharks. Bait was placed beneath the Seattle Aquarium pier situated on the waterfront in Elliott Bay, Puget Sound, Washington at 20m of water depth. Cameras and lights were placed around the bait box to record sixgill shark presence and behavior while feeding. Analysis of feeding behavior revealed that sixgills utilize a bite comparable to many other elasmobranchs and aquatic vertebrates, have the ability to protrude their upper jaw, change their feeding behavior based on the situation, and employ sawing and lateral tearing during manipulation. The versatility of their feeding mechanism and the ability of sixgills to change their capture and food manipulation behaviors may have contributed to the species’ worldwide distribution and evolutionary success.

Natural and synthetic vocalizations of brown rat pups, Rattus norvegicus, enhance attractiveness of bait boxes in laboratory and field experiments.

Rats are often neophobic and thus do not readily enter trap boxes which are mandated in rodent management to help reduce the risk of accidental poisoning or capture of non-target animals. Working with brown rats, Rattus norvegicus, as a model species, our overall objective was to test whether sound cues from pups could be developed as a means to enhance captures of rats in trap boxes. Recording vocalizations from three-day-old pups after removal from their natal nest with both sonic and ultrasonic microphones revealed frequency components in the sonic range (1.8-7.5 kHz) and ultrasonic range (18-24 kHz, 33-55 kHz, 60-96 kHz). In two-choice laboratory bioassays, playback recordings of these vocalizations induced significant phonotactic and arrestment responses by juvenile, subadult and adult female and male rats. The effectiveness of engineered 'synthetic' rat pup sounds was dependent upon their frequency components, sound durations and the sound delivery system. Unlike other speakers, a piezoelectric transducer emitting sound bursts of 21 kHz with a 63-KHz harmonic, and persisting for 20-300 ms, proved highly effective in attracting and arresting adult female rats. In a field experiment, a battery-powered electronic device fitted with a piezoelectric transducer and driven by an algorithm that randomly generated sound cues resembling those recorded from rat pups and varying in fundamental frequency (19-23 kHz), duration (20-300 ms) and intermittent silence (300-5000 ms) significantly enhanced captures of rats in trap boxes baited with a food lure and soiled bedding material of adult female rats. Our study provides proof of concept that rat-specific sound cues or signals can be effectively reproduced and deployed as a means to enhance capture of wild rats. © 2016 Society of Chemical Industry.

Opening Pandora's bait box: a potent vector for biological invasions of live marine species

AbstractAimFor over 80 years, the Maine baitworm trade has shipped live polychaete worms and packing algae ‘wormweed’ to distributors world‐wide, while also consistently transferring a wide diversity and abundance of hitchhiking organisms of all life stages to numerous recipient communities. Here, we investigate this potent, yet underestimated, invasion vector using an important recipient region (the Mid‐Atlantic) to examine the stepwise species transfer and survival along four stages of the vector.LocationMaine and Mid‐Atlantic region (New Jersey, Delaware, Maryland, Virginia and North Carolina), USA.MethodsWe quantified taxonomic identities and abundances of organisms associated with packing algae at four stages along the vector pathway during summer 2011: (1) Maine source habitats; (2) bait boxes from Maine distributors; (3) bait boxes from distributors in five Mid‐Atlantic States; and (4) bait bags from retailers in five Mid‐Atlantic States. We also examined functional diversity based on significant physical and life history characteristics and assessed genetic diversity for two common hitchhiking snail species.ResultsWe identified 17,798 live macro‐organisms across 58 taxa, including marine macro‐invertebrates, macroalgae, vascular plants and semi‐terrestrial or aquatic invertebrates, present in bait boxes and bags. In all measures of diversity and abundance, we observed decreases of live marine macro‐invertebrates across sequential stages of the vector from source to recipient regions. Significant differences in community composition were also observed between stages and were driven by isopods (taxonomic diversity) and isopods, amphipods and some gastropods (functional diversity).Main conclusionsThe lack of management in the face of the sheer magnitude and diversity of organisms that are transported via the live marine bait trade underscores how this is an underappreciated vector that could be a considerable source of successful invasions globally.

An experimental investigation into the colonization of concealed cadavers by necrophagous blowflies.

We used seven baited boxes with different combinations of access holes and odor diffusion surfaces to study the arrival of necrophagous flies. During laboratory experiments, 30 gravid Lucilia sericata females were kept in a chamber with one of the boxes. The box with the largest odor diffusion surface (99 cm2) combined with the lowest accessibility (one 1 cm2 entrance hole) was entered least (5 ± 3.7 flies per run). In contrast, the most frequently entered box (one 9 cm2 entrance hole with no additional odor diffusion surface) caught a mean of 24.6 ± 3.4 flies per run. These results indicate that 1) L. sericata entered nearly inaccessible places and 2) both odor diffusion and accessibility impacted the number of flies caught. During field experiments, the seven boxes were placed together outdoors. The box with the most entrances (ten 9-cm2 holes) caught the most flies (55.6–99.4% of the total). Only a few flies entered the other boxes. Access to the less accessible boxes (poor odor diffusion and small entrances) was also delayed. The major conclusions of the field experiments are that 1) boxes with low accessibility took longer to be accessed; 2) larger odor diffusion surfaces were more attractive to flies; and 3) flies accessed boxes more readily through larger holes than through an equivalent surface area made up of smaller holes. With these conclusions in mind, attempts to quantify the preappearance interval or to interpret the number of flies observed in indoor forensic entomology cases should be approached with caution.

Owl monkeys (Aotus nigriceps and A. infulatus) follow routes instead of food-related cues during foraging in captivity.

Foraging at night imposes different challenges from those faced during daylight, including the reliability of sensory cues. Owl monkeys (Aotus spp.) are ideal models among anthropoids to study the information used during foraging at low light levels because they are unique by having a nocturnal lifestyle. Six Aotus nigriceps and four A. infulatus individuals distributed into five enclosures were studied for testing their ability to rely on olfactory, visual, auditory, or spatial and quantitative information for locating food rewards and for evaluating the use of routes to navigate among five visually similar artificial feeding boxes mounted in each enclosure. During most experiments only a single box was baited with a food reward in each session. The baited box changed randomly throughout the experiment. In the spatial and quantitative information experiment there were two baited boxes varying in the amount of food provided. These baited boxes remained the same throughout the experiment. A total of 45 sessions (three sessions per night during 15 consecutive nights) per enclosure was conducted in each experiment. Only one female showed a performance suggestive of learning of the usefulness of sight to locate the food reward in the visual information experiment. Subjects showed a chance performance in the remaining experiments. All owl monkeys showed a preference for one box or a subset of boxes to inspect upon the beginning of each experimental session and consistently followed individual routes among feeding boxes.

Response of Wedge-tailed Shearwaters (Puffinus pacificus) to Eradication of Black Rats (Rattus rattus) from Moku‘auia Island after Reinvasion1

Moku‘auia is a 5-ha island off northeastern O‘ahu, Hawai‘i, that supports several thousand nesting Wedge-tailed Shearwaters (Puffinus pacificus) and several species of migratory shorebirds and is critical habitat for the federally endangered ‘ohai plant (Sesbania tomentosa). The island is separated from Mālaekahana State Recreation Area on O‘ahu by a channel 230 m wide and 1 m deep and receives numerous human visitors. Black rats (Rattus rattus) were first documented on Moku‘auia in 1967 and were eradicated in the 1990s, but rats recolonized the island and were eradicated again in 2006. We re-eradicated black rats in November 2011 following another recolonization, using snap traps and diphacinone in bait boxes spaced 25 m apart. Pre-eradication, 80% of tracking tunnels contained rat tracks. After 14 days, no more rats were trapped, bait take dropped to almost zero, and no rats have been detected since. Eradication of rats resulted in a doubling of Wedge-tailed Shearwater reproduction in 2006 and 2012 and is expected to enhance regeneration of native plants. Black rats may recolonize Moku‘auia periodically in the future because of its proximity to O‘ahu and the frequency of human visitation, but its small size and simple terrain make rats easy and inexpensive to eradicate, and the natural resources present warrant continued management.

The influence of bait presentation on bait uptake by mice (Mus domesticus) in infested urban domestic dwellings

Several researchers have established a link between the presence of house mouse (Mus domesticus) infestations and detrimental effects on human health. Controlling mouse infestations therefore requires methods that are quick, safe and effective. A tamper-resistant bait station with a wax block which is manufactured to fit within it so that it cannot be shaken out is considered the safest way to present the bait. However, some authors have expressed concern about the efficacy of this method. Research to examine the effects of bait stations on the feeding of mice infesting domestic dwellings was undertaken in the city of Manchester, UK. Working in conjunction with Manchester City Council, suitable sites were found. A balanced Latin Square experimental design was employed to overcome any operational biases that could have occurred. Non-toxic baits were presented in one of four ways: whole wheat in a cardboard box; whole wheat in a open tray; whole wheat in a tamper-resistant box; and a non-toxic wax block in a tamper-resistant box. Baits were placed in four different locations within dwellings and during the feeding trial; the bait stations were rotated, so that each bait type was presented in each location. The bait take from 12 dwellings within 3 housing blocks was recorded. Three-quarters of the bait consumed during the trial was taken from the cardboard box. No bait was taken from the tamper-resistant box containing the wax block.Risk assessments should drive the approach adopted in presenting rodenticide. Dwellings where vulnerable adults/children/pets are present may represent a risk of accidental poisoning may require a regime with tamper-resistant bait boxes containing wax blocks, to prevent baits being accessed. However, a balance between the safest and the most effective presentation of bait is needed and in areas where there is unlikely to be any access to baits (e.g. behind kitchen kickboards), use of alternatives must remain to ensure the shift resolution of infestations. Where bait can be placed safely and there are no children or pets present, cardboard boxes provide an effective means of ensuring that bait is consumed by the mice infesting domestic dwellings.

Suspected Cholecalciferol Rodenticide Toxicosis in Avian Species at a Zoological Institution

Over a 2-month period, individual birds belonging to species in multiple avian families, including Bucerotidae, Sturnidae, Columbidae, Corvidae, and Anatidae, were presented to the Animal Care Center at the Phoenix Zoo for emergency medical care. Common clinical findings were subdued behavior, weight loss, and an inability to fly. Biochemical abnormalities commonly included high calcium and uric acid concentrations and high to high-normal phosphorus concentrations. In cases in which necropsies were done, mineralization of organs often was present, frequently of the kidneys and cardiovascular system. Because of the high calcium and phosphorus concentrations, mineralization of tissues, cases representing multiple avian species, and the recent addition of rodent bait boxes containing cholecalciferol to the zoo's pest control program, a presumptive diagnosis of cholecalciferol toxicosis was made. Treatment most commonly consisted of daily fluid diuresis. These cases demonstrate that, although cholecalciferol is considered unlikely to cause relay toxicosis, primary toxicosis still should be considered in cases with sudden onset of nonspecific signs when exposure to cholecalciferol was possible.

Multi-species predator eradication within a predator-proof fence at Ka‘ena Point, Hawai‘i

Ka‘ena Point Natural Area Reserve on O‘ahu hosts one of the largest seabird colonies in the main Hawaiian Islands and supports three species of endangered plants. In order to stop chronic predation by invasive alien mammals on native species, a peninsula-style predator-proof fence was constructed around a 20-ha portion of the reserve in 2011. Multi-species predator removal efforts began upon fence completion; diphacinone poison in bait boxes spaced 25 m apart was used to remove black rats, house mice, and small Indian mongooses. House mice also were removed with multiple-catch live traps spaced 12.5 m apart. Feral cats were removed with padded leg-hold traps. Feral cats and mongooses were eradicated in 1 month, black rats were eradicated in 2.5 months, and house mice were eradicated in about 9 months. Since eradication, incursions of cats and mongoose have been rare (1/7.2 months), but incursion frequency has been higher for black rats (1/56 days) and house mice (1/36–47 days). Buffer predator control was conducted to limit predator access and prevent reinvasion around the fence ends along the shoreline. Even with the high initial fence cost and ongoing predator incursion management, this method is expected to become more cost effective than previous predator control efforts after 16 years. Record numbers of Wedge-tailed shearwaters and Laysan albatrosses have fledged from the reserve after predator eradication, and regeneration of native plants and invertebrates is being observed. With careful planning and persistence, predator fences can be a cost-effective method of protecting natural resources, and multiple species of predators can be eradicated with traps and first-generation anti-coagulents.

Elimination of Borrelia burgdorferi and Anaplasma phagocytophilum in Rodent Reservoirs and Ixodes scapularis Ticks Using a Doxycycline Hyclate-Laden Bait

A field trial was conducted in a Lyme disease-endemic area of New Jersey to determine the efficacy of a doxycyline hyclate rodent bait to prophylactically protect and cure small-mammal reservoirs and reduce infection rates in questing Ixodes scapularis ticks for Borrelia burgdorferi and Anaplasma phagocytophilum. The doxycycline-laden bait was formulated at a concentration of 500 mg/kg and delivered during the immature tick feeding season in rodent-targeted bait boxes. The percentage of infected small mammals recovered from treated areas after 2 years of treatment was reduced by 86.9% for B. burgdorferi and 74% for A. phagocytophilum. Infection rates in questing nymphal ticks for both B. burgdorferi and A. phagocytophilum were reduced by 94.3% and 92%, respectively. Results from this study indicate that doxycycline-impregnated bait is an effective means of reducing infection rates for B. burgdorferi and A. phagocytophilum in both rodent reservoirs and questing I. scapularis ticks.

Bait worm packaging as a potential vector of invasive species

Invasive species have become an increasingly greater concern for the ecological health of coastal ecosystems, yet vectors of these introductions often are unclear. This project evaluated the potential for the brown seaweed Ascophyllum nodosum ecad scorpiodes (Hauck) Reinke, packaged with bait worms (Nereis virens) harvested from the coast of Maine (USA), as a vector of invasive marine fauna and flora. Often, the seaweed and contents of the bait boxes are discarded into the water by recreational fishermen after using the bait worms, and any included non-native species may then be introduced. Bait boxes were purchased from several commercial vendors in Connecticut and New York over a two-year period. Subsamples of the seaweed were placed in laboratory culture and the growth of associated macro- and microalgae was monitored. Marine invertebrate species present in the samples were also identified and quantified. Results indicated 13 species of macroalgae and 23 species of invertebrates were associated with baitboxes. Among the highly diverse microbial assemblage detected, two species of potentially toxic marine microalgae, Alexandrium fundyense Balech and Pseudonitzschia multiseries (Hasle) Hasle, were found both prior to and after incubation at various temperatures, indicating these harmful algae are brought to and can survive in receiving waters. These findings highlight the need to consider alternative choices of bait box packaging materials or appropriate disposal methods of the seaweed in order to minimize the transport of species which are not native to the receiving coastal waters.

Effects of tamper-resistant bait boxes on bait uptake by Norway rats (Rattus norvegicus Berk.)

We compared the quantity of wheat bait consumed by Norway rats (Rattus norvegicus) from: (i) wooden bait trays, made as safe as possible from non-target animals using materials available at trial sites, and (ii) three different, proprietary tamper-resistant rat bait boxes. A balanced Latin square experimental design was used to overcome operational biases that occur when baits of different types are applied simultaneously at the same sites. The consumption of bait from the four different types of bait placement differed significantly and accounted for more than 76% of the total variation. The amount of bait eaten by rats from the bait trays was approximately eight times greater than the quantity eaten from the tamper-resistant bait boxes. The three bait box designs appeared to deter bait consumption by rats to a similar extent. Tamper-resistant bait boxes are essential tools in the application of rodenticides in many circumstances but their use should not be mandatory when it is possible to make baits safe from non-target animals by other means.

Ability of 4-Poster Passive Topical Treatment Devices for Deer to Sustain Low Population Levels ofIxodes scapularis(Acari: Ixodidae) After Integrated Tick Management in a Residential Landscape

In a recent study, the combined use of 4-Posters and Maxforce TMS bait boxes along with a barrier application of deltamethrin resulted in accelerated control of Ixodes scapularis Say by sequentially attacking each postembryonic life stage. We report the results of a follow-up study to test the ability of 4-Posters used alone to sustain the high levels of control achieved through the integrated tick management (ITM) approach after withdrawal of the bait boxes. In the first year after withdrawal, we observed declines in the level of control of larvae on small mammals, as well as of numbers of host-seeking larvae in the treatment area. There was no difference in the level of control of host-seeking adults in the treatment area after 2 yr. Within 2 yr, we observed a decline in control of subadult ticks infesting small mammals, but continued to see significant control of both host-seeking nymphs (85.9%) and larvae (89.0%) in the treatment area. The inconsistency that we observed between the apparent ability of 4-Posters to sustain high levels of control of host-seeking ticks, although having less effect on tick burdens on small mammal hosts, may be explained by the host-seeking ecology of immature I. scapularis.