Bait Acceptance Research Articles

A review of recent non-target toxicity testing of vertebrate pesticides: establishing generic guidelines

An analysis of the range, extent and importance of New Zealand-based ecotoxicology studies has been completed to better understand the hazards and non-target risks associated with new toxins and baits. This review focuses on compounds that have been recently developed for incorporation into bait for terrestrial vertebrate pest control, namely cholecalciferol, para-aminopropiophenone (PAPP) and zinc phosphide and the effects of these toxins on non-target species. Testing of these compounds has included cage and pen toxicity and bait acceptance studies. Locally conducted acute toxicity studies clarify overseas data and enhance risk assessments. Consistency in approach and selection of surrogate species, and careful selection of native non-target species for acute toxicity testing in cage and pen trials are recommended as important steps before field trials. We propose a systematic approach to cage and pen trials and offer guidelines on species selection.

Winter ecology of house mice and the prospects for their eradication from Steeple Jason (Falkland Islands)

Invasive house mice Mus musculus are known to impact on seabird, invertebrate and plant communities on temperate and subantarctic islands, particularly where they are the sole rodent species. Steeple Jason, in the Falkland Islands, is an island which supports globally important seabird populations as well as introduced mice. To evaluate the prospects for mouse eradication, we investigated mouse ecology and undertook bait uptake trials on Steeple Jason in late winter. Mice were present in all habitats but were most abundant in tussac Poa flabellata where they occurred at 20–35 mice ha−1. From 58 mature perforate females, 16 % were pregnant, with litters of 4–8 pups. The first lactating female was caught at the end of August, suggesting that breeding had recently begun. Bait trials replicating an aerial eradication were undertaken on two trapping grids of 7.7 and 6.8 ha, with non-toxic pellets containing the biomarker pyranine spread at 7.5–7.7 kg ha−1. All 447 mice captured after baiting had consumed bait. The relatively low winter density, distribution and biology of house mice on Steeple Jason are similar to those observed before other successful mice eradications, and the study indicated 100 % bait acceptance. Before an eradication attempt, we suggest investigating whether breeding ceases completely earlier in the winter and urge careful consideration of non-target species.

Management of raccoon roundworm in free‐ranging raccoon populations via anthelmintic baiting

ABSTRACTRaccoon roundworm (Baylisascaris procyonis), a common gastrointestinal parasite of the raccoon (Procyon lotor), has been implicated in population declines of Allegheny woodrats (Neotoma magister). Medicinal baiting is a viable tool in wildlife disease management although unique challenges exist for pathogenic systems in which the host can be immediately re‐infected following treatment. Our goals were to evaluate the efficacy of using monthly distribution of anthelmintic baits to reduce the prevalence of B. procyonis infection in raccoons and to quantify patterns and rates of bait acceptance among populations repeatedly exposed to medicinal baits. We distributed baits monthly at a density of 200/km2 throughout 300‐m buffer areas surrounding woodrat habitats in Indiana. We conducted raccoon latrine surveys annually to quantify the effect of treatment on roundworm prevalence and used remote cameras to identify the species contacting baits and determine the rate at which baits were removed. We observed declines in B. procyonis prevalence in response to treatment, but our ability to resolve statistical differences was limited by low pretreatment prevalence and high annual variability. Baits were removed rapidly from camera stations with 60% taken within 24 hours, 80% within 48 hours, and 90% within 72 hours. Virginia opossums (Didelphis virginiana) removed 51% of baits whereas raccoons removed 44%. Identification of opossums as the predominant consumer of baits emphasizes the limitations imposed by non‐target bait consumption for mitigation of B. procyonis and other wildlife diseases. The rapid removal of baits despite repeated bait exposure suggests that habituation did not result in bait aversion and fishmeal baits are a viable delivery system for mitigation of raccoon‐borne diseases requiring repeated treatments. Similar treatment measures may facilitate conservation of Allegheny woodrats in habitats with high rates of B. procyonis‐related mortality and could be used to reduce human exposure to this zoonotic parasite. © 2013 The Wildlife Society.

Asymmetrical Behavioral Response Towards Two Boron Toxicants Depends on the Ant Species (Hymenoptera: Formicidae)

Urban ants are a worldwide critical household pests, and efforts to control them usually involve the use of alimentary baits containing slow-acting insecticides. A common toxicant used is boron, either as borax or boric acid. However, the presence of these compounds can affect the consumption of baits by reducing their acceptance and ingestion. Moreover, as feeding motivation varies widely, according not only to food properties but also to colony conditions, bait consumption might be diminished further in certain situations. In this study, we compared the feeding response of ants toward two boron toxic baits (boric acid and borax) in low motivation situations that enhance any possible phago-deterrence the baits may produce. Most studies investigating bait ingestion evaluate whole nests or groups of ants; here, we analyzed the individual ingestion behavior and mortality of the Argentine ant, Linepithema humile (Mayr), and the carpenter ant, Camponotus mus (Roger), for two boron baits, to detect which compound generates a higher rejection in each of these species. Although these two species have similar feeding habits, our results showed that ants under low motivation conditions reduced the acceptance and consumption of the toxic baits asymmetrically. While L. humile mostly rejected the borax, C. mus rejected the boric acid. These results denote the importance of considering the preference of each species when developing a pest management strategy.

EFFICIENCY OF LIBRAXR AS AN ANTISTOMACHEC TO OVERCOME BAIT SHYNESS OF ZINC PHOSPHIDE TO BLACK RAT, RATTUS RATTUS

Some laboratory trials were conducted to increase the bait acceptance of zinc phoshide against black rat, Rattus rattus, using LibraxR drug (chlordiazepoxid 5mg + clidinium bromide 2.5mg) as antistomachec. LibraxR 0.001% was tested alone and combined with different concentrations of zinc phosphide bait using non and free choice feeding methods. Results showed that in both methods, LibraxR alone and mixed with zinc phosphid bait significantly increased the average daily consumption and the acceptability of rats. Also it enhanced the percent of mortality comparing with zinc hosphide bait lone.

Effects of different essential oils on the acceptability and palatability of cereal-based baits for laboratory mice

The aim of our study was to investigate the possibility of application of essential oils as additives in cereal-based rodenticide baits, at rates which prevent mould development and are applicable in humane medicine. Also, the purpose of these oils would be to extend the utility value of baits and reduce the use of antifungal ingredients that usually affect bait acceptance. The effects of essential oils of ten different plant species, applied at rates of one and two ml per kg of plain bait, on bait acceptance and palatability in choice feeding tests for Swiss mice were studied under controlled laboratory conditions. Baits were prepared according to relevant EPPO standards (2004). The effects of essential oils on bait acceptance and palatability for Swiss mice were determined in choice feeding tests using a formula by Johnson and Prescott (1994). There was no significant statistical difference in effects between groups and sexes regarding weight change in the experiment. During the experiment and recovery period, neither change in mice behavior no deaths were observed. Cinnamon and anise essential oils, commonly used as attractants, and clove oil, were most effective because they had no negative effect on bait acceptance and palatability, while fenchel and bergamot oils showed repellent activity that grew as the oil content in baits increased.

Strategies for controlling the ghost ant, Tapinoma melanocephalum (Hymenoptera: Formicidae) with liquid bait

The ghost ant, Tapinoma melanocephalum (F.), is a household pest and a considerable nuisance. The aim of this study is to demonstrate the toxicity and control efficacy of boric acid in liquid bait against queen and worker ghost ants. The LT50 values for workers fed with 0.5%–2.5% boric acid and 2% chicken peptone in 20% sucrose water solutions were 4.3–2.4days. The lethal times (LT50=5.2–7.6days) for queen ghost ants fed with various concentrations of a boric acid solution depended on the feeding behavior of the queens. The high boric acid (4%) content solutions were not repellent to the ghost ant workers. The liquid bait formulation of 1% boric acid, which caused a 100% worker, brood, and queen population reduction in 4, 4, and 5weeks, respectively, was significantly more effective than the solid bait formulation containing the same concentration (p≦0.05). The simulation tests involved using chicken peptone and sucrose as the attractant, and colonies were provided an alternate food source (20% sucrose solution and dog food) to achieve a more accurate assessment of bait acceptability in screening for the efficacy of the liquid boric acid bait. The control efficiency attained 99.9% in week 4. The results demonstrated that liquid bait, containing 2% chicken peptone, 20% sucrose as a food attractant, and 1% boric acid as the toxin, is efficient and highly recommended for ghost ant control.

Control of terrestrial animal rabies in Anne Arundel County, Maryland, after oral vaccination of raccoons (1998–2007)

To evaluate the effectiveness of an oral rabies vaccination (ORV) project conducted from 1998 through 2007 in Anne Arundel County, Md, for the control of rabies in terrestrial animals. Retrospective analysis of surveillance data (1997 through 2007). Free-ranging raccoons (Procyon lotor) and other terrestrial mammals. Vaccinia-rabies glycoprotein recombinant virus oral rabies vaccine-bait units were distributed annually by aircraft and ground teams targeting free-ranging raccoons. Approximately 2 to 4 weeks following the vaccine-bait placement, raccoons were live trapped, sedated, processed, and then released. Serologic samples were tested for the presence of rabies virus-neutralizing antibodies (RVNAs). Bait acceptance was estimated by analysis of tetracycline biomarking of sampled teeth. Rabies incidence was determined by the passive identification of rabid terrestrial animals. The incidence of rabies in terrestrial animals decreased 92% between 1997 (the year prior to the start of the ORV project) and 2007. The mean RVNA prevalence across all years was 33% among trapped raccoons in areas baited with a fish meal polymer bait type, whereas the mean bait acceptance was 30%. Adult raccoons had a seropositivity rate twice that of juvenile raccoons, whereas the bait acceptance rate between adults and juveniles did not differ significantly. For areas baited with a coated sachet bait, adults and juveniles had the same seroprevalence. Juveniles had better seroprevalence when the annual campaign started in September and October, compared with August. The ORV project contributed to a significant decrease in annual incidence of terrestrial animal rabies in Anne Arundel County, Md, during the 10-year project period. For fish meal polymer baits, juvenile raccoons accessed bait at the same rate as adult raccoons but had a significantly lower prevalence of RVNAs. For coated sachet baits, seroprevalence was the same in both age groups. The time of year the bait distribution occurred and the bait type used may be partial explanations for the difference in RVNA seroprevalence between adults and juvenile raccoons.

Optimising the palatability and longevity of stoat baits

In New Zealand, introduced stoats (Mustela erminea) are significant predators of many native bird species. Trapping for stoat control is currently undertaken, but imposes logistical and cost constraints on the frequency and area over which their impacts can be mitigated. We sought to identify a highly acceptable stoat bait formulation with an extended field life that could be used for delivery of appropriate poisons. In feeding trials with wild-caught stoats, we screened 6 meat bases and > 20 humectant, preservative, binder or palatant compounds for acceptance and palatability. Significant differences in bait acceptance between female and male stoats were found. A humectant–preservative combination of polyethylene glycol (PEG 20,000) and sorbitol in rabbit mince was identified as optimal with over 80% acceptance by both male and female stoats and higher palatability (73.5%) than plain rabbit mince. This bait combination was acceptably ‘long-life’, with 80% of stoats eating PEG + sorbitol bait weathered for 28 days. This bait formulation thus has useful application in current stoat trapping programmes but also potential in future delivery of selective poisons, such as para-aminopropiophenone, to manage field populations of stoats.

Critical Timings of Rodenticide Bait Application for Controlling Rodents in Sugarcane Crop Grown in Situations Like Punjab, India

Farmer field trials on determination of critical timings of rodenticide bait application in sugarcane crop were conducted in two districts of Punjab (India) during 2007–2010 for modification in already recommended practice. Sugarcane crop at all the experimental locations was surrounded by rice–wheat crops in rotation and infested predominantly with Bandicota bengalensis. Results of experiments conducted during 2007 and 2008 at two locations each revealed no significant difference in overall reduction in rodent activity and damage between fields given single (during October–November) and double (first in July and second in October–November) rodenticide treatments due to rapid rebuild up in rodent population after every treatment thus indicating the need of two treatments as per the previous recommendation. Results of experiment conducted during 2009–2010 at two locations revealed significantly (P < 0.05) higher reduction in rodent activity and damage in fields given third treatment during December–January with 0.005% bromadiolone @ 2 kg/ha than in fields given third treatment with 2% zinc phosphide @ 2 kg/ha and fields given only first two treatments. This may be due to significantly (P < 0.05) low acceptance of zinc phosphide bait compared to bromadiolone bait by rodents in these months. Present studies suggest that for protecting sugarcane fields from rodent damage at different crop stages, three rodenticide treatments, first in July, second in October–November with two rodenticide baitings @ 1 kg/ha each at the interval of 15 days and third treatment in December–January with single baiting of 0.005% bromadiolone @ 2 kg/ha may be applied.

The Applicability of Burrow Fumigants for Controlling Belding’s Ground Squirrels in Alfalfa

Rodenticides are often used to control burrowing rodents but have not been overly efficacious for Belding’s ground squirrels due to poor bait acceptance. This has left alfalfa growers searching for alternative options for controlling this rodent species. As such, we tested aluminum phosphide and gas cartridge burrow fumigation in an alfalfa field in Butte Valley, CA, to determine if either of these approaches were efficacious and cost effective for controlling Belding’s ground squirrels. A comparison of the number of burrows treated and the number of burrows reopened 48-hours post-treatment indicated that both burrow fumigants were highly effective (aluminum phosphide = 94-98%, gas cartridges = 100%). The average cost per application was $1.05 and $2.92 for aluminum phosphide and gas cartridges, respectively. Given the almost 3-fold difference in cost of application between the two approaches, aluminum phosphide appears to be the more practical approach for Belding’s ground squirrel control. Although we currently lack an approach for estimating the amount of damage that Belding’s ground squirrels are likely to cause to an alfalfa field, it seems plausible that burrow fumigation could be a cost effective approach to reduce damage caused by this species, particularly if long-term control can be obtained. Possible long-term management options for Belding’s ground squirrels are discussed.

Evaluation of bait acceptance by wild boar and non-target species - test of different distribution modalities and seasonal variations - implication for oral vaccination efficiency against classical swine fever virus

Field assessment of the proportion of target and non-target individuals that consume baits is crucial to evaluate and optimize the cost-efficacy of a baiting campaign. In our study, different pre-baiting and baiting systems were tested at a long time scale (12 months) to try to improve vaccination efficiency of wild boars against classical swine fever virus. Evaluation of seasonal variation in natural food resources (competition with bait consumption) and life cycle succession of wild boar from piglets to adults is included and consumption of baits by non-target species is discussed.

Tools for managing invasions: acceptance of non-toxic baits by juvenile Nile monitor lizards and Burmese pythons under laboratory conditions

Nile monitor lizards (Varanus niloticus) and Burmese pythons (Python molurus bivittatus) are large, invasive, predatory reptiles, which are now well established in south Florida. Acetaminophen was recently shown to be lethal to both animals and therefore has potential for inclusion in an integrated pest management effort to control these species. However, acceptable bait matrices for both species are still needed to deliver the toxicant. We tested nine candidate bait matrices on juvenile Nile monitor lizards and Burmese pythons in the laboratory. Baits were tested fresh and also after aging at 30°C and 50% relative humidity for 24 h. Six of the nine baits were well accepted by the monitors in both fresh and aged conditions (dead neonatal mouse, dead quail chick, ground turkey, chicken liver, tilapia, and zebra finch egg). Only the fresh dead neonatal mouse and fresh dead quail chick were well accepted by the pythons. As far as we are aware, these tests are the second of such bait matrix preference tests conducted for reptiles. The implications of our results are discussed regarding further development and testing of baits in a natural setting.

Target-specificity of feral pig baits under different conditions in a tropical rainforest

Context The mitigation of feral pig (Sus scrofa) impacts in north Queensland’s World Heritage tropical rainforests is constrained by the lack of an effective and target-specific poison baiting method. Aims This study aimed to determine whether easily implemented bait presentation methods or seasonal variation in bait acceptability could be used to selectively reduce the consumption of feral pig baits by non-target species. Methods We exposed manufactured feral pig baits to pigs and non-target species in the field, and compared bait encounter, sampling and consumption rates for different functional groups of species among three different types of bait presentation and composition. We then exposed baits under different seasonal conditions and related bait encounter and consumption by different functional groups to seasonally variable phenomena. Key results Shallow burial greatly reduced bait consumption by most non-target species, but not dingoes (Canis lupus dingo). Nocturnal bait distribution and seasonal baiting were less useful. Pigs showed substantial seasonal variation in physiological condition, suggesting that pigs should be more susceptible to consuming novel foods, such as baits, after periods of low rainfall. However, few pigs consumed the manufactured baits used in this study. Conclusions Manufactured baits are not currently suitable for widespread use in the region. However, shallow burial should provide an effective method of reducing non-target bait-take if baits can be made more attractive and acceptable to pigs and less acceptable to dingoes. Implications Future efforts to enable effective feral pig control in the region should focus on developing baiting materials that are more attractive to pigs and unappealing to dingoes.

Acceptance and palatability for domestic and wildlife hosts of baits designed to deliver a tuberculosis vaccine to wild boar piglets

Tuberculosis (TB) caused by Mycobacterium bovis, a member of the Mycobacterium tuberculosis complex, is an important health problem worldwide. The control of TB through vaccination of wildlife reservoirs may potentially have advantages over other management strategies. The most practical approach to deliver vaccines to wildlife is using oral baits that are stable under field conditions and effective in reaching the target species. Baits were developed in our laboratory to deliver oral vaccines to wild boar piglets. However, these baits were well accepted by other wild species. Therefore, bait consumption by different M. bovis hosts was evaluated herein. The results showed that the baits were well accepted by cattle, feral pigs, and adult red deer whereas small mammals like badgers and possums showed varying bait acceptance. Bait acceptance by different species has the advantage of targeting more than one wildlife reservoir when they coexist in the same area and need to be vaccinated for TB control. However, bait delivery methods such as the use of selective feeders to target the desired species should be developed to avoid bait consumption by other species.

Presence of conspecific odours enhances responses of commensal house mice (Mus musculus) to bait stations

Currently, baiting is the most common method for controlling mouse populations. Behavioural responses to bait stations may affect the acceptance of baits. We studied the effect of mouse odour on the number of entries into and time spent within bait stations under semi-natural conditions. Commensal house mice (Mus musculus musculus) were allowed to choose between two identical bait stations, one of which was scented with a conspecific odour. The donors of the odours were socially experienced or inexperienced male and female mice. The results showed that house mice preferred scented bait stations over non-scented controls. This preference was not significantly affected either by sex of the tested mice or by sex and/or experience of the scent donor. Nevertheless, the preference was especially apparent in males allowed to enter bait stations scented with the odour of adult, sexually- and socially-experienced conspecifics. In conclusion, our results show that not only the bait station itself, but also accompanying social odours, attract house mice, and thus may considerably enhance the effectiveness of baits. Furthermore, our results indicate that excessive cleaning of scented bait stations may decrease the efficacy of rodenticide baiting.

Use of Rhodamine B to Reveal Patterns of Interspecific Competition and Bait Acceptance in Raccoons

Abstract: Passive treatment of raccoons (Procyon lotor) through distribution of vaccine‐laden baits recently has emerged as a potential solution to address health and economic conflicts associated with raccoon rabies and may have applications in the management of other pathogens carried by raccoons if frequent bait deployments are used. Consumption of baits by nontarget species reduces the efficiency in which baits can be used to manage wildlife disease, although no study has explicitly evaluated the influence of bait competitor density on the ability to treat raccoons. Our objectives were to use the biomarker Rhodamine B (RB) to 1) evaluate patterns of raccoon bait acceptance as a function of competition with Virginia opossums (Didelphis virginiana), the dominant bait competitor; 2) characterize attributes of opossum bait acceptance to improve efficiency of raccoon treatment; and 3) evaluate the effect of repeated bait exposure on rates of bait acceptance as may be required in the management of wildlife disease issues beyond rabies. Identifying bait consumption by individuals based on the presence of an RB mark in a sample of whiskers, we used logistic regression to model raccoon and opossum bait acceptance as a function of bait availability, previous exposure to baits, demographic attributes, and an index of time spent in the baited area (residency index). For both raccoons and opossums, the best measure of bait availability was the variable number of baits per opossum. The most parsimonious logistic regression model for raccoon bait acceptance included the variables baits per opossum, exposure history, and residency index. The strength of the variable baits per opossum relative to competing measures of bait availability indicated bait consumption by opossums significantly limited the ability to treat raccoons. The most parsimonious model for opossum acceptance was composed of the variables baits per opossum, sex, weight, residency index, baits per opossum X sex, and weight X sex. Patterns of opossum bait acceptance likely were driven by effects of bait availability and sex‐dependent differences in movement. Our results call attention to the importance of bait competition in limiting the ability to effectively treat raccoon populations through distribution of baits and suggest managers incorporate information on density of bait competitors, particularly opossums, in allocation of baits.

Use of Rhodamine B to Reveal Patterns of Interspecific Competition and Bait Acceptance in Raccoons

Passive treatment of raccoons (Procyon lotor) through distribution of vaccine-laden baits recently has emerged as a potential solution to address health and economic conflicts associated with raccoon rabies and may have applications in the management of other pathogens carried by raccoons if frequent bait deployments are used. Consumption of baits by nontarget species reduces the efficiency in which baits can be used to manage wildlife disease, although no study has explicitly evaluated the influence of bait competitor density on the ability to treat raccoons. Our objectives were to use the biomarker Rhodamine B (RB) to 1) evaluate patterns of raccoon bait acceptance as a function of competition with Virginia opossums (Didelphis virginiana), the dominant bait competitor; 2) characterize attributes of opossum bait acceptance to improve efficiency of raccoon treatment; and 3) evaluate the effect of repeated bait exposure on rates of bait acceptance as may be required in the management of wildlife disease issues beyond rabies. Identifying bait consumption by individuals based on the presence of an RB mark in a sample of whiskers, we used logistic regression to model raccoon and opossum bait acceptance as a function of bait availability, previous exposure to baits, demographic attributes, and an index of time spent in the baited area (residency index). For both raccoons and opossums, the best measure of bait availability was the variable number of baits per opossum. The most parsimonious logistic regression model for raccoon bait acceptance included the variables baits per opossum, exposure history, and residency index. The strength of the variable baits per opossum relative to competing measures of bait availability indicated bait consumption by opossums significantly limited the ability to treat raccoons. The most parsimonious model for opossum acceptance was composed of the variables baits per opossum, sex, weight, residency index, baits per opossum × sex, and weight × sex. Patterns of opossum bait acceptance likely were driven by effects of bait availability and sex-dependent differences in movement. Our results call attention to the importance of bait competition in limiting the ability to effectively treat raccoon populations through distribution of baits and suggest managers incorporate information on density of bait competitors, particularly opossums, in allocation of baits.

Efficacy of Rodenticide Baits for the Control of Three Invasive Rodent Species in Hawaii

We tested the efficacy and palatability of nine commercial rodenticide bait formulations on Polynesian rats (Rattus exulans), roof rats (R. rattus), and house mice (Mus musculus). Efficacy varied by rodenticide tested and rodent species. Generally, rodenticides were more effective against mice than for either of the rat species, and mice tended to consume more rodenticide bait than the laboratory chow alternative food. Efficacy was generally highest for the second-generation anticoagulants tested; however, this varied across products and one-first-generation rodenticide had similar effectiveness. Bait acceptance (palatability) also varied both by rodenticide and by rodent species. Acceptance was the lowest for the acute rodenticides. Bait acceptance appeared to substantially affect the efficacy of rodenticides; materials that were not well accepted produced lower mortality rates. Rodenticide products currently registered for use in Hawaii performed less effectively in this study than other available products not yet registered. Although markets for rodent control products for use on islands are limited, there are advantages to having additional products registered for island use in agriculture, conservation, and public health.

AERIAL DISTRIBUTION OF ONRAB® BAITS AS A TACTIC TO CONTROL RABIES IN RACCOONS AND STRIPED SKUNKS IN ONTARIO, CANADA

During August 2006 and 2007, baits containing oral rabies vaccine, live adenovirus vector, known as ONRAB , were aerially distributed in SW Ontario, Canada. Bait acceptance during 2006 was 62 and 74% in raccoons (Procyon lotor) in areas baited at 150 baits/km(2) and 75 and 77% in plots baited at 300 baits/km(2). During 2007, bait acceptance for raccoons ranged between 59% and 80%, and 83% and 87%, in areas baited at 75 and 400 baits/km(2), respectively. Bait acceptance by skunks varied among plots (5-24%). Rabies virus-specific seroconversion during 2006 averaged 66 and 81% in raccoons in areas baited at 150 and 300 baits/km(2), respectively. During 2007, seroconversion by raccoons was 76 and 84% in areas baited at 75 and 400 baits/km(2), respectively. Seroconversion by skunks varied among plots (17-51%). Vaccine efficacy, as judged by the percentage of animals that consumed a bait and seroconverted, averaged 79 and 87% during 2006 for raccoons in areas baited at 150 and 300 baits/km(2), respectively, and 81 and 90% in areas baited during 2007 at 75 and 400 baits/km(2), respectively. Because tetracycline marking was poor in skunks, an estimate of vaccine efficacy was not possible. Aerial distribution of ONRAB vaccine baits seems to be a feasible tactic for controlling rabies in skunks and raccoons.