Slug foraging behaviour: Attraction to food items from a distance

Slug foraging paths recorded using time lapse video techniques under infra-red light were fitted to a correlated random walk model. Analyses were carried out on slugs in arenas where no food was present, as well as those containing commercial molluscicides at two rates of application. Slugs were found to search randomly in empty arenas and those containing commercial metaldehyde baits, but deviated from random search patterns when in the presence of commercial methiocarb bait. Differential attraction from a distance is suggested as a cause of these differences.     

The Use of Metaldehyde Against Slugs

One part of metaldehyde in thirty parts of bran by volume is the minimum effective concentration for obtaining an economic kill of slugs under average weather conditions. For use against Milax gracilis Leydig. heaps of bait should not be normally more than 2 yd. apart and against Arion hortensis Fer. not more than 3 ft. apart. The mortality of slugs attracted to metaldehyde-bran baits is dependent on the drying property of the soil and atmosphere around the baits. D.D.T. flea-beetle dust and powdered pyrethrum flowers are sufficiently distasteful to slugs to prevent their consuming a lethal dose of the poison mixed with bran. The addition of 10%, by volume, of dried blood to metaldehyde-bran bait increases the catch of some slugs under certain conditions but does not increase the mortality. The addition of 10%, by volume, of dextrose increases the mortality produced by metaldehyde but does not increase the numbers attracted to the bait. A metaldehyde-bran bait compacted into 'biscuit' form with anhydrous calcium sulphate catches more slugs than an ordinary metaldehyde-bran bait, but almost completely counteracts the effect of the metaldehyde. A metal-dehyde-bran-casein glue bait in 'biscuit' form increases the catch and kill of Milax gracilis and Agriolimax reticulatus Müll., but not of Arion hortensis . Metaldehyde-bran-casein glue bait broadcast in 'broken biscuit' form is effective over a longer period, thus producing a greater kill of slugs, than a broadcast metaldehyde-bran bait.     

Feeding behaviour and mortality of the slug, Deroceras reticulatum in relation to control with molluscicidal baits containing various combinations of metaldehyde with methiocarb

In terms of control of slug pests, the differing modes of action of the two molluscicides metaldehyde and methiocarb appear to provide some advantages for the former during warm, dry weather and for the latter during cool, wet weather. With a view to exploiting these different modes of action, the feeding behaviour of Deroceras reticulatum (Müller) presented with molluscicidal baits containing various combinations of metaldehyde with methiocarb was investigated. Voluntary feeding trials conducted in the laboratory with both candidate and standard treatments (containing metaldehyde or methiocarb alone) are described. By combining the two active ingredients in certain ratios the total concentration of active ingredients may be reduced without adversely affecting the efficacy of a bait formulation in terms of slug mortality.     

Effects of metaldehyde and methiocarb on feeding preferences and survival of a slug predator (Pterostichus melanarius (F.): Carabidae,Pterostichini)

The potential for reducing slug populations in crops through predation by generalist carabid beetles is well documented. However, few studies have considered interactions between biological and chemical control agents of slugs. Laboratory assays supported previous findings that the consumption of metaldehyde by slugs (Deroceras reticulatum) leads to increased duration of feeding bouts by carabid beetles (such as Pterostichini) on sub‐lethally affected individuals. However, a similar effect was not found for Pterostichus melanarius exposed to slugs fed on the other widely applied pelleted molluscicide formulation (methiocarb). Examination of beetle survival after consumption of slugs containing molluscicides demonstrated the strong biocidal properties of methiocarb, whereas metaldehyde consumption (ingested through slug predation) did not differ from control slugs killed by freezing. Beetle avoidance of slugs containing a more toxic molluscicide compound and the interaction between slug mucus production and beetle attack rates are discussed.     

Complementary video and acoustic recordings of foraging by two pest species of slugs on non-toxic and molluscicidal baits

The effects of adding the molluscicides methiocarb and metaldehyde to pelleted foods on the encounter, acceptance, feeding and post-meal stages of the foraging sequence of the slugs Deroceras reticulatum and Arion distinctus have been studied using two complementary laboratory techniques - video and acoustic recordings. Whereas non-feeding slugs encountered wheat grains at random, slugs which fed on wheat grains or pellets encountered them more frequently because of changes in locomotor pattern and olfactory attraction. Slugs would almost always feed on the first pellet they found, regardless of the presence or absence of molluscicide: thereafter they fed on only one pellet in every four encountered. Far fewer slugs accepted wheat grains. Slugs ate much less from pellets containing molluscicide, and meals were more irregular. The relative amounts of non-toxic pellets of various types which were eaten gave no indication of the relative amounts eaten when molluscicide was added. Meal length did not correlate well with meal size on different pellet types because softer pellets were eaten faster. Most Deroceras fed several times on non-toxic pellets or pellets containing methiocarb, although subsequent meals were shorter than the first meal. Most returned to shelters by dawn. In contrast, metaldehydefed slugs were rapidly immobilised; they seldom fed again, moved little, and few regained shelter. Arion were also inhibited after methiocarb meals but Deroceras were not. Arion distinctus moved less, ate less during a meal, and had fewer meals on nontoxic baits than Deroceras reticulatum.     

Improving slug baits: the effects of some phagostimulants and molluscicides on ingestion by the slug, Deroceras reticulatum (Miiller) (Pulmonata: Limacidae)

The effects of seven potential phagostimulants and of four molluscicidal compounds on feeding were examined by confining slugs with agar gels containing the chemicals in varying concentrations. Sugars generally increased the amount of gel ingested; sucrose more than glucose, lactose and fructose. Feeding increased with increasing sucrose concentration to a maximum and then fell progressively: the optimum concentration lay between 2.5% and 5%. The sweeteners saccharin and aspartame at concentrations up to 2.5% did not increase feeding. Addition of the molluscicides metaldehyde, methiocarb and ferric acetylacetonate to gels containing 2.5% sucrose progressively reduced feeding at concentrations of 0.001% and above. Metaldehyde reduced ingestion more than methiocarb and ferric acetylacetonate was intermediate. The molluscicidal herbicide Ioxynil deterred feeding completely at concentrations of 0.001%. The implications for slug bait development are discussed.     

Overall Versus Band Application of the Nematode Phasmarhabditis hermaphrodita With and Without Incorporation into Soil, for Biological Control of Slugs in Winter Wheat

In two concurrent field experiments, the effects of three types of soil cultivation and two patterns of nematode application were studied in order to investigate their effects on damage to winter wheat by slugs (assessed at Zadoks Growth Stage 12). In experiment 1, infective juveniles (IJs) of the nematode Phasmarhabditis hermaphrodita were applied to soil as an overall spray or as a band spray (8-cm wide), centred on the drill rows (16.7-cm apart). Nematodes were either left undisturbed on the soil surface or harrowed into the soil immediately after application. The control provided by nematodes was compared with that provided by metaldehyde and methiocarb pellets broadcast at the recommended rate immediately after drilling. In this experiment, winter wheat on plots treated with IJs showed significantly less slug damage than on wheat plots treated with metaldehyde or methiocarb pellets or untreated plots. There was no significant difference in plant damage between plots treated with band and overall spray applications of IJs, nor was there any significant difference between plots with and without harrowing. There was also no significant difference between untreated plots and plots treated with metaldehyde or methiocarb pellets, probably because rainfall shortly after treatment rendered the pellets ineffective. In experiment 2, nematodes were applied as an overall spray or plots were not treated with nematodes before soil was cultivated with tines, Roterra or Dutzi cultivators. Nematode application before soil cultivation using tines or Roterra reduced the number of plants damaged significantly. However, nematodes applied before Dutzi cultivation appeared to be rendered ineffective. Damage to winter wheat was lowest in plots that had been sprayed with nematodes and subsequently cultivated with tines or Roterra.     

Wild carnivore acceptance of baits for delivery of liquid rabies vaccine

A series of experiments are described on the acceptance, by red foxes (Vulpes vulpes) and other species, of two types of vaccine-baits intended to deliver liquid rabies vaccine. The baits consisted of a cube of sponge coated in a mixture of tallow and wax, or a plastic blister-pack embedded in tallow. All baits contained tetracycline as a biological marking agent: examination of thin sections of carnivore canines under an ultraviolet microscope revealed a fluorescent line of tetracycline if an individual had eaten baits. Baits were dropped from fixed-wing aircraft flying about 100 m above ground at approximately 130 km/h. Flight lines followed the edges of woodlots midway between parallel roads. Baits were dropped at one/sec, resulting in one bait/36 m on the ground, or 17 to 25 baits per km2. Crows (Corvus brachyrhynchos) removed many baits, but did not appear to lower the percent of the fox population which took bait. Dropping baits only into corn and woodland to conceal baits, to reduce depredation by crows, reduced acceptance by foxes. Acceptance by foxes ranged between 37 and 68%. Meat added as an attractant did not raise acceptance. Presence, absence, color and perforations of plastic bags did not alter bait acceptance. Dispersal by juvenile foxes probably lowered the estimates of bait acceptance. It took 7 to 17 days for 80% (n = 330) of foxes to eat their first bait. The rapidity with which foxes picked up their first bait appeared more affected by unknown characteristics of years or study areas than by experimental variables. Skunks (Mephitis mephitis) and raccoons (Procyon lotor) also ate these baits, but acceptance was lower. Small mammals contacted baits, but rarely contacted the vaccine, which had the potential for vaccine-induced rabies in some species. Aerial distribution of baits was more cost-effective than ground distribution as practiced in Europe. This system has potential for field control of rabies, although higher acceptance will be desirable.     

Biocontrol of Slugs in Protected Lettuce Using the Rhabditid Nematode Phasmarhabditis hermaphrodita

In two experiments, the rhabditid nematode Phasmarhabditis hermaphrodita, a parasite of slugs, was cultured in vitro and applied as a drench to soil at four dose rates (3 108, 1 109, 3 109 and 1 1010 ha-1) 1 or 4 days before planting lettuce seedlings in a polythene tunnel. The effects of the four nematode doses on slug damage during the first 3 weeks after planting and on the numbers of slugs found within and below lettuce plants at harvest were measured. Results were then compared with untreated plots and with plots where methiocarb pellets were applied at the recommended field rate. In the first experiment, methiocarb pellets significantly reduced the percentage of plants damaged by slugs, but the nematode did not. In the second experiment, methiocarb pellets and the second highest dose of nematodes significantly reduced the percentage of plants damaged by slugs. The different effect of the nematode in the two experiments may have resulted from differences in the timing of nematode application and/or differences in the pattern of slug damage between experiments. At the end of the first experiment, the highest two doses of nematodes and methiocarb pellets had significantly reduced the number of slugs found within lettuce plants at harvest and on the soil surface below the plants. At the end of the second experiment, analysis of variance showed no significant effects of any treatment on slug numbers or biomass, but regression analysis showed significant negative relationships between nematode dose and total slug numbers, numbers of Arion ater agg. and biomass of Deroceras reticulatum. In both experiments, increasing nematode dose significantly reduced the numbers of slugs found contaminating the harvested lettuce. At the end of the second experiment, the mean weight of individuals of A. ater agg. increased with rising nematode dose.     

Speed of efficacy and delayed toxicity characteristics of fast-acting fire ant (Hymenoptera: Formicidae) baits

Efficacy and speed of action of fire ant (Hymenoptera: Formicidae) baits that claim fast control of colonies were compared with a standard bait. More than 85% of red imported fire ant, Solenopsis invicta Buren, laboratory colonies provided bait containing the active ingredient indoxacarb died within 3 d, and all colonies were dead in 6 d. Standard bait containing hydramethylnon resulted in death of 60% of the colonies in 9 d. Bait containing spinosad did not cause colony death. Under field conditions, one-half of the areas treated with the indoxacarb bait did not have any active fire ant nests within 3 d, whereas 11 d was needed to reach the same level of control with the hydramethylnon bait. Spinosad had a maximum of 17% of the treated areas without nests after 3 d. The delay in death of S. invicta adults treated in the laboratory with the indoxacarb and spinosad baits was shorter than the standard hydramethylnon bait, which had mortality similar to the traditional delayed toxicity criterion of < 15% mortality after 24 h and > 89% mortality over the test period. Indoxacarb caused mortality of 57% at 24 h and 100% at 48 h; however, visual symptoms of toxicity were not readily observed for at least 8 h before the abrupt increase in death. Spinosad caused 96% mortality by 24 h, and initial mortality became apparent at 4 h. Time required for death of 15% of a treated population (LT15) of spinosad, indoxacarb, and hydramethylnon was 3, 9, and 16 h, respectively. Delayed toxicity characteristics of the fast-acting indoxacarb bait may be useful for the development of other fast-acting ant baits.     

A method to study slug predation on seedlings in the field

Dandelion is a common Asteraceae species that populates disturbed sites and gaps within swards where it becomes an important competitor of grasses. The natural control against dandelion includes seedling predation, with slugs, particularly Arion lusitanicus, being the most important in the Czech Republic. However, the study of slug seedling consumption is difficult because naturally established seedlings are not always available. Therefore, we developed a method of exposing laboratory‐grown seedlings as bait for slug predation. Dandelion seeds were sown in plastic cups containing a bottom layer of moist substrate. The emerged seedlings were thinned to 20 and displayed in an open area. During 2008–2010, the seedling baits were placed at 15 sites at 1 month intervals throughout the dandelion vegetative season, in parallel with plasticine baits that monitored slug feeding activity. For each 1 month interval, seedling survival was observed for a period of 8 days, and the estimated time to death was calculated; the percentage of surviving seedlings was then recorded. This method of seedling presentation demonstrated that local and temporal variation in seedling survival is correlated with slug feeding activity. The advantage of this technique is that the seedlings in baits may be presented at any place and time, as required by the experimental design; however, we found that the estimated time to seedling death was shorter for the exposed baits than for the naturally established seedlings. The method is suitable for the study of plant species other than dandelion, and also for aims other than the study of spatiotemporal trends in seedling consumption by slugs.     

A study of the investigatory behavior of the dairy cow

A commission to investigate the possible ingestion by dairy cattle of air-dropped wildlife baits for vaccination against sylvatic rabies provided an excellent opportunity for a detailed study of bovine investigatory behavior. Twelve unarmed baits (half of which were placed in a bag with liver slurry serving as a fox attractant) were placed in each of two pastures. A group of 9 cows was then allowed to graze freely on each of the pastures from approximately 08.00 to 15.00 h for 5 consecutive days. Continuous direct observation revealed that the tendency of the cows to approach the baits varied with the type of bait encountered, and habituated over the 5-day study. However, once an investigation was initiated, the likelihood of contacting the bait and the manner in which the bait was contacted was not readily influenced by prior exposure to the baits. The type of bait being investigated did not influence the likelihood of a cow making contact, but did influence the manner in which the bait was contacted. Flehmen, which only occurred following head contact with a bait, most commonly followed mouth or tongue contact and was less likely to be employed as cows habituated to the objects being investigated.     

Influence of toxic bait type and starvation on worker and queen mortality in laboratory colonies of Argentine ant (Hymenoptera: Formicidae)

The efficacy of toxic baits should be judged by their ability to kill entire ant colonies, including the colony queen or queens. We studied the efficacy of four toxic baits to the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae). These baits were Xstinguish that has the toxicant fipronil, Exterm-an-Ant that contains both boric acid and sodium borate, and Advion ant gel and Advion ant bait arena that both have indoxacarb. Experimental nests contained 300 workers and 10 queen ants that were starved for either 24 or 48 h before toxic bait exposure. The efficacy of the toxic baits was strongly influenced by starvation. In no treatment with 24-h starvation did we observe 100% worker death. After 24-h starvation three of the baits did not result in any queen deaths, with only Exterm-an-Ant producing an average of 25% mortality. In contrast, 100% queen and worker mortality was observed in colonies starved for 48 h and given Xstinguish or Exterm-an-Ant. The baits Advion ant gel and Advion ant bait arena were not effective against Argentine ants in these trials, resulting in <60% mortality in all treatments. Because of the strong influence of starvation on bait uptake, control efficacy may be maximized by applying bait when ants are likely to be starved. Our results suggest queen mortality must be assessed in tests for toxic bait efficacy. Our data indicate that of these four baits, Xstinguish and Exterm-an-Ant are the best options for control of Argentine ants in New Zealand.     

The inhibitory effects of the molluscicide metaldehyde on feeding, locomotion and faecal elimination of three pest species of terrestrial slug

Single meals on maize flour pellets containing 0, 0·5, 1, 2, 4, 6, and 8% metaldehyde were analysed in Arion hortensis (agg), Deroceras reticulatum and Deroceras caruanae, by attaching the pellets to a mechanical transducer from which signals were ultimately fed into a BBC microcomputer for on-line analysis. Post-feeding tests were used to investigate toxic effects of metaldehyde and the recovery of slugs was examined daily for 7 days. Bite rates were slightly lower and more irregular on metaldehyde meals especially in A. hortensis. The meal length and number of bites per meal were markedly inhibited by metaldehyde and inversely proportional to the concentration. The size of the bites was also reduced, by about 30%, in meals on 6% pellets compared with 0%. Clear symptoms of poisoning became evident during the meal or normally in the 16-min test period immediately afterwards. In these tests slugs which fed on metaldehyde pellets showed a disruption of their ability to right themselves (after being placed on their side), less activity and a reduced probability of accepting a ‘dummy’ pellet containing no metaldehyde. It is hypothesised that feeding is prematurely terminated primarily because of the toxic effects of the metaldehyde and that aversion also acts to terminate the meal early, by decreasing the probability of continuing to feed as the meal proceeds. At higher concentrations of metaldehyde aversion may be more important than the toxic effects in ending the meal. Faecal elimination is delayed after metaldehyde meals and this contributes to mortality. The estimated lethal doses were about 0·2 mg/g body weight of slug in Deroceras spp. A. hortensis was less susceptible. To increase the likelihood of a lethal dose being ingested the inhibition of feeding needs to be overcome, at least partly, and the results presented indicate the need for a bait formulation which reduces the rate of absorption of the molluscicide from the gut.     

Slug activity in relation to weather

Multiple regression analysis was carried out on the effect of certain meteorological factors on the numbers of slugs attracted by metaldehyde and bran biscuits at Cardiff in the autumn months. By far the greatest reduction in the variance in numbers of slugs attracted each morning was achieved by taking out the effects of two factors: (1) the length of time the biscuits had been exposed, and (2) the average night air temperature. The percentage relative humidity considered alone had little effect on the variance. Regression coefficients, at each site, for factors (I) and (2) on slug numbers appeared to be in close agreement and it is suggested that these figures would serve as a measure of slug activity. Arion hortensis behaved differently from the other species studied, its day-to-day variation in numbers not being tied so closely to the meteorological factors examined.
Methods of assessing slug numbers in the field usually rely on the animals' activity. Barnes & Weil (1944) made direct counts on the slugs observable in half-hourly periods, and Thomas (1944) based estimates of the number attracted to metaldehyde and bran biscuits overnight; Duthoit (1961) used baits of wheat seed in making weekly estimates. Measures of activity, however, may be less directly related to the actual population present than to day-to-day climatological variations. The aim of the work described below was to find if it was possible to arrive at more reproducible population estimates by using standard slug biscuits, and allowing for the effect of some of the meteorological variables.     

Influence of carrion smell and rebaiting time on the efficiency of pitfall traps to dung beetle sampling

Dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) are very useful insects, as they improve the chemo-physical properties of soil, clean pastures from dung pads, and help control symbovine flies associated with bovine cattle. Their importance makes it fundamental to sample and survey them adequately. The objectives of the present study were to determine the influence of decaying insects trapped in pitfalls on the attractiveness of Moura pig Sus scrofa L. (Suidae) and collared peccary Tayassu tajacu (L.) (Tayassuidae) dung used as baits to lure dung beetles, and to establish how long these baits remain attractive to dung beetles when used in these traps. Some dung beetle species seemed to be able to discriminate against foul smell from decaying insects within the first 24 h, hence decreasing trap efficiency. This was more evident in peccary dung-baited traps, which proved to be the least attractive bait. Attractiveness lasted only 24 h for peccary dung, after which it became unattractive, whereas the pig dung bait was highly attractive for 48 h, after which its attractiveness diminished but was not completely lost.     

Community structure and the habitat templet: ants in the tropical forest canopy and litter

The tropical forest canopy and litter differ in physical structure, resource availability, and abiotic conditions. We used standardized bait experiments in the canopy and litter of four neotropical tree species to explore how these differences shape the behavior, morphology, and diversity of ant assemblages. Ant activity (biomass at a bait after 32 min) was higher in the canopy, and higher on protein baits than carbohydrate baits. Aggressive bait defense occurred more frequently in the canopy (60%) than in the litter (32%), but was not associated with tree species or bait type in either habitat. The median size of workers of species in the canopy and litter was nearly identical, but body size distribution was unimodal in the canopy and bimodal in the litter. The colony size of the most aggressive species was an order of magnitude larger in the canopy. Species richness at a bait was relatively uniform across tree species and habitats. Litter and canopy shared no species, but overlap among tree species was three times higher in the litter assemblages. Litter assemblages showed less activity, less interference, less differentiation across the landscape, and different size distributions than canopy assemblages. The canopy and litter templets subsume a number of environmental gradients that combine to shape ant community structure.     

Do colours that deter birds affect cereal bait acceptance by possums (

Poisonous baits used for pest control in New Zealand commonly contain green dye and cinnamon oil to make them less attractive to birds. Research aimed at reducing the impact of poison based pest control on birds has shown that some birds are initially deterred from feeding on blue or, to a lesser extent, green coloured food and are attracted to yellow or red food. We determined whether colours that deter or attract birds affected the acceptance of non-toxic and toxic cereal baits by captive brushtail possums (Trichosurus vulpecula). Individual possums were offered, daily, a choice between a standard green dyed non-toxic cereal bait and either a blue dyed(17 possums) or yellow dyed non-toxic bait (16 possums) for 10 days. Following this, for the first group of 17 possums, 1080 toxin was added to either the green bait (9 possums) or blue bait (8 possums) and possums were offered the green versus blue choice again. Two additional groups that had not previously been fed cereal baits were also given a choice between blue and green baits, one of which was toxic. All possums offered non-toxic bait ate less on the first day of presentation than on subsequent days. There was no difference in acceptance of either blue or yellow coloured non-toxic bait compared to the standard green non- toxic bait on any days. Bait colour appeared to be unimportant in cereal bait choice and did not deter possums from eating any of the baits. The addition of toxin to baits did not significantly alter bait choice in any groups, although some individuals which had no previous experience with baits ate more toxic than non-toxic bait. These data suggest that adding a stronger bird deterring colour (i.e., blue) to poisonous baits is unlikely to adversely affect the acceptance of baits by possums.     

Bait Uptake and Caching by Red Foxes and Nontarget Species in Urban Reserves

Abstract: The management of biodiversity in urban areas provides a challenge for conservation managers who are interested in the recovery of native species by controlling exotic species. Exotic-animal control programs using poisons can be contentious in terms of the health and safety of nontarget species, including people. Managing exotic predators in urban areas must be effective at 2 levels: controlling the target species and minimizing impacts to nontarget species. We investigated the feasibility of instigating a poison-baiting program to control nonindigenous European red foxes (Vulpes vulpes) in city conservation reserves (Perth, Australia). We selected 3 reserves to assess the safety and efficacy of baiting for foxes by maximizing bait uptake by the target species, and minimizing uptake by nontarget species. We tested 2 types of meat bait using 4 bait presentation methods (untethered, uncovered; untethered, covered; tethered, uncovered; tethered, covered). Bait uptake by foxes was highest in urban reserves compared to that in a peri-urban reserve. Bait type and presentation method equally explained bait uptake by foxes. Untethered and uncovered baits were removed 10% more often by foxes, and untethered baits had been cached more often than tethered baits. Baits cached by foxes for up to 1 week were not removed by species other than foxes. Domestic dogs and native birds were common nontarget species to remove baits. Dogs showed no aversion to removing any bait type, nor did bait presentation method influence bait removal. Birds removed fewer baits that had been tethered and covered. We provide an evidence base to demonstrate that bait uptake by nontarget species can be minimized, although we suggest that a fox control program is likely to be more of an organizational challenge to change public attitudes toward responsible dog ownership rather than a technical challenge to poison foxes.     

A new flavor-coated sachet bait for delivering oral rabies vaccine to raccoons and coyotes

Research was conducted during 1996-2000 to develop baits for delivering an oral rabies vaccine to raccoons (Procyon lotor) and coyotes (Canis latrans). A bait was sought that: (1) was attractive to the target species, (2) could be distributed by aircraft, (3) was as effective (or more so) than the currently used fish meal polymer bait, and (4) could be produced in large numbers by automated procedures and could be purchased by user groups at substantially lower cost. Ten field trials were conducted to document raccoons' bait flavor preferences, evaluate a new vaccine sachet bait coated with various attractants, and determine if the sachet bait would effectively deliver Raboral V-RG oral rabies vaccine (Merial Limited, Athens, Georgia, USA) to this species. Raccoons preferred fish and crustacean-based flavors over those derived from plant materials. Raccoon visits to tracking stations, frequency of bait removals, and percent of sachets discarded by this species that were emptied of placebo vaccine indicated efficacy of the new bait was equal or superior to the currently used fish meal polymer bait. A field trial conducted in fall 1998 compared aerially distributed vaccine-laden sachet and polymer baits and showed there was no difference between the percent of raccoons from the test and reference areas subsequently found positive for rabies antibody. Four bait trials to determine coyote response to sachet baits were conducted in 1997-98. The propensity for canids to gulp or bolt smaller food items is well known. Thus, a first trial involved offering fish-flavored sachet baits of different sizes to 30 captive coyotes to determine if smaller size baits were more frequently swallowed intact. Two field trials were also conducted in fall 1997 to determine if free-ranging coyotes discriminated among sachet baits coated with different attractants. Finally, Raboral V-RG-laden poultry-flavored sachet baits were aerially dropped and the percent of seropositive coyotes was compared with coyotes from surrounding areas where fish meal polymer vaccine baits had been distributed. Captive coyotes did not swallow sachet baits intact, regardless of size. Bait preference field trials indicated that coyotes preferred poultry, cheese/beef tallow, and fish-flavored sachet baits and that such baits were taken at the same rate as polymer baits. A sample of coyotes from the area baited with vaccine-laden sachet baits had a markedly higher (P = 0.01) seropositivity rate than coyotes from areas where vaccine was distributed in polymer baits. Sachet bait production could be facilitated by automated technology and sachet baits used either as an alternative vaccine delivery device or in combination with the fish meal polymer bait.