Effectiveness of Theobromine and Caffeine Mixtures in...

©2012, Sheep & Goat Research Journal Sheep & Goat Research Journal, Volume 27, 2012 - December 26

Summary

Predators are capable of causingdamage to domestic livestock through-out North America. Lethal responses formanaging livestock depredations mayinclude the use of sodium cyanide in M-44 devices. Currently, several states havebanned the use of M-44s and severalother states are forecast to ban thesedevices. Therefore, additional tools arebeing sought to expand the repertoire ofoptions available for managing coyotedepredations on domestic livestock. Weevaluated the use of a theobromine:caf-

feine mixture delivered within a CoyoteLure Operative Device (CLOD) as anadditional predacide for coyotes (Canislatrans). Results from six trials involving38 captive coyotes were ambiguous.Issues related to the attractiveness of theCLOD, palatability of the compound,and absorption of the theobromine:caf-feine mixture produced mortality levelsbelow the desired >90-percent-mortalityrate deemed adequate for laboratory effi-cacy study to the United States Environ-mental Protection Agency (EPA) regis-tration and operational use. While manycoyotes died from consumption of the

theobromine:caffeine mixture, severalcoyotes recovered with symptoms of poi-soning disappearing within 12 hours inthose animals that survived exposure tothe toxicant. Several issues related topalatability of the mixture and com-pound delivery, as well as coyote behav-ior, sensory abilities, and physiology,indicated the use of a theobromine:caf-feine mixture in a CLOD may not be aneffective method for managing coyotedepredations on domestic livestock.

Key Words: Caffeine, Canis latrans,CLOD, Coyote, Mortality, Theobromine

Effectiveness of Theobromine and Caffeine Mixtures in Coyote Lure Operative Devices

as a Predacide: A Simulated Field Study

Eric M. Gese1, Patrick A. Darrow1, John A. Shivik1, Bruce A. Kimball2,John D. Eisemann3, and Julie K. Young1

1 United States Department of Agriculture, Animal and Plant Health Inspection Service,Wildlife Services, National Wildlife Research Center, Logan Field Station, Utah State University, Logan, UT 84322;

2United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, Monell Chemical Senses Center, Philadelphia, PA 19104;

3United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, 4101 LaPorte Avenue, Fort Collins, CO 80521

Corresponding author: Eric Gese, [email protected]; USDA/APHIS/WS/National Wildlife Research Center; Department of Wildland Resources; Utah State University; Logan, UT 84322

Volume 27, 2012 – December

Acknowledgements

Funding and logistics provided by the United States Department of Agriculture, Animal and Plant Health Inspection Service,Wildlife Services, National Wildlife Research Center. We thank the assistance of the facility staff for animal care and maintenanceof coyotes at the United States Department of Agriculture, National Wildlife Research Center, Predator Research Facility, Mil-lville, Utah; the United States Department of Agriculture Sheep Experiment Station, Dubois, Idaho, for use of their large pens; andL. Clark and M. E. Tobin for reviews of the manuscript.

Introduction

Predators cause more than $16 mil-lion in damage to sheep producers everyyear (United States Department of Agri-culture 2000). The predator with thelargest impact, by far, is the coyote (Canislatrans). The United States Departmentof Agriculture’s Wildlife Services (WS)responds to requests to address livestocklosses attributed to predation andremoves approximately 80,000 coyotesper year to reduce losses of domestic live-stock (United States Department ofAgriculture 2011). Toxicants are part ofan integrated pest management programthat may involve both lethal and non-lethal methods to reduce predation onlivestock (Knowlton et al. 1999).Sodium cyanide and sodium fluoroac-etate (Compound 1080) are the onlyrestricted use pesticides registered withthe United States Environmental Protec-tion Agency for use on coyotes. How-ever, several states (California, Colorado,Arizona) have prohibited the use ofsodium cyanide and Compound 1080.Public sentiments towards the use of tox-icants for managing predators (Arthur1981, Andelt 1987, Reiter et al. 1999)will likely lead to other states prohibitingthe use of these chemicals as well. Suchbans severely restrict the ability of ranch-ers, federal and state agencies, and pestcontrol operators to limit livestock lossesand other damage (e.g., disease transmis-sion, irrigation system damage, croplosses, game predation, aircraft hazards,human health and safety) caused byproblematic coyotes. As urban wildlife-human conflicts increase in frequency, itis likely that the need for a coyote-con-trol device that is acceptable for use insemi-urban areas will increase. Desirablequalities for such a coyote-control deviceinclude being safe to humans and pets, aswell as being safe for non-target wildlifespecies and the environment, and socialacceptability. As such, it would be advan-tageous if the coyote-control compoundinduced mortality with minimal pre-mor-tality symptoms and if an antidote orreversal therapy were available for inad-vertently exposed commensal dogs.

Criteria for the selection and devel-opment of a predacide include effective-ness, taste and odor, speed of action, haz-ard to humans, antidote/therapy, envi-ronmental safety, regulatory concerns,cost, and availability (see Fagerstone et

al. 2004 for more details). With respectto a methylxanthine (theobromine:caf-feine mixture) coyote-control com-pound, these criteria were addressed inFagerstone et al. (2004). Briefly: (1) Effectiveness — Methylxanthinescan induce acute toxicity in canids asthe propensity for domestic dogs tooverdose on methylxanthines via inges-tion of chocolate is well documented(Farbman 2001, Gwaltney-Brant 2001,Pittenger, 2002). The most abundantmethylxanthines in chocolate are theo-bromine and caffeine. The toxicity ofthese methylxanthines to coyotes issummarized in Johnston (2005). (2) Taste and odor — As indicated byarticles in the literature, chocolate isconsumed readily by canids (Farbman2001, Gwaltney-Brant 2001, Pittenger,2002). Additionally, coyotes have read-ily ingested methylxanthine fortifieddog food and lard (Johnston 2005). Itappears methylxanthine can be formu-lated to be palatable to canids. (3) Speed of action — Following inges-tion of methylxanthines, coyotes typi-cally exhibit no symptoms for severalhours. This lag time offers a margin ofsafety with respect to non-target pets byproviding a window of opportunity forveterinary intervention to reverse thetoxicity of accidentally exposed ani-mals. Because symptoms may not beimmediately apparent, the delivery sys-tem should incorporate a dye markinganimals that have consumed the toxicmatrix. Furthermore, signage should beused to alert pet owners to potentialhazards and to provide the appropriateresponse to exposure, as indicated bythe dye, and before onset of rapid mor-tality after symptoms are apparent. (4) Antidote — The availability of anantidote or effective medical treatmentto reverse the toxic effects of apredacide increases its safety. Given thefrequent exposure of dogs to chocolate,veterinary supportive-therapy proce-dures are well documented (Hornfeldt1987, Farbman 2001). As there is typi-cally a significant lag time betweeningestion and the onset of symptoms,inclusion of a dye in the formulationshould facilitate identification and sub-sequent veterinary intervention of acci-dentally exposed dogs before the onsetof toxicosis. (5) Hazard to humans — All currentlyregistered predacides are toxic to

humans. For theobromine, the rat oralLD50 is 1,250 mg/kg (U.S. Environmen-tal Protection Agency 2012), andhumans are likely more tolerant of caf-feine and theobromine. Even thoughhumans are exposed to high amounts ofcaffeine and theobromine by consumingcoffee, tea, cola beverages, and choco-late, there has been no documentedhuman mortality in association with theconsumption of these products. (6) Environmental safety — Selectiv-ity of toxicity to the target animal isdesirable to minimize accidental poison-ing of non-target animals. Methylxan-thines appear to be selectively toxic tocanids, as reports of accidental poison-ings due to the consumption ofmethylxanthines have mainly been lim-ited to canids. (7) Cost and availability — Pure ana-lytical grade methylxanthines, such ascaffeine, theobromine, and theophyllineare widely available through chemicalsupply sources. The delivery device forpest coyotes would likely need to con-tain approximately 6 g (see reasoningbelow) of active ingredient. (8) Regulatory concerns – With theexception of 31 compounds consideredby the EPA to be of negligible or mini-mum risk, all pesticides includingpredacides must be approved for use bythe EPA. Acceptance criteria includeefficacy, safety and environmental haz-ards. Methylxanthines, such as theo-bromine, should display high levels ofefficacy and selectivity towards canidpredators while being environmentallybenign. The EPA’s published standardfor the laboratory efficacy of rodenti-cides is 90 percent mortality of theexposed animals (U.S. EnvironmentalProtection Agency, 1991). There are nopublished standards for the laboratoryefficacy of predacides, consequently, ourtarget mortality for these trials was 90percent.

Johnston (2005) found that caffeinewas toxic to coyotes, however the symp-toms accompanying toxicosis were sub-optimal because caffeine-induced mor-tality was preceded by severe convul-sions and seizures. Theobromine was lesstoxic to coyotes, but symptoms, such asconvulsions and seizures were mild tonon-existent. Oral methylxanthine (5:1theobromine:caffeine) administration tocoyotes appeared to represent the opti-mal mixture of theobromine (minimal

27 Sheep & Goat Research Journal, Volume 27, 2012 - December ©2012, Sheep & Goat Research Journal


undesirable symptoms) and caffeine(potency) (Johnston 2005). Howeverthe toxicity of this mixture dictates thatabout 6 g of theobromine:caffeine wouldbe required for an effective coyotepredacide. This may limit the number ofpotential delivery devices available forthis mixture. The Coyote Lure Opera-tive Device (CLOD; Marsh et al. 1982,Berentsen et al. 2006a, b) can deliver atotal volume of formulation containing 6g of toxicant. It should be noted thatJohnston (2005) obtained lethal doses incoyotes using oral gavage, or using aCLOD in a pan, which allowed coyotesto consume the entire contents of themixture, including spillage of the com-pound. Therefore, use of the CLODunder simulated field conditions is morerepresentative of an actual managementaction.

As development and required EPAregistration of new toxicants typicallytakes 5 years to 10 years, it behooves thewildlife-management community toproactively develop a new coyote-con-trol compound that is efficacious, costeffective, induces mortality with mini-mal undesirable pre-mortality symptoms,and possesses registration potential withthe EPA. For this reason, we evaluatedthe potential of a theobromine:caffeinemixture delivered via the CLOD toinduce mortality in coyotes under simu-lated-field conditions. The main objec-tives of the study were: (1) to determinethe number of coyotes that will beattracted to, chew on, and consume con-tents of CLODs containing a theo-bromine:caffeine mixture, and (2) toestimate what proportion of coyotes thatchew on CLODs ingest a lethal dose ofthe theobromine:caffeine mixture andthe time interval between consumptionand mortality.

Materials and Methods

Six different trials using a mixture oftheobromine and caffeine as thepredacide were designed and conducted.These trials were conducted sequentiallywith modifications to the compound orbait mixture made from informationacquired from the previous trial. Theresearch was conducted using captivecoyotes in large pens at either theUSDA Sheep Experiment Station nearDubois, Idaho (Trial 1), or theUSDA/NWRC Predator Research Facil-

ity in Millville, Utah (Trials 2-6). Ineach pen enclosure, shade structures andnatural bedding were provided. Food wasprovided daily, while water was providedad libitum. This study was reviewed andapproved by the Institutional AnimalCare and Use Committee (IACUC) atthe National Wildlife Research Center.

Johnston (2005) demonstrated that,when a coyote received a theo-bromine:caffeine mixture via oral gav-age, or in a pan placed in a kennel, theresult was usually death of the animal.However, for application to a field set-ting that would mimic a managementscenario, it was necessary to test thesame dosage of the compound by deliv-ering the compound in a CLOD anddetermine whether an appropriate lethaldose could be administered. In the cur-rent 6 trials, the CLOD consisted of a 60ml plastic bottle and a stake that affixedthe CLOD to the ground (Figure 1). A5-part theobromine: 1-part caffeine mix-ture was combined with a meat matrix(water with either canned, wet dog foodor hamburger), and corn syrup andplaced in a CLOD. All ingredients werecombined and mixed in a blender untilhomogeneous. The mixture of cornsyrup, meat matrix, and active ingredi-ents were then transferred to the 60 mlCLOD. In the mixture, a maximum doseof 19.6 g of active components (16.3 g oftheobromine and 3.3 g of caffeine) wasin each CLOD. However, doses werevariable as the coyotes were self-admin-istering the test compound. CLODs wereprepared at the USDA/NWRC chem-istry labs.

Trial 1

The first trial utilized a CLOD con-taining 25 percent active ingredient (16.3g theobromine: 3.3 g caffeine) in a granu-lar form, 37.5 percent dog food, and 37.5percent corn syrup (to enhance palatabil-ity). This trial was conducted in a 65-haenclosure with four CLODs placed withinthe enclosure. The coyotes were pre-baited with CLODs containing dog foodand corn syrup for 1 week before the toxicCLODs were placed in the pen. TheseCLODs also had an attractant-infused,wax coating on them.

Trial 2

Following the results from Trial 1,there was a desire to have a marker in theCLOD to inform pet owners in the event

of an accidental dosing. Therefore, Rho-damine B was added (0.04 percent wetweight) to the same mixture as describedfor Trial 1. The use of Rhodamine Bwould act as a marker (Evans and Griffith1973, Marsh et al. 1982) by making theanimals lips turn red upon exposure sig-naling to a pet owner that their animalhad ingested something unusual, andthereby allowing a pet owner to get thepet to a veterinarian for treatment. Cornsyrup was applied liberally to the outsideof the CLOD to encourage the coyote tolick and chew the CLOD. Trial 2 wasconducted in a 6-ha pen with one CLODplaced in the pen.

Trial 3

Following the lower efficacy foundin Trial 2, there was concern the Rho-damine B may have limited the absorp-tion of the compound, as well as concernthat using commercial dog food would bea registration issue. Therefore, the dogfood was replaced with hamburger thathad been cooked in a microwave as themeat matrix, and the Rhodamine B wasremoved. Additionally, the amount ofactive ingredient was reduced to 8.15 gtheobromine: 1.65 g caffeine (5:1 mix-ture) in granular form to determine if thislower dosage would increase palatability,yet remain effective. Corn syrup wasapplied liberally to the CLOD to encour-

Figure 1. Coyote Lure OperativeDevice containing the theobromine-caffeine mixture that has been chewedon by a coyote (photo courtesy of P.Darrow).

age the coyote to lick and chew theCLOD. Trial 3 was conducted in a 6-hapen with one CLOD placed in the pen.

Trial 4

Data from Trial 3 indicated that thelower dosage of active ingredient resultedin lower efficacy. Therefore, Trial 4employed double (16.3 g theobromine:3.3 g caffeine in granular form) the dosageof Trial 3. The bait formula consisted of21 percent (wet weight) theobromine, 4percent caffeine, ground beef (12.2 per-cent wet weight), water (24.4 percent wetweight), corn starch (1.8% percent wetweight), and corn syrup (36.6 percent wetweight). Corn syrup was applied liberallyto the CLOD to encourage the coyote tolick and chew the CLOD. Trial 4 wasconducted in a 6-ha pen with one CLODplaced in the pen.

Trial 5

The previous trials (1-4) were stilllower than the desired level of mortality(90 percent) for EPA registration andsome coyotes would not consume the con-tents of the CLOD. Therefore themethylxanthine mixture was micro-encapsulated (50 percent) with a propri-etary lipid coating (Maxx Performance,Inc., Chester, N.Y.) in an attempt toincrease palatability, and thereforeincrease consumption of the compound.Because micro-encapsulation decreasedthe volume of the active ingredient thatcould be mixed homogenously in theCLOD, the CLOD contained a maximumdosage of 10.4 g theobromine: 2.1 g caf-feine. The meat component of the mix-ture was removed to maximize the amountof theobromine and caffeine that could beplaced in the CLOD. Corn syrup wasapplied liberally to the CLOD to encour-age the coyote to lick and chew theCLOD. Trial 5 was conducted in a 0.1-hapen with one CLOD placed in the pen.

Trial 6

Due to the lower mortality demon-strated in Trial 5, there was concern thatmicro-encapsulation of the active ingre-dients had lowered absorption in the gut.Therefore, for Trial 6 a spherical form ofthe active ingredients was used toincrease consumption without compro-mising absorption. A wetted-methylxan-thine mixture was subjected to extrusionspheronization resulting in uniform parti-cles of approximately 1 mm diameter.

The use of a spherical form of the com-pound would, in theory, limit solubilityin the mouth by reducing the surface areaof the compounds. The CLOD was pre-pared with the active ingredients in a21:4 (wet weight) mixture of 16.3 g theo-bromine: 3.3 g caffeine in spherical formmixed with a corn syrup and meat(ground beef) matrix. Corn syrup wasapplied liberally to the CLOD to encour-age the coyote to lick and chew theCLOD. Trial 6 was conducted in a 0.1-hapen with one CLOD placed in the pen.

For each trial, a single coyote wasplaced in a large enclosure and allowed toacclimate to the pen for 48 hrs to 72 hrs.After the acclimation period, a CLODcontaining the theobromine: caffeinemixture was placed in the pen. The coy-ote was observed remotely with a spot-ting scope, thermal imager, or remote-controlled camera. Motion-activatedInternet Protocol (IP) cameras were usedto monitor the CLOD. When the coyoteapproached the CLOD, the camerawould take a picture and send a text mes-sage to the observer’s phone. Theobserver could then view the pictures on-line to note when the coyote approachedand consumed the CLOD. In Trials 1through 4, the coyotes were fitted withVHF radio-collars to facilitate locatingthe coyote in the larger pens by theobserver. Observations recorded includedthe time the animal approached andchewed on the CLOD, the estimatedamount of the CLOD consumed, and thetime of death. If the animal consumed apart, or all, of the CLOD, the behavior ofthe animal was observed to determinethe symptoms of toxicosis. Animals con-suming a part, or all, of the compoundwere observed for 24 hr post-consump-tion, or until mortality occurred. Coyoteswere observed for 5 days after placementof the CLOD in the pen. As this was asimulated field test, after placing coyotesin the study pen, human-coyote interac-tions (including coyote monitoringbefore the toxicant is consumed) wereminimized to reduce disturbance andallow the animal to approach and con-sume the contents of the CLOD.

Study Design and Statistical Analyses

The purpose of the study was todetermine what proportion of coyotesinteracted with the CLODS, and ofthose animals, what proportion suc-

cumbed to the toxicant in an acceptablemanner. Thus, the experimental designwas observational and statistical analyseswere limited to descriptive statistics (i.e.,proportions) and their associated meas-ures of variability (range). The EPA’spublished standard for the laboratoryefficacy of rodenticides is 90 percentmortality of the exposed animals (U.S.Environmental Protection Agency,1991). There are no published standardsfor the laboratory efficacy of predacides,consequently, our target mortality forthese trials was 90 percent.

Results

Trial 1 exposed 11 coyotes to theCLODs, of which 9 animals consumedsome of the compound resulting in sevenmortalities (Table 1), giving an overallmortality of 64 percent. While this 64-percent mortality was less than thedesired 90-percent mortality, the result-ant deaths of seven animals indicatedthat the CLOD could deliver a lethaldose of the compound, and thus theaddition of a marker appeared justified toreduce the risk to non-target pets. Withthe addition of Rhodamine B to thecompound, the results from Trial 2 indi-cated there might be an issue of lowerabsorption or palatability with the addi-tional marker, as overall mortality wasonly 20 percent in Trial 2. Therefore themarker was not added in subsequent tri-als. In addition, the use of a commercialdog food as a bait matrix may preventsubsequent registration with the EPA,thus the matrix was changed to groundbeef for subsequent trials.

With the marker no longer added tothe compound, and the bait matrix con-sisting of ground beef, results from Trial 3showed 100 percent of the coyotes con-sumed part or all of the CLOD, but over-all mortality (60 percent) was still lessthan the desired 90 percent threshold(Table 1). Results from Trial 3 indicatedthat the combination of hamburger andlower methyxanthine concentration pro-duced 100-percent consumption. How-ever, the new dosage was sub-lethal.Therefore in Trial 4, the dosage of theactive ingredient was doubled. Trial 4showed 100 percent of the coyotes fed onsome or all of the CLOD, but overall mor-tality was 60 percent. Poor palatabilitywas assumed to impact consumption. ForTrial 5, the active ingredient was micro-


encapsulated with a lipid coating in anattempt to increase consumption byblocking the interaction of the bittermethylxanthines and oral taste receptors.Results from Trial 5 indicated that micro-encapsulation did not increase consump-tion, nor did it increase mortality as over-all mortality in Trial 5 was only 17 per-cent. It was concluded the micro-encap-sulation likely reduced absorption in thegut. The lack of meat in the mixture mayhave increased the motility of the com-pound through the gut (Kunze and Fur-ness 1999, Olsson and Holmgren 2001),thereby lowering the absorption of thecompound. Much of the issue in lowermortality was limited consumption and/orabsorption of the theobromine:caffeinemixture by the coyotes. Therefore, forTrial 6 we used the spherical form of thecompound in an attempt to increase con-sumption while not compromisingabsorption. Results from Trial 6 showedhigher overall mortality of 67 percent, butstill below the 90 percent level. In addi-tion, the spherical form resulted in thelongest average time to death, thus indi-cating that solubility of the methylxan-thines was lower in the oral cavity and inthe gut.

Of 18 coyotes in which the time wasobserved from consumption of theCLOD to death, the time to death variedamong the trials and compounds (Figure2). Few coyotes (28 percent) died in <2hours, with most of the mortalities tak-ing >2 hours (72 percent).

Coyotes consuming enough of theCLOD content to show signs of toxicosisoften showed initial signs of increasedexcitation and sensitivity to sounds orother stimuli. As part of the increasedexcitation, coyotes would spend agreater amount of time running around

their pen. Coyotes also seemed to expe-rience hypersalivation, as well as poly-dipsia, as they would increase their con-sumption of water. A few coyotes wereseen vomiting within a few hours of eat-ing the compound. As toxicosis pro-gressed, the coyote would lose coordina-tion and would no longer be able to walkor stand. The coyotes would then lie in alateral recumbent position with legs,head, and tail outstretched, muscles rigidand respiration elevated. Some coyoteswould pedal infrequently with their feet.Though most coyotes died after assum-ing the laterally recumbent position, onecoyote did make a recovery after lying onthe ground for several hours.

Conclusions

None of the trials resulted in the 90-percent mortality desired for EPA regis-tration of the theobromine:caffeine mix-

ture as a predacide for coyotes. Reasonsfor the below-par efficacy are many. Inthe early trials, many coyotes would notchew on the CLOD, suggesting an issueof attractiveness of the CLOD to precip-itate chewing by the coyotes. Subse-quent trials incorporated corn syrup tomake the CLOD more attractive to con-sumption. Generally, coyotes desirecompounds that contain sugar (Marsh etal. 1982, Mason and McConnell 1997).Another problem was spillage of themixture from the CLOD after the coyotehad bitten the plastic container, therebypreventing complete consumption.

The theobromine:caffeine mixtureappeared to have low palatability as thecoyotes would often cease consumptiononce they chewed on the CLOD. Manytimes the coyotes would bite the CLOD,cease consumption, and the compoundwould then leak out and spill onto theground. Therefore, palatability of thecompound was in question during theearlier trials, with subsequent trials usingeither the micro-encapsulated or spheri-cal form of the compound in an attemptto increase palatability. However, theseforms appeared to affect absorption ofthe compound and hence lower morbid-ity following consumption of the theo-bromine:caffeine mixture.

Observations of coyotes that sur-vived consuming the contents of theCLOD also indicated other issues inwhether the theobromine:caffeine mix-ture could provide a lethal dosage to thecoyote. Some animals would drink copi-


Table 1. Results of 6 trials involving coyotes being exposed to CLODscontaining a theobromine:caffeine mixture.

# (%) of test subjects consuming (%) of test Mean time

#test part or all subjects that [range] to Trial subjects of the CLOD # died death (hrs)1 11 9 ( 82%) 7 (64%) 6.0 [2.0 - 12.0]2 5 4 ( 80%) 1 (20%) 4.03 5 5 (100%) 3 (60%) 2.2 [2.0 - 2.5]4 5 5 (100%) 3 (60%) 3.5 [2.0 - 4.5]5 6 4 ( 67%) 1 (17%) 4.06 6 6 (100%) 4 (67%) 12.5 [2.0 - 24.0]

Figure 2. Frequency of time to death for coyotes exposed to thetheobromine:caffeine mixture contained in a Coyote Lure Operative Device.

ous amounts of water after showing signsof toxicosis and they would survive.Fluid uptake may increase excretion andprevent reabsorption through the uri-nary bladder, and administering fluids todomestic dogs accidentally ingestingchocolate is recommended as treatment(Farbman 2001). Also, some animalsregurgitated the compound and subse-quently survived. Coyotes may have rec-ognized the onset of symptoms andinduced regurgitation. Because the pHlevel of the animal stomach contentscould greatly influence absorption anduptake of the theobromine:caffeine mix-ture, insufficient amounts of the mixturemay have been absorbed before regurgi-tation began.

While the time to death is not astandard used for registration, the coy-ote’s time to death in these trials waslengthy and may not be acceptable tothe general public (Andelt 1987). Sur-veys of the general public have repeat-edly shown the use of toxicants to be theleast favored method for managing pred-ators (Arthur 1981, Andelt 1987, Reiteret al. 1999). However, this long-timeperiod is desirable for it allows for treat-ment of domestic dogs that may be acci-dentally dosed. Use of some form ofmarker that does not interfere witheither palatability or absorption of themixture is desirable to alert pet ownersin the event of an accidental dosing andthe need for subsequent veterinary treat-ment of their dog.

It is realized that many of these vari-ables (i.e., access to water, amount offood in the stomach, coyote physiology,and a coyote’s ability to regurgitate thecompound) are all beyond the control ofwildlife managers, particularly in a fieldsetting. However, the use of the theo-bromine:caffeine mixture in a CLOD, asadministered in this experiment, maynot be an effective toxicant for manag-ing coyote depredation events. At aminimum, future research needs to beperformed that will identify coyote sen-sory sensitivities, as they appear morethan capable of detecting the theo-bromine:caffeine mixture. The sensorysensitivity of coyotes to bitter-tastingcompounds has received limited research(e.g., Mason and McConnell 1997).Equally important is whether the CLODis the proper delivery device for adminis-tering a lethal dose of a toxicant, partic-ularly for coyotes, which are extremely

wary of novel objects (Windberg andKnowlton 1990, Windberg 1996, Harrisand Knowlton 2001, Séquin et al. 2003).

Literature Cited

Andelt, W. F. 1987. Coyote predation.Pages 128-140 in M. Novak, J. A.Baker, M. E. Obbard, and B. Mal-loch. Wild furbearer managementand conservation in North Amer-ica. Ontario Ministry of NaturalResources, Toronto, Ontario,Canada.

Arthur, L. M. 1981. Coyote control: thepublic response. J. Range Manage.34:14-15.

Berentsen, A. R., R. H. Schmidt, and R.M. Timm. 2006a. Repeated expo-sure of coyotes to the Coyote LureOperative Device. Wildl. Soc. Bull.34:809-814.

Berentsen, A. R., J. J. Johnston, R. E.Mauldin, and R. H. Schmidt.2006b. Using the CLOD to deliverpentachlorobenzene to coyotes(Canis latrans). Vert. Pest Conf.22:277-281.

Evans, J., and R. E. Griffith. 1973. A flu-orescent tracer and marker for ani-mal studies. J. Wildl. Manage.37:73-81.

Fagerstone, K. A., J. J. Johnston, and P. J.Savarie. 2004. Predacides for canidmanagement. Sheep Goat Res. J.19:76-79.

Farbman, D. 2001. Death by chocolate?Methylxanthine toxicosis. Vet.Tech. 3: 146-147.

Gwaltney-Brant, S. 2001. Chocolateintoxication. Vet. Med. 2:108-111.

Harris, C. E., and F. F. Knowlton. 2001.Differential responses of coyotes tonovel stimuli in familiar and unfa-miliar settings. Can. J. Zool.79:2005-2013.

Hornfeldt, C. S. 1987. Chocolate toxic-ity in dogs. Mod. Vet. Practice68:552-554.

Johnston, J. J. 2005. Evaluation ofcocoa- and coffee-derived methylx-anthines as toxicants for the controlof pest coyotes. J. Agric. FoodChem. 53:4069-4075.

Kunze, W. A. A., and J. B. Furness. 1999.The enteric nervous system and reg-ulation of intestinal motility. Ann.Rev. Physio. 61:117-142.

Knowlton, F. F., E. M. Gese, and M. M.Jaeger. 1999. Coyote depredation

control: an interface between biol-ogy and management. J. RangeManage. 52:398-412.

Marsh, R. E., W. E. Howard, S. M.McKenna, B. Butler, and D. A. Bar-num. 1982. A new system for deliv-ery of predacides or other activeingredients for coyote management.Vert. Pest Conf. 10:229-233.

Mason, J. R., and J. E. McConnell. 1997.Hedonic responsiveness of coyotesto 15 aqueous taste solutions. J.Wildl. Res. 2:21-24.

Olsson, C., and S. Holmgren. 2001. Thecontrol of gut motility. Comp.Biochem. Physio. Part A 128:481-503.

Pittenger, S. 2002. Chocolate (methylx-anthine) intoxication. HarrisCounty Vet. Med. Assoc. Newslet-ter. February 2002. 2 pp.

Reiter, D. K., M. W. Brunson, and R. H.Schmidt. 1999. Public attitudestoward wildlife damage manage-ment and policy. Wildl. Soc. Bull.27:746-758.

Séquin, E. S., M. M. Jaeger, P. F. Brus-sard, and R. H. Barrett. 2003. Wari-ness of coyotes to camera traps rela-tive to social status and territoryboundaries. Can. J. Zool. 81:21015-2025.

USDA. 2000. Sheep and goats predatorloss. National Agricultural StatisticsService, Agricultural StatisticsBoard, Washington, D.C.

USDA. 2011. Wildlife Services’ 2011program data reports. Washington,D.C. <www.aphis.usda.gov/wildlife_damage/prog_data/2011_prog_data/content/wp_c_index.shtml>

USEPA. 1991. Standard Norway rat/roofrat anticoagulant dry bait laboratorytest method. OPP Sesigna-tion:1.203. USEPA, WashingtonD.C., 4 pp.

USEPA. 2012. Reregistration eligibilitydecision. Washington, D.C. http://www.epa.gov/pesticides/reregistra-tion/status.htm

Windberg, L. A. 1996. Coyote responsesto visual and olfactory stimulirelated to familiarity with an area.Can. J. Zool. 74:2248-2254.

Windberg, L. A., and F. F. Knowlton.1990. Relative vulnerability of coy-otes to some capture procedures.Wildl. Soc. Bull. 18:282-290.


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