Protecting Raptors from Rodenticides 2

VOLUME XXVII, NUMBER 1-4, SPECIAL ISSUE 2011 (PUBLISHED JANUARY 2013) Protecting Raptors from Rodenticides 2

Common Sense Pest Control XXVII(1-4) Special Issue 2011 2 Box 7414, Berkeley, CA 94707 3

Protecting Raptors Atkinson Mike courtesy Photo from Rodenticides

By William Quarles Poisoning of People and Pets ats and mice have been pests throughout recorded Each year about 13,000-20,000 R history. They eat and con- people in the U.S. are poisoned by taminate food, and help transmit rodenticides (See Table 1). Most of human diseases, including plague. these are children under the age of Pest management as a profession five. About 78-83% of the exposures started with rats and mice, and and 76-82% of the hospitalizations they are common elements in litera- are due to second generation anti- ture and in our cultural history. coagulants, primarily brodifacoum Who can forget The Plague by Albert (see Box A). Less than 6% of the Barn owl, Tyto alba Camus, or the Pied Piper of Hamlein hospitalizations are due to acute folktale? (Corrigan 1997) toxicants such as bromethalin, vita- consumers have been able to buy The best way to control rodents is min D3, and zinc phosphide. Less rodenticides formulated as treated by combining sanitation, exclusion, than 2% are due to the first genera- grain or loose bait. This kind of habitat management, and traps in tion anticoagulant, warfarin packaging makes poisons easily an integrated control program. (See (Bronstein et al 2011; Watson et al. accessible to children. To reduce the second article in this issue.) 2005). exposures, the EPA in 2011 This combination can work well for About 95,000 pet poisonings due required manufacturers to produce structures, but urban conditions to rodenticides were reported to baits only in tamper resistant bait can lead to rats breeding in sewers, American Poison Control Centers in stations for the consumer market. vacant lots and other situations. 2010. About 75% of the animals Some companies have refused to Public health requires control, and poisoned were dogs (Bronstein et al. comply (EPA 2008; EPA 2011). often, resources to provide urban 2011). A study done by the Humane cleanup and integrated manage- Society shows that 74% of their pet Poisoning of Wildlife poisoning cases are due to second ment are not available (Olkowski et generation anticoagulants, primarily As well as people and pets, a wide al. 1991). As a last resort, poison brodifacoum. Less than 14% are variety of wild bird and mammal baits have been used to reduce rat due to acute toxicants such as species are being killed by rodenti- populations. Poison has also been bromethalin, vitamin D , and zinc cides. Both primary and secondary used for voles, gophers, prairie 3 phosphide. Only 2% are due to war- poisoning has occurred. Foxes, rac- dogs, ground squirrels and other farin (Erickson and Urban 2004). coons, coyotes, opposums, squir- such pests (Hygnstrom et al. 1994). Poisonings of children and dogs rels, bobcats, wild pigs, deer, even Primary and Secondary have occurred probably because mountain lions have been killed by Poisoning Rodenticides should be used as a last resort because children, pets, and wildlife can be accidentally killed or injured. Primary poisoning is a problem when a non-target animal directly eats a rat bait, secondary poisoning occurs when a predator or scavenger eats a rodent that is full of poison. The potential for non-target poisoning can vary with the active ingredient, with the formulation, and with the bait deploy- ment methods (see below) (see Box A. Primary and Secondary Poisoning). The purpose of this article is to identify the most problem- atic rodenticides and suggest less harmful alternatives. Emphasis is on secondary poisoning of raptors.

Common Sense Pest Control XXVII(1-4) Special Issue 2011 3 Box 7414, Berkeley, CA 94707 4

caused bleeding, but not death is quickly eliminated, with a half (Mendenhall and Pank 1980). In life of 22 hours. However, hawks another experiment, when six barn could show effects of sublethal owls were fed brodifacoum mice, exposure by as little as 3.5 g of liver four of them died (66%). Just three from diphacinone poisoned rats mice were enough to cause death (Rattner et al. 2011). (Newton et al. 1990). An EPA review summarized labo- Field Studies ratory experiments with brodifa- There is also evidence of second- coum in 2004. When 149 raptors or ary poisoning of raptors from field scavengers were fed brodifacoum studies. In one experiment brodifa- poisoned prey in the laboratory, 42% of the birds died of secondary coum scatter bait was used to con- poisoning (Erickson and Urban trol voles, Microtus spp. in apple 2004). So secondary poisoning of orchards. Radio transmitters were Bald eagle, predatory birds and scavengers attached to owls and hawks to Haliaeetus with brodifacoum has been well monitor their progress. Problems leucocephalus documented by laboratory experi-

ments. Jacksy Bob courtesy Photo rodenticides (Stone et al. 1999; Hosea 2000; Eason et al. 2002). Raptors Show Increased Raptors in the U.S., Canada, Sensitivity France, Great Britain and elsewhere Part of the problem is that raptors are dying from consuming rodents are relatively sensitive to anticoagu- poisoned with second generation lants. Rattner et al. (2011) studied anticoagulants such as brodifa- primary poisoning of American coum and bromadiolone. Owls, kestrels, Falco sparverius, with hawks, and eagles have been affect- diphacinone in the laboratory. ed (Albert et al. 2010; Stone et al. Kestrels were 20-30 times more Eastern screech owl, Otus asio 2003; Walker et al. 2008). sensitive (LD50 = 96.8mg/kg) to the lethal effects of diphacinone than How do we Know Raptors the Northern bobwhite, Colinus vir- are Being Poisoned? ginianus; or mallards, Anas occurred when raptors fed on voles platyrhynchos; bird species often in the treated orchards. If more Direct information on the poison- than 20% of the foraging range had ing problem has come from labora- used in EPA tests for toxic pesticide effects. been treated with brodifacoum, tory experiments where birds are minimum mortality of screech owls, fed poisoned rodents, and from field But diphacinone is much less of a Otus asio, was 58%. If less than studies where birds are monitored secondary poisoning problem than 10% of the foraging area had been by radio tags after rodent baits are brodifacoum, and Rattner et al. treated, mortality was 17%. deployed. Indirect evidence is com- (2011) calculated that secondary Because of the severe impact, brod- ing from surveillance programs poisoning “risk associated with a where dead birds are found and single day exposure to diphacinone ifacoum is not used for vole control turned in to a government agency would be low” for hawks and owls. in the U.S. (Hegdal and Colvin or a wildlife care clinic. Most of the The risk is low because diphacinone 1988). problems are due to the second Secondary poisoning problems are ht oreyUiest fMinnesota of University courtesy Photo generation anticoagulant brodifa- greatest when the target rodent coum (Erickson and Urban 2004). species is a common food source for the predator, and the poisoning Secondary Poisoning in occurs inside the predator’s forag- the Laboratory ing range. In the experiment above, screech owls were affected, but The secondary poisoning threat of barred owls, Strix varia, foraged brodifacoum has been known since mostly in woodlands and avoided its registration. In one experiment, the treated orchards (Hegdal and 36 owls were fed rodents killed with Colvin 1988). 6 different anticoagulants. Dead rats containing brodifacoum killed Extended Exposures in the 5 of 6 owls exposed (83%). Bromadiolone treated rats killed Food Chain one of six owls (17%). Rats contain- If baits are deployed for roof rats, American kestrel, ing other anticoagulants such as Falco sparverius predator species that do not eat diphacinone and chlorophacinone roof rats should not be at risk.

Common Sense Pest Control XXVII(1-4) Special Issue 2011 4 Box 7414, Berkeley, CA 94707 5

Unfortunately, non-target rodents Sublethal Effects study area had also died from anti- often consume rat baits. For coagulants (Riley et al. 2007). Raptors are dying from lethal instance, Brakes and Smith (2005) There can also be sublethal exposures, but also sublethal found that woodmice, field voles, effects on reproduction in raptors. amounts are making them more and bank voles were being poisoned Nestling barn owls, Tyto alba, in susceptible to disease and acci- by rat bait boxes. Populations of test areas baited with brodifacoum dents (Lemus et al. 2011; Stone et these animals dropped, exposing weighed 13% less than those in al. 2003). According to Stone et al. their predators both to secondary untreated areas. Wingspans (15%) (2003), “Sublethal hemorrhage may poisoning and a reduced food sup- and tail lengths (18%) were also interfere with locomotion, predis- ply. shorter. One nestling had mal- posing animals to predation, acci- Insectivorous birds have died dental trauma, and reduced food formed feathers, rendering it flight- after eating insects feeding on brod- intake.” There is also the “possibili- less (Naim et al. 2010). It is well ifacoum bait in bait stations (Hosea ty of toxic injury to the liver.” known that anticoagulants cause 2000). Secondary poisoning can Synergistic effects between anti- birth defects in humans, so repro- also occur in humans when rodents coagulants and disease have also ductive effects of secondary poison- are a food source, though this is been found in mammals. For ing in raptors should be investigat- not a problem in the U.S. (Fiedler instance, one study in Southern ed further (Stevenson et al. 1980). 1990). Secondary poisoning of California showed that 90% of bob- humans is possible when deer, wild cats, Lynx rufus, in the area had Persistence a Problem pigs, and other game animals have been poisoned with anticoagulants. Although first generation antico- been poisoned with anticoagulants. Anticoagulants correlated with inci- agulants are eliminated fairly quick- The poison is not destroyed by dence of lethal mange, and 100% of ly, second generation products cooking (Eason et al. 2002; Stone et bobcats dead from mange had been linger in the bloodstream, and the al. 1999). exposed. Two mountain lions in the liver acts like a sponge. Large

Box A. Primary and Secondary Poisoning There are two general kinds of rat Anticoagulants and birds are affected by secondary poisons—acute poisons and chronic exposures in laboratory tests (Littrell The need to provide added safety poisons (Meehan 1984). Until 1950, 1990; Mendenhall and Pank 1980). for rat baits led to the invention of only acute poisons were available. Effects of secondary poisoning from the anticoagulants. Early first gener- With an acute poison, one encounter first generation anticoagulants are ation anticoagulants include war- with the bait is enough to kill a rat. minimized because the poison is farin, chlorophacinone, and diphaci- Various compounds such as arsenic, quickly eliminated by the rodent, none. Most anticoagulants are strychnine, red squill powder and amounts do not accumulate chronic baits, and with many of the obtained from the lily, Urginea mar- (Hadler and Buckle 1992). older first generation compounds, itima, sodium monofluoroacetate Secondary poisoning became a daily doses over several days are (Compound 1080), vitamin D real problem with the development of 3 needed to kill a rat or a non-target (cholecalciferol; Terad3®), zinc phos- second generation anticoagulants animal. All the anticoagulants work phide (ZP Rodent Bait®; Ridall®), such as brodifacoum, bromadiolone, in the same way; enzymatic synthe- and bromethalin (Tom Cat®) have all and others. These are more acutely sis of vitamin K is blocked. Vitamin been used (Meehan 1984; Erickson toxic and are extremely persistent. K is essential for proper clotting of and Urban 2004). One feeding on a second generation blood, and once vitamin K levels There are three problems with bait provides a lethal dose. But drop below a critical threshold, acute baits. One, Norway rats, because a rat does not die right internal bleeding occurs and death Rattus norvegicus; and roof rats, away, repeated feeding can occur, follows. Rattus rattus, tend to view with sus- leading one rat to accumulate 20-40 The first-generation anticoagulants picion any new item in their environ- lethal doses (Erickson and Urban are much safer than acute poisons ment (neophobia). Two, if they con- 2004). because several encounters are gen- sume a sublethal amount of an Since predators prefer to eat live erally needed to produce a problem acute bait, they will avoid eating any rats, quick-acting acute poisons pro- in a non-target species, and vitamin more (bait shy). The other problem duce very few secondary poisonings. K is an antidote to anticoagulant is that acute baits are extremely Rats die slowly from anticoagulant poisoning (Hadler and Buckle 1992). dangerous to pets and children, as baiting, however, and the possibility one encounter can make them very of secondary poisoning increases sick or kill them (Meehan 1984). Secondary Poisoning with time. Poisoned rats tend to die Non-target poisoning with acute Although anticoagulants reduce in the open, and may be moving baits is called primary poisoning, as the risk of primary poisoning, the slowly and erratically just before the animal directly eats the bait risk of secondary poisoning increas- death. Such rats make good targets (Erickson and Urban 2004). es. Secondary poisoning results for predators such as owls and foxes when a predator or a scavenger eats (Meehan 1984; Cox and Smith a poisoned rodent. Both mammals 1992).

Common Sense Pest Control XXVII(1-4) Special Issue 2011 5 Box 7414, Berkeley, CA 94707 6 amounts accumulate in the liver of animals are also poisoned (Eason et to 2003 was at risk of death from rodents, and subsequently in the al. 2002). anticoagulants especially brodifa- livers of predators. Repeated feed- coum and bromadiolone (Albert et ings allow an accumulation of tox- Owls in Canada al. 2010). ins to lethal levels over time Another Canadian study used a When 164 owl carcasses in west- (Erickson and Urban 2004). statistical method to estimate that ern Canada were analyzed for anti- Second generation anticoagulants about 11% of the great horned owl coagulants, 72% had residues of at are also extremely persistent. For population of Canada was at risk of least one anticoagulant in their liv- instance, after field populations of being killed by second generation ers. Frequency varied with species: voles in France were baited with anticoagulants (Thomas et al. barn owls (62%), Tyto alba; great bromadiolone, 50-80% of surviving 2011). horned owls (70%), Bubo virgini- voles had detectable residues 135 anus; and barred owls (92%), Strix days later. About 59% of the varia. Barred owls encountered poi- Raptors in New York residue was concentrated in the liv- soned rodents more often because When 265 dead raptors from 12 ers. Longterm persistence in the they hunt mostly in urban and sub- species were collected and analyzed pest population can lead to cumula- urban sites (Albert et al. 2010). in New York (1998-2001), anticoag- tive risk for predators (Sage et al. Brodifacoum and bromadiolone ulant residues were found in 49%. 2008). According to a review by were the most frequently detected Brodifacoum was detected in 84% Eason et al. (2002), sublethal anticoagulants at liver concentra- of the positive cases, and was con- amounts of brodifacoum and bro- tions up to about 1 mg/kg. Levels sidered the principal or probable madiolone are likely to persist 6-12 cause of death in 27 of 28 deaths months.

ht oreyJeVincent Joe courtesy Photo attributed to anticoagulants. Of Surveillance Programs raptors exposed, brodifacoum may have killed 21% of them. If the Another source of information sample was representative of the about secondary poisoning is gov- raptor population, then very rough- ernment surveillance programs. ly at least 10% of New York raptors Dead birds found in the environ- that died during this sampling peri- ment are submitted to monitoring od were likely killed by brodifa- agencies. Birds are then analyzed coum. (There was no systematic for poison. For instance, anticoagu- monitoring across the state. But the lant rodenticides were found in the estimate is likely to be a lower limit livers of 48% of 265 raptors collect- because dead birds die in out of the ed in New York. Of those exposed, way locations, and few are brought anticoagulants were related to their in by the public for analysis. deaths in about 22% of the cases Scavengers also feed on the (Stone et al. 2003). corpses.) Also, 37% of 351 owls in Great Some species are more at risk Britain and 72% of 164 owls in due to food preferences and sensi- Canada had detectable concentra- Barred owl, Strix varia tivity to brodifacoum. Anticoag- tions of anticoagulant rodenticides ulants were found in 81% of great in their livers (Ratner et al. 2011). horned owls, Bubo virginianus, and Concentrations in at least 21% of 58% of red tailed hawks, Buteo the Canadian owls were large of anticoagulants were high enough jamaicensis. Brodifacoum was the enough to be life threatening (Albert to cause bleeding in 92% of the principal or probable cause of death et al. 2010). cases. Anticoagulants were directly in about 21% of the great horned Wildcare, an animal rehabilitation the cause of death in 3.6% of the owls and about 27% of the red center in Marin County, CA is see- cases, 6% had liver concentrations tailed hawks exposed to anticoagu- ing poisoning in 58% of the bird (>0.6 µg/g) known to correlate with lants (Stone et al. 2003). and mammal patients. In death, and 15% had liver concen- Bromadiolone was detected in Massachusetts, of 161 raptors trations (>0.2 µg/g) likely to corre- 22% of the positive anticoagulant admitted to a wildlife clinic, 86% late with death (Newton et al. cases, but was likely involved in had brodifacoum anticoagulant 1999). About 32% of the owls had only two deaths. Chlorophacinone, residues in their livers (Murray liver concentrations (>0.1 µg/g) that diphacinone, and warfarin were 2011). some studies have associated with detected in some cases, but led to Cases from surveillance programs lethal risk in owls (Thomas et al. no deaths (Stone et al. 2003). are likely the tip of the iceberg, as 2011; Newton et al. 1998). many bird poisonings go unnoticed, From these data, if dead owl sam- Raptors in California and since the corpses decay quickly in ples were representative of the gen- out of the way locations. Toxic car- eral owl population, at least 11% Massachusetts casses are also eaten by scavengers and up to 23% of the owl popula- California Department of Fish and or predatory mammals, and these tion in western Canada from 1988 Game collected 74 animals from

Common Sense Pest Control XXVII(1-4) Special Issue 2011 6 Box 7414, Berkeley, CA 94707 7 ht oreyMr Payne-Gill Mark courtesy Photo ht oreyGog Jameson George courtesy Photo exposed to second generation anticoagulants over a five year observa- tion period (Walker et al. 2008). Over a 15 year period, 28% of dead barn owls, Tyto alba, contained residues of these anticoagulants. About 48% of the owls had died from auto accidents and 31% from starvation. The residues increased over the years, and 40% of the birds were positive for the anticoagulants at the end of the experiment in 1998 (Newton and Wylie 2002). When 401 wild or domestic animals were examined in Spain, about 39% had been exposed to Great horned owl, anticoagulants, either through pri- Bubo virginianus mary or secondary poisoning. Of Tawny owl, Strix aluco those exposed, 90% had died from 1994-1999. Residues of anticoagu- the poison. About 62% of dead rap- On the mainland in areas where lants were found in 74% of the tors and 38% of carnivorous mam- brodifacoum is used, 63% of dead mammals and 68% of the birds col- mals had died from the poison. birds have residues in their livers. lected. About 61% of the mammals Widespread exposure occurred and 55% of the birds contained through treated grain spread on the Mammals are also at risk, as 60% brodifacoum. About 19% of the soil surface (Sanchez-Barbudo et al. of wild pigs, 33% of deer, 80% of birds were exposed to bromadi- 2012). wildcats, and 85% of stoats sam- olone, 10% contained diphacinone, pled have residues in their livers. and 10% chlorophacinone. Most Raptors in New Zealand Deer poisoning is likely primary frequently exposed were coyote, Brodifacoum and second genera- poisoning from feeding directly on Canis latrans; bobcats, Lynx rufus; tion anticoagulants are widely used the bait (Eason et al. 2002). golden eagles, and barn owls. About in New Zealand. Aerial applications one-third of the birds exposed were are used to clear islands of rats. Where are Rodenticides owls, about 55% other predatory With island applications, 80-90% of Used? birds (Hosea 2000). some bird species were killed by a Rodenticides are used in urban Of 161 raptors collected in a combination of primary and second- situations to reduce rat popula- Massachusetts wildlife clinic from ary poisoning. On one island, about tions. They are used in agricultural 2006-2010, 85% tested positive for 21% of the native owl morepork, situations to remove gophers and brodifacoum. Species included red- Ninox sp., were presumably killed voles from crops, and in wildlife sit- tailed hawks, Buteo jamaicensis; by secondary poisoning. uations to reduce populations of barred owls, Strix varia, eastern prairie dogs, and ground squirrels. screech owls, Megascops asio, and Velte Patricia courtesy Photo But second generation anticoagu- great horned owls, Bubo lants are registered only for struc- virginianus. At least 6% of the birds tural pest control in the U.S. First had died from poisoning (Murray generation chlorophacinone and 2011). diphacinone baits are used for voles, gophers, and ground squir- Raptors in Europe and the rels (Erickson and Urban 2004; UK Hygnstrom et al. 1994). In Demark, a total of 430 raptors from 11 species were analyzed for Declining Raptor anticoagulants. Frequency of anti- Populations coagulant liver residues varied with Secondary poisoning effects on species, but residues were found in bird and mammal populations are 84-100% of the bird species ana- localized to the treated area. Birds lyzed. Amounts also varied by or mammals must be feeding on the species, but about 13-37% of treated rodents to get poisoned. In residues in the livers were large the case of brodifacoum, one rat enough to have caused poisoning can contain 30-40 times a lethal symptoms or death (Christensen et dose (Erickson and Urban 2004). al. 2012). But if large areas are treated, In Britain, 20% of the tawny owl, Red tailed hawk, predator populations in large areas Strix aluco, population had been Buteo jamaicensis

Common Sense Pest Control XXVII(1-4) Special Issue 2011 7 Box 7414, Berkeley, CA 94707 8 can be affected. Owls in western last resort because accidental poi- Canada are declining (Albert et al. Resources sonings can occur, and dead 2010). Kestrels and some owl American Bird Conservancy, PO rodents can lead to odors in struc- species are declining in the U.S. Box 249, The Plains, VA tures and production of other pests (Smallwood et al. 2009). 20198; 202-234-7181, such as flies (Olkowski et al. 1991). Various published studies cited www.abcbirds.org If a rodent bait is necessary, first above have found these species are Golden Gate Audubon, 2530 San generation materials such as war- often exposed to secondary rodenti- Pablo Ave, Ste G, Berkeley, CA farin, diphacinone, or chlorophaci- cide poisoning (Stone et al. 2003; 94702; 510-843-9912, www- none should be used. Where Hosea 2000; Albert et al. 2010). goldengateaudubon.org rodents are known to be resistant Predatory birds such as kestrels are Golden Gate Raptor Observatory, to warfarin, acute baits such as Bdlg 1064, Ft. Cronkhite, more sensitive to anticoagulants bromethalin or vitamin D3 may be than grain eaters such as bob- Sausalito, CA 94965; 415- needed. All baits used by con- whites or mallards (Rattner et al. 331-0730, www.ggro.org sumers should be contained within Hungry Owl Project, 179 The 2011). Rodenticides are likely one a tamper resistant bait station. Alameda, San Anselmo, CA factor in areawide population 94960; 415-454-4587, decline. www.hungryowlproject.org Conclusion Raptors are the Solution, Thousands of children in the U.S. Raptors are the Solution www.raptorsarethesolution.org are exposed to rodenticides each Raptors should be encouraged as Rodenticide Free Project, PO Box year. About 76% of the hospitaliza- part of an integrated rodent control 892. Bolinas, CA 94924; 415- tions are due to brodifacoum and program. In Malaysia on 188 oil 786-8467, www.rodenticide- second generation anticoagulants. palm plantations where barn owl freeproject.org About 74% of pet poisonings are boxes were built, there was a Wildcare, 76 Albert Park Lane, primarily due to brodifacoum. In decline in rat numbers and damage San Rafael, CA 94901; 415- areas where brodifacoum is used, 456-7283, www.wildcareb- (Basri et al. 1996). Barn owl boxes at least 11% of the raptors may be yarea.org on a rice plantation reduced rat at lethal risk from secondary poi- damage from about 6.5% to 2.5% soning. First generation anticoagu- (Mohamad and Goh 1991). Another lants such as warfarin, chloropha- coum, are the major cause of acci- experiment showed that barn owl cinone, and diphacinone are caus- dental poisonings in humans and boxes were most effective when ing sublethal effects, but are rarely rodent numbers were low (Chia et pets. They are also causing second- determined to be a direct cause of al. 1995). Barn owl boxes and blue- ary poisoning of wildlife and espe- death in raptors, and cause only a prints for their construction are cially raptors. The EPA reviewed small percentage of human poison- available on the Internet. problems with rodenticides in 2008. ings. To reduce exposures, all man- As a result, second generation anti- ufacturers should follow EPA regu- New EPA Regulations coagulants were banned in the con- lations that eliminate second gener- sumer market, and bait stations ation anticoagulants and mandate From the information above, it is were required for all rodenticides tamper resistant bait stations for clear that second generation antico- sold in this market. The rules were the consumer market. agulants, and especially brodifa- implemented in June 2011. Many companies have complied, but three References

oreyUSDA Courtesy companies are fighting the new reg- Albert, C.A., L.K. Wilson, P. Minaeau, S. Trudeau ulations (EPA 2008; EPA 2011). and J.E. Elliott. 2010. Anticoagulant roden- The new EPA regulations do not ticides in three owl species from western affect the professional market and Canada, 1988-2003. Arch. Environ. Contam. Toxicol. 58:451-459. applications on farms. Although Basri, M.W., S. Ismail and N. Kamarudin. 1996. second generation anticoagulants The extent of biological control of rats with are not registered for agricultural barn owls in Malaysian oil palm plantations. Planter 72(838):5-8. [CAB Abstracts] pests such as gophers and voles, Borrecco, J.E. and R.E. Marsh. 1992. farmers are allowed to use them for Proceedings of the Fifteenth Vertebrate Pest rat and mouse control in and Conference. University of California, Davis, California. 415 pp. around structures (EPA 2011). Brakes, C.R. and R.H. Smith. 2005. Exposure of non-target small mammals to rodenticides: Best Methods for Rodents shortterm effects, recovery and implications for secondary poisoning. J. Appl. Ecol. The best way to control rodents is 42(1):118-128. with an IPM program featuring sev- Bronstein, A.C., D.A. Spyker, L.R. Cantilena, J.L. Green, et al. 2011. 2010 Annual Report of eral different methods. Habitat the American Association of Poison Control management, sanitation, and exclu- Centers’ National Poison Data System (NPDS): sion can be combined with trap- 28th Annual Report. Clin. Toxicol. 49:910- Dimensions of a barn owl box 941. ping. (see the next article) Chia, T.H., J.L. Lim and B. Buckle. 1995. Barn Rodenticides should be used as a owls for rat control on oil palm plantations-

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do they work? Planter 71(828):109-117. Massachusetts, 2006-2010. J. Zoo Wildl. [CAB Abstracts] Med. 42(1):88-97. Christensen, T.K., P. Lassen and M. Elmeros. Naim, M. H.M. Noor and A. Kasim et al. 2010. 2012. High exposure rates of anticoagulant Growth performance of nestling owls in rat rodenticides in predatory bird species in baiting area in Malaysia. J. Agric. Biol. Sci. intensively managed landscapes in 5(6):1-13. [CAB Abstracts] Denmark. Arch. Environ. Contam. Toxicol. Newton, I., I. Wyllie and P. Freestone. 1990. 63:437-444. Rodenticides in British barn owls. Environ. Corrigan, R. 1997. Rats and mice. In: Mallis, A. Pollution 68:101-117. 1997. Handbook of Pest Control, 8th ed. S.A. Newton, I., L. Dale, J.K. Finney et al. 1998. Hedges, ed. Mallis Handbook and Technical Wildlife and Pollution: 1997/1998 Annual Training Company. pp. 11-105 of 1453 pp. Report, JNCC Rpt. No. 285. [cited in Albert Cox, P. and R.H. Smith. 1992. Rodenticide eco- et al. 2010] toxicology: pre-lethal effects of anticoagu- Newton, I., R.F. Shore, I. Wiley et al. 1999. lants on rat behavior. In: Borrecco and Empirical evidence of side effects of rodenti- Marsh, pp. 165-169. cides on some predatory birds and mam- Davis, L.R., R.E. Marsh and D.E. Beadle. 1990. mals. In: D.P. Cowan and C.J. Feare, eds. Proceedings of the Fourteenth Vertebrate Pest Advances in Vertebrate Pest Management. Conference. University of California, Davis, Filander Verlag, Furth, pp. 347-367. California. 372 pp. Newton, I. and I. Wyllie. 2002. Rodenticides in Eason, C.T., E.C. Murphy, G.R.G. Wright and British barn owls. In: I. Newton, R. E.B. Spurr. 2002. Assessment of risks of Kavanagh, J. Olsen et al. eds. Ecology and brodifacoum to non-target birds and mam- Conservation of Owls, pp. 286-295. mals in New Zealand. Ecotoxicol. 11:35-48. Olkowski, W., S. Daar and H. Olkowski. 1991. EPA (Environmental Protection Agency). 2008. Common Sense Pest Control. Taunton Press, Risk mitigation decision for ten rodenticides. Newtown, CT. 715 pp. 60 pp. www.epa.gov/oppsrrd1/reregistra- Rattner, B.A., K.E. Horak, S.E. Warner et al. tion/rodenticides/finalriskdecision.htm 2011. Acute toxicity, histopathology, and EPA (Environmental Protection Agency). 2011. coagulopathy in American kestrels (Falco Cancellation process for certain rodenticides. sparverius) following administration of the 3 pp. www.epa.gov/pesticides/mice-and- rodenticide diphacinone. Environ. Toxicol. rats/rodent-bait-station.html Chem. 30(5):1213-1222. Erickson, W. and D. Urban. 2004. Potential risks Riley, S.P.D., C. Bromley and R.H. Poppenga et of nine rodenticides to birds and non-target al. 2007. Anticoagulant exposure and mammals: a comparative approach. Office of notoedric mange in bobcats and mountain Prevention, Pesticides and Toxic Substances, lions in urban southern California. J. Wildl. EPA, Washington, DC. 230 pp. www.regula- Manag. 71(6):1874-1884. tions.gov, docket no. EPA-HQ-OPP-2006- Sage, M., M. Coeurdassier, R. Defaut et al. 2008. 0955 Kinetics of bromadiolone in rodent popula- Fiedler, L.A. 1990. Rodents as a food source. In: tions and implications for predators after Davis et al., pp. 149-154. field control of the water vole, Arvicola ter- Hadler, M.R. and A.P. Buckle. 1992. Forty five restris. Sci. Total Environ. 407:211-222. years of anticoagulant rodenticides—past, Sanchez-Barbudo, I.S., P.R. Camarero and R. present and future trends. In: Borrecco and Mateo. 2012. Primary and secondary poison- Marsh, pp. 149-155. ing by anticoagulant rodenticides of non-tar- Hegdal, P.L. and B.A. Colvin. 1988. Potential get animals in Spain. Sci. Total Environ. hazard to eastern screech owls and other 420:280-288. raptors of brodifacoum bait used for vole Smallwood, J.A., M.F. Causey, DH. Mossop et al. control in orchards. Environ. Toxicol. Chem. 2009. Why are American kestrel (Falco 7:245-260. sparverius) populations declining in North Hosea, R.C. 2000. Exposure of non-target America? Evidence from nest-box programs. wildlife to anticoagulant rodenticides in J. Raptor Res. 43(4):274-282. California. In: T.P. Salmon and A.C. Crabb, Stevenson, R.E., M. Burton, G.J. Ferlauto and eds. 19th Vertebrate Pest Conference. UC H.A. Taylor. 1980. Hazards of oral anticoag- Davis, Davis, CA. ulants during pregnancy. JAMA 243:1549- Hygnstrom, S.E., R.M. Timm and G.E. Larsen, 1551. eds. 1994. Prevention and Control of Wildlife Stone, W.B., J.C. Okoniewski and J.R. Stedelin. Damage. University of Nebraska, Lincoln. 2 1999. Poisoning of wildlife with anticoagu- vols. lant rodenticides in New York. J. Wildl. Dis. Lemus, J.A., C. Bravo, M. Garcia-Montijano et 35(2):187-193. al. 2011. Side effects of rodent control on Stone, W.B., J.C. Okoniewski and J.R. Stedelin. non-target species: rodenticides increase 2003. Anticoagulant rodenticides and rap- parasite and pathogen burden in great bus- tors: recent findings from New York, 1998- tards. Sci. Total Environ. 409:4729-4734. 2001. Bull. Environ. Contam. Toxicol. 70:34- Littrell, E.E. 1990. Effects of field vertebrate pest 40. control on nontarget wildlife. In: Davis et al., Thomas, P.J., P. Mineau, R.F. Shore et al. 2011. pp. 59-61. Second generation anticoagulant rodenti- Meehan, A.P. 1984. Rats and Mice: Their Biology cides in predatory birds: probabilistic char- and Control. Rentokil, East Grinstead, West acterization of toxic liver concentrations and Sussex, United Kingdom. 383 pp. implications for predatory bird populations Mendenhall, V.M. and L.F. Pank. 1980. in Canada. Environ. Int. 37:914-20. Secondary poisoning of owls by anticoagu- Walker, L.A., A. Turk, S.M. Long et al. 2008. lant rodenticides. Wildl. Soc. Bull. 8(4):311- Second generation anticoagulant rodenti- 315. cides in tawny owls from Great Britain. Sci. Mohamad, C. and N.S. Goh. 1991. The use of Total Environ. 392(1):93-98. barn owl (Tyto alba) to control ricefield rats- Watson, W.A., T.L. Litovitz, G.C. Rodgers, Jr. et an experience in Seberang Perak. MAPPS al. 2005. 2004 Annual Report of the Newsletter 15(2):20. [CAB Abstracts] American Association of Poison Control Murray, M. 2011. Anticoagulant rodenticide Centers Toxic Exposure Surveillance System. exposure and toxicosis in four species of Am. J. Emerg. Med. 23(5):589-666. birds of prey presented to a wildlife clinic in

Common Sense Pest Control XXVII(1-4) Special Issue 2011 9 Box 7414, Berkeley, CA 94707 10 Managing Rats and Minimizing Rodenticides By William Quarles

odents most often encountered as structural pests include the Norway rat, Rattus norvegicus; R the roof rat, Rattus rattus; and the house mouse, Mus musculus. The Norway rat, considered the most Roof rats, Rattus rattus, have long tails and slender bodies. important pest rat in the U.S., is also known as the brown, wharf, house, grey, or sewer rat. (Albino forms of the Norway rat are used for scientific research.) It length, the roof rat’s tail is longer than the head and occurs in every state and is widely distributed around body. Including the tail in the measurement, both rats the world. The roof rat, also known as the ship or black grow to an overall length of about 16 inches (40 cm) at rat, occurs mainly in the coastal U.S., including the adulthood. The Norway rat is a larger, heavier rat, but Pacific Coast states, the Gulf states, and the Southeast has smaller eyes and a blunter snout than the roof rat and some Middle Atlantic states. The house mouse is (Ingles 1965; Meehan 1984). House mice are much found throughout the U.S. (Marsh 1994; Corrigan smaller than rats. Their bodies and tails are each about 1997). 3.5 inches (9 cm) long, and they can gain entrance Both Norway rats and roof rats are omnivores, and through holes as small as a dime. Mice can be distin- will feed on almost anything. Unlike mice, rats require guished from immature rats by their large ears, and water daily, and prefer to nest where water is available. their heads and feet are smaller relative to their body In general, Norway rats build their nests in under- size (Olkowski et al. 1991). ground burrows or in ground level areas in buildings. If rats are not seen, the species involved can be Roof rats prefer living in elevated areas and build nests deduced from their excrement. Norway rat droppings in trees, vine-covered fences, and roofs, attics, and are larger and more ovoid than roof rat droppings, walls, although they will nest at ground level if arboreal which tend to be longer and more cylindrical (Weber habitat is limited. Roof rats often enter buildings from 1982). Each pest has a different biology and manage- the roof or via overhead utility lines, which they use to ment methods must take this into account. Due to travel from area to area. They are often found living on space limitations, rodent biology will not be covered the second floor of buildings, whereas Norway rats are here. The reader is referred to other sources (Olkowski more likely to occupy the first or basement floor et al. 1991; Corrigan 1997; Simon and Quarles 2004). (Meehan 1984). Mice prefer to nest inside dwellings— Presented here is an IPM blueprint that can lead to wall voids, cabinets, furniture, and appliances are effective rat management and reduction of rodenticides. favorite targets (Olkowski et al. 1991). An IPM Approach How to Identify a Rat The best approach to rat management is a combina- The Norway rat and the roof rat differ from other rats tion of monitoring, exclusion, habitat management and and mice in that their tails are noticeably scaly. The sanitation to prevent infestations. Once an infestation Norway rat’s tail is shorter than its head and body occurs, exclusion efforts should be intensified, and res- ident rats should be removed by traps. In some cases, a rodenticide may be necessary (Frantz and Davis 1991). Until rat problems are under control, any attractive food, even closed packages of crackers or candy, can be temporarily stored in the refrigerator. Since hungry rats will eat nearly anything, even bars of soap may have to be refrigerated. Large bags of flour, grain, dry pet or livestock food that are stored in basements or sheds should be placed on open-wire metal shelving that offers little rat harborage and is elevated at least 18 inches (45.7 cm) from the floor (Olkowski et al. 1991; Timm 1994). Outdoor Garbage Management Norway rats, Rattus norvegicus, have short tails and stout bodies. Proper disposal of organic garbage is essential to keep rats at bay. Organic wastes should be separated

Common Sense Pest Control XXVII(1-4) Special Issue 2011 10 Box 7414, Berkeley, CA 94707 11 from metal, glass and plastic. In some locations, green into the upper portions of buildings and trees that are recycling cans are provided for organic waste. Check brushing up against the structure give rodents access every evening to make sure there is no garbage lying on to the roof (Marsh 1994). the ground around the cans, and lids are securely in place. Outdoor cans with holes or lids that do not fit Rat-Proofing Buildings tightly should be replaced or repaired. Where rat prob- Exclusion of rodents by rat-proofing a building is very lems are compounded by raccoons or dogs tipping over important. Entry points into buildings should be thor- garbage cans, spring-type or stretchy fasteners can be oughly rat-proofed by plugging holes larger than 1/2 used to keep lids tightly closed (Olkowski et al. 1991; inch (1.3 cm) in diameter, installing guards to prevent Timm 1994). rats from moving along pipes and wires, screening drains in basement and shower room floors, and plac- Reducing Landscape Habitat ing barriers between and within walls to prevent rodent Both Norway and roof rats can harbor in dense vege- travel. Wooden doors should have metal kickplates at tation, which provides them both habitat and food. the bottom to discourage rodents from gnawing their Keep woody shrubs and ground covers adjacent to way inside along the bottom corners of the door (Scott buildings pruned to expose the lower 18 inches (45.7 1991; Timm 1994). Rodent-proofing against roof rats cm) of trunk. This facilitates inspection for burrows usually requires more time to find entry points than for and discourages Norway rats because of their greater climbing ability rat harborage by (Marsh 1994). exposing the area Storage rooms should be reorganized to eliminate as to light (Frantz much clutter as possible to facilitate inspection and 1988). Large leaf reduce rat harborage. Broken sewer pipes should be Algerian ivy, repaired as rats can dig into them and swim up the Hedera canarien- trap in a toilet to enter a building. Toilet bowl drains sis, is a favorite can be rat-proofed by feeding the pipe from the toilet hiding place for bowl into a pipe section of larger diameter (Frantz and rats, particularly Davis 1991). when grown in dense monocul- The Better Rat Trap tures and allowed When rats are present inside the house, trapping to cover fences should be the primary approach used in an IPM pro- and trees. Roof Garbage cans should be gram (Hedges 1995). There are a number of advantages tightly closed. rats also feed on to traps compared to poisons. Traps provide physical the ivy berries. If evidence of capture, and there is less risk to non-target you have this organisms. They are also usually quicker in ridding plant in your landscape, it should be trimmed to a your house of rats. When poison is used, there is the height of at least 30 cm (11.8 in), or replaced with possibility that rats may die in wall voids and sub- English ivy, Hedera helix (Frantz and Davis 1991). floors, where it is difficult to find and remove them. Avoid planting large areas of uniform ground cover These carcasses cause unpleasant odors and attract that allows rats to run for long distances unseen. flies, carpet beetles, and other pests. Break up existing dense plantings with exposed path- ways, stretches of lawn or very low ground cover. Rats do not like to move across areas where they can be easily seen. Fallen fruit, nuts and similar foods may be feeding rats around buildings. They should be shoveled, raked or swept up and put into rat-proof garbage containers or green recycling cans. Trees such as date palms offer both food and harborage for roof rats. These trees should be thinned, the low-hanging branches pruned off, and a rat guard attached around each trunk. Rat guards on trees should be checked annually and released as necessary to prevent girdling (Frantz and Davis 1991; Olkowski et al. 1991). Rats will also feed Roof vents should Entry points around plumb- on cat, dog, and horse feces, so these must be picked be screened. ing should be secured. up daily around infested areas. A gap of at least one meter (3 ft) should be main- tained between buildings and adjacent trees and Traps should be placed in attics, basements, or shrubs so that branches do not enable rats to jump to locked storage rooms where children and pets or other and from roofs or ledges (Frantz and Davis 1991). non-target animals will not have access to them. If this Debris heaps, woodpiles or construction debris near is impossible, traps can be placed in tamper resistant buildings should also be removed. Power lines running bait stations.

Common Sense Pest Control XXVII(1-4) Special Issue 2011 11 Box 7414, Berkeley, CA 94707 12

Rats are extremely wary of new objects in their envi- ronment. Traps, baits and bait stations may be avoided for several days after initial placement. Even after this period, rats will be very cautious in approaching them. If a rat nibbles on a bit of poison bait that later Set traps with triggers toward the wall or set two makes it sick without killing it, the rat will avoid simi- traps in parallel with triggers in opposite directions. lar baits or bait stations in the future, and, if it is a female, will teach its young to do the same. Thus, it is difficult to make a substantial long-term reduction in a Traps should be set along walls or other runways rat population through trapping and baiting alone leading to the holes. Other good trap locations include: (Olkowski et al. 1991; Timm 1994). near droppings, gnaw marks or other signs of rat damage; under and behind objects likely to harbor rats; in Kinds of Traps dark corners; along rafters or other protected areas where rats are likely to travel. Note that traps or baits There are three types of traps—snap traps, live traps placed on the ground or floor may catch very few roof and glue boards. Live traps are not generally recom- rats unless they are positioned at the very points that mended for rat removal. Sometimes, pest control pro- rats traverse from above down to a food source (Marsh fessionals use them so that the rat can be checked for 1994). ectoparasites or disease. Glue boards may not be effec- A sufficient number of traps must be used in order to tive for rats, and when used for mice can produce be effective. Depending on the size of the infestation, a inhumane results. Snap traps are probably the best to house may require a dozen traps. In an active corner of use in a rat infestation, although they may require a room, 5 to 10 traps should be set. Three traps set in some care, time, and persistence (Hedges 1995; a row ensures that a rat trying to jump over the traps Corrigan 1997). These traps capture and instantly kill will be caught. If rat activity in an area is unknown, single rats, and can be placed on floors for Norway rats traps should be set 10 to 20 feet apart (3.0 to 6.0 m) or nailed to beams for roof rats. When handling traps, along possible runways (Timm 1994). gloves should always be worn for protection from dis- Traps must be checked daily and fresh bait added as eases. Care should be taken because snap traps have needed. Moving traps after three or four days is advised very strong springs, and accidental release may dam- if there is no sign of activity. age an exposed hand or foot. Always keep them out of If there are many rats in the house and most of the the reach of children and pets (Olkowski et al. 1991). rats have been trapped, it can be hard to catch the last A rat trap called the Rat Zapper® provides an alter- few because they may be trap-shy. In such cases, the native to a snap trap as long as infestations are limited. traps can be removed for a week, then set in new loca- The trap uses 4 AA batteries to power an electric shock tions using the pre-baiting method described below. unit. It is a covered trap and can be used outside as Insecticides should not be sprayed on the traps and well as inside. A bit of dry pet food is used to lure a they should not be stored with insecticides, rodenti- rodent inside the trap. The shape of the rodent triggers cides or application equipment. These smells can a lethal electroshock. A red light goes on that signals make the rats avoid the traps when they are next used the trap is in use. The rodent slides easily out of the (Corrigan 1997; Olkowski et al. 1991). trap into a plastic sack or a garbage can. According to company literature, it is safe for children and non-tar- Food Baits get organisms. It is difficult for children or pets to trigger it; the electroshock causes a reflex withdrawal of a Traps should be baited if food for rats is limited. If hand or a paw, and current transfer is limited because there is plenty of food around, the traps will be more it is battery operated (AgriZap 2012). Woodstream also effective without bait. Alternatively, an extremely sells an electric trap for mice (see Resources). attractive food bait can be used. Baits can be tied to the trigger using string or dental floss to ensure that Setting and Placing Traps the rat will spring the trap when investigating the bait. Suggested baits for Norway rats are pieces of hot dog, bacon, liver, peanut butter or nut meats. Suggested baits for roof rats are nuts, dried fruits, or fresh fruits such as bananas or apples. Other baits include fruit, marshmallows, raisins, or peanut butter mixed with rolled oats. If rats are feeding on other foodstuffs present, these items can be tried as baits. Cereal (like oat- meal) can be sprinkled around the traps to make them more attractive (Timm 1994; Marsh 1994). Pre-baiting Traps If baited traps are initially unsuccessful, place baited A baited snap trap but unset traps out for one to three days so rats become accustomed to them. Traps should be checked to see if the bait is being eaten—if not, another bait

Common Sense Pest Control XXVII(1-4) Special Issue 2011 12 Box 7414, Berkeley, CA 94707 13 should be tried. Once bait is being eaten, the traps Use Bait Stations should be rebaited and this time set (Timm 1994). When used, poison baits must be placed in high pro- file, tamper-resistant bait stations that lock (see Biological Control Resources). Bait stations are useful because they pro- Predators and diseases can produce substantial tect the bait from moisture and dust; provide a protect- reductions in rat populations, but the effect is usually ed place for rats to feed, making them feel more secure; temporary (Frantz and Davis 1991). Snakes, owls and keep other animals and children away from the poison; other birds of prey, coyotes, dogs and cats are natural allow placement of bait in locations where it would oth- enemies of rats. It should be noted that beneficial pred- erwise be difficult; help prevent accidental spilling of ators can be killed by consuming poisoned rats. In bait; and allow easy inspection of bait to see if rodents addition, rats may cache (hide) food that may or may are feeding on it. Waxy bait blocks that can be not be eaten, taking the poison bait to a place where anchored to the bait station are the best formulation other animals can find it, or to other locations the label (Timm 1994; Corrigan 1997). does not allow. Thus, trapping is preferred over baiting for rat suppression activities (Hedges 1995). Which Rat Baits? When possible, warfarin (Kaput®), chlorophacinone When to Bait (Rozol®)or other first-generation anticoagulants are pre- Pesticides must be used properly in accordance with ferred. They present less hazard to humans and pets their label directions. Protective gear should always be than second-generation anticoagulants (Frantz 2004). worn during pesticide applications. Outdoors, poison First generation anticoagulants also present fewer baits should be used only when trapping is not effec- problems for wildlife, including raptors, as secondary tive; in emergency situations where there are very high poisoning problems are minimized (Erickson and Urban numbers of rats; and to prevent rats from migrating to 2004). neighboring areas when a building is being rat-proofed Where rodent resistance to warfarin seems sure, an or demolished. Poisons are also justified where rat pop- acute bait such as bromethalin (Tom Cat®) or vitamin ulations are carrying plague (Zinsser 1935; McNeill D3 (Terad3®) may be necessary. Research results up to 1976; Weber 1982; Craven et al. 1993). now show that secondary poisoning of raptors, pets,

Box A. Monitoring and Locating Rats

The first step in a rat management program is finding Check for leaks and any standing water such as irriga- areas of infestation. Try to identify as many of the areas tion or drainage ditches, stagnant pools, ornamental as possible that provide rodents harborage, food, water ponds, and fountains. On the roof, check air condition- and access to the building. Check doorways for gaps or ing units that might provide water and harborage for holes and note windows without screens or glass. Look rats (Corrigan 1997; Olkowski et al. 1991; Timm 1994). for other openings in the house such as holes, vents without screens, holes around pipe and electrical wire Monitoring Tools and Techniques entry points. Entry points can be openings as small as 1/2 inch (1.2 cm) in diameter in walls, around pipe All potential rat habitats and areas of activity such as entries, sewer outlets, and under doors. Unscreened attics, basements, garbage cans, and stored materials sewer outlets and even toilets can give rats access to should be thoroughly inspected. It may be useful to do buildings. Inspect all planters, woodpiles, vegetation. this at night, when the rats are most active. For night- Look for water leaks and rooms where water condens- time inspections, use a powerful flashlight with a red fil- es on the walls. Rodents like to follow edges; inspect ter, which is less likely to scare rats away from view. these areas for feces, rub marks, urine or other indica- If holes are found, they should be temporarily closed tions of activity. [Note: Rub marks are grease spots with soil, aluminum foil, sawdust or crumpled paper, resulting from repeated contact of a rat with a surface.] and inspected 24 hours later to see whether they have After checking the main floor of the house, particularly been reopened or if the paper has been moved or the kitchen, continue into the basement and attic to chewed. If so, it can be assumed that the hole is actively look for holes, nests, feces, and rub marks. As noted being used by one or more rats. earlier, Norway rats tend to seek harborage on lower lev- If necessary, talcum powder can be sprinkled near els and roof rats on higher levels of a building. suspected harborage or entry points to gain further Always be on the lookout for piles of trash, clutter, or information. Rat footprints and rattail drag lines across other debris. Nests are often composed of things like the powder confirm an infestation. A piece of white shredded paper, pieces of plastic, and bits of fabric gath- paper or cardboard can be temporarily placed in dark or ered together into a 5 inch (12.7 cm) diameter mass for hard-to-reach areas, and inspected for fecal pellets or mice and 8 to 12 inch (20.3 to 30.5 cm) diameter for other signs of rat activity. Rat signs, including drop- rats. If you find clothing or paper that looks torn or pings and sawdust from gnawed wood should be swept shredded but doesn’t look like a nest, you will most like- up. If new droppings or other clues are found a couple of ly find the nest nearby. days later, an active infestation is confirmed (Olkowski et al. 1991; Timm 1994).

Common Sense Pest Control XXVII(1-4) Special Issue 2011 13 Box 7414, Berkeley, CA 94707 14

ht oreyBl Labs Bell courtesy Photo avoid the bait or cache it. When the BIRC (Bio-Integral Resource Center). 2012. The baiting program is over, all bait sta- 2012 Directory of Least-Toxic Pest Control Products. IPM Practitioner 25(11/12): 1-52. tions should be collected and stored Corrigan, R.M. 1997. Rats and mice. In: Mallis, (Timm 1994). pp. 11-105. Craven, R.B., G.O. Maupin, M.L. Beard, T.J. Quan and A.M. Barnes. 1993. Reported Conclusions cases of human plague infections in the When rat infestations are discov- United States, 1970-1991. J. Med. Entomol. 30(4):758-761. ered, there are five steps in an IPM EPA (Environmental Protection Agency). 2008. program for controlling them: 1) Risk mitigation decision for ten rodenticides. improve sanitation and garbage 60 pp. www.epa.gov/oppsrrd1/reregistra- tion/rodenticides/finalriskdecision.htm management practices; 2) ratproof EPA (Environmental Protection Agency). 2011. buildings and alter landscape plant- Cancellation process for certain rodenticides. ings and other features that provide 3 pp. www.epa.gov/pesticides/mice-and- rats/rodent-bait-station.html rat access and harborage; 3) use Erickson, W. and D. Urban. 2004. Potential risks traps to reduce the existing rat pop- of nine rodenticides to birds and non-target Rat baits should be ulation; 4) if trapping is not effec- mammals: a comparative approach. Office of secured in bait stations. tive, supplement with poison baits Prevention, Pesticides and Toxic Substances, EPA, Washington, DC. 230 pp. www.regula- placed in tamper-proof bait stations tions.gov, docket no. EPA-HQ-OPP-2006- and checked frequently; 5) continue 0955 and wildlife is less of a problem monitoring periodically to ensure Frantz, S.C. 1988. Architecture and commensal with these materials. Because there vertebrate pest management. In: Kundsin, that rats are not recolonizing. pp. 228-295. are no convenient antidotes to Frantz, S.C. and D. Davis. 1991. Bionomics and acute baits such as these, they References integrated pest management of commensal should always be used in tamper rodents. In: Gorham, pp. 243-313. AgriZap. 2012. The Rat Zapper. Frantz, S.C. 2004. Personal communication. New resistant bait stations, or in areas www.agrizap.com York State Department of Health, Wadsworth where children and pets will not Center, Division of Infectious Disease, encounter them (Erickson and Empire State Plaza, PO Box 509, Albany, NY Urban 2004; EPA 2008; EPA 2011; 12201. Resources Gorham, J.R. 1991. Ecology and Management of Meehan 1984). Food-industry Pests. FDA Technical Bull. 4. Bait Stations— Bell Laboratories Inc., Association of Official Analytical Chemists. Baiting Procedures 3699 Kinsman Blvd., Madison, WI Arlington, VA. 53704; 608/241-0202, Fax Hedges, S. 1995. What’s for supper? Pest Control When baiting, leave a prominent 608/241-9631; www.belllabs.com. Technology 23(8):30, 31,35, 36, 86, 98. warning label on the bait station JT Eaton & Company, Inc., 1393 E. Hygnstrom, S.E., R.M. Timm and G.E. Larson. Highland Rd., Twinsburg, OH 1994. Prevention and Control of Wildlife box, and posted in the immediate Damage. USDA/APHIS, University of 44087; 800/321-3421, 330/425- area of baiting. Place bait stations Nebraska Cooperative Extension, Lincoln, 7801, Fax 330/425-8353; where rats have been found to be Nebraska. www.jteaton.com. Lipha Tech, 3600 Ingles, L.G. 1965. Mammals of the Pacific States. most active. In the case of roof rats, W. Elm St. , Milwaukee, WI 53209; Stanford University Press, Stanford, secure bait stations above the 888/331-7900, 414/351-1476, Fax California. 506 pp. ground in areas such as attics, 414/247-8166; www.liphatech.com Kundsin, R.B., ed. 1988. Architectural Design roofs or trees, or at the base of Bromethalin (0.01%) (Tom Cat®)— Bell and Indoor Microbial Pollution. Oxford Univ. Labs, see above Press, New York. trees or other heavily vegetated McNeill, W.H. 1976. Plagues and People. Chlorophacinone (0.005%)(Rozol®)— Anchor/Doubleday, Garden City, New York. structures such as fences over- Liphatech, see above grown with ivy. Space bait stations 340 pp. Diphacinone (0.005%)(Ditrac®)— Bell Mallis, A. 1997. Handbook of Pest Control, 8th 15 to 50 feet apart (4.6 to 15.2 m), Labs, see above ed. S. Hedges and D. Moreland, eds. Mallis and leave them in place for a few Rat and Mouse Traps (Victor®)— Handbook and Technical Training Company. days to determine if the bait is Woodstream Corp., 69 N. Locust Cleveland, OH. 1453 pp. Marsh, R.E. 1994. Roof rats. In: Hygnstrom et being taken. Rats may take a week St., Lititz, PA 17543-0327; 800/800-1819, 717/626-2125, Fax al., pp. B-125 to B-132. to begin consuming the bait. If after Meehan, A.P. 1984. Rats and Mice: Their Biology 717/626-1912; www.woodstream- a week none of the bait has been and Control. Rentokil, East Grinstead, West pro.com Sussex, United Kingdom. 383 pp. consumed, move the station to a Rat Zapper, Agrizap, www.agrizap.com Olkowski, W., S. Daar and H. Olkowski. 1991. new location. Vitamin D3 (Terad3®)—Bell Labs, see Common Sense Pest Control. Taunton Press, Once it is observed that the bait above Newtown, Connecticut. 715 pp. is being taken, the stations should Warfarin (0.025%)(Kaput® Blocks)— Scott, H.G. 1991. Design and construction: building out pests. In: Gorham, pp. 331-343. be left in place for a week or more Scimetrics, PO Box 1045, Wellington, CO 80549; 866/442- Simon, L. and W. Quarles. 2004. Integrated rat since the rats are now accustomed 3467, 970/482-1330, www.kaput- management. Common Sense Pest Control Quarterly 20(1):5-16. to them. Bait stations should be products.com Timm, R.M. 1994. Norway rats. In: Hygnstrom et checked and rebaited regularly— *A more complete list of products can al., pp. B-105 to B-120. rats seldom feed on bait that is be found in the IPM Practitioner’s Weber, W.J. 1982. Diseases Transmitted by Rats spoiled. The correct amount of bait 2012 Directory of Least-Toxic Pest and Mice. Thomson Publications, Fresno, should be used—too little can make Control Products, BIRC, PO Box California. 182 pp. 7414, Berkeley, CA 94707; Zinsser, H. 1935. Rats, Lice and History. Little, the rats bait-shy or be ineffective; www.birc.org Brown, and Company. 301 pp. however too much will cause rats to

Common Sense Pest Control XXVII(1-4) Special Issue 2011 14 Box 7414, Berkeley, CA 94707 15

Bio-Integral Resource Center (BIRC) is now on Facebook and Twitter For BIRC members and others who favor social media, BIRC is now on Facebook and Twitter. A convenient way to find us is to go to the BIRC website, www.birc.org. There are links there to Facebook and Twitter social media pages. We also estab- lished a crowdfunding appeal on CauseVox to help raise money for this issue of the Quarterly. BIRC thanks Maggie Ruffo of the Hungry Owl Project and Jennifer Bates of BIRC for donations toward production of this Quarterly. We also thank BIRC members who responded to our annual appeal. Our publications are dependent on donations and member support. Six Million Voters in California Want Genetically Engineered Food Labeled California voters in November had a chance to mandate labeling of genetically engineered food. A yes vote on Proposition 37 meant labeling would be required. An early vote count on November 9 showed the measure was defeated 4,326,770 (47%) yes and 4,884,961 (53%) no. A final tally on the California Secretary of State Website in Dear BIRC Members January 2013 that included absen- tee and provisional ballots showed Decreased income due to the 6,088,714 (48.6%) yes and recession has forced us to delay 6,442,371 (51.4%) no. publication dates, and to reduce The election was swayed by nega- the number of issues of the tive advertising funded by food and Quarterly that we produce each chemical corporations. Early polls year. This Special Issue of had Proposition 37 winning before Common Sense Pest Control the advertising barrage started. Quarterly will be the only Despite $46 million in negative Quarterly produced for 2011. advertising, the measure lost by only 353,657 votes. The $46 million in For the calendar year 2011, advertising represents almost $7 for Quarterly Members have also every no vote, and about $131 for received three Special Issues of each deciding vote. the IPM Practitioner—the Products The labeling measure generally Directory, Genetically Engineered won in most of the urban California Crops, and Honey Bee Death and counties, such as those in the San Decline. Francisco Bay Area and Los Angeles, and it generally lost in rural and We are slowly recovering from the agricultural counties. economic downturn. We appreci- The fight for Genetically Modified ate your support, and hope you Organism (GMO) labels is not over. will continue as BIRC members. The vote in California is a preview of a national effort. With nearly half of Thank you, voters politically committed to GMO William Quarles, Ph.D. labels, it is just a matter of time BIRC Executive Director until GMO labels are a reality.

Common Sense Pest Control XXVII(1-4) Special Issue 2011 15 Box 7414, Berkeley, CA 94707