Mammal repellents

Birds and squirrels at capsaicin-treated food. Top Bluejay (Cyanocitta cristata) feeds on capsaicin-treated birdseed, while gray squirrel (Sciurus cadrolinensis) simultansously feeds on untreated birdseed. Bottom Simultaneously, bluejay feeds on birdseed treated with capsaicin (a mammal repellent), and a gray squirrel feeds on birdseed treated with methyl anthrandate, a bird repellent... 

This real-world exercise tests the efficacy of a feeding repellent in free-ranging mammals. It constitutes the counterpart to the repellent effect of methyl anthranilate on feeding by birds (see Chap. 3). The experiment works at any place with wild squirrels and in any season. The many mammal repellents on the market are aimed against deer, predators such as raccoons, foxes and coyotes, and rodents such as voles, mice, squirrels, woodchucks, and others. Mammal repellents are known under names such as copper naphthenate, trimethacarb, zinc naphthenate, and ziram. 

The weevils do not linger to feed and breed in seed cones as they do in pollen cones, even though starch is plentiful here as well. This behavioral difference is not yet completely understood, but it seems that the cones of female plants contain an active poison called beta-(methylamino)alanine (BMAA). This substance is a recognized neurotoxin for mammals and is believed to affect insects as well. The male plants pollen cones also contain BMAA, but in a bound form that renders it harmless, allowing the weevils to nest and feed with impunity. In contrast, seed cones contain free toxic BMAA that presumably repels weevils and causes them to depart after quick examination and inadvertent pollination. 

A third ICIPE study focuses on identifying tsetse repellents. Field biologists recognized long ago that tsetse flies bite some wild animals but not others. We now know that flies shun such animals as waterbucks, elands, and zebras, because the odors of these mammals contain fly repellents. This discovery precipitated a search for odor components that deter tsetse and led eventually... 

Table 13.1 Structure-function relationships in repellents opposite effects on a bird and a mammal...

Table 13.2 Some factors that affect chemical repellent efficacy in mammals...

USEPA (2001) Selected Mammal and Bird Repellents 9,10-Anthraquinone (122701), 1-Butanethiol (1-Butylmercaptan) (125001), Fish Oil (122401), Meat Meal (100628), Methyl Anthranilate (128725), Red Pepper (Chile Pepper) (070703) Fact Sheet http //www.epa.gov/oppbppdl/ biopesticides/ingredients / factsheets / factsheeLmam -bird-repel.htm (last accessed 30 April 2010). 

We will examine whether the small mammals vulnerable to predation will avoid fresh predator odors in their home ranges. For this purpose we place in the woods live traps that are scented with odors from red fox and wolf. This experiment teaches not only basic ecology, but also the very practical skill how to test potential chemical repellents for rodent pests. 

Sullivan TP, Crump DR, Sullivan DS (1988) Use of predator odors as repellents to reduce feeding damage by herbivores. III. Montane and meadow voles Microtus montanus and Microtus penniy/vonicMi). JChem Ecol 14 363-377ResultsResponsesofSmaUMammalstoPredatorOdors in the Field4 Responses of Small Mammals to Predator Odors in the Field... 

The biological functions of such plant secondary metabolites (PSMs) have been debated for a long time. They often have antimicrobial functions, but also serve as repellents and feeding inhibitors against herbivorous insects and vertebrates, notably birds and mammals. Animals have evolved many mechanisms to cope with phenolics in their diet. These start with food processing. For instance, beavers consume experimental sticks of the phenolics-rich witch hazel only after leaving them in the water for 2-3 days, apparently to leach out unpalatable compounds (Miiller-Schwarze et al. 2001). Many birds and mammals eat clay to adsorb phenolics so they never will be absorbed in the intestines. If they are taken up in the blood stream, such PSMs will eventually be rendered harmless by oxidation and other processes, followed by conjugation, in the liver. They then will be excreted in the urine. 

The CBs used as pesticides are N-substituted esters of carbamic acid. CBs developed in the 1950s as insect repellents were found to have insecticidal activity, leading to the development of the napthyl CBs with high anti-ChE activity and selective toxicity against insects. One example is carbaryl it is widely used because of its low toxicity to mammals and its degradability. Aldicarb, a plant systemic, is more toxic than carbaryl. A few years ago aldicarb was associated with a July 4th holiday incident when West Coast residents complained of anticholinergic symptoms after eating aldicarb-contaminated watermelon. 

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