J. Russell Mason

Effects of Predator Odors on Feeding in the Mountain Beaver ( Aplodontia rufa )

Consumption of food by Aplodontia rufa from bowls scented with control odors, secretion from anal glands of minks ( Mustela vison ) or urine from minks, bobcats ( Felis rufus ) and coyotes ( Canis latrans ) was studied. In two-choice control tests, subjects indiscriminately consumed apple from unscented bowls and from bowls scented with urine from an unfamiliar herbivore ( Cavia porcellus ), or with butyric acid. During two-choice tests offering apple from bowls scented with secretion from anal glands of minks and from bowls scented with butyric acid, significantly less apple was consumed from bowls containing mink scent. In two-choice tests in which apple was offered from bowls scented with urine from either mink, bobcat, coyote, or domestic dog, all predator urines reduced feeding. Habituation was studied by measuring consumption of dry pellets during continuous exposure to coyote urine for 5 days. Significantly less chow was consumed from bowls scented with coyote urine than from control bowls, indicating a lack of habituation to the predator scent. We conclude that predator scents act as natural repellents. The responsiveness to scents from several sympatric predators as well as from domestic dogs suggest an innate reaction to a signal, which is common to carnivores. The utility of predator scents in the control of browsing damage by mountain beavers should be explored.

Taxon-specific differences in responsiveness to capsaicin and several analogues: correlates between chemical structure and behavioral aversiveness

The present set of experiments was designed to explore avian insensitivity to capsaicin. Based upon a molecular model of avian chemosensory repellency, we hypothesized that structural modifications of the basic capsaicin molecule, which is itself not aversive to birds, might produce aversive analogues. To this end, European starlings (Sturnus vulgaris) and Norway rats (Rattus norvegicus) were given varied concentrations of synthetic capsaicin and four analogues (methyl capsaicin, veratryl amine, veratryl acetamide, vanillyl acetamide) in feeding and drinking tests. The results agreed with a model that we are developing to describe the chemical nature of avian repellents. Synthetic capsaicin and vanillyl acetamide were not repellent to birds, owing to the presence of an acidic phenolic OH group. Conversely, veratryl acetamide was aversive, due to the basic nature of this compound. For rats, repellent effectiveness among compounds was reversed: synthetic capsaicin was the best repellent while veratryl acetamide was the worst. We speculate that this taxonomic reversal may reflect basic differences in trigeminal chemoreception. In any case, it is clear that chemical correlates of mammalian repellents are opposite to those that predict avian repellency.

Tolerance of Bitter Compounds by an Herbivore, Cavia Porcellus

Many plant defensive chemicals are bitter to humans. Because of this taste characteristic, and because bitter compounds are often toxic, such substances, and the plants that contain them, are regarded as generally unpalatable to wildlife. These assumptions may be unwarranted. To test the hypothesis that herbivores are indifferent to ‘bitter’ tastants, we investigated the responsiveness of guinea pigs (Cavia porcellus) to denatonium benzoate, denatonium saccharide, limonene,l-phenylalanine, naringin, quebracho, quinine, Ro-Pel (a commercial animal repellent containing denatonium saccharide) and sucrose octaacetate. Only quinine and sucrose octaacetate slightly but significantly reduced feeding (P<0.05). Our findings are inconsistent with the notion that herbivores generally avoid what humans describe as bitter tastes.

AVOIDANCE OF BIRD REPELLENTS BY MICE (Mus musculus)

It is believed that mammalian chemosensory irritants are not aversive to birds and vice versa. Nevertheless, few avian repellents have been tested against mammals. For that reason, we evaluated the efficacy of 1.0% w/v methyl anthranilate, orthoaminoacetophenone, 2-amino-4′,5′-methoxyacetophenone, 2-methoxyacetophenone, and veratryl amine as mouse repellents in 3-hr no-choice drinking tests. Relative to ingestion of plain water, all test substances significantly reduced (P < 0.05) intake. Orthoaminoaceto-phenone was the most effective repellent, with intake reduced to levels statistically indistinguishable from zero.

Evaluation of neem as a bird repellent chemical

Abstract Neem extract (Azadirachta indica) is effective as an insect antifeedant, and limited evidence suggests that it may be useful as a repellent for birds. The present experiments were designed to test this proposition. In Experiment 1, European Starlings [Sturnus vulgaris) were presented with feed adulterated with a commercially available neem preparation (Nimin®). The results showed that the highest test concentration (1.5% m/m) was avoided. In Experiment 2, starlings were presented with an aqueous extract of neem leaves and serial dilutions of that extract. All extract concentrations were avoided relative to untreated water. We conclude that neem is an economical and biologically safe bird repellent and that it may be useful in developing nations where neem is indigenous or introduced, and when synthetic pesticides are difficult to obtain or expensive.

Potential repellents to prevent mountain beaver damage

Mountain beaver (Aplodontia rufa) damage to trees in the Pacific Northwest is economically serious. At present, few strategies are available to control damage, and new chemical repellents are being sought. Samples of two preferred plants, Douglas fir (Pseudotsuga menziesii) and salal (Galtheria shallon), were treated with mink urine, coyote urine, o-aminoacetophenone, or denatonium benzoate and presented to mountain beavers. All treatments reduced clipping (p < 0.05) of salal, but mink and coyote urines were most effective. Mink and coyote urines were the only treatments to significantly reduce clipping (p < 0.05) of Douglas fir.

Prediction of avian repellency from chemical structure: The aversiveness of vanillin, vanillyl alcohol, and veratryl alcohol

Abstract The effectiveness of bird repellents is associated with the presence of an electron-withdrawing group (carbonyl or carboxyl) and an electron-donating group in resonance on a phenyl ring. The present experiments were designed to examine the relative importance of these structural features. European starlings (Sturnus vulgaris) were presented with vanillin, vanillyl alcohol, and veratryl alcohol in two-cup and one-cup feeding trials and in one-bottle drinking tests. In feeding trials, veratryl alcohol was significantly more aversive than the other two chemicals. In drinking tests, veratryl alcohol was repellent only at the highest concentration (0.5% ml/ml), and was lethal at that concentration and at 0.1 and 0.05% ml/ml. Together, the findings have several implications. From a basic perspective, the data emphasize the importance of electron-donating groups on the phenyl ring of repellent chemicals. From the practical perspective, the data suggest veratryl alcohol as an avian toxicant, and warn against generalization from feeding to drinking tests. We propose that avian repellents must be tailored to the specialized settings in which they are used.

Role of avian trigeminal sensory system in detecting coniferyl benzoate, a plant allelochemical.

Coniferyl benzoate, a secondary metabolite found in quaking aspen (Populus tremuloides) and other plants, is an avian feeding deterrent of ecological and potential commercial importance. This study was conducted to determine if coniferyl benzoate is a trigeminal stimulant for birds and to ascertain if trigeminal chemoreception of coniferyl benzoate can mediate avian feeding behavior. Five European starlings (Sturnus vulgaris) with bilateral nerve cuts (ophthalmic branch of the trigeminal nerve) and four starlings that had sham surgeries were fed a commercial diet treated with coniferyl benzoate. Birds receiving bilateral nerve cuts ate significantly more feed than intact birds, indicating trigeminal detection of coniferyl benzoate and trigeminal mediation of feeding behavior. In the past, trigeminal chemoreception has not been recognized as important in the detection of plant secondary metabolites despite the irritant or astringent properties of a number of them.

Grazing repellency of methyl anthranilate to snow geese is enhanced by a visual cue

anthranilate formulations reduced goose activity. At 14 and 21 days post-treatment, however, dropping weights were significantly lower in plots treated with methyl anthranilate and Ti03 than in plots treated with formulated methyl anthranilate alone. These results show that visual cues can enhance the durability of methyl anthranilate repellency.

Effectiveness of odour repellents for protecting ornamental shrubs from browsing by white-tailed deer

Abstract Big Game Repellent (BGR), SeaCure (a sulfur-containing topical fertilizer), or 3-methyl-2-hexanoic acid (the principal odour in human sweat) were applied to yews (Taxus spp.), rhododendrons (Rhododendron spp.), or arborvitae (Thuja spp.), and the effectiveness of these treatments as white-tailed deer (Odocoileus virginianus) odour repellents was evaluated. In experiment 1, 16 residential sites were identified, and three plants at each site were selected for treatment. One plant at each site was covered with Deer-X netting, and another was sprayed with an agricultural spreader/sticker (0.14 ml l−1). The third plant at each site was treated with spreader/sticker and one of the repellents. At five sites, SeaCure was applied (8.0 ml l−1). At another six sites, 3-methyl-2-hexanoic acid was applied (0.42 ml l−1). At the remaining five sites, BGR was applied as an even coating (manufacturers instructions). At each site, plants were approximately 10 m apart. After 6 weeks, only plastic netting and BGR appeared to reduce browse damage. SeaCure and 3-methyl-2-hexanoic acid were ineffective. In experiment 2, ten of the original 16 residential sites were selected. SeaCure and 3-methyl-2-hexanoic acid were reapplied at ten times the concentration used in experiment 1, and damage was evaluated 3 weeks later: neither substance reduced damage. In experiment 3, plants at the remaining six sites were sprayed with BGR or spreader/sticker, or were netted. Plants were spaced ∼30 m apart, and damage was evaluated after 3 weeks. Neither BGR nor netting conferred significant protection.