Landscape Plants, Forest Trees, and Crops Most Resistant to Mammal Damage: an Overview

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln

Great Plains Wildlife Damage Control Workshop Wildlife Damage Management, Internet Center Proceedings for

April 1991

LANDSCAPE PLANTS, FOREST TREES, AND CROPS MOST RESISTANT TO MAMMAL DAMAGE: AN OVERVIEW

Rex E. Marsh University of California, Davis

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Marsh, Rex E., "LANDSCAPE PLANTS, FOREST TREES, AND CROPS MOST RESISTANT TO MAMMAL DAMAGE: AN OVERVIEW" (1991). Great Plains Wildlife Damage Control Workshop Proceedings. 34. https://digitalcommons.unl.edu/gpwdcwp/34

This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Great Plains Wildlife Damage Control Workshop Proceedings by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 122 LANDSCAPE PLANTS, FOREST TREES, AND CROPS MOST RESISTANT TO MAMMAL DAMAGE: AN OVERVIEW

REX E. MARSH, Department of Wildlife and Fisheries Biology, University of California, Davis, California 95616

Proceedings 10th Great Plains Wildlife Damage Conference (S.E. Hygnstrom, R.M. Case, and R.J. Johnson, eds.) Published at the University of Nebraska-Lincoln, 1991.

To capitalize on mammal-resistant A few examples are offered to illustrate plants, several approaches may be taken. the practical value of careful and deliberate The most common is to select crops not variety or cultivar selection. Where deer are highly prone to mammal damage (i.e., a serious problem, standard size apple trees resistant crops). If a generally susceptible suffer less damage than dwarf or semidwarf crop is to be grown, the more resistant apple trees because a greater proportion of varieties or cultivars of that crop can be the flowering buds are above the deer's selected, if known. An approach that has reach (Moen 1983). The same, of course, is not received the attention it warrants is the true of other kinds of dwarf fruit trees. selection of parent stock with resistant Clements (1980) pointed out that with sugar- characteristics and the selective breeding of cane cultivars the persistence of the leaves useful species to develop strains, hybrids, or including sheaths influences the amount of cultivars with improved mammal resistance. rat {Rattus spp.) damage suffered. The "self- For several reasons, this latter approach stripping" type canes, such as "H37-1933," shows the most promise for forest tree are much more susceptible to rat damage species. than the so-called "trashy" canes. Russian comfrey (Symphytwn sp.) has been used in It has long been known that most England and elsewhere in Europe for stock mammal pest species, herbivorous or feed and as compost for small farms and omnivorous, have a preference for feeding gardens. Unlike alfalfa, comfrey is not on some plants or crops and not others. damaged by rabbits and some bird species Food preferences consist of gradient values because of the bristles on the plant (Hills and relate to a variety of factors, some 1954). innate and others learned. It has also been observed that certain varieties or cultivars of While many farmers know from normally susceptible crops are fed upon to experience that pest mammals cause damage different degrees. For example, 2 or 3 to specific crops, unfortunately very little has cultivars of the same crop grown in the same been published on which varieties, strains or field may differ dramatically in severity of cultivars should be selected to avoid the damage by deer (Odocoileus spp.) or rabbits more serious mammal damage problems. (Lepus spp. and Sylvilagus spp.). All other factors being equal, a grower would select Those researching bird depredation those cultivars least likely to sustain losses. problems on agricultural crops have made significant strides in selecting or developing

For more information visit http://wildlifedamage.unl.edu 123 bird-resistant hybrids and cultivars of Where deer are a problem, and no sorghum, sunflower, and corn (Parfitt and deer-proof fence exists, artichokes, tomatoes, Fox 1986, Dolbeer and Woronecki 1988). squash, rhubarb, or chives may be planted to Much is known of the plant chemistry and help buffer the rest of a backyard garden. the morphological characteristics of those English and black walnuts, figs, crop cultivars that are most or least pomegranates, persimmons, olives, date susceptible to bird damage (Weatherhead palms, and prickly pears are also relatively and Tinker 1983, Bullard et al. 1989). unpalatable to deer. Some of the most Research on the selection and development common deer-susceptible fruit and nut trees of plants more resistant to mammal damage are apples, apricots, plums, prunes, cherries, significantly lags behind that directed toward peaches, oranges, almonds, and grapes. resolving bird problems. However, there is Beans, peas, carrots, and strawberries rank some renewed interest in mammal-resistant especially high in deer preferences. A deer- tree species for forest regeneration. With the proof fence may be needed to profitably emphasis on reforestation, Hansson (1988) grow these in some areas of high deer presented a review of some of the research populations. in the natural resistance of plants to pest rodents and an insight into some of the Pocket Gophers mechanisms by which they work. Gardeners have identified a few SELECTING CROPS, CULTIVARS, ornamentals, such as marigolds, narcissus, AND ORNAMENTAL and daffodils, that are not fed upon by PLANTS LESS DAMAGE PRONE pocket gophers.

Deer According to some authorities, alfalfa cultivars with creeping or several large roots Through trial and error, and are less easily damaged by pocket gophers accompanied by some research, it has been (Thomomys spp. and Geomys spp.) than possible to rank ornamental plants for alfalfa plants with single taproots (Melton et landscape purposes that are relatively al. 1988). Less susceptible alfalfa varieties resistant to specific mammal damage in a such as Rambler, Teton, and Travois were particular area. Several such lists have been specifically mentioned with reference to developed and contain some useful Nebraska (Case and Stubbendieck 1976). selections. The most notable is the list of More recent studies in Nebraska indicate that mule deer (Odocoileus hemionus) resistant Spredor 2 may be more resistant to gophers plants, primarily ornamentals, principally than the Wrangler (Jasch, pers. commun.). used in California (Cummings et al. 1980). Several other lists of deer-resistant Rats ornamental plants in the West have also been published (Cummings et al. 1963, To avoid roof rats (Rattus rattus) in Anon. 1966, Hogan 1988). In a Connecticut landscaped areas, lists of plants that are not study, Conover and Kania (1988) identified good harborage for roof rats in California and ranked a wide range of ornamental plant have been developed (Santa Clara County species as to their susceptibility to white- Health Department, n.d.; Anonymous 1978) tailed deer (O. virginianus) browsing. Those along with a list of plants highly favored by species with little or no deer damage are rats and which often harbors them (Table 2). provided in Table 1.

For more information visit http://wildlifedamage.unl.edu 124 Table 1. Ornamentals found to be browsed Table 2. Ornamentals found to harbor roof little or not at all by white-tailed deer rats (Rattus rattus). This list was developed (Odocoileus virginianus) in a landscape by the Santa Clara County Health nursery study conducted in Connecticut. Department, California. These should be This list is after Conover and Kania (1988). avoided where roof rats are a potential problem.

COMMON NAME SCIENTIFIC NAME COMMON NAME SCIENTIFIC NAME

American dogwood Cornus sericea American holly Ilex opaca Algerian ivy Hedera canariensis Bridal-wreath Spiraea spp. Arborvitae Platycladus Chinese holly Ilex cornuta orientalis spp. Colorado blue spruce Picea pungens Bamboo Bambusa spp. Common boxwood Buxus sempervirens Date palm Phoenix dactylifera Common lilac Syringa vulgaris Hall's honeysuckle Lonicera japonica Doghobble Leucothoe halliana fontanesiana Himalayan blackberry Rubus procerus Douglas fir Pseudotsuga menziesii Italian cypress Cupressus Evergreen hybrid sempervirens rhododendron Rhododendron spp. Lombardy poplar Populus nigra italica Flowering dogwood Cornus florida Pampas grass Cortaderia selloana Fraser fir Abies fraseri Star jasmine Trachelospermum Golden-bells Forsythia spp. jasminoides Japanese cedar Cryptomeria japonica Tamarix juniper Juniperus sabina Kousa dogwood Cornus kousa tamariscifolia Lily-of-the-valley Variegated Algerian Hedera canariensis bush Pieris japonica ivy variegata Magnolia Magnolia spp. Mountain laurel Kalmia latifolia Mountain pine Pinus mugo As mentioned earlier, certain varieties of Norway spruce Picea abies sugarcane are more susceptible to rat Pear Pyrus communis damage. Varietal characteristics of rat- Rose-of-Sharon Hibiscus syriacus resistant sugarcane are thick-barreled, Scotch pine Pinus sylvestris moderate-to-hard-rinded, grow erect, and are Shadbush Amelanchier spp. not prone to lodging (Barnes 1974, King et Snowball viburnum Viburnum tomentosum al. 1965). In Taiwan the variety POJ2725, Weeping birch Betula pendula which is soft-rinded with inclined stems, White pine Pinus strobus suffers greater rat damage than POJ2878, White spruce Picea glauca which is hard-rinded with more upright growth (Blackburn 1984).

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Rabbits and Hares were found less acceptable to rodents than those of western hemlock and Douglas-fir Sheail (1971), a British author, provided (Moore 1940). For some regions such a relatively short list of ornamentals resistant information is useful where natural or to feeding by the European rabbit artificial seeding is relied upon as a (Oryctolagus cuniculus). How pertinent that reforestation strategy. list would be for our rabbit species is unknown. Unfortunately, these lists are not Tree Squirrels as comprehensive as landscape designers would like, but nevertheless they are highly A study of bark-stripping damage valuable and provide a basis for further work conducted in England showed that the and list expansion. introduced gray squirrel (Sciurus Carolinensis) had a definite preference for The browse preferences of white-tailed beech, oak, and western hemlock of the jackrabbits (Lepus townsendii) and eastern major species, and sycamore and sweet cottontails (Sylvilagus floridanus) for some chestnut of the minor species (Rowe and species commonly used in shelterbelt Gill 1985). The conifers were generally plantings in Minnesota and elsewhere in the avoided. Such information is of value in midwest were studied by Swihart and establishing new woodlots and in Yahner (1983). The genera which include reforestation practices. A study by Williams black locust (Robinia), Russian-olive and Van Sambeek (1984) demonstrated that (Elaeagnus), spruce (Picea) and northern both gray and fox squirrels (S. niger) had a white-cedar (Thuja) were among the least preference for black walnuts (Juglans nigra) preferred by eastern cottontails. White-tailed from certain trees or families of trees. They jackrabbits had a low preference for concluded that the possibility exists for Austrian, Scotch, and pitch pines (Pinus breeding walnuts from squirrel-resistant seed spp.). Pear, cotoneaster, and buffaloberry sources for direct seeding. were much preferred by both jackrabbits and cottontails, but pine and honeysuckle RESISTANCE AND MECHANISMS (Lonicera) were resistant to both (Swihart OF RESISTANCE and Yahner 1983). Some 30 shelterbelt species in all were ranked for cottontails and Certain plants may be rejected because 13 genera for white-tailed jackrabbits as to of their spines, thorns, or prickly leaf their preferred and least-preferred species. structure. Plant-produced secondary These provide a basis for avoiding serious chemical compounds may be taste repellents, rabbit problems in shelterbelts by planting toxic to various degrees, cause postingestinal the least-susceptible species. stress, or interfere with the digestive process. Considerable information has been published Seed-eating Rodents on secondary compounds and their effects on mammals and for the sake of brevity will In reforestation efforts in the west, it not be reviewed here. Secondary has been found that white fir seed was less compounds are thought to provide much preferred by seed-eating rodents, such as greater protection to the plants than would deer mice (Peromyscus maniculatus) than simple food preferences (based on subtle that of Douglas-fir (Krauch 1945). Seeds of taste differences), low palatability or Port-Orford-cedar, the true firs, and red alder digestibility, or low nutrient values. Mammals that are stressed for food due to

For more information visit http://wildlifedamage.unl.edu 126 shortages often feed on plants not normally feed on different plants or parts of plants at highly preferred or that are low in needed different times. nutrients. Mammal resistance, like insect resistance in plants, may be based on 1 or a Certain learned behavioral traits of the combination of several factors or mammal species may make it more difficult mechanisms. to resolve some pest problems. A case in point are deer that for years have been Resistance is frequently not an all-or- coming from their natural habitat to feed on none rating. Hence, the term "resistant" a particular irrigated alfalfa field. They may must be interpreted relatively loosely continue that feeding pattern if the alfalfa is because, as stated previously, a pest species removed and planted with another crop not severely pressed for food may feed upon usually damaged by deer. In this instance, plants which it normally would not touch the deer have habituated to the feeding site and which may be detrimental to its health, and it may take some time to abandon the especially if consumed over a long period. area and find a new feeding ground. Unlike Resistance per se is often dependent on pest birds, which may immediately move whether or not other more preferred alternate substantial distances for more preferred foods are available. For example, certain foods, troublesome mammals are relatively varieties of strawberries are preferred by sedentary once their home ranges have been deer over others when planted in the same established. field. However, if the preferred cultivars are eliminated and only the least preferred Introduced (non-native) plants, which planted, severe damage may still occur if all include a good many of our ornamentals and strawberry cultivars are more preferred than most of the crops we grow, are often subject any other plants (natural or cultivated) in the to greater mammal damage than native immediate area. A farmer who selects a species, presumably because they did not more damage-resistant cultivar of a crop evolve together. Many crops could not be may benefit; however, if all the farmers in profitably grown if surrounded by expansive the area do the same, it is very possible that areas of natural habitat that supported no one will gain, and the economic losses moderate-to-large populations of native overall will remain about the same. mammals. Most of our crops lack defensive Alternative food availability, in amount and chemicals (i.e., secondary compounds), variety, as well as preferences, play which is why they are palatable and highly interrelated roles in animal damage problems preferred by humans and domestic animals. and represent a basic principle that must be Because crops are selected for their edible considered with the use of more resistant value, and since crop-breeding efforts are crops or plants. Alternative food availability generally directed towards improving these and associated preferences of plants vary qualities, it is unlikely that much selective with season, growth phase, and climate and crop breeding can be conducted to make generally do not remain static. For example, crops less palatable to pest mammals without young succulent new growth of conifers or affecting their value as crops. Possible other trees may be browsed by deer, but exceptions are those crops from which we when that growth hardens, damage ceases. eat or utilize only the fruit or seed and the Likewise, the nutritional needs of the pest pest mammals cause their damage by eating species may change over the year with the only the vegetative parts of the plants. sex, age, reproductive status, and other factors influencing diets, causing them to

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Crop Abandonment an area would probably have significant economic ramifications and bring about When vertebrate pest problems are severe regional economic hardship. Yet in exceptionally severe with no practical or the long run changing crop phenology is a economical solution, the crop may have to sound ecological approach to avoiding be abandoned in favor of another which does agricultural problems with mammal and not suffer to the same extent. As an avian pests. Planting less-susceptible crops example, in some South Pacific islands in a major way, however, is not apt to come sweet potatoes cannot be grown because the about voluntarily or without strong economic damage by rats (Rattus spp.) is so severe and incentives. extensive that few potatoes are left to be harvested (Howard, pers. commun.). Pocket RESEARCH PROGRESS IN gophers (Thomomys spp.) or jackrabbits SELECTIVE PROPAGATION AND (Lepus spp.) in some local areas of the BREEDING western United States are so numerous that alfalfa cannot be profitably grown in spite of Research progress to date on the control efforts. selection and development of mammal- resistant plants has been focused for the The abandonment of certain or all crops most part on forest trees. Though not does not occur often in countries with highly extensive, it is important because it provides developed agriculture except possibly for optimism to stimulate continued efforts. land being cultivated and cropped for the Research has resulted in several significant first time. For most agricultural regions, this advances that are important to vertebrate has been sorted out long ago, and only crops pest management, and they illustrate that can be grown economically have potentially useful principles and concepts evolved as mainstay agriculture. In which have long been used in pest insect and developing countries where agriculture is on plant disease management. the increase and new land is constantly coming under cultivation, the problem of Foresters have long noted that mammal damage influencing the crops that individual tree seedlings within the same can be grown is most significant (e.g., species may be fed upon or rejected by deer, elephants in Africa). It is not unlike the hares, voles, tree squirrels, or pocket experience of our early forefathers in this gophers, which suggests that genetic make- country. Giving up certain crops prone to up and variability undoubtedly contribute to extensive mammal damage was very these differences. In this country, research prevalent during the time of the early along these lines has periodically received pioneers because there were few methods some significant attention, but progress on available for animal damage control. the development of resistant strains of trees for solving mammal damage problems in Referring to growing pest bird problems reforestation remains limited for a multitude in North America and Africa, Dyer and of reasons (Dimock 1974). In agriculture, a Ward (1977) stated: "... damage avoidance vole-resistant apple variety, "Novole," has by crop substitution or changes in crop resulted from relatively recent research, and phenology ought to be contemplated." The this represents a significant step. same statement applies to pest mammal problems. At least in North America, While genetic manipulation is a significant changes in major crops grown in potentially effective way of increasing

For more information visit http://wildlifedamage.unl.edu 128 mammal resistance in certain forest tree research, the "Novole" crab apple emerged, species and possibly in some ornamental which is highly resistant to the gnawing of plants, this approach has less merit for many the pine vole (M. pinetorum) and meadow agricultural crops. Making certain crops vole (M. pennsylvanicus) (Cummins et al. unpalatable to mammals would run the risk 1983, Cummins and Byers 1984). of reducing their value as food items for humans or domestic animals. The Novole has also been used as rootstock for Mclntosh and Northern Spy Foresters and forestry researchers have varieties. The Cornell Research Foundation spent and continue to spend more time and holds the patent and has licensing effort researching the development of agreements with nurseries for its mammal-resistant trees than has the propagation and distribution. agricultural industry in developing cultivars less prone to mammal damage. Presently There appears to be no published because of the seriousness of some of their information of Novole being tested or problems, the Scandinavian countries seem planted in the west, either as a crab apple to be doing the most in this area (Hansson variety or rootstock for other varieties. 1988, Rousi 1988, Rousi 1990), but others However, there is preliminary evidence from are also active. the state of Washington which suggests that the rootstock may not solve its vole problem Voles (Askham pers. commun.). No known comparable research is under way in the Various species of voles (Microtus spp.) northwest apple-growing region. cause extensive and serious damage by girdling the roots or crown bark of Relevant to forestry, research being deciduous orchard trees, particularly apple conducted in Finland appears promising for orchards that are maintained with permanent breeding birch (Betula spp.) for resistance vegetative ground cover. The discovery of against voles, mainly Microtus agrestis apple rootstocks apparently resistant to pine (Rousi 1988, 1990; Rousi et al. 1988). vole damage has led apple tree breeders in Other interesting results with regard to voles the east to add this line of resistance to their come from Canada, where it was determined list of disease and production characteristic that the phenol compounds of coniferous objectives. For the last 10 years or so, trees play a significant role in deterring considerable efforts in New York and meadow voles (M. pennsylvanicus) from Virginia have been directed towards debarking, which suggests that some determining which apple varieties were most selective breeding may be rewarding in susceptible or resistant to vole damage. preventing vole depredation (Roy and Byers and Cummins (1977) published their Bergeron 1990). research findings on variation in susceptibility of apple stems to attack by Pocket Gophers pine voles, and the influence of texture and taste on gnawing by the same species was Foresters in Oregon observed the studied by Geyer and Cummins (1980). In ponderosa pines appeared more heavily other studies, series of apple clones were damaged by pocket gophers than Jeffrey or also evaluated for susceptibility to Microtus lodgepole pines. This led to a study by (Pearson et al. 1980, Wysolmerski et al. Crouch (1971) who found in his field 1980). As a direct result of this and other experiment that all 3 species were severely

For more information visit http://wildlifedamage.unl.edu 129 and equally damaged. This points out that Douglas-fir suggests that resistance based on much is yet to be learned regarding the nonpreference is strongly inherited and susceptibility of 1 species over another and chiefly additive. This was further supported the various contributing factors. by Silen et al. (1986) in their measurement of genetic parameters of Douglas-fir relative The feeding preferences of pocket to deer damage. gophers for ponderosa pine strains was the subject of a masters thesis (Cummins 1975). Various chemical components (e.g., In another study of ponderosa pine, essential phenols, terpenes, resins, essential oils) of oils and their terpenoid components were forest tree species have been studied to evaluated to determine if these secondary determine the relationship between plant chemicals were implicated in the secondary compounds and resistance to susceptibility or rejection by pocket gophers animal damage with both positive and of individual plants of this species (Radwan negative results (Oh et al. 1967, Radwan and et al. 1982). In this study gophers dis- Ellis 1975, Tucker et al. 1976, Radwan criminated among pine seedlings grown from 1978, Radwan and Crouch 1978, Connolly et seed collected from different sources (states) al. 1980, Radwan et al. 1982, Welch et al. with damage rated from 0 to 31%. How- 1983, Rousi and Haggman 1984, ever, the authors reported no apparent Tahvanainen et al. 1985, Hansson et al. morphological or measurable chemical 1986, Roy and Bergeron 1990). Much has differences among the sources to explain the been learned from these studies although feeding variability. many questions remain.

Tree Squirrels It's worth mentioning that pine oil is now being seriously evaluated as a repellent In Taiwan studies have determined that for deer, voles, and hare. Its repellent action the higher resin content of the bark of the is thought to be based on interference in the Chinese fir (Cunninghamia lanceolata), the food digestive process (Bell and Harestand greater the rejection by the red-bellied tree 1987). This coincides and is consistent with squirrel (Calloscirus erythaeus) (Hwang et the research previously cited by Oh et al. al. 1985). They conclude from this that the (1967), Radwan (1978), Connolly et al. breeding of squirrel-resistant strains of (1980) and others. Chinese fir is possible. SUMMARY Deer, Rabbits, and Hares The selection of crops and cultivars or Research on genetic resistance of plants less prone to mammal damage is a Douglas-fir genotypes to snowshoe hare potentially effective management option. (Lepus americanus) and black-tailed deer has But in reality, with a few exceptions, its also received some attention (Radwan 1972, practice is currently limited because other Dimock et al. 1976). In other studies it was factors are often much more compelling in shown that progeny seedlings of ponderosa making crop cultivar and ornamental plant pine from different geographic sources selections. This appears to be changing with significantly influenced browsing by black- greater restrictions being placed on the tailed jackrabbits (Read 1971). Dimock et population reduction of various pest species, al. (1976) concluded that genetic analysis in especially more limited use of pesticides. Organic and sustainable agricultural

For more information visit http://wildlifedamage.unl.edu 130 objectives are also very instrumental in Anonymous. 1978. Roof rats in changing pest management practices. suburbia—what to do? Sunset, September 1987. pp. 218-219. The selection of more naturally resistant Barnes, A. C. 1974. The sugar genotypes or selective breeding of forest tree cane.Leonard Hill Books, London. 572 species in a deliberate attempt to increase pp. their resistance to mammal damage has Bell, C. M., and A. S. Harestead. 1987. received attention over the last two decades Efficacy of pine oil as repellent to and continues to receive some serious wildlife. J. Chem. Ecol. 13:1409-1417. attention by researchers, but the progress to Blackburn, F. 1984. Sugar-cane. date in this country provides very little that Longman, London. 414 pp. is useful at this time to foresters. Several of Bullard, R. W., P. P. Woronecki, R. A. the Scandinavian countries are currently Dolbeer, and J. R. Mason. 1989. energetically researching this area relative to Biochemical and morphological reforestation. characteristics in maturing achenes from purple-hulled and oilseed sunflower New and changing concepts relevant to cultivars. J. Agric. Food Chem. 37:886- natural plant defenses (i.e., secondary 890. compounds), in-depth studies of the chemical Byers, R. E., and J. N. Cummings. 1977. components of plants, the effects of plant Variations in susceptibility of apple stems chemistry on animal feeding behavior, and to attack by pine voles. J. Amer. Soc. the potential of genetic engineering on crop Hort. Sci. 1092:201-203. protection all contribute to a potentially Case, R. M., and J. L. Stubbendieck. 1976. brighter outlook for an increase in useful Plains pocket gophers and their control. vertebrate-resistant plants for the future. Univ. Nebraska-Lincoln, Coop. Exten. Serv. NebGuide G76-319. 4 pp. Acknowledgements: Funding for assembling Clements, H. F. 1980. Sugarcane crop this review was provided by the University logging and crop control. Univ. Press of of California Sustainable Agriculture Hawaii, Honolulu. 520 pp. Research and Education Program. This Connolly, G. E., B. O. Ellison, J. W. paper represents part of a larger project Fleming, S. Geng, R. E. Kepner, W. M. entitled "The evaluation of nonpesticide Longhurst, J. H. Oh, and G. F. Russel. methods for vertebrate pest control relevant 1980. Deer browsing of Douglas-fir trees to sustainable agriculture." Some support in relation to volatile terpene composition also came from the University of California and in vitro fermentability. Forest Sci. Statewide Integrated Pest Management 26:179-193. Project. Thanks goes to Dorothy E. Beadle Conover, M. R., and G. S. Kania. 1988. for her editorial assistance. Browsing preference of white-tailed deer for different ornamental species. Wildl. LITERATURE CITED Soc. Bull. 16:175-179. Crouch, G. L. 1971. Susceptibility of Anonymous. 1966. If the deer are ponderosa, Jeffrey, and lodgepole pines to breakfasting on your favorite garden pocket gophers. Northwest Sci. 45:252- plants. Sunset, September 1966. pp. 74- 256. 77. Cummings, M. W., M. H. Kimball, and W. M. Longhurst. 1963. Deer-resistant plants for ornamental use. Univ. Calif. Div. Agric. Sci. Leaflet 167. 8 pp. For more information visit http://wildlifedamage.unl.edu 131

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