THE ECONOMIC IMPACT OF WILDLIFE DAMAGE ON HUDSON VALLEY ORCHARDS
The impact of wildlife damage on the profitability of apple farming in New York's Hudson Valley was determined by vise of a Standard Net Present Value (NPV) analysis as a means to measure long-term impact. Data were gathered through questionnaire and interview of a stratified random sample of 39 growers that represented 17% of the regional growers. Data concerning species causing damage, extent of wildlife damage and types of controls used were combined with current and long-range costs including revenue lost through damage and control costs. Limitations of the analysis are discussed along with results that indicate an annual equivalent cost flow for all wildlife damage between $3.8 and $3.85 million or $184 to $188 per acre. This study shows that a typical grower experienced combined revenue losses and control costs of $12,500 during 1986. Fifty-two percent of this was associated with wildlife controls, 40% with revenue losses and the remainder with tree replacement costs. Over a 25-year period beginning in 1985, the NEV of control costs and revenue losses is projected to total between $53 and $62 million depending upon whether a 3.5% or 5.0% discount rate is used. I/Research Associate, Dept. of Agricultural Economics, Cornell Univ. 2/Professor, Dept. of Pomology, Hudson Valley Lab., Cornell Univ. 3/ Associate Professor, Dept. of Agricultural Economics, Cornell Univ. 4/Associate Professor, Dept. of Natural Resources, and Leader, NY Cooperative Fish & Wildlife Research Unit, Cornell Univ. INTRODUCTION Wildlife damage a variety of crops produced in the United States such as grains, orchards, vegetables, and ornamentals (Byers, 1984: Caslick and Decker, 1977; Katsma and Rusch, 1979; Tobin, 1986; McDowell and Pillsbury, 1959). The extent of the damage varies by region due to differences in climate terrain, crops, and wildlife. Despite the implementation of numerous control strategies, wildlife continue to be a severe problem in some parts of the country. This is because wildlife are extremely adaptable and in some cases thrive in areas where man has significantly altered the original habitat. For example, deer populations in New York are much larger than in the past because of the creation of fields and meadows while orchards are an ideal habitat for voles (Sauer, 1984; Byers, 1984). Hudson Valley apple orchards are particulary susceptible to damage caused by pine and meadow voles, deer, woodchucks, and a variety of birds. The primary objective of this study was to estimate the impact of wildlife damage on the profitability of producing apples in four counties of the Hudson Valley, New York. These counties were: Ulster, Columbia, Dutchess, and Orange. The first objective is important for several reasons. First, apple production is an integral part of the agricultural sector of the region. In 1985, 234 farms produced apples which had a total gross revenue ranging between $35-$45 million. Second, most fruit growers obtain most of their revenue from the sale of apples since half of the regional fruit farm acreage in the Hudson Valley is planted with apple trees (New York Crop Reporting Service, 1986; see Table 1). This implies that if wildlife cause extensive
EECOLOGICAL CONSIDERATIONS IN THE MANAGEMENT OF WILDLIFE DAMAGE COLOGICAL
Strategies for managing wildlife damage may be divided into 3 broad categories: direct manipulation of populations, manipulation of behavioral or ecological traits of pest species, and manipulation of environmental features. For each of these categories, I review the importance of ecological considerations in determining the effectiveness of management strategies. Proper incorporation of ecological information is important to the success of management strategies in all 3 categories. I predict that future demands will increase for ecologically-based strategies that require minimal intervention, and for integration of management strategies that simultaneously address problems posed by both vertebrate and invertebrate pests. Several recent ecologically-based techniques are discussed, and pioneering efforts at comprehensive programs of integrated pest management are identified. Successful management of wildlife damage requires balancing ecological, sociological, and economic concerns. Attaining this balance in the future ultimately may depend upon our ability to develop new strategies of managing damage and to foster among the public an increased understanding of ecological processes pertaining to damage and its management. Ecological considerations are of paramount importance to the wildlife professional in formulating strategies for managing wildlife populations. In fact, wildlife management in its simplest form may be defined as the application of ecological knowledge to vertebrate populations. My objectives are to provide an overview of how ecological considerations presently are or could be incorporated into strategies for management of wildlife damage and to identify some ecologically-based strategies which may prove useful in the future. Effective strategies for reducing damage rely upon an understanding of the biological factors that lead to damage. Population size often is a principal determinant of the extent of damage. In addition, numerous behavioral and ecological attributes of individuals may influence the extent of damage, including foraging habits and food preferences, mobility, habitat requirements, and various aspects of behavior (Fig. 1). Three general approaches to managing damage can be identified within this framework. Damage may be reduced by: (1) direct manipulation of population levels; (2) indirectly, by manipulation of behavioral or autecological characteristics; or (3) indirectly, by manipulation of naturally occurring environmental features. I will summarize selected examples of these 3 approaches in the following sections. I am grateful to M. R. Conover and D. Williams for providing useful comments on a draft of the manuscript. This is Purdue University Agricultural Experiment Station Paper Number 13175. DIRECT MANIPULATION OF POPULATIONS The efficiency with which the abundance of a pest population can be reduced may be improved by basing management strategies on ecological and life history characteristics of the species. I use 2 examples to illustrate the potential impact of ecological factors on strategies designed to directly reduce population numbers. Fig. 1. Some key components contributing to the type and extent of damage caused by a wildlife population. Although not shown in the diagram, ecological and behavioral characteristics of individuals may be altered by changes in population size. Development and selection of effective rodenticides can be enhanced by considering several features associated with selection of food by voles. Like other rodents, voles presumably use sensory stimuli such as smell and taste to select their food, as well as associative learning (Garcia and Hankins 1975, Swihart 1990). Consequently, bait formulations that closely mimic a preferred taste presumably enhance the acceptability of a bait (Reidinger and Mason 1983). The degree to which 15 Pros. East. Wildl. Damage Control Conf. 5:15-23. 1992. Voles Voles (Microtus) cause extensive damage to apple trees in orchards of eastern North America (Anthony and Fisher 1977, Ferguson 1980), typically by gnawing phloem and cambium tissue of the main stem and large lateral roots. Gnawing often reduces tree vigor and yield, and increases mortality of affected trees (Sullivan et a1.1980, Richmond et a1.1987). Various toxic baits commonly are used to reduce vole populations in orchards, including acute toxicants such as zinc phosphide and multipledose toxicants such as chlorophacinone and diphacinone. 16 ECOLOGICAL CONSIDERATIONS • Swihart ingestion of a bait is associated with subsequent illness also can influence a compound's effectiveness. For instance, ingestion of a sublethal dose of zinc phosphide can result in subsequent bait shyness. And finally, many rodents are capable of generalizing learned aversions to similar-tasting foods (Nachman et a1.1977). Thus, in orchards where > 1 toxicant is applied, either baits with dissimilar taste features should be used, or in the case of sequential applications, a bait should be used that produces minimal bait shyness following consumption of a sublethal dose (Reidinger and Mason 1983). Interspecific differences in ecological and life history traits may also affect the success of a strategy for controlling voles. Forinstance,both meadow voles (Microtuspennsylvanicus) and pine voles (M. pinetorum) inhabit eastern orchards. However, life history traits differ markedly between the species: meadow voles produce larger litters (meadow vole X = 5.0, pine vole x = 2.2; Keller 1985), reproduce at an earlier age (Reich 1981, Schadler and Butterstein 1979), and have a shorter gestation period than pine voles (Kirkpatrick and Valentine 1970, Reich 1981). Reproductive rates of meadow voles apparently are not density dependent, whereas reproduction of young female pine voles is pheromonally suppressed by adult females (Anonymous 1985). Overall, then, meadow voles have a greater biotic potential than pine voles. Meadow voles also move over more extensive areas and occupy a wider variety Of habitats than pinr voles (Miller and Getz 1969, FitzGerald and Madison 1983, Getz 1985, Swihart et al. 1988). Pine voles are primarily fossorial, whereas meadow voles travel along surface runways (Wolff 1985). In addition, meadow voles expand their movements under snow cover (Madison and McShea 1987). Coupled with their high biotic potential, these traits suggest that meadow voles are capable of recolonizing and repopulating treated orchards more rapidly than pine voles. From these data we can infer that: (1) similar reductions in populations of pine and meadow voles will have a longer-lasting effect on the former, and (2), a single application of toxic bait in autumn will be less effective at reducing vole problems in orchards where meadow voles are abundant in adjacent habitats, unless these habitats also ace treated are hazardous to farm machinery, livestock, and laborers. Gas cartridges placed in burrows often are used to reduce woodchuck populations in problem areas (Phillips et al. 1987). The effectiveness of gas cartridges can be enhanced by taking into account several ecological and behavioral attributes of woodchucks. For instance, the temporal distribution of above ground activity of woodchucks is multimodal, with peaks in early morning, early-afternoon, and early-evening hours (Bronson 1962, Merriam 1966), although more lateevening activity (2100-2200 hr) than early-morning activity (0700-0800 hr) was noted by Merriam (1966). Clearly, selecting treatment periods when most woodchucks are below ground is advisable. Treatment of burrows during spring also can increase efficiency because burrows are not yet concealed by vegetation, and because juveniles have not yet dispersed from natal burrows. Size of burrows also may influence success of a fumigation program. Woodchuck burrows can differ dramatically in size and number of entrances (Henderson and Gilbert 1978), and woodchucks are less susceptible to fumigation when occupying larger burrow systems with multiple entrances (Dolbeer et al. 1991). Hence, > 1 cartridge may be required for successful fumig'atio'n of largeburrows. Finally, movements and habitat use of woodchucks may be influential in determining the long-term effectiveness of a management program relying primarily on gas cartridges. In addition to using burrows in cultivated fields, meadows, and orchards, woodchucks often use burrows in woods, along fencerows, and in other nonagricultural habitats adjacent to these sites (Grizzell 1955, Henderson and Gilbert 1978). For instance, females use burrows in woodland edges disproportionately often as natal sites, and adults continue to use these areas heavily after the breeding season (Swihart 1992). Typically, only 1 woodchuck occupies a burrow at any given time during the postbreeding season, but considerable time-sharing of over burrows occurs (swihart 1992) woodchucks also range fairly large areas that usually encompass several habitat types, and their ability to recolonize sites is quite good (Davis et al. 1964). Consequently, the effectiveness of a fumigation program is dependent upon treatmentofadjacentnonagriculturdl areas, monitoring of treated burrows, and the extent to which treated areas are embedded within a mosaic of untreated areas that serve as source populations from which recolonization can occur (de Vos and Merrill 1957, Davis et a1.1964, Byers 1980, Dolbeer et al. 1991). MANIPULATION OF BEHAVIORAL OR ECOLOGICAL CHARACTERISTICS Most damage problems are associated with wildlife feeding on domesticated plants or animals. Crops prone to damage typically are highly palatable, abundant, and easily accessible to wildlife. Nonetheless, wildlife species generally also feed upon a wide array of naturally occurring foods. Efficient foraging thus entails maximization of nutritional and/or caloric Y se s Differences in social structure and foraging behavior also can influence the effectiveness of a particular control strategy. Pi
Palaeocarpinus (Extinct Betulaceae) from Northwestern China: New Evidence for Paleocene Floristic Continuity between Asia, North America, and Europe
Spiny-bracted fruits of Palaeocarpinus Crane, a genus of Betulaceae previously known only from Europe and North America, have been discovered in the Paleocene of Altai, northwestern China. The fruits are found in association with abundant Corylus-like foliage and staminate catkins containing Corylus-like pollen. Because of problems distinguishing leaves of Corylus from those of extinct betulaceous genera, we place these leaves in the genus Corylites Gardner ex Seward & Holttum. The fruits, staminate catkins, pollen, and leaves from Altai were probably all produced by a single species. Palaeocarpinus orientalis is nearly identical in its morphology to Palaeocarpinus joffrensis from the Paleocene of North America except in the more rounded primary bracts of the associated staminate catkins. The species is less similar to Palaeocarpinus laciniata from the Paleocene of southern England.