Wildlife Damage Management, Internet Center for


Date of this Version

April 1991


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