Utah State University From the SelectedWorks of Robert H. Schmidt January 1, 1992 The Lagomorphs: rabbits, hares, and pika G. A. Guisti Robert H. Schmidt, Utah State University R. M. Timm J. E. Borrecco T. P. Sullivan Available at: https://works.bepress.com/robert_schmidt/ 194/ SECTION FOUR SILVICULTURAL METHODS IN RELATION TO SELECTED WILDLIFE SPECIES Chapter 14 The Lagomorphs: rabbits, hares, and pika GREGORY A. GlUSTI ROBERT H. SCHMIDT, ROBERT M. TIMM, JOHN E. BORRECCO, AND THOMAS P. SULLIVAN Abstract Rabbits, hares, and pika have all been implicated in causing damage to trees in the Pacific Northwest Damage is generally to seedlings, limbs, and saplings smaller than 2 5 inches in diameter, with damage involving either clipping of the stem or bark removal as the lagomorphs are feeding Damage prevention methods include syn- thetic or biological repellents, exclusion (individual seedling protectors or fencing), or lethal control methods such as poisoning or shooting Silvicultural methods useful in reducing lagomorph damage include vegetation management, thinning, fertilization, and selection of browsing-resistant seedling sizes Keywords Lagomorpha, Sylvilagus, Lepus, Ocotona, Brachylagus, rabbits, hares, pikas, snowshoe hares, silviculture, forestry, animal damage control, vertebrate pest control GREGORY A GIUSTI is wildlands ecology advisor, University of California, Cooperative Extension, Agricultural Center, Ukiah, CA 95482 ROBERT H SCHMIDT was wildlife and natural resource specialist, Department of Forestry and Resource Management, University of California, Berkeley, CA 94720 and currently is assistant professor, Department of Fisheries and Wildlite, Utah State University, Logan, UT 84322-5210 ROBERT M TIMM is superintendent and wildlife specialist, University of California, Hopland Field Station, 4070 University Road, Hopland, CA 95449 JOHN E BORRECCO is regional pesticide-use specialist, U S Department of Agriculture, Forest Service, 630 Sansome Street, San Francisco, CA 94111 THOMAS P SULLIVAN is assistant professor, Department of Forest Sciences, Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1 W5 289 Introduction Lagomorphs (rabbits, hares, and pikas) occur throughout the world. They are an integral part of the biotic landscape on many continents both as major consumers of vegetation and as food for carnivorous mammals, birds, and reptiles. In the Pacific Northwest, lagomorphs, especially snowshoe hares, cause damage to both managed and unmanaged forest stands (Lawrence and others 1961). This chapter outlines basic differences between rabbits and hares, their behaviors, habitat needs, breeding biology, and damage factors. The chapter also reviews methods of animal damage management that reduce lagomorph damage, and it describes silvicultural alterna- tives to help forest managers decide which option would most effectively prevent or reduce damage in a given situation. The discussion concentrates on rabbits, hares, and pikas distributed in northern California, Oregon, Washington, southern British Columbia, Idaho, and western Montana, and it focuses on the timber-producing areas of each state. Some lago- morph species included in this chapter occur both in forested and nonforested habitats Timber species may vary greatly over such a large geographic region, but feeding damage and management strategies for rabbits may be similar to those for hares. Taxonomy and The taxonomic order Lagomorpha includes all rabbits, hares, and pika The genus Description Sylvilagus includes the true rabbits, Lepus includes hares, and Ocotona includes the pika. In all lagomorphs, a small "pegged" tooth is located directly behind each top incisor tooth. This characteristic separates members of the lagomorph order from the order Rodentia. As in rodents, the incisors of lagomorphs grow constantly. Lago- morphs lack canine teeth, and a long gap or diastema occurs between the incisors and the molars Rabbits, technically, can be distinguished from hares by the presence of a distinct and unfused interpanetal bone in the skull (Hall 1981). Maxillary bones, both for rabbits and hares, are highly fenestrated (containing a lattice network of porous bony tissue). True rabbits, or cottontails, are separated into eight species (Chapman and others 1982, Chapman and Flux 1990). They include the eastern, desert, brush, Nuttall's, swamp , marsh, New England, and pygmy rabbits. Cottontails are widely distributed throughout the United States and Canada. Within the Pacific Northwest, there are four major species: the eastern, Nuttall's, brush, and pygmy rabbits (fig. 1). In addi- tion, the range of the desert cottontail extends into northern California, where it may occasionally cause problems There are eight species of hares within the United States and Canada (Dunn and others 1982, Bittner and Rongstad 1982). They are the black-tailed jackrabbit, the white-tailed jackrabbit, the antelope jackrabbit, the white-sided jackrabbit, the Alaskan hare, the arctic hare, the snowshoe hare and the (introduced) European hare. Within the Pacific Northwest, there are only three hares the black-tailed jackrabbit, the white-tailed jackrabbit, and the snowshoe hare Some geographic overlap occurs (fig. 2), but each species of hare usually is found within its own ecological niche, thus simplifying species identification. 290 The third member of this order is the pika. There is only one species of concern in the Pacific Northwest (Hall 1981). Pikas are widely distributed (fig. 2), but stringent habitat requirements keep their presence rather localized. This species therefore receives only a cursory examination in this chapter. Rabbits all share some basic biological traits. They are relatively small animals, ranging from about 10 inches in length (pygmy rabbit) to about 18 inches (eastern cottontail; Hall 1981). All are drab in color, varying from shades of black to rusty brown. They all have relatively large ears and large rear feet. Female rabbits and hares tend to be larger than males. Hares share some characteristics with rabbits. They have large ears and large feet (the hind foot is usually larger than 4.2 inches long for adult hares; Hall 1981). Hares, however, generally are much larger than rabbits and range in size from 5J5 to 7.5 pounds and from 14.5 to 25 inches in length. Color patterns differ greatly among this group The black-tailed jackrabbitjis gray to blackish in color with black-tipped ears and a black streak on the top of the tail. The white-tailed jackrabbit and the snowshoe hare both can change from a br'own or gray summer pelage to a winter coat of white. It is during the winter when confusion can occur with species identification. The white-tailed jackrabbit has a tail that is nearly always white above and below, and the white winter pelage is made up of completely white hairs. The white winter pelage of the snowshoe hare is made up ofjdarker hairs with white tips. In the southern parts of its range, the snowshoe hare does not lose its summer coloring during the winter molt (Flux and Angermann 1990) Pikas, sometimes known as conys, are small, rat-sized lagomorphs, generally between 4 to 6 ounces in weight and 6 to 8 5 inches in length (Burt and Grossenheider 1964). They are grayish to brownish with no visible tail, and have been described as "round-eared rabbits" Small piles of fresh grass or forbs in rockslides is a good indicator of the presence of these animals (Smith and others 1990). Reference guides should be consulted for specific identification of any of these species. The mammal identification guide authored by Burt and Grossenheider (1964) should prove sufficient, although regional guides also exist Reproduction The reproductive season for rabbits is influenced by day length, geographic latitude, ambient temperatures, and other environmental variables As day length increases, a reproductive hormone, (follicle-stimulating hormone) is released (Chapman and others 1982). Female rabbits then come into estrus (heat) and maintain this state until copulation. Ovulation follows copulation, usually within 10 hours. This physiological process is termed induced ovulation, because copulation is required before ovulation occurs. Without copulation, a female may remain in a preestrus condition for long periods of time. There is considerable latitude, therefore, in the timing of the breeding period. Cottontails breed in a synchronous fashion. If a sexually active male is present, the copulation immediately follows parturition (birth). Female rabbits often are pregnant while nursing a litter in the nest. Breeding can occur the first spring after birth, and juvenile rabbits, therefore,are usually sexually mature between 6 and 9 months of age (Chapman and others 1982) 293 Gestation periods are consistent among all rabbit species in the Pacific Northwest and average about 27 to 28 days in length. The breeding season can begin as early as December (California) or February (Oregon) and last until August, depending upon the species, location, and food supply (Mossman 1955, Chapman and Harman 1972, Chapman and others 1982). Litter size differs among rabbit species and generally exhibits an inverse relation with latitude. Mean litter sizes generally range between 3 to 5 young per litter (Chapman and others 1982). Because of the rabbits' ability to breed in a synchronous manner, however, 1 female can produce several young over the course of one breeding season Eastern cottontails reportedly produce as many as 39 young