Ecology and Physiology of Napaeozapus Insignis (Miller) and Other Woodland Mice Author(s): James E. Brower and Tom J. Cade Reviewed work(s): Source: Ecology, Vol. 47, No. 1 (Jan., 1966), pp. 46-63 Published by: Ecological Society of America Stable URL: http://www.jstor.org/stable/1935743 . Accessed: 24/12/2011 11:58 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. http://www.jstor.org ECOLOGY AND PHYSIOLOGY OF NAPAEOZAPUS INSIGNIS (MtILLL,"R)AND OTHER WOODLAND MICE J.AMESE. BROWER AND ToM J. CADE Deparhimlcilt of Zoology, Syracuse University, Syracuse, Nczv York -11bstract. The distribution and ecology of the woodland jumping mouse, Napacoz-aplus uisuipliis, were studied in the light of its behavior in the field, its physiology in the laboratory, and by comparison with other species of small rodents. Data from 36 traplines show that jumping mice have no preference for habitats near water. Shrubby ground cover appears to be the most important factor affecting their local abundance. Napaeozaputs has probably been associated so often with streams because these areas favor growth of good ground cover. Woodlan(1 jumping mice were found in nonwooded areas where shrubby ground cover was found. In one nonwooded area it replaced the meadow jumping mouse, Zapus hudsomins. Removal of the population of woodland jumping mice in the fall was followed by the estab- lishment of the meadow species the next spring. Woodland jumping mice and redback voles seldom occurred together in abundant numbers. This separation was partly the result of distinct habitat differences, but in some areas of mixed woods having ground cover, the presence of voles was accompanied by an absence of jumping mice. When jumping mice were present, redback voles were few or absent. This pattern of distribution could not be explained by differences in habitat selection or by competition. Some form of interference could be involved. Woodland jumping mice show a tendency to be more active on colder nights. This behavior contrasts with o1)servations on deer mice by other workers who state that these mice are more active onI warm, cloudy nights. The high population densities of Napavozaputs found in this study were in an area of New York State having boreal elements. The lower densities reported for western and southern areas of the northeastern United States indicate that its overall distribution is affected by the presence of horeal vegetation. Ad libitiml. water consumption shows that redback voles drink more than twice as much as their predicted weight-relative value. Woodland jumping mice drank normal weight-relative amounts, but deer mice drank less. The rate of evaporation in Napaeozapus was considerably lower than that found in sympatric Peromyscus inaniculatus. Its rate of evaporation was closer to values found for some populations of mice from drier climates. These results suggest that moisture is not a critical limiting factor in the distribution of woodland jumping mice. The low rate of evaporation in Napaeozapus could be an adaptation against desiccation during hibernation. The spreading of saliva by the deer mice is an important cooling device. At 37?C deer mice lost 72% of their heat production through evaporation. At this same ambient temperature, jumping mice lost only 38% of their heat by evaporation. Deer mice were able to withstand 39' with no ill effects, but few jumping mice survived 37?C. Hyperthermia associated with low metabolism was observed in the deer mice. This could be the result of vasoconstriction in nonvital organs, thereby limiting substrates and 09 to the cells of these organs. Such an adjustment would not only limit the rate of metabolism but would also increase the body temperature by limiting transfer of heat by the blood. The decreased metabolic rate and the increased rate of evaporation by spreading saliva would increase the efficiency of cooling at high ambient temperatures. Basal metabolic values of deer mice and jumping mice are near their predicted weight- relative values. The high lower critical temperatures in jumping mice are consistent with the idea that hibernators have high rates of heat loss. Jumping mice appear to have more precise thermoregulation over a wider range of ambient temperatures than do deer mice during the summer period. Metabolic patterns of several small rodents are compared. These patterns show little association with specific climatic conditions among distantly related, sympatric forms. The deer mouse complex, the jumping mice, the voles, and the pocket mice seem to have their own distinctive metabolic and thermoregulatory patterns, which may be associated with phy- logeny. Some physiological adaptation to climate seems to be indicated within these phylo- genetic patterns, as exemplified by populations of Peromyscus, while some of the more specialized phylogenetic patterns, such as the one which characterizes the genus Perognathus, seem to have evolved in the ancestral populations to suit specific climatic conditions. INTRODUCTION which are distributed through the temperate and The woodlandjuumping mouse -Napaeozapus in- boreal regions of the Northern Hemisphere. Only signis (Miller) belongs to a small family of hiber- recently have physiologists (Johansen and Krog nating rodents, the Zapodidae, the members of 1959; Morrison and Ryser 1962a; and Neumann Winter 1966 ECOLOGY AND PHYSIOLOGY OF WOODLAND MICE 47 and Cade 1964) begun to study the members of areas were sampled in the summers of 1961, 1962, this phylogenetically old family, which is repre- and 1963, but the bulk of the data was collected sented by fossil forms possibly as far back as the in 1962. Two types of Sherman live-traps were Eocene (Wood 1955). used, the larger spring-floor box traps and the Napaeozapus is found generally over a wide smaller folding traps. Rolled oats were used in range in northeastern North America from the the small traps and a mixture of peanut butter and limits of the boreal forest in Quebec and Labrador, rolled oats in the larger. Traps were set at the south through the Appalachian system to Georgia, bases of stumps and trees, near logs, holes in the and westward from the Atlantic coast to Minnesota ground, and at any other spots where a small and Saskatchewan (Hall and Kelson 1959). Often mammal might pass. All mice were removed from rare within this range, woodland jumping mice the sites and were not released. We obtained may be quite abundant locally (Sheldon 1934, records from a total of 4,024 trap-nights. Trap- 1938; Hamilton 1935; Preble 1956). E. A. Preble lines were set for 3 to 5 days in one place. Results (1899), Hamilton (1935), N. A. Preble (1956) are expressed in number of mice trapped per 100 and others have emphasized a preference by this trap nights. We designate the animals as 1) species for cool, moist, wooded habitats along abundant if 5 or more; 2) common, if 2.5 to 5; streams or other bodies of water, implying a strong 3) few, if at least 1.0, and 4) rare, if less than 1.0 association with water. Connor (1960) and were caught per 100 trap-nights. Whitaker (1963a), on the other hand, feel that The general habitat of the trapping areas was surface water is not an essential part of the habitat recorded in terms of dominant vegetation, amount for these mice. Snyder (1924) and Whitaker of brushy ground cover, and approximate distance (1963a) believe that ground cover is the most from water. The dominant types of vegetation important component of their habitat. were classified as coniferous woods, deciduous We have tried to gain some insight into the woods, mixed woods, shrub community, or field factors which govern the geographic and ecological community. Cover, in the form of shrubs or small distribution of Napaeozapus by studying its be- trees (up to 6 or 8 feet above the ground) was havior in the field and by examining its metabolic rated as dense (difficult to walk through), inter- and thermoregulatory characteristics in the labo- mediate (vegetation close but easy to maneuver ratory. To assess the distributional significance through), or sparse (little or no shrub-like vege- of our findings on Napaeozapus, we have made tation present). Distance from water was divided extensive comparisons with other species of small into three categories: adjacent to water (less than rodents. 200 ft), close to water (200 to 600 ft), and far from water (estimated greater than 600 ft). All METHODS AND MATERIALS water bodies were streams or brooks. Field study The second portion of the field work entailed Whiteface Mountain, in the northern Adiron- maintaining a grid from August 10, 1962 to Sep- dack Mountains of New York State, was selected tember 13, 1962, on an old, abandoned ski slope, for a field study for several reasons. Preliminary on Marble Mountain at an elevation of 1,900 ft. trapping during the summer of 1961 revealed This area proved almost ideal. It had an abundant jumping mice to be abundant in a number of lo- population of jumping mice, four contrasting but calities. A mountain highway and chair lift made closely situated habitats, was easily accessible, numerous areas accessible. The State University of New York Atmospheric Sciences Research Center located there provided a convenient source for information on weather (1963).