Eugene D. Fleharty

Body Composition, Energy Content, and Lipid Cycles of Four Species of Rodents

Gross body composition, energy content, and lipid cycles of Peromyscus maniculatus , Reithrodontomys megalotis, Sigmodon hispidus , and Microtus ochrogaster were studied. Ash values for adults ranged from 14.2 to 16.1 per cent of dry body weight, and water content varied from 61.5 to 74.2 per cent. Lipid content ranged from a low of 14.6 per cent dry body weight in M. ochrogaster to a high of 25.6 per cent in S. hispidus . Annually, kilocalories per gram live weight averaged 1.61 in P. maniculatus , 1.65 in R. megalotis , 1.74 in S. hispidus , and 1.42 in M. ochrogaster . Energy content of subadults and adults of S. hispidus differed significantly during summer, autumn, and winter; no such differences were noted for age categories of the other species. The four species exhibited three different types of lipid cycles: in both P. maniculatus and R. megalotis , lipid content was lowest in summer and highest in winter; in S. hispidus , the lowest readings were in spring and the highest in winter; in M. ochrogaster , lipid content fluctuated on a monthly basis but exhibited no annual cycle. We postulate that annual lipid cycles reflect the Zoogeographic history of the species, and might thus serve as a measure of physiological adaptation to climatic conditions unlike those that existed at the respective times and places of evolution of the four species.

Summer Food Habits of Microtus Ochrogaster and Sigmodon Hispidus

Stomach contents were analyzed for 97 Microtus ochrogaster haydenii and 86 Sigmodon hispidus texianus to determine what plant species were utilized, the effect of plant availability on diet, and the degree to which both species utilized identical foods. Based on per cent volume consumed, Sigmodon utilized Triticum aestivum, Kochia scoparia, Sporoholus asper, Bromus japonicus, Rumex crispus, and Xanthium commune the most during June and July from two areas. In the same areas, Microtus concurrently found S. asper, K. scoparia, Bouteloua gracilis, B. japonicus, R. crispus, and Digitaria sanguinalis the most palatable. Availability of plants was found to be an influencing factor on what was eaten, but certainly was not the only factor, because many plant species that were not dominant were seemingly selected on the basis of their growth stage and palatability. Although the same species of plants comprised most of the food eaten by the two rodents, it is likely that competition existed for space rather than food, as ample food was available throughout the study.

HABITAT PREFERENCE AND SPATIAL RELATIONS OF SIGMODON HISPIDUS ON A REMNANT PRAIRIE IN WEST-CENTRAL KANSAS

During a 47-month live-trap study conducted in a remnant grass- land in west-central Kansas, Sigmodon hispidus preferred habitats with dense under- growth and protective overstory and used less favored habitats primarily when population densities were high. Seasonal home ranges based on the exclusive boundary-strip method averaged significantly larger (P < 0.01) for males (0.96 acre) than for females (0.54 acre). Males were more nomadic than females, but both sexes traversed smaller areas during periods of high density than during low density. No indication of territorial defense was evident. The geographic range of the hispid cotton rat, Sigmodon hispidus Say and Ord, extends northward from Panama as far as southern Nebraska (Hall and Kelson, 1959: 673; Genoways and Schlitter, 1967). The continuing northward dispersal of this Neotropical immi- grant onto the Great Plains (Hoffmann and Jones, 1970) during the past 25 years has been well documented (Cockrum, 1948, 1952; Hall, 1955; Jones, 1960, 1964). As the range of the species has moved north- ward, cotton rats must have coped with a progression of different environmental factors and habitats. The purposes of this study were to elucidate the environmental interactions, habitat preference, home range, greatest distance traveled, and territoriality of Sigmodon hispi- dus in a mature grassland near the present northern limit of the range of the species.

Bioenergetic Strategies of the Cotton Rat, Sigmodon hispidus

Bioenergetic strategies of hispid cotton rats on a relict grassland in west-central Kansas were assessed for the period December 1967 through November 1968. Less than 1.0 per cent of the yearly net primary production of the grassland was ingested by cotton rats. Of the energy assimilated throughout the year, all but 2.2 per cent was utilized in maintenance. Energy flow channeled into secondary production ranged from a low of −2.4 kilocalories per hectare per day in January to a high of 22.6 in September. Accordingly, population density was at a low of 8.8 rats per hectare in April but increased to 19.4 by September. Seasonal fluctuations in relative amounts of energy utilized in secondary production probably reflect physiological adaptations to withstand adversities of climatic seasonality.

Structural Ecological Parameters of a Population of Peromyscus maniculatus in West-Central Kansas

Structural ecological parameters of a population of Peromyscus maniculatus were investigated following a four year live-trap study conducted on a remnant mixed prairie in west-central Kansas. Deer mice had a non-random distribution on the study area, and preferred habitats dominated by Andropogon gerardi, A. scoparius, and Bouteloua curtipendula; they specifically avoided a weedy community dominated by Helianthus annuus and Kochia scoparia. The lowest crude densities (1.8/ha) were recorded in spring of 1968, and the highest (17.7) occurred in autumn of 1966. Ecological densities ranged from spring and summer lows (4.0/ha) in the weedy community to autumn highs of (19.3/ha) in the A. gerardi habitat. Over the four years, the population invariably peaked in midautumn to early winter, was least dense in mid-winter to early spring, experienced a minor peak in spring, and declined slightly in summer. Population turnover was 43% complete in six months and 95% complete in twelve months. Males and females that were caught more than once averaged 154 and 147 days on the study area, respectively. Significantly more males than females were captured during the study, but no significant differences between males and females were noted in greatest distance traveled. Certain individuals moved more than 245 m in one day. Home ranges of males (0.11-0.72 ha) and females (0.12-0.77 ha) did not differ significantly, but home ranges (0.31 + 0.02 ha) of both sexes pooled during spring and summer were significantly greater than those (0.27 + 0.02 ha) pooled during autumn and winter. Territoriality was more pronounced in females than males. Few studies of the deer mouse (Peromyscus maniculatus) have been conducted using identical sampling techniques in the same area for longer than a few weeks or months (summarized by Terman 1968). Such investigations carried out over longer periods are needed if trends or fluctuations in natural populations are to be elucidated, because extrapolation of results gathered from data for less than one year are susceptible to bias. Additionally, analyses of population fluctuations based on samples taken during only one year cannot account for the variable conditions that a natural population is subjected to over longer time spans.

Distribution of Peromyscus leucopus (Woods Mouse) in Western Kansas

The affinity of Peromyscus leucopus (Rafinesque) for a wooded habitat in Kansas has been noted by many workers such as Hibbard (1933, 1944) and Black (1937) and more recently by Cockrum (1952), Hall (1955), and Andersen and Fleharty (1967). Thus, in the more arid regions of western Kansas this species has a dendritic distributional pattern being limited primarily to the riparian communities. Cockrum (1952), in his treatise on Kansas mammals, illustrated P. leucopus as being absent from many counties in west-central Kansas. Halls (1955) map shows no additional localities in western Kansas, although he does propose a somewhat different subspecific alignment than did Cockrum. Nothing more concerning leucopus distribution in Kansas is reported until Frydendall (1961) noted P. 1. aridulus from as far west as Ellis County. Collecting since 1962 has revealed the presence of the woods mouse in many counties heretofore unrecorded. These distributional county records are probably due more to extensive and intensive collecting in favorable habitats rather than in any major movement of the woods mouse into the area.

Energy Flow in Spermophilus franklinii

The energy flow value of Spermophilus franklinii based on results from oxygen and food consumption experiments for an estimated one animal per hectare for 1 day was 123.8 kilocalories. This value would be nearly equivalent to the energy of maintenance as a negligible amount would be used for growth in such a brief period. Actual metabolizable energy calculated from food consumption experiments was about double the estimated resting metabolizable energy ascertained from oxygen consumption. Oxygen consumption can be expressed as Y = 1.73–0.041 X for metabolic responses to ambient temperature changes below 26.5°C. The thermoneutral zone (26.5 to 31°C) gave a value of 0.64 cubic centimeters of oxygen per gram per hour. These values were close to those predicted by relating metabolism to body weight.

Natural History Notes on Franklin's Ground Squirrel in Boone County, Nebraska

The Franklin ground squirrel (Spermophils franklinii) is common in central Nebraska in low-lying areas of silty soil overgrown with Bromzls inermix, which provides concealment and nest material for the squirrels.The burrows range from simple to complex in structure but seldom vary in depth (17 inches) and diameter (31/4 inches). Emergence from hibernation in 1969 and 1970 was in early May and, thereafter, the daily activity occurred predominantly about 4 and 7 hours after sunrise and 5 hours prior to sunset. Weather conditions did not seem to affect the daiIy life patterns of S. Iranklinii.

Mass and Energy of Detritus Clipped from Grassland Vegetation by the Cotton Rat (Sigmodon hispidus)

Piles of vegetational clippings made by Sigmodon hispidus in a remnant grassland area were collected and analyzed for vegetational composition, dry weight, and caloric content. Population densities of S. hispidus were estimated monthly and correlated with the number of clipped piles of vegetation collected each month. During the 1-year study period, Sigmodon clipped 315.1 kilograms of vegetation on the 4.85-hectare study area. This amounted to 136.1 × 104 kilocalories. Grasses (mainly Andropogon gerardi, A. scoparius , and Bouteloua curtipendula ) accounted for 54 per cent of the vegetation clipped, Ambrosia psilostachya and Kochia scoparia 40 per cent, and Helianthus annum 6 per cent. Seventy-two per cent of the clippings occurred from September to November. The amount of clipped material per rat per month varied from zero in May to 1.3 kilograms in October. The amount of material clipped may not be dependent solely on the density or activity of S. hispidus , but possibly also on the condition of the vegetation. Of the net primary production in this area during the study period, 0.4 per cent was clipped by S. hispidus .

Additional Records of the Least Weasel (Mustela nivalis) in Kansas

The least weasel was first recorded from Kansas (Jones, Am. Midl. Nat., 73:247, 1965) on the basis of an adult male collected on 13 March 1964 near Marysville in Marshall County. Two more least weasels have been taken and are now in the Museum of the High Plains, Zoology Department, Fort Hays Kansas State College. These records further confirm the long postulated occurrence of the least weasel in northern Kansas (Hall, Misc. Publ. Mus. Nat. Hist., Univ. Kansas, 7:246, 1955, and Jones, Univ. Kansas Publ., Mus. Nat. Hist., 16:279, 1964). On 2 5 January 1965, Mr. Paul Roberts, biology instructor of the Mankato High School, turned over to us a skinned specimen of Mvxtela nivalis Linnaeus, the least weasel. It was captured by Mr. Gerald Thompson, a local landowner, on 16 January 1965 at R7W, T3S, SE 1/4 Sec. 5, Jewell County, Kansas. The area consists of a vacant farmstead. Several piles of old lumber and baled hay were present in the immediate area. Due to heavy snow cover the only vegetation visible was Russian thistle (Salxola kal). Later western ragweed (AmbroZa pxilostachya), Artemisia spp., tall dropseed (Sporobol cper), and puffsheath dropseed (Sporobols neglectX) were identified. Mr. Thompson was feeding cattle in the barn lot when he observed a small weasel carrying a dead rat, presumably Rgttvs olorwegic (Berkenhout), from a lumber pile across the lot to a small pile of limestone rocks near the southeast corner of an old barn. Mr. Thompson stated the rat appeared large in comparison to the weasel and the animal was having diiculty in moving it. By placing a cardboard box near the rock pile he was able to drive the weasel into it. He felt that the weasel was so engrossed with the rat that it paid little attention to his attempt to capture it. Upon capture it was turned over to a high school student who subsequently presented it to Mr. Roberts. The animal died after one day in captivity and the specimen was skinned and the skin treated with an alum solution. The skull was left in the skin and it and the legs were