John A. Sealander

The Influence of Body Size, Season, Sex, Age and Other Factors Upon Some Blood Parameters in Small Mammals

Measurements were made of hemoglobin concentration, hematocrit ratio, mean corpuscular hemoglobin concentration (MCHC) and erythrocyte diameter in 34 species of wild mammals from widely separated areas in the United States and Canada representing 5 orders, 10 families and 25 genera. Included in these determinations were measurements on two races of Tamias striatus , two races of Oryzomys palustris , two races of Peromyscus leucopus and three races of Peromyscus maniculatus . Differences in blood values related to species, age, body size and other factors were evident. Hemoglobin concentrations, hematocrit ratios and MCHCs showed a correlation with body size, smaller species generally having higher blood values. A number of exceptions were noted which were probably related to season, altitude, behavior or special physiological adaptations. Members of the families Soricidae and Vespertilionidae which include many small-bodied forms with high rates of metabolism generally had the highest blood values. Pregnant and lactating females usually had lower mean blood values than non-gravid females and males, but no significant differences were found between adult non-gravid females and males. Hemoglobin and hematocrit values in juveniles were often significantly lower than in adults. There was some indication that erythrocyte size was larger in juveniles than in adults, and this may have compensated in some unexplained way for the lower hemoglobin and hematocrit values. No significant differences were noted between the blood values of immatures (subadults) and adults. Seasonal differences in mean blood values were observed in cotton rats ( Sigmodon hispidus ), harvest mice ( Reithrodontomys fulvescens ) and deer mice ( Peromyscus leucopus , P. maniculatus and P. boylii ). Lower blood values in summer in cotton rats could possibly be correlated with either increase in weight or increase in the ambient temperature of the environment during this season. A tendency for high-altitude forms to have higher mean blood values than forms living at low altitudes was noted, but it was inferred from the data that the differences were probably mainly due to differences in ambient temperature. High blood oxygen capacities associated with high hemoglobin and hematocrit values in species of small body size with high metabolic rates would be a distinct advantage in increasing the delivery of oxygen to the tissues. The advantage of increased blood oxygen capacity of the smaller species coupled with a higher carbonic anhydrase activity in their red cells is discussed.

Diets of Bobcats in Arkansas with Special Reference to Age and Sex Differences

Relationships between diet of bobcats (Lynx rufus) and season, region, age, and sex were studied in Arkansas, based on contents of 150 stomachs collected between June 1970 and April 1972. Rabbits (Sylvilagus sp.), squirrels (Sciurus niger, S. carolinensis, Tamias striatus, Glaucomys volans), and rats and mice (Sigmodon hispidus, Neotoma floridana, Peromyscus sp., Microtus pinetorum, Reithrodontomys sp.) were found in 39, 22, and 21 percent of stomachs, respectively. Consumption of rabbits and deer (Odocoileus virginianus) peaked in autumn. Occurrence of rabbits (P < 0.025) and rats and mice (P < 0.01) was greater in stomachs from the Gulf Coastal Plain region; occurrence of squirrels (P < 0.005) was greater in the Interior Highlands. Diets of kittens, juveniles, and adults were similar. Occurrence of rats and mice was greater in females than in males (P < 0.025), suggesting that females selected smaller or more abundant

Relative Efficiency of Different Small Mammal Traps

At some time in any study of small mammal populations the investigator is faced with the problem of whether the particular kind of trap used will adequately sample the population. It is common knowledge that exclusive use of one type of trap will tend to bias the estimate of population density due to varying amounts of selectivity in obtaining a population sample, since different types of traps vary in efficiency with respect to numbers, genera and species caught. Trap size and the correlated mechanical sensitivity of the trap also are obviously selective with respect to the size of specimen taken. An apparent avoidance of certain kinds of traps by some genera and species may involve odor, the appearance of the trap to the animal, or trap placement. However, certain anthropocentric concepts are involved here which are difficult to evaluate. Painting traps or camouflaging them in various ways have been used by some to overcome any real or assumed behavior of this sort without giving much quantitative evidence of success. Successful fur-trappers apparently employ these methods with considerable success to overcome reaction of the animal to the trap. There may also be individual variation in response to traps, as suggested by Young et al. (1952), Tanaka (1952, 1956) and Geis (1955), which would, if present, introduce a bias with respect to numbers of particular species trapped. The behavior of individuals and species is thus an important factor to consider in sampling any small mammal population. Although bait preferences (Fitch, 1954) may play an important part in seasonal trap response, they are probably of little importance in determining success of different trap types and use of the same bait in all traps compared at the same season would tend to nullify this factor. Cockrum (1947) found that live-trapping provided …

Annual lipid cycle of the gray bat, Myotis grisescens

Abstract 1. 1. Fat indices in Myotis grisescens ranged (May–October) from 0·09 to 1·38 units in males and 0·08–1·45 units in females. In percentage fat, sample means ranged from 11·7 to 52·5 in males and 10·6–55·8 in females. 2. 2. Rapid fat deposition began sooner (September) in females than males (October), and their fat utilization rate was approximately double (5·4mg/g fat-free dry weight (FFDW) per day) that of males (2·7 mg/g FFDW per day) in the last two weeks of hibernation (1–15 March). 3. 3. Maximum mean water indices of 2·68 and 2·70 were noted in July for both sexes. The minimum water index for males was 2·20 (May) and for females 2·22 (February). FFDW remained constant throughout the year in both sexes.

Reproductive Biology and Population Characteristics of Bobcats (Lynx rufus) in Arkansas

Reproductive tracts were examined from 74 male and 64 female bobcats ( Lynx rufus ) collected in Arkansas between June 1970 and April 1972. Ages of 174 specimens were established using dental criteria. Males were sexually mature by their second winter and appeared to remain fertile the year around; females reproduced first at 1 or 2 years of age. The main reproductive period began in December and continued at least through April. A high percentage of females were not fertilized during their first estrus of the season. Average litter size was 2.5. Sex ratio among 180 adult and immature specimens was 1.7 males per female. Age structure of the sample suggested a low adult mortality rate.

Hematological Values in Deer Mice in Relation to Botfly Infection

An incidence of 31.8 per cent infection with botflies ( Cuterebra sp.) was found in a population of deer mice ( Peromyscus leucopus noveboracensis ) trapped near the Queens University Biological Station, Chaffeys Locks, Ontario, during July and August 1958. No infections were observed in mice trapped prior to 23 July. Infected mice had significantly lower hemoglobin concentrations and packed cell volumes than noninfected mice trapped during the same period. The possibility that reduced blood values resulting from myiasis might lower physiological resistance to environmental stressors sufficiently to contribute to population declines is considered.

Myotis austroriparius in Arkansas

Myotis austroriparius has not been recorded from the region between central Louisiana and southern Illinois. Two specimens of this species in the mammal collection of the University of Arkansas (U.A.Z., nos. M52-27 and M52-29), taken by F. B. Truett on November 27, 1952, in an abandoned mine shaft twelve miles northwest of Hot Springs, Garland County, Arkansas, extend the known range of Myotis austroriparius 200 miles to the north of the nearest locality from which the species was previously known …

Reproductive Biology of Wild Canis (Canidae) in Arkansas

Reproductive organs from 136 male and 127 female wild canids collected during each month from July 1968 through February 1972 in Arkansas were examined. The maximum potential breeding period for male coyotes extended from late November through March. Pregnant female coyotes examined bred from mid-February through the first week of March. Some male coyotes appeared capable of mating during their first breeding season. No female coyotes taken during their first potential breeding season or before their second season had mated. Approximately 74 percent of the female coyotes captured during or after their second breeding season were pregnant or had produced pups. An average of 6.2 ova were produced per breeding female coyote per season, of which an average of 4.5 implanted and developed into embryos. The breeding season of other canids examined, including wild dogs, a possible red wolf, coyote × dog hybrids, and coyote × red wolf hybrids, overlapped with those of coyotes indicating that hybridization is physiologically possible.

Home Ranges of Deer Mice in Southern Arkansas

Measurement of home range size has become a more or less routine part of many mammal population studies (Hayne, 1950); a great deal of effort has been expended (Calhoun, 1955; Davis, 1953; Hayne, 1949; Stickel, 1954) in determining the amount of variation in size of the calculated home range which may be attributed to factors which are inherent in the trapping methods (traprevealed range) as compared to variations resulting from such variable factors in the environment as food, cover, topography, weather and fluctuations in population density per se . Nevertheless, some of the techniques of home range measurement have been widely enough adopted so that some reasonably valid comparisons of home range size can sometimes be made. With a continued accumulation of home range data in the literature it may become possible to determine, at least on a roughly quantitative basis, the influence of such factors as latitude with its related climate, seasonal availability of food and variation in cover types. In this connection, it may be noted that relatively few determinations of home range size have been reported from the southern United States, and consequently the information provided here may prove useful for comparison with more northern faunas. The following study was made during 1955 and 1956, incident to other mammal population studies, in an area located approximately 10 miles north of Pine Bluff, Jefferson County, Arkansas, on the western side of the Arkansas river. The study area consisted of a 153-acre portion of immature oak-pine forest which was divided into one-acre plots. The principal dominants in the association were oaks (southern red oak, Quercus falcata ; post oak, Quercus stellata ; white oak, Quercus alba ), which comprised about 57 per cent of the assemblage, and pines (loblolly pine, Pinus taeda ; yellow pine, pinus echinata …

Effect of Forced Swimming on Body Temperatures and Eosinophil Levels in Cotton Rats (Sigmodon Hispidus)

Cotton rats, Sigmodon hispidus, were forced to swim in water at 2 and 10° C. Body temperatures (TB) declined most rapidly during the first 6 minutes of the swim and the rate of fall was nearly halved during the remainder of the swim. the rate of decline in TB was more rapid in the 2 than in the 10° C bath, but the per cent change in TB at the end of the swimming was about the same at both bath temperatures (about 43 per cent). the mean TB of the 26 cotton rats tested was 21.4 ± 0.6° C at the end of swimming, and there was no significant difference in the total decline in TB at the two bath temperatures. the eosinophil count declined by 52.5 and 63.0 per cent in cotton rats swimming at 2 and 10° C, respectively, and there was no evident correlation between the magnitude of the eosinophil response and body weight, swimming time or percentage decrease in TB.