Reithrodontomys Fulvescens Research Articles

Species Removal Effects on Movements of Sigmodon hispidus and Reithrodontomys fulvescens

The effects of interspecific interactions on movements of hispid cotton rats (Sigmodon hispidus) and fulvous harvest mice (Reithrodontomys fulvescens) were examined by experimental removal of species. For both Sigmodon and Reithrodontomys, the average distance moved by individuals (AvD,) was greater for males than females. The average distance moved by the population within trap periods (AvD,) was negatively correlated with Sigmodon density only in a field with low resource abundance whereas the AvDp for Reithrodontomys was negatively correlated with density in all fields. Species removal did not affect AvDp of either species. Seasonal differences in AvDp for R. fulvescens suggested an intraspecific effect on movement. Reithrodontomys used the vertical component of the habitat to a significantly greater extent when Sigmodon was present. There was no difference between experimental and control fields in vertical habitat structure, suggesting an interspecific effect of Sigmodon upon movement of Reithrodontomys. Variation in movement may result from differences in available habitat for Sigmodon, but not for Reithrodontomys.

Effects of Species Removal on Resource Utilization in a Texas Rodent Community

Species removal experiments were conducted to determine the effects of competition upon resource use by Sigmodon hispidus and Reithrodontomys fulvescens on the Texas coastal prairie. Food and habitat use were measured in control (both species present) and experimental (one of the species removed) fields. Joint multivariate samples of these variables showed that diet was most important in differentiating the species niches. Niche shift was not detected after species removal for either species, suggesting that exploitative competition was of minor importance.

Karyotypes of Some Harvest Mice, Genus Reithrodontomys

Karyotypes of six species of harvest mice, representing both the sub-genus Reithrodontomys ( humulis, sumichrasti , and fulvescens ) and the subgenus Aporodon ( gracilis, mexicanus , and creper ), are described. The karyotype of R. sumichrasti (2n = 40) resembles those previously reported for R. megalotis and R. raviventris , which possess mainly metacentric chromosomes. Reithrodontomys humulis (2n = 51), R. fulvescens (2n = 50), R. gracilis (2n = 52), R. mexicanus (2n = 52), and R. creper (2n = 52) exhibit a large proportion of acrocentric chromosomes. Karyotypic evidence suggests that intrageneric relationships of Reithrodontomys may not be accurately reflected by use of the subgenera Aporodon and Reithrodontomys .

Experimental Species Removal: Demographic Responses by Sigmodon hispidus and Reithrodontomys fulvescens

Experimental species removal was conducted for three years to assess the demographic consequences of interspecific interactions between cotton rats ( Sigmodon hispidus ) and fulvous harvest mice ( Reithrodontomys fulvescens ). Six 1.6-hectare (ha) plots were monitored monthly by live-trapping; two control, two Sigmodon -only, and two Reithrodontomys -only plots were maintained by appropriate species removal. Frequent trapping and habitat discontinuities between plots minimized the effect of interplot movement and maintained the experimental perturbation. Seasonal vegetation analyses were conducted on each field. Density, percent reproduction, and expectation of further life but not survival were significantly lower for both Sigmodon and Reithrodontomys on experimental plots (codominant species removed). Lower density for both species and lower reproduction for Reithrodontomys were significantly correlated to lower abundance of preferred habitat on these plots. Lower expectation of further life reflected increased mobility ( AvD p ) of Sigmodon on experimental plots, thereby contributing to lower densities and decreased reproduction through lower mate contact. Cotton rat mean individual body weight was significantly lower and male harvest mouse mean body weight significantly higher on experimental plots; lower cotton rat body weight reflected immigration onto experimental plots in response to a density gradient. Sigmodon sex ratio was skewed toward males on control plots, whereas Reithrodontomys sex ratio was skewed toward males on both plots; differential movement or trappability by either sex may be responsible for this result. The significantly lower proportion of adults and young adults on Sigmodon experimental plots was due to emigration; there was no between-plot age class difference for Reithrodontomys . Most demographic differences between control and experimental plots are explained by differential movement, survival, or abundance of preferred habitat. However, increased mean body weight of male Reithrodontomys and earlier appearance of Reithrodontomys juveniles on experimental plots remain unexplained. These results suggest interspecific interactions and/or behavioral interactions may be of secondary importance in determining the demographic structure of rodents in this system.

Species Removal Studies. I. Dispersal Strategies of Sympatric Sigmodon hispidus and Reithrodontomys fulvescens Populations

Sigmodon hispidus and Reithrodontomys fulvescens are the codominant rodent species of the Texas coastal prairie. Eight isolated 1.6 hectare replicated plots were used to study dispersal strategies of these rodents. Each replicate was live-trapped for nineteen months. For two control replicates all captured individuals were identified, sexed, weighed, marked, and released. In two perturbed replicates all Reithrodontomys were removed, in two perturbed replicates all Sigmodon were removed, and in two other perturbed replicates both species were removed. Monthly dispersal of individuals into plots where that species was previously removed was measured. The number of dispersers of both sexes of Sigmodon and Reithrodontomys were positively correlated with monthly changes in control (resident) density. Sex ratio comparisons between dispersers and residents reflected nonsignificant differences for both species. The rank-order of weight (age) classes of dispersers was positively correlated with the classes found in control plots for female Sigmodon and male Reithrodontomys entering both types of perturbed conditions. Pre-emption by Reithrodontomys appeared to inhibit the immigration of the larger (adult) classes of Sigmodon males. Higher proportions of Reithrodontomys females, compared to males, invaded both types of perturbed plots. Resident populations of both species appeared to inhibit conspecific immigration. The rank-order templated dispersal strategy found during this study has the advantage of introducing a stabilized age structure into newly acquired habitat space.

Experimental Manipulation of Population Density in Three Sympatric Rodents

Three abundant rodents, the cotton rat (Sigmodon hispidus), the harvest mouse (Reithrodontomys fulvescens), and the rice rat (Oryzomys palustris) are sympatric in southeast Texas. From January 1970 to May 1970, six presumably homogeneous areas, three control, were live—trapped. Mark—release—recapture and selective removal techniques were used to monitor species composition within the areas. Estimates of the number of individuals per species, body weights, and sex ratios were obtained at 2—week intervals. When cotton rats were experimentally removed, no change in the mean weights of harvest mice or rice rats were revealed by linear regression analysis. When harvest mice and rice rats were removed, cotton rat females exhibited a significant increase in mean weight. A significant change in sex ratio of cotton rats, from a greater proportion of males to a greater proportion of females, was recorded in the areas where harvest mice and rice rats were removed. Although the number of captures per species declined, comparisons of the different experimental manipulations could be made throughout the study.

Population Ecology of Desert Rodent Communities: Habitats and Environmental Complexity

We investigated the relative densities of granivorous, nocturnal desert rodents in small plots within two arid regions of Arizona to study how sympatric species avoid competitive extinction. The most common rodents were kangaroo rats, Dipodomys spp., and pocket mice, Perognathus spp. We attempted correlating the density of each species with several environmental measurements, derived from the soil's i) depth; ii) texture or iii) resistance to sheer stress; or from the plant's i) species diversity; ii) growth forms or iii) foliage density. Successful variables were derived from plant growth form and foliage density. The soil's resistance to sheer stress also seemed important for a few species. In general, kangaroo rats were associated with sparseness of vegetation; pocket mice with denseness. One group of mice, which we term bush mice, seemed to require bushes and included two Perognathus spp., three Peromyscus spp., and probably a harvest mouse (Reithrodontomys fulvescens). Two other Perognathus spp. were taken in grassy habitats. Some suitable habitats tended to be complementary to others, suggesting that species associated with them are competitors. Comparisons of the density and distribution of D. merriami, present in both regions but under different biotic circumstances, reinforces the opinion that competition is responsible for the complementariness of habitats. In some cases the evidence suggests that competitive coexistence is accounted for by the fact that different specializations are needed to escape predation in different environments. We use variables which correlate with the relative density of various species to construct a model of habitat complexity. The rodent species diversities obtained in our plots can be approximately accounted for by this model. The model is based on the premises that the rodents collectively discriminate four qualities of soil surface, and three heights and two densities of vegetation. In general, specializations based on biotic variables appear most important.

An Ecological Study of the Fulvous Harvest Mouse in Eastern Texas

Populations of fulvous harvest mice, Reithrodontomys fulvescens, were studied on three areas in Nacogdoches Co., Texas. One area in a pine forest and another in a grass-pine plantation provided comparative population data from 1955-1963. Data secured from the third area, located in a grass-pine ecotone, were useful in determining microhabitat distribution and movements of the differcnt sex and age groups. Fulvous harvest mice occurred predominantly in grassland, pinegrass ecotone, and grass-brush habitat. They were significantly absent from pine-type habitat, possibly because this habitat was occupied by cotton mice, Peromyscus gossypinus, and golden mice, Ochrotomys nuttalli. Fulvous harvest mice were most abundant in winter and to a lesser extent in summer. Peak populations occurred in 1957 in the grass-pine plantation and in 1958 in the adjacent pine forest. The exclusive boundary strip method of analysis of trap range data revealed that harvest mice range over approximately one-half acre. Females had a slightly larger trap range (= home range), .59 acre, than did males, .47 acre; young females averaged greatest linear movements. Neither sex displayed marked territorial behavior. Actual and estimated densities revealed approximately three fulvous harvest mice per acre in the pine-grass ecotone area (probably the optimal area of the three for these mice). There were slightly more males than females on all the areas studied. On the pine-grass ecotone, there were significantly greater numbers of adult males than adult females. Two principal breeding peaks, one in March and a second in July, were detected. Fulvous harvest mice seemed extremely tolerant of one another when confined under laboratory conditions. Mice born in captivity became independent of the female at approximately 3 weeks (the time of weaning). Under controlled laboratory conditions, captives displayed an activity rhythm seemingly correlated to the onset of dark periods. In the absence of well-defined light-dark cycles, activity occurred at times of natural darkness.

Quarantine Problems Associated with the Importation of Bananas from Mexico

U. S. Public Health Service quarantine personnel inspected 100 trucks carrying Mexican bananas as they were unloaded in Brownsville, Texas, in 1964-65. Of the animals recovered of possible public health interest, 5 species of vertebrates and 31 species of invertebrates have been identified. Included are several species not established in the United States. Rice rats, Oryzomys couesi (Alston), and harvest mice, Reithrodontomys fulvescens J. A. Allen. were the commonest rodents taken. An average of a rat or a mouse was captured for approximately each 2 trucks examined. This study suggests that present quarantine regulations should be strengthened to prevent more effectively the entrance of potential reservoirs and vectors of zoonotic infections in bananas and other fruit or vegetables imported by land vehicles.

Reithrodontomys fulvescens from Crawford County, Kansas

The specific identificatioin of the fulvous harvest mouse (Reithrodontomyx fglvexcen) in the vicinity of Pittsburg, Kansas has been in doubt. Although this locality is within the probable range set forth by Hall and Kelson (1959) no specimens have been reported taken from Crawford County. Long and Wiley (1961) referred material from owl pellets found near Pittsburg to R. megalotis. Long (1961) reported R. montanvx from McDonald County Missouri and R. montv1Zvx has also been collected in Ottawa County Oklahoma (KU 81948). A specimen (KSCP 620-B) of R. fulvexcenx was collected on 17 March 1966 at the Kansas State College of Pittsburg Natural History Research Reserve. This adult male mouse weighed 13.0 grams and had standard measurements of 158 X92 X 20 X 12 mm. This is the first recorded specimen of R. fglvexcenx collected from Crawford County.

Fulvous Harvest Mouse in Missouri

Fulvous Harvest Mouse in Missouri Get access Charles A. Long Charles A. Long Department of Zoology and Museum of Natural History, University of Illinois, Urbana Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 46, Issue 3, 26 August 1965, Page 506, https://doi.org/10.2307/1377651 Published: 26 August 1965 Article history Accepted: 10 May 1965 Published: 26 August 1965

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 MCHC's 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.

The Yellow-nosed Cotton Rat, Sigmodon ochrognathus, in Arizona

In southeastern Arizona the yellow-nosed cotton rat, Sigmodon ochrognathus, inhabits grassy, rocky slopes, in or near the oak belt in the same habitat as Thomomys umbrinus and Reithrodontomys fulvescens. The cotton rats form extensive surface runway systems con- necting surface nests and burrow openings. Surface nests, constructed of grass and placed in dense thickets, are 7 to 16 in. in diameter. Abandoned burrows of Thomomys umbrinus are used by cotton rats and appear to. be a limiting factor in their distribution. Wild animals are much more active during daylight hours than at night. However, one captive male ran an exercise wheel an average of 31,836 ft per night for 100 consecutive nights. In the wild, S. ochrognathus feeds extensively on blue grama; in captivity a diet of salad greens and dry lab chow is adequate. Caged animals do not require free water if fresh plant material is provided every 2 or 3 days. Females breed as early as 45 days of age and 2 individuals had gestation periods of 33 and 36 days. Litter size varies from 2 to 6 and young can be weaned by the 15th day, probably sooner. The furred newborn are precocial with the eyes opening during the first 24 hr. At 2 days of age they can climb the hardware-cloth sides of the cage. Growth is rapid. After 100 days, there is little' increase in total and tail-length; after 40 days, in hind foot-length. By 2 V/2 month of age, the skull has attained over 90% of adult size in greatest length, zygomatic breadth, mastoid breadth, and length of upper toothrow. Estimations of the ages of wild-taken specimens indicate that animals rarely live for more than 4 months in the wild since 96% are less than 4 months old and 83% are less than 2V2 months old. 'Characters for distinguishing S. ochrognathus from S. minimus and S. hispidus in Arizona are listed. Certain distinguishing features of the baculum, interparietal, foramen ovale, and foramen magnum have not been previously reported. The yellow-nosed cotton rat, Sigmodon ochrognathus, has a limited range in the Southwest and, judging from the few specimens in collec- tions, is an uncommon animal. Our own recent field work in Arizona has enabled us to recognize the signs and habitat of this species and once aware of these, we were able to obtain numerous specimens from 15 localities in southeastern Arizona. Discussions of the habitat, be- havior, growth, and general characteristics of this species are based upon field observations in Arizona and upon 7 wild-caught animals and

A Live-Trap Study of Small Mammals in Louisiana

Two 15-acre areas were selected in a typical cutover, loblolly-shortleaf pine forest near Ruston, Louisiana for a live-trap study. One objective of the study was to determine the effect of controlled burning on small mammals. One hundred live traps were used on each site, and the length of the trapping periods varied from five to six days. The study was begun in January, 1959 and ended in April, 1961. Species trapped included Peromyscus nuttalli, Peromyscus gossypinus, Blarina brevicauda, Reithrodontomys fulvescens , and Microtus pinetorum . All mammals captured were marked for later identification and released. Peromyscus nuttalli and Peromyscus gossypinus were recaptured in sufficient numbers to calculate home range and density per acre. The mean home range of Peromyscus nuttalli was 1.31 acres on the control plot and 1.07 acres on the burned plot. The mean home range of Peromyscus gossypinus was 1.2 acres on the control plot and .74 acres on the burned plot. The highest trap-revealed densities for these two species were 2.79 Peromyscus nuttalli per acre and 1.22 Peromyscus gossypinus per acre. The burn on 23 February 1959 had a negligible effect on the small mammals and was followed by a decrease in trap-revealed rodents for less than a month. Food habit studies by the author have indicated that small mammals are consumers of pine seeds in the loblolly-shortleaf pine association of Louisiana and thus affect pine regeneration. The study was designed to determine the species, abundance, movements and fluctuations of small mammals in a typical cutover, loblolly-shortleaf pine forest, and to evaluate the impact on animal life of the removal of low vegetation and forest litter by fire.

The Fulvous Harvest Mouse in New Mexico

Four specimens of the fulvous harvest mouse, Reithrodontomys fulvescens (Allen), were captured by us on three successive nights, January 27–30, 1957, 22 miles south and two miles east of Rodeo, Hidalgo County, New Mexico. The site of capture is located in the Peloncillo Mountains at the point where the Geronimo Trail (the road between Douglas, Arizona and the Animas valley, New Mexico) crosses the crest of the range at an altitude of approximately 5,900 feet. The animals were trapped …

Mammals from Owl Pellets Taken in Coahuila, Mexico

Massive limestone outcrops rim many of the canyons in the mountainous country of Coahuila, Mexico. Caves and fissures in these cliffs afford living places for bats, owls, woodrats and other animals. In the course of field studies of the mammals of this Mexican state, many such places have been investigated in the hopes of obtaining specimens. On July 6 and 7, 1952, three members of a University of Kansas field party, Albert A. Alcorn, Jack M. Mohler, and Peter S. Chrapliwy, searched a cave three miles northwest of the city of Cuatro Cienegas in central Coahuila. No bats were found but approximately one-half peck of owl pellets, most of which were partly disintegrated, were collected. No owls were seen in or near the cave, but, judging from the large size of the pellets, they pertained either to the great-horned owl (Bubo virginianus) or to the barn owl (Tyto alba). This cave is situated approximately 100 feet up the west side of a narrow canyon above the road from Cuatro Cienegas northwestward towards Ocampo. A small stream fed by springs in the canyon flows southeastward through Cuatro Cienegas and the intermontane basin surrounding it and eventually leads into the Rio Salado. To the north and northwest the canyon leads on to a higher and more extensive desert basin which extends northward to the Texas Big Bend. The area surrounding Cuatro Ciengas has been well described by Gilmore (Jour. Mammalogy, 28:147-152, May 19, 1947), who reported on mammals taken there from archeologic cave-sites. The cave in question here is not one from which his archeologic materials were obtained. In all, 195 specimens were preserved well enough for accurate identification; this was done principally by the study of entire or partial crania. These specimens belong to 14 species which are listed as follows along with the number of each species present: Notiosorex crawfordi, 2; Antrozous pallidus, 6; Thomomys bottae, 1; Perognathus flavus; 42; Perognathus hispidus, 51; Perognathus nelsoni, 4; Perognathus penicillatus, 31; Dipodomys merriami, 22; Reithrodontomys fulvescens, 2; Onychomys torridus, 1; Peromyscus eremicus, 3; Peromyscus maniculatus, 1; Sigmodon hispidus, 23; Neotoma micropus, 5.