Neotoma Cinerea Research Articles

The effects of moonlight on nocturnal activity in bushy-tailed wood rats (<i>Neotoma cinerea</i>)

The effects of moonlight on nocturnal activity in bushy-tailed wood rats (<i>Neotoma cinerea</i>)

Mating patterns and reproductive success in the bushy-tailed woodrat ( Neotoma cinerea ), as revealed by DNA fingerprinting

The mating patterns and reproductive success of the bushy-tailed woodrat (Neotoma cinerea) were investigated over a 3-year period (1992–1994) using DNA fingerprinting. Paternity was determined by genetic analysis of 58 juveniles of known maternity from 35 litters. Analysis of DNA fingerprints revealed that all offspring within a litter were fathered by a single male; the statistical probability of detecting multiple males mating with a female was high, indicating that multiple paternity would have been detected had it occurred. However, individual males did not father more than one litter from a given female either within or between years. At least 75% of females and 57% of males successfully produced offspring each year. The finding that all littermates are first-order relatives may contribute to the high level of female cooperation in this species.

Response of Bushy-Tailed Woodrats (Neotoma cinerea) to Late Quaternary Climatic Change in the Colorado Plateau

Temperature profoundly influences the physiology and life history characteristics of organisms, particularly in terms of body size. Because so many critical parameters scale with body mass, long-term temperature fluctuations can have dramatic impacts. We examined the response of a small mammalian herbivore, the bushy-tailed woodrat (Neotoma cinerea), to temperature change from 20,000 yr B.P. to present, at five sites within the Colorado Plateau. Our investigations focused on the relationship between temperature, plant composition and abundance, and woodrat size. Body size was estimated by measuring fossil fecal pellets, a technique validated in earlier work. We found significant and highly covariable patterns in body mass over the five locations, suggesting that responses to temperature fluctuations during the late Quaternary have been very similar. Although woodrat mass and the occurrence of several plant species in the fossil recordweresignificantly correlated, in virtually all instances changes in woodrat size preceded changes in vegetational composition. These results may be due to the greater sensitivity of woodrats to temperature, or to the shorter generation times of woodrats as compared to most plants. An alternative hypothesis is that winter temperatures increased before summer ones. Woodrats are highly sensitive to warmer winters, whereas little response would be expected from forest/woodland plants growing at their lower limits. Our work suggests that woodrat size is a precise paleothermometer, yielding information about temperature variation over relatively short-term temporal and regional scales.

Sex-biased mortality in woodrats occurs in the absence of parental intervention

Male-biased mortality in young animals is often viewed as adaptive discrimination against male offspring by parents unable to raise reproductively competitive sons. Unequivocal evidence of the presence or absence of parental discrimination against males is lacking, however, and the adaptive interpretation of male-biased mortality is confounded by an alternative explanation that it reflects differential energetic requirements between the sexes (due to sexual selection for large size in mature males) independent of parental manipulation. To determine whether maternal discrimination against offspring explains postnatal mortality in a sexually dimorphic rodent, we examined patterns of growth and mortality in offspring of food-restricted and food-enriched lactating bushy-tailed woodrats,Neotoma cinerea. We also monitored mothers and their litters daily throughout lactation for evidence of maternal discrimination against offspring. Offspring of food-restricted mothers showed depressed growth, and mortality of offspring born to both food-restricted and food-enriched mothers was male-biased, but in the absence of maternal discrimination. Offspring that died were no less likely to be attached to their mother's teats in the 10 days prior to death than were offspring that successfully weaned. Similarly, offspring of food-restricted mothers were attached as often as were offspring of food-enriched mothers. In a series of behavioural arena trials in the first 10 days after birth, restricted mothers were no less attentive toward their sons than they were to their daughters, nor did mothers treat their offspring that did not survive to weaning differently from those that survived. Our findings provide empirical evidence that postnatal, sex-biased mortality in offspring is not necessarily due to parental intervention, and they call into question the adaptive interpretations of previous examples of sex-biased offspring mortality.

Evolutionary and ecological response of pocket gophers (Thomomys talpoides) to late-Holocene climatic change

Late-Holocene evolutionary and ecological response of pocket gophers (Thomomys talpoides) and other species to climatic change is documented by mammalian fossils from Lamar Cave, a palaeontological site in northern Yellowstone National Park. Pocket gophers illustrate ecological sensitivity to a series of mesic to xeric climatic excursions in the sagebrush-grassland ecotone during the last 3200 years, increasing in abundance during mesic intervals, and declining in abundance during xeric intervals. Four other small mammal taxa (Microtus sp., Peromyscus maniculatus, Neotoma cinerea and Spermophilus armatus) also show response to climatic change, increasing or decreasing in abundance in accordance with their preferred habitat requirements. To determine evolutionary response to climate, two craniodental characters for the northern pocket gopher (Thomomys talpoides) are investigated in modern representatives within a 400 km radius of Lamar Cave and then tracked through the time spanned by the fossils. One morphologic character shows that variation in body size, primarily a plastic response to the environment, demonstrates few taxonomically consistent patterns of geographic variation across 39 modern localities. In contrast, the other character indicates genetic relatedness within subspecies. Stasis in the genetically controlled character indicates that the same subspecies of pocket gopher (T. talpoides tenellus) has occupied northern Yellowstone for at least 3200 years. However, T. t. tenellus does show plastic response to climatic change because pocket gophers during the Medieval Warm Period were smaller than at any other time spanned by the deposit.

Molecular Phylogeny of the Neotoma floridana Species Group

A phylogeny of the Neotoma floridana species group of woodrats was inferred using mi-tochondrial-DNA (mtDNA) restriction sites identified by 17 type-II restriction endonucleas-es. Wagner, Dollo, and generalized parsimony analyses revealed a sharp dichotomy among populations of Neotoma albigula found east and west of the Rio Grande. Additional polymorphism among samples of N. albigula from northern Mexico also was detected. Data from mtDNA suggest paraphyly exists within N. albigula and that at least two cryptic species are present within the taxon. Phylogenetic and phenetic analyses of the mtDNA data reveal a sister-group relationship between Neotoma micropus and N. albigula , whereas N. floridana and Neotoma magister form sister taxa to this group. These results clarify discrepancies reported for this species group based on morphologic, allozymic, and karyotype data. Additionally, Neotoma phenax, Neotoma cinerea, Neotoma mexicana , and Neotoma stephensi were included to provide an intrageneric perspective on relationships within the N. floridana species group. N. mexicana and N. stephensi formed a clade associated with the N. floridana species-group clade with N. phenax and N. cinerea appearing as sole members of branches basal to the remaining Neotoma .

Foraging movements of female bushy-tailed wood rats (Neotoma cinerea)

Nocturnal foraging movements of female bushy-tailed wood rats (Neotoma cinerea) in the Canadian Rocky Mountains, Alberta, were monitored using radiotelemetry over two breeding seasons (1993–1994). Total distance moved and maximum foraging radius from the nest per night were calculated for individual females throughout the breeding season. Movements during pregnancy, lactation, and the postreproductive period did not differ significantly. Females moved much farther (up to 470 m) from the nest than previously reported for this species (60 m). Such long-distance movements may be related to the availability of an appropriate food supply.

Spatial distribution in the bushy-tailed wood rat (Neotoma cinerea) and its implications for the mating system

We examined the spatial distribution of reproductively active bushy-tailed wood rats (Neotoma cinerea) over three breeding seasons (1992–1994), using radiotelemetry. An index value was calculated for each animal to describe the degree of intersexual and intrasexual overlap. We tested the prediction that our pattern of spatial distribution would resemble that of a polygynous mating system, which has been suggested for this species. Over the three seasons of study, no significant differences were observed between the degrees of intersexual and intrasexual overlap of males. Females exhibited either similar degrees of intersexual and intrasexual overlap (1992 and 1993) or a greater degree of intersexual than intrasexual overlap (1994). Such a pattern of spatial overlap does not support the predictions of a polygynous mating system. We suggest that bushy-tailed wood rats display a pattern of spatial organization that is consistent with a promiscuous mating system.

Home range size of Bushy-tailed Woodrats, Neotoma cinerea, in southwestern Alberta

Home range size of Bushy-tailed Woodrats, Neotoma cinerea, in southwestern Alberta

Evolution of Body Size in the Woodrat over the Past 25,000 Years of Climate Change

Microevolutionary changes in the body size of the bushy-tailed woodrat ( Neotoma cinerea ) since the last glacial maximum were estimated from measurements of fecal pellets preserved in paleomiddens from the Great Basin and Colorado Plateau of the United States. The changes closely track regional temperature fluctuations simulated by the Community Climate Model of the National Center for Atmospheric Research and also those estimated from deuterium isotope ratios of plant cellulose recovered from paleomiddens. Body size decreased during periods of climatic warming, as predicted from Bergmann's rule and from physiological responses to temperature stress. Fossil woodrat middens, by providing detailed temporal sequences of body sizes from many locations, permit precise quantification of responses to climatic change that have occurred in the past and may occur in the future.

Variation in Sex Ratios of Offspring in Wild Bushy-Tailed Woodrats

We investigated the effects of maternal weight and age and density of breeding females on sex ratio (percentage of males) in litters of wild bushy-tailed woodrats ( Neotoma cinerea ), a sexually dimorphic rodent. Sex ratios in full-sized litters (i.e., those that had not likely experienced mortality during gestation or lactation) were unaffected by experimentally reduced densities of females, nor did they differ between litters born to yearling and adult (≥2 years) mothers. However, sex ratios in litters were strongly correlated ( R = 0.71, P = 0.0001) with prebreeding body weight in adult mothers, suggesting that adult woodrats adjust sex ratios in litters at conception or early gestation in relation to maternal condition. Although yearling mothers did not appear to adjust prebirth sex ratios, postbirth loss was more strongly male-biased in litters born to yearling mothers than in those born to adults, and we suggest that yearlings may adjust sex ratios during the investment period from birth to weaning.

Pollen Limitation and Population Growth in a Herbaceous Perennial Legume

woodrat, Neotoma cinerea. University of California Publications in Zoology 110:1-121. Gutierrez, R. J. 1985. An overview of recent research on the spotted owl. Pages 39-49 in R. J. Gutierrez and A. B. Carey, technical editors. Ecology and management of the spotted owl in the Pacific Northwest. U.S. Forest Service General Technical Report PNW-185. Menkens, G. E., Jr., and S. H. Anderson. 1988. Estimation of small-mammal population size. Ecology 69:1952-1959. Montgomery, W. I. 1987. The application of capture-markrecapture methods to the enumeration of small mammal populations. Symposia of the Zoological Society of London 58:25-57. Old-Growth Definition Task Group. 1986. Interim definitions for old-growth Douglas-fir and mixed-conifer forests in the Pacific Northwest and California. U.S. Forest Service Research Note PNW-447. Quinn, J. E, and A. E. Dunham. 1983. On hypothesis testing in ecology and evolution. American Naturalist 122:602617. Rosenberg, D.K., and R. G. Anthony. 1992. Characteristics of northern flying squirrel populations in young secondand old-growth forests in western Oregon. Canadian Journal of Zoology 70:161-166. Rosenberg, D. K., C. J. Zabel, B. R. Noon, and E. C. Meslow. 1994. Northern Spotted Owls: influence of prey base-a comment. Ecology 75: 1512-1515. Sakai, H. E, and B. R. Noon. 1993. Dusky-footed woodrat abundance in different-aged forests in northwestern California. Journal of Wildlife Management 57:373-382. Thomas, J. W., E. D. Forsman, J. B. Lint, E. C. Meslow, B. R. Noon, and J. Verner. 1990. A conservation strategy for the northern spotted owl. Report of the interagency committee to address the conservation strategy of the northern spotted owl. U.S. Forest Service, Portland, Oregon, USA. Volz, K. 1986. Habitat requirements of northern flying squirrels in west-central Oregon. Thesis. Washington State University, Pullman, Washington, USA. Witt, J. W. 1992. Home range and density estimates for the northern flying squirrel, Glaucomys sabrinus, in western Oregon. Journal of Mammalogy 73:921-929. Zar, J. H. 1984. Biostatistical analysis. Prentice Hall, Englewood Cliffs, New Jersey, USA.

Philopatry and mother-daughter associations in bushy-tailed woodrats: space use and reproductive success

Social groups in mammals are often based on overlapping generations of philopatric females, yet few researchers have examined fitness consequences of associations between females and their daughters. We examined survival and reproductive consequences of sharing a natal site with one's mother or daughter in wild bushy-tailed woodrats (Neotoma cinerea). Bushy-tailed woodrats reside on discrete rocky outcrops, and females tend to spend their entire reproductive life on their natal outcrop. Mothers and daughters that co-existed on the natal outcrop were closely associated in space. Juvenile females were more likely to survive their first winter to become breeding yearlings at their natal site if their mother was also present at the natal site during the winter. Juveniles survived equally well with or without their mother where densities of adult females were experimentally reduced, suggesting that females enhance their daughter's survival by facilitating their access to limited resources. Yearling females exhibited no reproductive costs from association with their mothers at the natal site during the breeding season; in fact, yearlings that bred at the natal site simultaneously with their adult mothers tended (P = 0.07) to experience fewer reproductive failures than did those that bred in the absence of their mothers. Mothers did not experience any detectable costs when sharing a natal site with a daughter. We conclude that bushy-tailed woodrats exhibit stable, fitness-enhancing associations among mothers and their philopatric daughters.

Philopatry and mother-daughter associations in bushy-tailed woodrats: space use and reproductive success

Philopatry and mother-daughter associations in bushy-tailed woodrats: space use and reproductive success

Northern Spotted Owls: Influence of Prey Base‐‐A Comment

Conflicts between the needs of the Northern Spotted Owl (Strix occidentalis caurina) and the maintenance of a timber-based economy in the Pacific Northwest have motivated research on the habitat and area requirements of the owl. The Northern Spotted Owl has been studied extensively throughout its range and consistently has been found to select older forest stands for foraging, roosting, and nesting (reviewed in Thomas et al. [1990]). At least six hypotheses have been proposed to account for selection of older forests by Spotted Owls (Forsman et al. 1977, 1982, 1984, Carey et al. 1990, 1992, Rosenberg and Anthony 1992). Two of these relate to their prey. The prey hypotheses suggest that prey are more available to Spotted Owls by either or both of two mechanisms: (1) prey are simply more abundant in older forests (prey abundance hypothesis), and (2) prey are more efficiently hunted in older forests because of an increase in the ability of owls to forage through more open understory structure (prey availability hypothesis). Carey et al. (1992) recently reported on associations between Spotted Owls and their prey in Oregon and Washington. They concluded that the abundance of prey across a landscape determined the carrying capacity for Spotted Owls and that within-landscape features such as stand age and forest fragmentation affected the abundance and demographic characteristics of prey. Northern flying squirrels (Glaucomys sabrinus) and dusky-footed and bushy-tailed woodrats (Neotoma fuscipes and N. cinerea, respectively) are the most common prey of the Northern Spotted Owl throughout its range, constituting the majority of the biomass consumed by owls (Forsman et al. 1984). Carey et al. (1992) concluded that northern flying squirrels were more abundant in older forests, populations were more

Isolation of Borrelia burgdorferi from the blood of a bushy-tailed wood rat in California.

Borrelia burgdorferi was isolated from the blood of a bushy-tailed wood rat (Neotoma cinerea) from northeastern California, USA. This is the first isolation of live B. burgdorferi spirochetes from a wild animal in California. Spirochetes were observed in stained tissues from the brain, liver, spleen, and kidneys.

Behavioural asymmetries and cohesive mother–offspring sociality in bushy-tailed wood rats

Bushy-tailed wood rats (Neotoma cinerea) are usually confined to highly clumped resource patches (i.e., rock outcrops), and potentially compete for limited den sites within outcrops. Adults may breed on the same outcrop over several years, and philopatric yearlings usually breed in proximity to close kin. We investigated the influence of kinship and reproductive status on the nature and stability of wood rat sociality. Behavioural interactions among mother–offspring and adult female – nonkin dyads from the wild were quantified in a neutral arena during (i) the autumn when offspring were immature subadults, and (ii) the following spring, when all dyad members were reproductively active. Nonkin dyads were characterized almost entirely by agonistic behaviour. Virtually all amicable behaviour was directed toward close kin, and most interactions among kin dyads were amicable. Further, these strong kin-based behavioural asymmetries did not differ between the autumn and the subsequent breeding season, and could not be explained by postweaning familiarity (i.e., residency on a common habitat patch) alone. Wood rat sociality appears to be characterized by two elements: (i) divisive agonism directed toward nonkin, and (ii) stable, cohesive relationships among close kin (mother–offspring). Possible causes and consequences of sociality in bushy-tailed wood rats are discussed.

Reproduction and nutrient reserves of bushy-tailed wood rats (Neotoma cinerea)

Body composition and energy content of female bushy-tailed wood rats (Neotoma cinerea) were examined in relation to reproductive status. We assessed the extent to which nutrients for offspring were obtained from endogenous reserves, and whether use of these reserves might influence the timing of spring breeding. Among breeding females, fat levels were highest during pregnancy, and were depleted during lactation. The mean reduction in energy content from pregnancy through lactation (266 kJ) accounted for 21% of the estimated 1260 kJ contributed by a female to her offspring in this period. Females potentially gained 3.0 days of nutritional support from their endogenous reserves during winter, but this fell to 2.0 days during summer and was only 0.8 days during lactation. Thus, females support the nutritional demands of lactation primarily by increasing their ingestion of food. Nevertheless, large endogenous reserves may enable some females to begin breeding early in the spring, when the abundance of food is unpredictable.

New Host and Locality Records of Coccidia (Apicomplexa: Eimeriidae) from Rodents in the Southwestern and Western United States

One hundred forty-seven murid and heteromyid rodents were collected from various sites in the southwestern and western United States (Arizona, Colorado, New Mexico, Texas, and Utah) and Baja California Norte, Mexico, and their feces were examined for coccidial parasites. Of these, 53 (36%) were infected with at least 1 coccidian; 45 of 53 (85%) of the infected rodents harbored only 1 species of coccidian. Infected rodents included: 10 of 22 (45%) Neotoma albigula, 3 of 11 (27%) Neotoma floridana, 2 of 14 (14%) Neotoma lepida, 15 of 29 (52%) Neotoma micropus, 5 of 8 (63%) Peromyscus crinitis, 6 of 6 (100%) Peromyscus difficilis, 1 of 2 (50%) Peromyscus eremicus, 9 of 34 (26%) Sigmodon hispidis, and 2 of 3 (67%) Sigmodon ochrognathus; 4 Neotoma cinerea, 3 Neotoma devia, 3 Neotoma mexicana, 1 Peromyscus maniculatus, 1 Onychomys leucogaster, 1 Onychomys torridus, 3 Chaetodipus fallax, and 2 Chaetodipus penicillatus were negative. Although no new species was found, the following coccidians were identified from infected rodents: Eimeria albigulae from N. albigula, N. floridana, and N. micropus, Eimeria antonellii from N. albigula and N. micropus, Eimeria ladronensis from N. albigula, N. floridana, N. lepida, and N. micropus, Eimeria arizonensis and Eimeria lachrymalis from P. crinitis and P. difficilis, Eimeria lachrymalis from P. eremicus, Eimeria tuskeegensis from S. ochrognathus, and Eimeria roperi, Eimeria sigmodontis, Eimeria tuskeegensis, Eimeria webbae, and an unidentified species of Eimeria from S. hispidis. This report documents 12 new host and several distributional records for Eimeria species from murid rodents in Arizona, Texas, and Utah.

Techniques for immobilizing and bleeding marmots and woodrats.

Blood samples were obtained in the field by femoral vein puncture in bushy-tailed woodrats (Neotoma cinerea) and yellow-bellied marmots (Marmota flaviventris) that had been injected intramuscularly with ketamine hydrochloride. Dosages ranged from 50 mg/kg for marmots to 30 to 110 mg/kg for woodrats. Sedated animals were handled easily, and a volume of blood sufficient for hematological assays or electrophoresis could be collected.