Global ETD Search

1	Neurogenesis in the brains of subadult and adult South African ground squirrels (Xerus inauris) Chengetanai, Samson January 2014 (has links) Dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand in fulfilment of the requirements for the degree of Master of Science in Medicine School of Anatomical Sciences Faculty of Health Sciences University of the Witwatersrand / Neurogenesis is the ability of the brain to generate new neurons. Neurogenic sites and rates of neuronal proliferation were investigated in the brains of subadult and adult South African ground squirrels. Seven female ground squirrels were trapped; euthanised and their ages determined using body masses and paired dry lens masses. Their brains were perfusion fixed with 4% paraformaldehyde before sectioning at 50 μm in a sagittal plane from which every fifth section was stained with cresyl violet to determine the architecture of the brain. Immunolocalisation of Ki-67 for neuronal cell proliferation and doublecortin (DCX) for immature neurons was also carried out on adjacent sections to those stained for cresyl violet. Ki-67 immunopositive neurons were counted in the dentate gyrus of the hippocampus to determine the changes in the rate of cell proliferation with age. Proliferating and immature neurons, DCX immunopositive, were observed in the subventricular zone (SVZ) of the lateral ventricles, the subgranular zone (SGZ) of the dentate gyrus, the rostral migratory stream (RMS), olfactory bulb, piriform cortex and neocortex of both age groups. Adult squirrel brains were heavier than the subadult brains, but showed significantly lower numbers of proliferating neurons in the dentate gyrus when compared to subadult brains. Sciuridae
2	Response of small mammal mycophagy to varying levels and patterns of greentree retention in mature forests of western Oregon and Washington / Jacobs, Katherine M. January 1900 (has links) Thesis (M.S.)--Oregon State University, 2003. / Typescript (photocopy). Includes bibliographical references (leaves 87-97). Also available on the World Wide Web.
3	Prevalence a diverzita kryptosporidií infikujících veverky (Sciuridae) / Biology and diversity of Cryptosporidium infecting squirrels (Sciuridae) BARVÍŘ, Pavel January 2014 (has links) In total 399 samples from three species of squirrels (Sciurus vulgaris, Sciurus carolinensis and Callosciurus finlaysonii) were collected from 2010 to 2013. All samples were examined for the presence of Cryptosporidium using by molecular methods, which demonstrated by presence of Cryptosporidium specific DNA in 18 samples (4.5%). Out of them 12 samples were positive onCryptosporidium ferret genotype, 3 on Cryptosporidium skunk genotype, 1 on Cryptosporidium chipmunk genotype I and 2 samples onCryptosporidium ubiquitum. Statistical analyses did not reveal any influence of gender on the occurrence of Cryptosporidium. Juvenile individuals of squirrels from the family Sciuridae are more often infected by Cryptosporidium than the adult animals.
4	The Socioecology, Mating System and Behavior of Round-Tailed Ground Squirrels (Xerospermophilus tereticaudus) Munroe, Karen Elizabeth January 2011 (has links) Social organization of a species may impact behavior, reproductive ecology, mating system, population genetic structure and overall fitness. A spectrum of sociality exists from solitary individuals to aggregations to integrated, highly related groups. A large body of knowledge exists for sociality and life-history characteristics of ground-dwelling sciurids, including several overarching models to explain the evolution of sociality. These models predict round-tailed ground squirrels (Xerospermophilus tereticaudus) to be solitary based on small body size (~125g), relatively long period of activity (January-June) and a short period of adult-juvenile overlap. However, previous behavioral observations suggest round-tailed ground squirrels have a clustered matrilineal structure with a suite of social behaviors, suggesting that they may represent a unique outlier in ground squirrel sociality models. Within the population of round-tailed ground squirrels at the Casa Grande Ruins National Monument in Coolidge, Arizona, USA, rates of amicable and agonistic interactions between adults were low, with no relationship between relatedness of individuals and rates of social interactions. No population substructure was evident with Bayesian analyses, global or pairwise F(ST) values, and average relatedness among females did not differ from males. Contrary to previous behavioral studies, round-tailed ground squirrels did not have high levels of social behavior, nor did they form significant genetic subpopulation structuring. The active season of round-tailed ground squirrels closely followed patterns of precipitation and peak resource availability. Body mass differed between males and females, across years, and within seasons. Males were heavier than females at emergence, prior to mating and pre-hibernation, but not when females began gestation. Emergence of litters and litter size are related to amount and timing of winter rainfall. Foraging and vigilance behaviors compose 64-66% of the activity budget, but differ in that males spend a greater proportion of time foraging, whereas females spend a greater proportion of time vigilant. Round-tailed ground-squirrels have a polygynandrous mating system. Polygyny was evident in 2004, 2005, and 2006, and multiple paternity occurred in the majority of litters with 2.5 sires/litter; litter size was positively correlated with the number of sires. These findings support predictions generated by sociality models for ground-dwelling squirrels. Annual cycle Arizona Mating system Polygynandry Sciuridae Sociality
5	Sciurids (Rodentia: Sciuridae) of the Late Mio-Pliocene Gray Fossil Site and the Late Miocene Tyner Farm: Implications on Ecology and Expansion of the Sciurid Record Crowe, Cheyenne J 01 May 2017 (has links) Sciurids are one of the most diverse mammalian groups today, but the fossil record does not reflect that diversity. The purpose of this project was to identify sciurids from two late Miocene sites—the Gray Fossil Site (GFS) of Tennessee, and Tyner Farm of Florida—and use those identifications to infer the ecology of the two. From the GFS four sciurids were identified: Eutamias or Neotamias, Glaucomys, and two tree squirrels (Sciurini). Two sciurids were identified from Tyner Farm: a chipmunk attributed to Tamiina, and a ground squirrel attributed to Marmotina. Paleoenvironmental inferences based on the sciurids present at both sites are consistent with previous work. The GFS Eutamias or Neotamias is the first record of a western chipmunk population in eastern North America; the GFS tree squirrels are the earliest record of a tree squirrel in eastern North America. The GFS Glaucomys is the earliest record of the genus. Gray Fossil Site Tyner Farm Miocene Sciuridae squirrels Paleobiology Paleontology
6	Competition for Conifer Cones as a Potential Mechanism of Endangerment for the Mount Graham Red Squirrel Minor, Rebecca January 2010 (has links) Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. As species invasions continue to rise, it is important to understand how to mitigate this threat. Our field experiment quantified the impact of introduced Abert's squirrels (Sciurus aberti) on rates of food removal within the range of the critically endangered Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis). In the presence of Abert's squirrels, the time until 50% of cones were removed was 5.55 days faster than when Abert's squirrels were excluded (95% confidence interval 2.25 to 11.63 days). The impact on food availability as a result of cone removal by Abert's squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. Eradication of established non-native populations is rare. Management targeted at specific mechanisms by which non-natives cause endangerment is an essential tool for conservation. Arizona endangered species invasive species removal rate resource competition sciuridae
7	Space use in a population of least chipmunks in the Southwest Yukon Glennie, Linda Cuffableness January 1988 (has links) This thesis describes an investigation of space use in least chipmunks at Kluane Lake, in the southwest Yukon. I examined demography, home range and habitat use patterns in the population. Based on live-trapping data from two grids over two summers, mean number of animals on the study area was 22.6/grid, similar to chipmunk numbers measured there over the previous four years. The population was lower than is generally found in the same species further south, although year-to-year stability was typical. Chipmunks preferred open forest and shrub-land to closed-canopy forest, which is also typical of the genus. Home range sizes measured using telemetry averaged 4.86 ha, higher than in any previously published study of the genus. I examined the relationship between social spacing and space use. Home range overlap averaged 93.4%; chipmunks do not appear to defend exclusive core areas. Provoked interactions among neighbours suggested that social dominance was based on age, weight, and breeding condition, rather than ownership of space. Although provoked interactions were generally aggressive, the telemetry data suggest that such behaviour was artifactual. Comparing the encounter frequency of radio-collared animals to that generated by a random model showed that chipmunks avoided encounters, except when harvesting seasonally abundant food. Grid-trapping did not increase food or cover availability enough to affect home range size. There was evidence that the presence of traps affected use distribution but not enough to invalidate trap-based home range estimates. Comparison of trap and telemetry based estimates of home range size yielded no significant differences. / Science, Faculty of / Zoology, Department of / Graduate Chipmunks Sciuridae
8	Srovnání kondice populací sysla obecného v souvislosti se stanovištními podmínkami a hustotou populace / Fitness comparison of the European ground squirrel's populations living in different habitats and population density Novotná, Kristýna January 2013 (has links) Fitness in ground squirrels is a frequently discussed topic, reported in many publications, although it was rarely the subject of their study. The aim of this study was to determine which factors and find out how they affect the fitness of individuals, and thus the whole population of the European ground squirrel in Czech Republic. For this purpose we collected body mass data at three studied population, which are the main indicator of the fitness in ground squirrels. We also recorded information about injuries, reproduction status, ectoparasites and endoparasites. Moreover we collected all available data on the body mass of European ground squirrel in the central European region, and we compiled overview of body mass changes during the season. This enables us to compare our data with typical/common body mass value in particular sex, age and season. Recorded differences in body mass at three studied sites were related to sex, age, locality and season. We found positive correlation between the body mass and injuries from fights/reproduction activity in adult males. The relationship between body mass and reproduction activity of females was not found. Four species of ectoparasites, mostly occurring in adults, were recorded in studied populations. We also found five species of endoparasites, which...
9	Climate and Ecological Change in Oligo-Miocene Mammals Orcutt, John D. 12 1900 (has links) xiii, 198 p. : ill. (some col.) / Whether or not a causal relationship exists between climate and mammal body size is one of the longest-standing and most intractable questions in ecology. The classic model of body size evolution (Bergmann's Rule) holds that body size is driven by temperature, but more recent hypotheses have suggested that other climatic variables or biotic interactions may play a more important role. The use of paleoecological data to address this question allows variables that are tightly correlated in modern ecosystems to be teased apart and allows body size patterns to be observed through time, adding an extra dimension to analyses. This dissertation details the findings of two paleoecological tests of Bergmann's Rule in the Oligo-Miocene (30-5 Ma), one tracking body size and climate through time in the northwestern United States and another tracking geographic body size trends through time along the west coast of North America. In both cases, body size was analyzed in three representative families of mammals: equids, canids, and sciurids. Such large-scale analyses are dependent on fossils that can be placed in a reliable taxonomic, geologic, and temporal context, and this dissertation also focuses on a reevaluation of the canid fauna of Oregon's Juntura Formation that places a critically important Late Miocene carnivore fauna in just such a context. Two genera of canids - Epicyon and Carpocyon - are described from the fauna for the first time, with important implications for regional biostratigraphy. The body size analyses show no consistent relationship between body size and any climatic variable. Further, body size patterns vary widely between taxa at several levels, suggesting that one universal driver of body size evolution does not exist. Not only is there no evidence for Bergmann's Rule in Oligo-Miocene mammals, but comparative analyses of geographic body size patterns in the modern genera Odocoileus, Canis, and Spermophilus fail to show the latitudinal gradients upon which Bergmann's Rule is predicated. The apparent existence of such trends in some taxa may be the result of anthropogenic extirpation at low latitudes, further underscoring the importance of including paleontological data when formulating models predicting the response of biotic variables to environmental change. / Committee in charge: Dr. Samantha Hopkins， Chair； Dr. Gregory Retallack， Member； Dr. Rebecca Dorsey， Member； Dr. Stephen Frost， Outside Member Ecology Climate change Paleontology Macroecology Paleoecology Earth sciences Biological sciences Bergmann's rule Body size Canidae Equidae Sciuridae Oligo-miocene Mammals Climatic changes
10	Aplodontid, sciurid, castorid, zapodid and geomyoid rodents of the Rodent Hill locality, Cypress Hills formation, southwest Saskatchewan Bell, Sean Daniel 23 December 2004 The Rodent Hill Locality is a fossil-bearing site that is part of the Cypress Hills Formation, and is located roughly 15 km northwest of the town of Eastend, Saskatchewan. A number of fossil mammal and other vertebrate taxa are present at Rodent Hill; the primary objective of this project was to identify the fossil rodents of the families Sciuridae, Aplodontidae, Castoridae, Heliscomyidae, Heteromyidae, Florentiamyidae and Zapodidae. These taxa were correlated with rodents from other North American faunas to establish the age of the Rodent Hill Locality. <p>The species Haplomys cf. H. liolophus, Dakotallomys cf. D. pelycomyoides, Kirkomys milleri, Proheteromys nebraskensis, Agnotocastor cf. A. praetereadens, and possibly Cedromus cf. C. wilsoni support the Whitneyan age designation of the Rodent Hill Locality. Taxa that are described from Rodent Hill that are better known from earlier-age sites include Heliscomys vetus and H. hatcheri, Ecclesimus sp. and Oligotheriomys sp. Taxa that are younger than Whitneyan but have been recovered at Rodent Hill include Parallomys sp., Plesiosminthus sp., Protospermophilus sp., and Nototamias sp. Two new species in the genus Sciurion, and one new species in the genus Pseudallomys are described, and a new species of Heliscomys is identified but not formally named. <p>The rodents from the Rodent Hill Locality support the Whitneyan age assignment of the site. This is based on the presence of Whitneyan taxa, and the in situ co-occurrence of older and younger taxa within the site. Dakotallomys Pseudallomys Agnotocastor Oligotheriomys Palaeocastorinae Geomyoidea Heliscomyidae Heliscomys Heliscomys vetus Heliscomys hatcheri Syphyriomys Florentiamyidae Kirkomys Kirkomys milleri Ecclesimus Heteromyidae Proheteromys Proheteromys nebraskensis Sciuridae Parallomys Sciurion Castoridae Nototamias Protospermophilus Haplomys Campestrallomys Prosciurus Aplodontidae Cedromus Plesiosminthus Zapodidae North America Oligocene Whitneyan

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