Supernumerary Teeth in Pleistocene, Recent, and Hybrid Individuals of the Spermophilus richardsonii Complex (Sciuridae)

A supernumerary distal upper molar, always expressed bilaterally, occurred in Pleistocene (one of 204) and Recent (five of 1,667) specimens of the Spermophilus richardsonii complex. Among Recent specimens with the abnormality, three of four with known provenance came from adjacent colonies with hybrids of S. richardsonii (Richardson\u27s ground squirrel) and S. elegans (Wyoming ground squirrel). Elsewhere, the trait was rare in S. richardsonii (one of 947) and absent in S. elegans (out of 668). Affected individuals exhibited normal P3-M2, but two aberrant teeth distal to M2. Aberrant teeth exhibited a mosaic of features typical of M2, M3, and atypical of any normal tooth. The trait was inferred to be hereditary

P-29 Diversity and Species Turnover of Late Cenozoic Ground Squirrels in the Meade Basin, KS

The Meade Basin of southwestern Kansas preserves one of the richest fossil sequences from the late Cenozoic of North America. An ongoing study has documented a rich record of fossils, especially rodents; established episodes of especially rapid species turnover (when species appear or disappear from the local record); and has attempted to relate these processes to environmental change inferred from stable isotope and other proxies for ancient climate. Here, I report on fossil squirrels from the record. At least 7 genera and 13 species are present in the composite record. Species turnover occurs throughout the record, but an especially high turnover is associated with the transition between the warmer Pliocene and cooler Pleistocene. Documentation of the relationship between inferred paleoenvironmental change, diversity, and species turnover from the fossil record might shed light on plausible consequences of the current episode of anthropogenic environmental change

Odontometric Patterns in the Radiation of Extant Ground-dwelling Squirrels within Marmotini (Sciuridae: Xjrini)

I document odontometry variation across ground-dwelling squirrels of the Holarctic tribe Marmotini. Dental size, which correlates well with published average body mass values across species, accounts for most odontometric variation across the clade. Dental shape variation primarily reflects relative size of P3 (upper cheek teeth) and relative width of p4-ml + length of m3 (lower cheek teeth). Shape variables and relative tooth crown height covary significantly across species, suggesting a common functional complex or shared genetic control. When dental morphology is mapped on published DNA-based phytogenies, Sciurotamias (Chinese rock squirrels), Ammospermophilus (antelope squirrels), and basal subgenera within Spermophilus (ground squirrels [Callospermophilus and Otospermophilus]) are shown to retain inferred primitive dental morphology- small to moderate dental size, relatively small P3, relatively narrow p4-ml + shortened m3, and relatively low toothcrown height. Other clades depart from this morphotype in size (very small in Tamias [chipmunks] and very large in Marmota [marmots]), tooth shape (especially 2 clades representing Eurasian and North American subgenus Spermophilus), or in both attributes (notably Cynomys [prairie dogs]), with frequent homoplasy. A plot of odontometric distance against published estimates of divergence time between sister clades suggests a roughly clocklike accumulation of odontometric change through time but highlights episodes of rapid odontometric evolution during the origins of Marmota, Cynomys, and Spermophilus parryii (arctic ground squirrel). © 2009 American Society of Mammalogists

Field Documentation of Summer and Fall Diet in Thirteen-lined Ground Squirrels, Ictidomys Tridecemlineatus

Prior work has shown a shift in stable carbon isotope values of Ictidomys tridecemlineatus incisors and fecal pellets late in the active season (Jang et al., 2012 and Chacko, 2013). The purpose of this study was to find out if the diet of I. tridecemlineatus shifts from C3 to C4 plants during the late part of the active season through direct observation of feeding activities. Observations were made at the Andrews University Airpark in SW Michigan from July to late September, 2013. Representative samples of plant and insect material fed on were collected and analyzed for stable carbon and nitrogen isotopic composition. We found no shift from C3 to C4 plant diet. However, there was a C13 enrichment of plant and insect material over the course of the active season

Lower Incisors of Prairie Dogs (Cynomys) as Biorecorders of Hibernation and Season of Death

Incremental dentin and associated enamel, features visible at the surface of lower incisors of rodents, may chronicle important life-history information. This study investigated surface features of lower incisors representing 4 taxa of prairie dogs (Cynomys) in relation to hibernation and season of year. A set of abnormalities in dentin and enamel, observed on 20 of 138 incisors, always chronicled an event ending in late winter or early spring and was interpreted as a hibernation mark. Hibernation was recorded in the incisors of obligate hibernators, C. leucurus and C. gunnisoni, as well as in 20% of specimens of the facultative heterotherm, C. ludovicianus, with relevant winter growth record. Inspection of prairie dog incisors from museum collections elucidated patterns in the timing of spring emergence across species, sexes, and elevations. Growth rates of prairie dog incisors (estimated from thicknesses of circadian dentin increments) showed general seasonal patterns when pooled by sex and species, but daily growth rates recorded along individual incisors often fluctuated idiosyncratically through time. However, incisors that chronicled a significant temporal trend in daily growth rate registered either early-season (increased growth rate through time) or late-season growth (decreased growth rate through time). None of 11 late-Pleistocene fossil C. niobrarius churcherii exhibited a hibernation mark, but 4 of these exhibited significant decrease in growth rate along their incisors, probably indicating animals that died late in the active season. © 2006 American Society of Mammalogists

Investigation of Spatial Isotope Ratios in Soil and the Effects of Fertilizer on Plant Isotope Ratios

A previous Honors study analyzed diet of thirteen-lined ground squirrels at the Andrews University Airpark by studying δ13C and δ15N isotope values of their fecal pellets (Chacko, 2013). Fecal samples collected within 25m of a cornfield had elevated isotope values. High δ13C values indicate greater consumption of C4 plants, such as corn (Ehleringer et al., 1986); high δ15N values indicate increased consumption of animal matter (DeNiro and Epstein, 1981 ). However, the spatial pattern may be due to variation in the soil, reflecting long-term patterns in the vegetation. Soil samples were taken throughout the airpark and analyzed for δ13C and δ15N. These baseline values were removed from fecal values, but the patterns of the fecal samples still held. Application of fertilizer to vegetation resulted in a significant increase in δ15N. Thus, the δ15N pattern observed in the fecal samples appears to be due to enrichment in corn

Estimates of Body Mass for Fossil Giant Ground Squirrels, Genus Paenemarmota

Paenemarmota Hibbard and Schultz, 1948 includes 3 species of giant ground squirrels within Marmotini (Rodentia, Sciuridae) from the Late Miocene and Pliocene of central and western North America. We developed skeletal and dental models for estimating body mass across modern species of Marmotini and apply these models to Paenemarmota. The most reliable models for estimating body mass of modern species (on the basis of length and width of femur, lengths of p4 and P4) generally yielded lower estimates of body mass for Paenemarmota than less reliable models (on the basis of lengths of m1, m2, M1, and M2). Models that were most reliable across modern species yielded 2 nonoverlapping estimates for P. barbouri Hibbard and Schultz, 1948: 9.59.8 kg on the basis of femur dimensions, and 14.416.2 kg on the basis of lengths of premolars. On the basis of lengths of premolars, P. mexicana (Wilson 1949) closely resembled P. barbouri in estimated mass (14.415.7 kg), but P. sawrockensis (Hibbard 1964) was smaller (10.012.4 kg). These large ground squirrels probably differed in mass-dependent biological attributes from all modern marmotines. © 2012 American Society of Mammalogists

P-26 Hawksbill Turtle (Eretmochelys imbricata) Density and the Effect of Pollution Debris on the Crawling Rates of Hawksbill Hatchlings in Utila, Honduras

The hawksbill turtle (Eretmochelys imbricata) is a critically endangered species. Hence, various conservation efforts by groups such as ProTECTOR are taking place to stabilize its population. To support such efforts, my study focused on the turtle population in and around the island of Utila, Honduras. Specifically, I examined the critical migration period of hawksbill turtle hatchlings from nest to water to determine if various densities of plastic pollution had an effect on crawling times. A reduction in crawling time is critical for it could increase predation time. Furthermore, the pollution debris may deter movement, causing the hatchling to expand additional energy before they reach the ocean. To test the effect of plastic pollution, we constructed four experimental corridors (ranging from 8-10 m in length) with varying densities of pollution and recorded hatchling crawling time from start to finish (10 hatchlings/corridor). Crawling rates differed significantly across corridors (Kruskal-Wallis H test). In addition, a potential baseline pattern of turtle abundance at dive locations around the island was determined through a survey of turtle sightings. Through ArcGIS, these specific GPS points of reported turtle sightings was plotted to observe any patterns of distribution

Changes in Industrial and Occupational Structures of Texas Counties, 1960-80

This paper identifies and examines industrial and occupational changes that have accompanied population growth in Texas. According to the 1960 U.S. Census definitions for county size, Texas counties were grouped as metropolitan, urban-nonrnetropolitan, and rural-nonmetropolitan. Employment in 13 industrial and 9 occupational categories was used to measure sustenance differentiation. Industrial employment (SDI) diversified in both the sixties and seventies as nonrnetropolitan counties became more structurally homogeneous. Occupational employment (SDO) decreased in operative, labor, and farmer-farm worker jobs and increased in sales, crafts, clerical, and professional-technical-kindred jobs. Additionally, in 1980 SDI and SDO were markedly less correlated than in previous years, suggesting a change in previous structural relationships between industry and occupation. Migration rates were much more highly correlated with SDI than with SDO over the 20 years

Late Pleistocene Sciurids from Kokoweef Cave

Three local (Tamias panamintinus, Ammospermophilus leucurus and Spermophilus variegatus) and five extralocal (Tamias minimus, Tamias palmeri, Marmota flaviventris, Spermophilus townsendii, and Spermophilus lateralis) sciurid species (Sciuridae) were identified from the late Pleistocene-early Holocene Kokoweef Cave paleofauna. This fauna was the first documentation of T. minimus, T. palmeri and S. townsendii from the Pleistocene of the Mohave Desert. The 30-ft sedimentary sequence apparently recorded the mid-to late-Wisconsian introduction of S. lateralis into the Kokweef fauna but otherwise documented general taxonomic stability. The ecological diversity of the fauna was consistent with--but did not require--the hypothesis of more equable late Pleistocene climates, and the dominant taxa (S. townsendii, M. flaviventris and S. lateralis) suggested a complex local habitat suite dominated by high-elevation montane woodlands possibly with stands of and mid-elevation xeric sagebrush. Local xeric taxa were rare or absent. All three dominant extralocal sciurids occurred above a level associated with an early Holocene date (9830 +/- 150 YBP) indicating their local persistence through the significant climatic and vegetational changes that occurred around 11,000 YBP. They may have suffered local extinction during the further climatic changes at about 8,000 YBP which led to the implacement of present desert communities