Bryon K. Clark

Influence of Roads on Movements of Small Mammals

The landscape of the world is becoming more dissected by roads each year due to the growing human population. Numerous studies have documented the direct impact of roads on wildlife by examining mortality caused by vehicles but few have investigated indirect effects of roads on animals. We used capture-mark-recapture (CMR), fluorescent pigments, and radiotelemetry techniques to assess the influence of roads on movements of rodents. During CMR, only 5 of 53 (9.4%) individuals captured more than once spontaneously crossed roads, whereas 21 of 51 (41.2%) rodents that were displaced across roads when released returned to the side of their original capture. Only 1 of 54 (1.9%) rodents powdered with fluorescent pigment moved across the road when released at their capture site. In contrast, 7 of 53 (13.2%) displaced and powdered animals crossed the road. Six of 12 (50%) radiotagged animals were located on both sides of the road on at least 1 occasion; however, >90% of all locations were on the same side as the original capture for all individuals. Roads were partial barriers to movements of rodents; however, when displaced, animals exhibited a greater likelihood of crossing a road. Although proportion of rodents crossing roads varied among the 3 studies, all techniques yielded consistent results. RESUMEN-El paisaje del mundo se esta fragmentado mas cada anio por caminos debido al crecimiento de la poblaci6n humana. Numerosos estudios han documentado el impacto directo de las carreteras en la vida silvestre examinando la mortalidad causada por los vehiculos, pero pocos han investigado el efecto indirecto de los caminos en los animales. Usamos captura-marcarecaptura (CMR), pigmentos fluorescentes, y tecnicas de radiotelemetria para valorar la influencia de los caminos en los desplazamientos de los roedores. Durante CMR, s6lo 5 de 53 (9.4%) individuos capturados mas de una vez cruzaron los caminos espontaneamente, mientras que 21 de 51 (41.2%) de roedores que fueron llevados al otro lado de los caminos regresaron al lugar original de su captura. S61o 1 de 54 (1.9%) de los roedores espolvoreados con pigmento fluorescente cruz6 el camino cuando se les liber6 en su lugar de captura. En contraste, 7 de 53 (13.2%) animales desplazados y espolvoreados cruzaron la carretera. Seis de 12 (50%) animales con radiotransmisores fueron localizados en ambos lados del camino al menos en 1 ocasi6n; sin embargo, >90% de todas las localizaciones fueron en el mismo lado de la captura original para todos los individuos. Los caminos fueron barreras parciales para los movimientos de los roedores; sin embargo, cuando fueron desplazados, los animales exhibieron una posibilidad mayor de cruzar el camino. A pesar de que la proporci6n de roedores que cruza los caminos vari6 en los 3 estudios, todas las tecnicas produjeron resultados consistentes. Fifteen to 20% of the land cover in the United States is influenced by roads (Forman and Alexander, 1998) and numerous researchers have documented mortality of mammals and other wildlife on highways (Scott, 1938; Dickerson, 1939; Davis, 1940; Huey, 1941; Haugan, 1944; McClure, 1951; Sargeant and Forbes, 1973). However, fewer studies have addressed indirect effects of roads on movements of animals (Kozel and Fleharty, 1979; Wilkins, 1982; Garland and Bradley, 1984; Swihart and Slade, 1984; Richardson et al., 1997). Roads are becoming more widespread throughout the world due to the increasing human population; therefore, a better understanding of the impact of these potential barriers to movements of small mammals is warranted. Our objective was to use capture-mark-recapture (CMR), fluorescent pigments, and radiotelemetry techniques to assess the influence of roads on movements of small mammals. We tested the null hypothesis that similar proporE UTHWESTERN TURALIST 46(3):338-344 SEPTEMBER 2001 Clark et al.-Roads and small mammals tions of small mammals would spontaneously move between 2 traplines separated by either a road or an equal width of homogenous grassland. We also assessed whether displaced animals would cross the road at a greater frequency than nondisplaced animals. Lastly, we tested for differences in sensitivity of the 3 techniques in detecting movements of animals across

Seasonal variation in activity patterns of the endangered Ozark big-eared bat (Corynorhinus Townsendii Ingens)

Abstract We studied occupation and activity at a hibernaculum and a maternity cave used by the endangered Ozark big-eared bat (Corynorhinus townsendii ingens). Big-eared bats remained active throughout winter, with many individuals leaving and entering the hibernaculum during the first 2 h after sunset; however, no fresh guano was found on cave floors during winter. Big-eared bats used caves with the coldest internal temperatures in the region as hibernacula and also moved among caves throughout winter. The breakup of hibernating colonies in spring and the subsequent buildup of maternity colonies by adult females were gradual. Nightly activity patterns at the maternity cave changed throughout summer relative to parturition and maturation of young. Females returned to the maternity cave more frequently when their young were totally dependent on them for nourishment. As the young began foraging, females returned only once during the night, and eventually adults did not return to the cave until morning. Ozark big-eared bats emerged shortly after sunset, regardless of brightness at twilight or rainfall, but they emerged at a later time when the young could not fly.

Communities of Small Mammals in Six Grass-dominated Habitats of Southeastern Oklahoma

Abstract During autumn 1991, we sampled small mammals in six grass-dominated habitats including upland ungrazed native prairie, upland improved pastures, upland mowed native prairie, upland roadside fencerows, lowland ungrazed native prairie and lowland ungrazed native prairie with forbs and shrubs in southeastern Oklahoma. Eleven species of small mammals were represented in 405 captures. Species diversity (H′) was high in upland (1.57) and lowland (1.47) ungrazed prairie and least for upland fencerows (0.86). Evenness (J′) exhibited a similar pattern and was high in upland (0.88) and lowland (0.82) ungrazed prairie and least for lowland ungrazed prairie with forbs and shrubs (0.53). Community overlap (Ro) varied from 1.00 (upland improved pastures and upland roadside fencerows) to 0.57 (upland improved pastures and upland ungrazed prairie). Abundance of small mammals was greatest in fencerows, largely due to the prevalence of hispid cotton rats (Sigmodon hispidus). Different land-use practices elicited both positive and negative species-specific responses. Current human activity in some locations may produce habitat mosaics that result in an overall greater abundance and diversity of small mammals.

Effects of Plant Litter on Foraging and Nesting Behavior of Prairie Rodents

Interspecific differences in seed use and location of nest sites of Peromyscus leucopus, P. maniculatus, Reithrodontomys megalotis , and Microtus ochrogaster were found among experimental patches of habitat that differed only in amount of plant litter. P. leucopus and P. maniculatus foraged selectively in patches with sparse litter and used nest boxes in these patches more than expected. R. megalotis and M. ochrogaster foraged selectively and nested in patches with moderate litter; both nested more in litter than in nest boxes. All species consumed more seeds in patches with moderate litter on bright than dark nights. P. leucopus consumed fewer seeds and P. maniculatus tended to reduce consumption from dark to bright nights; however, R. megalotis and M. ochrogaster consumed similar amounts of seeds under both light conditions. P. leucopus and P. maniculatus forage in open habitats and may perceive changes in light intensity more readily than either R. megalotis or M. ochrogaster that forage in structurally complex habitats. Interspecific differences in activity between dark and bright nights may be related to the ability of each species to detect changes in risk of predation related to variation in light intensity.

Long-Distance Movements by Reithrodontomys megalotis in Tallgrass Prairie

-During 6 years of small mammal trapping on Konza Prairie Research Natural Area, Kansas, we documented long-distance movements (defined as movements >300 m) for 17 western harvest mice (Reithrodontomys megalotis). Linear distance moved ranged from 375 to 3200 m (median = 600 m; mean = 1049 m) for all individuals. Males moved significantly farther, but not more often, than females. Sixteen of the 17 animals that moved were adults and included reproductively active individuals. Although 300 m, the actual percentage should be much higher since our trapping efforts were limited in space and time. Since long-distance movements of individuals may have a marked effect on the genetic, social and demographic characteristics of populations, future studies of small mammals should be designed to better assess the influence of these movements on local populations.

Ability of Prairie Rodents to Find Seeds in Plant Litter

-Differential abilities of white-footed mice (Peromyscus leucopus), deer mice (P. maniculatus) and fulvous harvest mice (Reithrodontomys fulvescens) to find seeds covered by 0 and 75 g of litter were assessed during laboratory foraging trials. All individuals collected significantly fewer seeds in aquaria with litter. Mean percent reduction in seed harvest between 0 and 75 g of litter was significantly greater for P. leucopus than either P. maniculatus or R. fulvescens, which did not differ significantly. Mean grams of seeds harvested significantly decreased with increased amounts of litter (0, 25, 50, 75, 100 and 125 g) for P. leucopus and R. fulvescens. Interspecific differences for mean percent reduction in seed harvest for sparse (25 g) and deep/dense (100 and 125 g) litter were nonsignificant; however, seed harvest was significantly lower for P. leucopus than R. fulvescens in moderate litter (50 and 75 g). Our results imply that differences in the ability of grassland rodents to collect seeds in plant litter may be partially responsible for species-specific patterns of microhabitat

Prevalence of botfly (Cuterebra sp.) parasitism in populations of small mammals in eastern Kansas.

-Prevalence of botfly (Cuterebra sp.) parasitism in populations of small mammals was studied in tallgrass prairie of northeastern Kansas during 1985-1987. Four species of rodents, Neotomafloridana, Peromyscus leucopus, P. maniculatus and Reithrodontomys megalotis, were parasitized and all infestations occurred between 1 June and 30 September. Prevalence was greatest in July and August for all species. Proportions of N.floridana (0.31) and P. leucopus (0.24) parasitized were similar and significantly greater than those of P. maniculatus (0.08) and R. megalotis (0.02). Over 95% of the parasitized animals were adults with no differences noted due to sex. Parasitized individuals resided longer on the study area than unparasitized animals for N. floridana, P. leucopus and R. megalotis, but not P. maniculatus. The relationship between residence time and parasitism, as well as higher proportions of infestation for N. floridana and P. leucopus, probably was due to overlap in preferred habitat (woody vegetation in ravines and contiguous lowlands) between adult Cuterebra and these rodents.

Summer Status of the Endangered Indiana Bat in Iowa

The summer status and distribution of the endangered Indiana bat (Myotis sodalis) in Iowa were investigated during the summers of 1980 through 1983. Sixty-seven M. sodalis were netted, 5.6% of the 1199 bats captured. Indiana bats were taken at nine study sites in six southern Iowa counties, but none was captured at 23 sites in 10 central and northern counties even though these sites were selected because of their physiognomic and vegetational similarity to sites at which bats occurred. Reproductively active females or newly volant juvenile M. sodalis were taken at each southern site. Results suggest that the northwestern range limits of this species are influenced by climatic factors and distance to major hibernacula, whereas habitat availability and competition may be important in delimiting local patterns of distribution