Keith Geluso

Effects of Dietary Quality on Basal Metabolic Rate and Internal Morphology of European Starlings (Sturnus vulgaris)

European starlings (Sturnus vulgaris) were fed either a low‐ or high‐quality diet to test the effects of dietary quality on basal metabolic rate (BMR) and internal morphology. Basal metabolic rate did not differ significantly between the two dietary groups, but internal morphology differed greatly. Starlings fed the low‐quality diet had heavier gastrointestinal tracts, gizzards, and livers. Starlings fed the high‐quality diet had heavier breast muscles. Starlings on the low‐quality diet maintained mass, while starlings on the high‐quality diet gained mass. Dry matter digestibility and energy digestibility were lower for starlings fed the low‐quality diet, and their food and water intake were greater than starlings on the high‐quality diet. The lack of dietary effect on BMR may be the result of increased energy expenditure of digestive organs paralleling a reduction of energy expenditure of organs and tissues not related to digestion (i.e., skeletal muscle). This trade‐off in energy allocation among organs suggests a mechanism by which organisms may alter BMR in response to a change in seasonal variation in food availability.

BENEFITS OF SMALL-SIZED CACHES FOR SCATTER-HOARDING RODENTS: INFLUENCE OF CACHE SIZE, DEPTH, AND SOIL MOISTURE

Abstract Some granivorous rodents scatter hoard; they bury seeds in shallow pits throughout their territory. These buried caches can represent food stores for the hoarders, food for competitors, or a means of seed dispersal and propagation for plants. Large numbers of seeds may be buried in many caches throughout an area; thus, fate of caches has important consequences for granivores, other animals, and plants. This study examined the ability of Ords kangaroo rat (Dipodomys ordii) to exploit artificial caches of different sizes, at 2 depths, and in substrates of differing moisture content. Kangaroo rats harvested significantly more caches in moist substrates and at shallower depths; however, small caches containing ≤5 seeds were removed infrequently by individuals regardless of substrate moisture and depth. As cache size was increased in moist sand, a threshold existed at each depth where caches were greatly exploited by kangaroo rats. Results suggest that pilferage of caches under natural conditions is not linear with respect to cache size in moist substrates. As cache size was increased in dry sand, no threshold of increased exploitation was observed for cache sizes used in this experiment. Results also suggest that pilferage of caches under natural conditions is not strongly influenced by size in dry substrates for relatively small caches. Overall, size and depth of caches greatly influence their fate. Perturbations, such as rainfall, also alter detection of caches. To reduce detection of caches by competitors, scatter hoarders should distribute relatively small caches, especially during wet conditions.

WINTER ACTIVITY OF BATS OVER WATER AND ALONG FLYWAYS IN NEW MEXICO

Abstract During colder months in temperate regions, non-migratory bats are suspected to remain relatively inactive during hibernation. I examined activity of bats November–March in a region of North America with moderate winter temperatures. Bats were captured in nets over water and along flyways in southern and central New Mexico. In 47 nights, I captured 401 individuals representing 12 species. Captures for 10 species represent records of bats previously unknown outside roosts during colder months in New Mexico. The western pipistrelle (Pipistrellus hesperus), silver-haired bat (Lasionycteris noctivagans), California myotis (Myotis californicus), pallid bat (Antrozous pallidus), and Brazilian free-tailed bat (Tadarida brasiliensis) were captured frequently, whereas the western small-footed myotis (M. ciliolabrum), Townsends big-eared bat (Corynorhinus townsendii), big brown bat (Eptesicus fuscus), Allens big-eared bat (Idionycteris phyllotis), hoary bat (Lasiurus cinereus), fringed myotis (M. thysanodes), and Arizona myotis (M. occultus) were captured infrequently. Except for A. pallidus, I documented many individuals of the commonly captured species feeding November–March, and I also saw many individuals drinking during those months. Body masses of most species were lowest in March. During the study, activity of bats was positively, but not significantly, correlated with ambient air temperature at dusk. In this region of North America, many individuals of several species do not hibernate for the entire winter nor do they migrate from the region.

Winter Activity of Brazilian Free-Tailed Bats (Tadarida brasiliensis) at Carlsbad Cavern, New Mexico

Abstract The Brazilian free-tailed bat (Tadarida brasiliensis) generally is considered a migratory species in western North America. Throughout the southwestern United States, however, winter records are known from many scattered locations. Here I report on T. brasiliensis exiting and entering a cave in southern New Mexico from November to March. I observed that a winter colony of Brazilian free-tailed bats at Carlsbad Cavern was comprised of males and females of different ages, and in February and March, I documented that numbers of individuals inhabiting the cavern were much higher than previously reported. Nearly all individuals returning to the cavern fed in November, about one-half fed in January and February, and none fed in early December and late March. I suspect that individuals wintering in the cavern consume insects during all colder months in the region, and lack of observations of bats feeding in December and March only reflect extremely windy conditions on nights of sampling. From December to March, body masses of individuals declined about 15%. Although this study adds to our understanding of the natural history of T. brasiliensis in winter, why some individuals remain in such northerly areas and do not migrate farther south is not yet understood.

Seasonal link between food hoarding and burrow use in a nonhibernating rodent

Food-storage behaviors can be plastic for food-hoarding species. Some hibernating, granivorous rodents switch seasonally from scatter hoarding (storing food in small, separate caches) to larder hoarding (concentrating food in a central location). To date, little is known about seasonal food-hoarding behaviors of free-living rodents that forage and store food year-round (i.e., nonhibernators). Using direct observations, radiotelemetry, and tracking with fluorescent powder, we discovered a striking seasonal shift in food-hoarding behaviors for Ords kangaroo rat (Dipodomys ordii), a nonhibernating rodent in a region with dramatic seasonal climate (i.e., the Great Plains of the United States). In winter, D. ordii almost exclusively larder hoarded seeds in burrows and used a single burrow, which is consistent with the larder-defensibility hypothesis of food storage. The lack of suitable sites to scatter hoard due to snow cover and frozen soils likely contributed to larder hoarding in winter. In summer, most individuals scatter hoarded near seed sources, which is consistent with the rapid-sequestering hypothesis of food storage. In summer, individuals also commonly used multiple burrows, and differences in food-hoarding and burrow-use behavior were observed between sexes and between reproductively active and inactive females. By scatter hoarding and using multiple burrows in summer, kangaroo rats likely reduce costs associated with defending larder hoards while increasing benefits associated with reproduction. The seasonal interplay between food hoarding and burrow use by D. ordii appears to be important for securing and maintaining resources throughout the year in a temperate environment.

Effects of environmental factors on capture rates of insectivorous bats, 1971–2005

Abstract Understanding how environmental factors affect activity, number, and spatial distribution of bats in an area is necessary for interpreting capture rates and assessing abundance. Over a 34-year period, we examined the relationship between amounts of precipitation and activity of bats along a canyon floor in the San Mateo Mountains of New Mexico in the southwestern United States. For 1 night during each of 19 summers, we used identical sampling techniques to monitor this assemblage of insectivorous bats. Years included droughts with minimal surface water and wet years with abundant surface water in the canyon. Marked differences in available drinking water resulted in striking differences in yearly captures of bats, with a 30.8-fold difference between the fewest and most captures (6 versus 185 adults). Capture rates increased with less precipitation before sampling. In the 3-decadal period, precipitation accounted for 66% of the variation in capture rates, providing support that bats concentrate around accessible water to drink when surface water is scarce. Captures also were influenced by relative humidity on nights of sampling. From 1971 to 2005, we detected no change in species composition in this bat assemblage of 8 species, and after accounting for effects of precipitation, we detected no declines in population size for the 2 most common species, the long-eared myotis (Myotis evotis) and long-legged myotis (M. volans). Our study demonstrates the importance of long-term data sets to help elucidate patterns of variability in capture data and highlights the importance of how yearly variation in climate affects the behavior and ecology of bats.

Bats along the republican river and its tributaries in Southwestern Nebraska: distribution, abundance, and reproduction.

ABSTRACT. Thirteen species of bats occur in Nebraska, but limited information is available on those inhabiting southwestern parts of the state. We investigated the distribution, abundance, and reproductive activity of bats in 5 counties in extreme southwestern Nebraska (Chase, Hays, Dundy, Hitchcock, and Red Willow). From April 2007 to April 2008, we deployed mist nets on 15 occasions at 8 localities over the Republican River and its tributaries. We captured 100 individuals representing 5 species, including the evening bat (Nycticeius humeralis), eastern red bat (Lasiurus borealis), hoary bat (Lasiurus cinereus), big brown bat (Eptesicus fuscus), and silver-haired bat (Lasionycteris noctivagans). All species raised young in this region of Nebraska, except L. noctivagans, which was documented only during migration. Lactating females of N. humeralis captured on 15 June and volant young captured on 23 June extend known dates of reproductive activity for this species in the state, and an adult female captured on 30 April represents the earliest seasonal record of this species from Nebraska. Our records of evening bats also extend the known distribution of this species farther west in Nebraska than previously reported. Changes in land use throughout the Great Plains during the last century have altered many habitats, such as gallery forests associated with rivers, and distributions of mammals, including bats, have shifted to reflect those ecological changes.

USE OF BRIDGES BY BATS (MAMMALIA: CHIROPTERA) IN THE RIO GRANDE VALLEY, NEW MEXICO

Abstract During a 2-year study, we documented eight species of bats using bridges in the lower Rio Grande Valley of New Mexico. Of 17 bridges surveyed, 15 (88%) contained day-roosting bats and ≥8 bridges (47%) contained maternity colonies with one or more species, including the Arizona myotis (Myotis occultus), Yuma myotis (Myotis yumanensis), and Brazilian free-tailed bat (Tadarida brasiliensis). The pallid bat (Antrozous pallidus), big brown bat (Eptesicus fuscus), silver-haired bat (Lasionycteris noctivagans), California myotis (Myotis californicus), and fringed myotis (Myotis thysanodes) roosted infrequently in bridges. Use of bridges by day-roosting bats differed seasonally, with most individuals occupying bridges April–October. During November–March, relatively few individuals of only three species (L. noctivagans, M. yumanensis, and T. brasiliensis) occupied bridges. Individuals roosted at many sites in bridges, but 99.9% roosted in narrow cracks and crevices. A total of 36,629 day-roosting bats was counted, with 99.8% observed in bridges constructed from timbers and 0.2% observed in I-beam bridges constructed from concrete, metal, or both. Paucity of bats in I-beam bridges reflected lack of narrow spaces. Our study demonstrates that some bridges represent important roosting sites for bats in southern New Mexico. Bridges throughout the southwestern United States likely serve similar life-history functions for bats and should be managed as a resource, especially those occupied by maternity colonies or large numbers of individuals.

Subterranean Behavior and Other Notes for Ironoquia plattensis (Trichoptera: Limnephilidae) in Nebraska

ABSTRACT Ironoquia plattensis Alexander & Whiles (Trichoptera: Limnephilidae) was discovered along the Platte River in central Nebraska in the late 1990s, and basic information about its life history is not well understood. Here, we describe previously undocumented life-history traits that demonstrate strategies used by I. plattensis for surviving in fluctuating wetland environments in a landscape formally shaped by flooding. In an off-channel aquatic habitat along the Platte River, we observed 1) larvae residing in a slough that did not dry completely, 2) larvae emigrating from aquatic to terrestrial habitats 1 mo earlier than reported previously, 3) larvae moving above ground during the summer aestivation period, 4) larvae residing underground in soil during summer aestivation, and 5) mass emergence and swarming of adults after daybreak in autumn. Underground larval aestivation represents a previously undocumented behavior for this species. It is unclear whether aestivating underground represents an unreported common behavior or an infrequent response to local disturbances. At our site, insects may have been responding to a prescribed burn in April and introduction of cattle in mid-May that yielded the site unsuitable for aboveground aestivation. Additional studies on the life history for I. plattensis are warranted to help manage, locate, and protect the few sites where it occurs.

USE OF A MINE BY EASTERN PIPISTRELLES (PERIMYOTIS SUBFLAVUS) IN EAST CENTRAL NEBRASKA

Abstract The eastern pipistrelle (Perimyotis subflavus) is relatively common and widespread throughout the eastern United States. In recent decades, the distribution of P. subflavus has expanded westward across the Great Plains, and little information exists on its natural history in this region. In east central Nebraska, we monitored the use of a mine by eastern pipistrelles for >1 year. A few males occupied the roost in summer, but during the period of hibernation (late September–early May), the mine was used by at least 30 individuals composed of both sexes. Most individuals first entered the mine during late September through mid-October and exited by mid-May, with numbers of individuals fluctuating throughout winter. In winter, most individuals roosted along outer passageways of the mine, but in other seasons individuals were scattered throughout the mine. Females had significantly greater body masses than males upon entering the mine in autumn and before exiting the mine in spring. Both sexes had significantly heavier body masses in autumn than in spring. Overall, 55% of individuals marked in spring returned in autumn. Males had a higher return rate (69%) than females (46%) over a single summer. Many aspects of the natural history of P. subflavus in Nebraska are similar to those reported from eastern but not from southern parts of its distribution.