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Michael A. Bogan

Publications and source records attributed to Michael A. Bogan.

At least 19 recordsLinked to original sources
USGS2020

Zero or not? Causes and consequences of zero-flow stream gage readings

Streamflow observations can be used to understand, predict, and contextualize hydrologic, ecological, and biogeochemical processes and conditions in streams. Stream gages are point measurements along rivers where streamflow is measured, and are often used to infer upstream watershed‐scale processes. When stream gages read zero, this may indicate that the stream has dried at this location; however, zero‐flow readings can also be caused by a wide range of other factors. Our ability to identify whether or not a zero‐flow gage reading indicates a dry fluvial system has far reaching environmental implications. Incorrect identification and interpretation by the data user can lead to inaccurate hydrologic, ecological, and/or biogeochemical predictions from models and analyses. Here, we describe several causes of zero‐flow gage readings: frozen surface water, flow reversals, instrument error, and natural or human‐driven upstream source losses or bypass flow. For these examples, we discuss the implications of zero‐flow interpretations. We also highlight additional methods for determining flow presence, including direct observations, statistical methods, and hydrologic models, which can be applied to interpret causes of zero‐flow gage readings and implications for reach‐ and watershed‐scale dynamics. Such efforts are necessary to improve our ability to understand and predict surface flow activation, cessation, and connectivity across river networks. Developing this integrated understanding of the wide range of possible meanings of zero‐flows will only attain greater importance in a more variable and changing hydrologic climate.

WIREs Water↗
USGS2018

United States bat species of concern: A synthesis

In 1994 the federal government designated 24 species or subspecies of bats in the United States (U.S.) and its territories as Category 2 candidates for listing as Endangered or Threatened under the U.S. Endangered Species Act. Category 2 was eliminated in 1996, but taxa previously receiving this designation were informally considered “species of concern”. Various state and federal agencies and conservation organizations assigned bat species of concern to more formal conservation categories. Some of the original 24 taxa designated as Category 2 candidates in 1994 were later listed as Endangered, whereas others were subject to refinements in knowledge of their taxonomy and distribution. The remaining 20 species of bats have the subjects of increased research efforts over the past two decades, and are the focus of this review. Two species occur in the U.S. Territories. All of the 18 mainland species ranges include areas west of the Mississippi River (15 are found primarily in western states), and 13 occur in California (72% of the 18 mainland species). In this review, we provide a comprehensive summary of the literature pertinent to the conservation designations, systematics, distribution, habitats, relative abundance, foraging, diet, roosting ecology, population ecology, and management of each of these 20 species. The species of concern are distributed among four families of bats. The Samoan flying fox (Pteropus samoensis) belong to the old-world family Pteropodidae. The California leaf-nosed bat (Macrotus californicus), red fruit bat (Stenoderma rufum), and Mexican long-tongued bat (Choeronycteris mexicana) are members of the new-world family Phyllostomidae. Three species belong to the cosmopolitan family Molossidae: the greater bonneted bat (Eumops perotis californicus), Underwood’s bonneted bat (Eumops underwoodi), and the big free-tailed bat (Nyctinomops macrotis). Most bat species of concern are in the globally distributed family Vespertilionidae: Townsend’s big-eared bat (Corynorhinus townsendii), Rafinesque’s big-eared bat (C. rafinesquii), spotted bat (Euderma maculatum), Allen’s big-eared bat (Idionycteris phyllotis), southeastern myotis (M. austroriparius), western small-footed myotis (Myotis ciliolabrum), long-eared myotis (M. evotis), eastern small-footed myotis (M. leibii), Arizona myotis (M. occultus), fringed myotis (M. thysanodes), cave myotis (M. velifer), long-legged myotis (M. volans), and Yuma myotis (M. yumanensis). An impressive amount of knowledge has accumulated about these species since their informal designation as species of concern, but this knowledge is unevenly distributed. Comparatively little research has been conducted on the Samoan flying fox and the red fruit bat over the past decade in tropical territories, nor on the Mexican long-tongued bat and Underwood’s mastiff bat in the southwestern U.S. Within temperate regions of the U.S., habitat use of two eastern species that roost in hollow trees or caves (southeastern myotis and Rafinesque’s big-eared bat) has been the focus of much research, as have aspects of the biology of cave-roosting and tree-roosting western species, particularly where information about management of forests, caves and abandoned mines can be used to benefit bat conservation. Comparatively less information has accrued about species that roost in rock crevices and high on cliff faces. Other major gaps in information are also identified. We anticipate that this review will help guide future research and conservation efforts directed at the bat species of concern.

Proceedings of the California Academy of Sciences,↗
USGS2017

Landscape movements by two species of migratory nectar-feeding bats (Leptonycteris) in a northern area of seasonal sympatry

Animals often migrate to exploit seasonally ephemeral food. Three species of nectar-feeding phyllostomid bats migrate north from Mexico into deserts of the United States each spring and summer to feed on blooms of columnar cactus and century plants ( Agave spp.). However, the habitat needs of these important desert pollinators are poorly understood. We followed the nighttime movements of 2 species of long-nosed bats ( Leptonycteris yerbabuenae and L. nivalis ) in an area of late-summer sympatry at the northern edges of their migratory ranges. We radio-tracked bats in extreme southwestern New Mexico during 22 nights over 2 summers and acquired location estimates for 31 individuals. Both species cohabitated 2 major day roosts that were 30 km apart and in different mountain ranges, and individual bats sometimes moved between the roosts. Sampling was opportunistic and limited, but there were no obvious qualitative differences in observed patterns of movement between species or years, or among sex, age, and reproductive groups. Both species were observed foraging most often in the mountain range that had a relatively higher observed density of presumed food plants ( Agave palmeri ); when roosting in an adjacent mountain range, bats sometimes commuted >20 km one way to forage. Contrary to evidence indicating these species partition resources farther south in Mexico, our findings suggest that L. yerbabuenae and L. nivalis seasonally share common roost and food resources during late summer in this northern area of sympatry.

Western North American Naturalist↗
USGS2009

Does variation in cranial morphology of Myotis occultus (Chiroptera: Vespertilionidae) reflect a greater reliance on certain prey types?

Few studies have investigated the relationship between morphological variation and local feeding habits of bats in the United States. We used discriminant function analysis (DFA) to compare cranial morphology of Myotis occultus from southern Colorado, and central, and southern New Mexico. We analyzed guano collected from maternity colonies in southern Colorado and central New Mexico to compare food habits. Bats from southern Colorado had the smallest values on the first canonical variate (CV1) that also reflected the smallest measurements of key cranial and dental variables, including height of coronoid process, width of molar, and dentary thickness. Bats from central and southern New Mexico had intermediate and large CV1 values, respectively. Overall, CV1 discriminated individuals occurring in southern Colorado and central New Mexico from those in southern New Mexico. CV2 served best at discriminating bats of southern Colorado from those of central New Mexico. Comparison of food habits revealed that individuals from southern Colorado ate more soft-bodied prey items (e.g., flies) whereas bats from central New Mexico ate more hard-bodied prey items (e.g., beetles). As shown in earlier studies that investigated relationships between morphology and diet of insectivorous bats, we found differences in skull morphology of M. occultus that were correlated with differences in food habits.

Acta Chiropterologica↗
USGS2003

Western crevice and cavity-roosting bats

Among the 45 species of bats that occur in the United States (U.S.), 34 species regularly occur in western regions of the country. Many of these “western” species choose roost sites in crevices or cavities. Herein we provide an introduction to the biology of bats that roost in cavities and crevices and assess the challenges and opportunities associated with monitoring their populations. We reviewed recent studies and examined the U.S. Geological Survey Bat Population Database (BPD) for records of western bats using crevice and cavity roosts. We found records of 25 species of western bats that use crevice or cavity roosts for at least part of their annual cycle. There were relatively few (n = 92) observations or counts for these species in the BPD, representing only 6% of the observations in the database. This paucity of records likely reflects the difficulty of observing bats in such situations rather than actual use. We found no long-term data adequate for population trend analysis among this group of bats. Since the development of miniaturized radio transmitters, our knowledge about bats that roost in cavities and crevices has increased. Future challenges associated with monitoring these species will include understanding variability in the types of roosts used as well as the roost-switching behavior exhibited by many species.

Report↗
USGS2003

Western crevice and cavity-roosting bats

Among the 45 species of bats that occur in the United States (U.S.), 34 species regularly occur in western regions of the country. Many of these “western” species choose roost sites in crevices or cavities. Herein we provide an introduction to the biology of bats that roost in cavities and crevices and assess the challenges and opportunities associated with monitoring their populations. We reviewed recent studies and examined the U.S. Geological Survey Bat Population Database (BPD) for records of western bats using crevice and cavity roosts. We found records of 25 species of western bats that use crevice or cavity roosts for at least part of their annual cycle. There were relatively few (n = 92) observations or counts for these species in the BPD, representing only 6% of the observations in the database. This paucity of records likely reflects the difficulty of observing bats in such situations rather than actual use. We found no long-term data adequate for population trend analysis among this group of bats. Since the development of miniaturized radio transmitters, our knowledge about bats that roost in cavities and crevices has increased. Future challenges associated with monitoring these species will include understanding variability in the types of roosts used as well as the roost-switching behavior exhibited by many species.

Book chapter↗
USGS2000

The bats of Wyoming

We examined 1280 bats of 12 species submitted to the Wyoming State Veterinary Laboratory (WSVL) for ra­bies testing between 1981 and 1992. The most abundant species in the sample was Myotis lucifugus , followed by Epte­sicus fuscus , Lasionycteris noetivagans , M. ciliolabrum , and M. volans . Using the WSVL sample and additional museum specimens, we summarized available records and knowledge for 17 species of bats in Wyoming, Records of the WSVL show that, between 1981 and 1992, 113 bats actually tested positive for rabies. We examined 45 of those rabies­ positive bats; E. fuscus had the highest incidence (60%) in the sample, followed by L. noctivagans (11 %) and L. cinereus (9%).

Wyoming↗
USGS1999

Additional records of bats from the middle Rio Grande Valley, New Mexico

The resident and migratory bat fauna of the middle Rio Grande Valley in central New Mexico is inadequately known. Many of the specimen records from this valley are from Bosque del Apache National Wildlife Refuge, ca. 20 km S of Socorro, Socorro Co. Findley et al. (1975) reported Myotis lucifugus, M. yumanensis, Lasiurus cinereus, and Tadarida brasiliensis from the refuge to which Reith (1982) added Antrozous pallidus. During June and July 1994, we netted nine nights and conducted visual searches of known roosts to capture 67 bats of seven species as part of a baseline survey of bats on the refuge. We surveyed artificial wetlands in the transitional zone between riparian forest and adjacent desert-grassland, within ca. 2 km of the Rio Grande. Nearby agricultural fields and ponds managed primarily for use by waterfowl provided numerous sites suitable for foraging and drinking by bats. We report four new species records for the refuge, one of which is also a new county record. Voucher material is deposited in the Biological Survey Collection, Fort Collins (BS/FC), now housed in the Museum of Southwestern Biology (MSB), University of New Mexico.

Southwestern Naturalist↗
USGS1998

Southwest

The southwestern region of the United States is a land of extremes and contrasts. Elevations vary from below sea level in the Imperial Valley of California to mountain peaks approaching 4,000 meters. Landscapes are striking and variable and include mountains, foothills, canyons, deserts, plains, and rivers. The area is arid or semiarid and, depending on the location, may have mild winters and summers, periods of bitter cold, or intervals of intense heat. Climate is inextricably tied to water and its availability. Historically, water varied from abundant to sparse over the span of a year, and adaptations of native plants and animals reflect those extremes. Annual precipitation, usually in the form of rain, varies from 30 to 40 millimeters in the low-elevation Sonoran Desert to more than 1,000 millimeters in the high mountains (Brown 1982a; Bahre and Shelton 1993). This variation in topography and climate has produced great floral and faunal diversity.

Book chapter↗
USGS1991

Geographic variation in sea otters, Enhydra lutris

Univariate and multivariate analyses of 20 skull characters of 304 adult sea otters from throughout the geographic range strongly suggest that three subspecies should be recognized. The nominate form, Enhydra lutris lutris , occurs from the Kuril Islands north to the Commander Islands in the western Pacific Ocean. Individuals of E. l. lutris are characterized by large size and wide skulls with short nasal bones. E. l. nereis is found along the California coast and off San Nicolas Island, where the species recently has been reintroduced from coastal California. Specimens of E. l. nereis have narrow skulls with a long rostrum and small teeth, and usually lack the characteristic notch in the postorbital region found in most specimens of the other two subspecies. A new subspecies described by Don E. Wilson in this report, occurs throughout the Aleutian Islands and southward in the eastern Pacific to Washington. Specimens of the new subspecies are intermediate in size in most, but not all, characters and have longer mandibles than either of the other two subspecies.

Journal of Mammalogy↗
USGS1988

The importance of biological surveys in managing public lands in the western United States

Despite previous studies, incomplete knowledge of the mammalian fauna of many national parks hinders our ability to understand the consequences of either management actions of natural disasters to such preserves. Faunal losses have occurred and can be expected to continue (Newmark 1986a, 1986b). our studies in and near Dinosaur National Monument, one of the parks studied by Newmark (1986a, 1986b), have added 11 species to the known fauna. Some species have increased with human impact; other species have either disappeared or are declining. Finally, many species, which are uncommon and poorly known, may have rather specific habitat needs.

Report↗
USGS1978

A new species of Myotis from the Islas Tres Marias, Nayarit, Mexico, with comments on variation in Myotis nigricans

A new Myotis is described from the Islas Tres Marias, Nayarit, Mexico. the new species is distinct from related taxa n the adjacent Mexican mainland ( M. californicus, M. leibii , and M. carteri ), although most closely related to M. carteri as shown by univariate and canonical variates analyses. An analysis of six groups of M. nigricans from Middle and South America supports the elevation of M. nigricans carteri to specific status, confirms the distinctness of M. nigricus extremus , but fails to substantiate subspecific status for bats from Columbia and Ecuador, recent recognized as M. n. punensis .

Nayarit↗