Geology topics

A. L. Everette

Publications and source records attributed to A. L. Everette.

3 recordsLinked to original sources

USGS2005

Examining patterns of bat activity in Bandelier National Monument, New Mexico, using walking point transects

We conducted a preliminary study using small field crews, a single Anabat II detector coupled with a laptop computer, and point transects to examine patterns of bat activity at a scale of interest to local resource managers. The study was conducted during summers of 1996–1998 in Bandelier National Monument in the Jemez Mountains of northern New Mexico, a landscape with distinct vegetation zones and high species richness of bats. We developed simple models that described general patterns of acoustic activity within 4 vegetation zones based primarily on nightly variation and a qualitative index of habitat complexity. Bat acoustic activity (number of bat passes&sol point) did not vary dramatically among a limited sample of transects within a vegetation zone during 1996. In 1997 and 1998, single transects within each vegetation zone were established, and bat activity did not vary annually within these zones. Acoustic activity differed among the 4 vegetation zones of interest, with the greatest activity occurring in riparian canyon bottomland, intermediate activity in coniferous forest and a 1977 burned zone, and lowest activity in piñon-juniper woodlands. We identified 68.5% of 2,529 bat passes recorded during point-transect surveys to species using an echolocation call reference library we established for the area and qualitative characteristics of bat calls. Bat species richness and composition differed among vegetation zones. Results of these efforts were consistent with general knowledge of where different bat species typically forage and with the natural history of bats of New Mexico, suggesting such a method might have value for drawing inferences about bat activity in different vegetation zones.

Southwestern Naturalist↗

USGS2001

Cyclodiene insecticide, DDE, DDT, arsenic, and mercury contamination of big brown bats (Eptesicus fuscus) foraging at a Colorado Superfund site

Rocky Mountain Arsenal (RMA) National Wildlife Area, near Denver, Colorado, is a Superfund site contaminated by past military and industrial uses, including pesticide manufacturing. From an ecosystem standpoint, the most critical contaminants at RMA are certain cyclodiene insecticides and metabolites, p,p ′-DDE, p,p ′-DDT, arsenic, and mercury. Bats are important ecosystem components that can be impacted by persistent contaminants because of their position in the food chain and their potential longevity and thus duration of exposure. Big brown bats ( Eptesicus fuscus ) were captured (n = 51) while foraging at RMA in the summers of 1997 and 1998 for determination of concentrations of contaminants of concern in carcasses, brains, and stomach contents. Adult females (n = 15) were also tracked by radiotelemetry to determine locations of nearest maternity roosts for sampling of guano for contaminant analysis and inspection for potential contaminant-induced mortality. Bats captured while foraging at RMA had measurable quantities of dieldrin and DDE in masticated insect samples from stomach contents and significantly higher concentrations of dieldrin, DDE, DDT, and mercury (juveniles) in carcasses than big brown bats (n = 26) sampled at a reference area 80 km to the north. Concentrations of dieldrin and DDE in brains of bats captured while foraging at RMA were also greater than in bats from the reference area, but not high enough to suggest mortality. Maximum concentrations of DDE, DDT, and cyclodienes in brains of big brown bats were found in adult males from RMA. Guano from the two closest known roosts had significantly higher concentrations of dieldrin, DDE, and mercury than guano from two roosts at the reference area. Dieldrin concentrations in carcasses of bats from RMA were highest in juveniles, followed by adult males and adult females. DDE concentrations in carcasses were lowest in adult females at both sites and highest in adult males at RMA. No contaminant-related mortality was obvious at the small maternity colonies near RMA. Big brown bats show higher contamination than most other mammals previously sampled at this site. Concentrations and proportions of samples with detectable residues of dieldrin in carcasses of big brown bats from RMA were similar to or exceeded reports for this species from elsewhere in the United States some 25 years ago, prior to or just following restrictions on use of this compound.

Archives of Environmental Contamination and Toxico↗

USGS2001

Bat use of a high-plains urban wildlife refuge

Bats are significant components of mammalian diversity and in many areas are of management concern. However, little attention has been given to bats in urban or prairie landscapes. In 1997 and 1998, we determined species richness, relative abundance, roosting habits, and echolocation activity of bats at Rocky Mountain Arsenal National Wildlife Refuge (RMA), the largest urban unit in the United States refuge system, located on the high plains near Denver, Colorado. An inventory using mist nets revealed 3 species foraging at this site: big brown bats ( Eptesicus fuscus ), hoary bats ( Lasiurus cinereus ), and silver-haired bats ( Lasionycteris noctivagans ). Big brown bats comprised 86% of captures (n=176). This pattern was consistent with continental-scale predictions of bat species richness and evenness based on availability of potential roosts. Relative abundance based on captures was similar to that revealed by echolocation detector surveys, except that the latter revealed the likely presence of at least 2 additional species ( Myotis spp. and red bats [Lasiurus borealis ]). Echolocation activity was significantly greater (P=0.009) in areas with tree or water habitat edges than in open prairie, suggesting that maintaining such features is important for bats. Big brown bats commuted greater distances (9.2-18.8 km) from roosts in urban core areas to foraging sites on the refuge than typically reported for this species elsewhere, emphasizing the value of the site to these bats. Urban refuges can provide habitat of importance to bat populations, but may be characterized by abundant bats that roost in buildings if a variety of other kinds of roosting habitats are unavailable.

Colorado↗