R. Nathan Gwinn

Sciurillus pusillus (Rodentia: Sciuridae)

Abstract: Sciurillus pusillus (É. Geoffroy Saint-Hilaire, 1803) is a sciurid commonly called the Neotropical pygmy squirrel. S. pusillus is an exceptionally small species of tree squirrel that appears pale gray due to a grizzled pattern of light hair tips on the dorsal pelage. Ranging from Amazonian Peru and Brazil northeast to the Guianas with a patchy distribution, S. pusillus is a denizen of the upper canopy of lowland rain forest. This species is listed as “Data Deficient” by the International Union for Conservation of Nature and Natural Resources.

Microsciurus flaviventer (Rodentia: Sciuridae)

Abstract: Microsciurus flaviventer (Gray, 1867) is a Neotropical tree squirrel commonly known as the Amazon dwarf squirrel. Small bodied with dark brown dorsal pelage contrasted with a gray or yellowish gray venter, and a faintly banded tail. M. flaviventer is 1 of 4 species in the genus Microsciurus. The geographic range of M. flaviventer extends from the Amazon basin of South America throughout western and southeastern Colombia, Ecuador, southern Peru, Brazil west of Río Negro, and Madeira. It is most commonly associated with evergreen lowland tropical rainforest. Status of M. flaviventer is “Data Deficient” under the International Union for Conservation of Nature and Natural Resources Red List of Threatened Species; however, loss of habitat is a major concern.

Sciurus stramineus (Rodentia: Sciuridae)

Abstract:  Sciurus stramineus Eydoux and Souleyet, 1841, is a large-bodied squirrel commonly called the Guayaquil squirrel. S. stramineus is characterized by a distinct grizzled-gray pelage with dark feet and ears, a long tail, and a distinctive white “collar” behind the ears. It is native to the western slope of the Andes, occurring from dry or humid tropical forests at sea level to high-elevation montane forests up to 2,000 m in Ecuador and Peru. S. stramineus is adaptable, adjusting to anthropogenic changes and living close to human settlements, in coffee plantations, with an introduced population in Lima, Peru. Because of a tolerance for living in proximity to humans, S. stramineus is also a concern for transmission of diseases such as leptospirosis and Chagas disease.

Sciurus spadiceus (Rodentia: Sciuridae)

Abstract: Sciurus spadiceus Olfers, 1818, is a sciurid commonly known as the southern Amazon red squirrel. S. spadiceus is a large-bodied tree squirrel with a variable color pattern, but typically has a reddish brown dorsum, a dark midline, a white venter, and a brown and orange tail. S. spadiceus ranges from southern Colombia and Venezuela, south through Peru, western Brazil, Ecuador, and Bolivia in lowland rain forest. This species is listed as “Least Concern” by the International Union for Conservation of Nature and Natural Resources.

Virginia Opossum (Didelphis Virginiana Virginiana) from Yavapai County, Arizona

ABSTRACT. The Virginia opossum (Didelphis virginiana) is the only marsupial native to the United States. In recent times, D. virginiana has expanded its range through natural movements and anthropogenic introductions. Didelphis virginiana has been present in southern Arizona owing to range expansion by the Mexican subspecies (D. v. californica) and anthropogenic introductions of the eastern subspecies (D. v. virginiana). Here, we document the recent collection of an opossum in central Arizona. We also discuss how it possibly moved there and report on its stomach contents at the time of collection.

Sigmodon arizonae (Rodentia: Cricetidae)

Abstract Sigmodon arizonae Mearns, 1890, is a cricetid commonly called the Arizona cotton rat. S. arizonae is a large species of cotton rat with brownish black dorsal pelage and silvery or whitish underparts. Ranging from central Arizona in the United States south to Nayarit in Mexico with a disjunct population along the lower Colorado River in southwestern Arizona and California, it is primarily associated with riparian corridors, but also is found in more arid habitats such as semidesert grassland. Two subspecies of S. arizonae appear to be extinct and a 3rd subspecies is imperiled. However, in the majority of its range, S. arizonae is considered common and is not of conservation concern.

ENDANGERED MOUNT GRAHAM RED SQUIRREL (TAMIASCIURUS HUDSONICUS GRAHAMENSIS) USES NEST FOLLOWING LIGHTNING STRIKE

Abstract Few studies have documented behavioral response of small mammals to fire. Here we report use of a nest by an adult Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis), an endangered subspecies endemic to the Pinaleño Mountains of southeastern Arizona, following a direct lightning strike to a tree. After 2 days, the squirrel nested in this tree and remained in the area for another 136 days. This is evidence that red squirrels may tolerate some degree of fire on the landscape.

Response in Abert's Squirrel Abundance to Forest Treatments on Camp Navajo, Arizona

Abstract. Aberts squirrels (Sciurus aberti) are dependent upon ponderosa pine (Pinus ponderosa) forests in northern Arizona. Aberts squirrels feed primarily on the inner bark of ponderosa pine branches, as well as the trees seeds and the hypogenous fungi associated with ponderosa pines. Aberts squirrels require interlocking tree canopies for escape cover and for feeding, particularly in winter months when snow impedes ground travel and the ability of Aberts squirrels to access fungi and hoarded food. In the Southwest, land managers in the ponderosa pine belt are implementing large-scale forest restoration treatments to reduce fire risk and return forest structure to pre-European settlement conditions. Restoration may decrease intrastand structural diversity and interstand heterogeneity for several decades, reducing the amount of habitat available to Aberts squirrels and reducing overall abundance. We estimated Aberts squirrel densities by enumerating squirrel feeding sign (branch clippings, clipped cones, truffle digging) over 9 years on 15 sites on Camp Navajo, an Arizona Army National Guard base in northern Arizona. Sites were treated at different times throughout the duration of the study. We evaluated the effects of forest restoration treatments on Aberts squirrel densities. We found no difference in Aberts squirrel densities on sites experiencing different treatment types. However, we did find a difference in Aberts squirrel densities between years.

Population Characteristics of Big Brown Bat and Arizona Myotis Using Artificial Roosting Structures in Northern Arizona

Abstract. Big brown bats (Eptesicus fuscus) and a close relative of Arizona myotis (Myotis occultus), the little brown bat (Myotis lucifugus) in the eastern United States, are among those species experiencing unprecedented population declines related to white-nose syndrome (WNS). Determining population characteristic baselines for big brown bat and Arizona myotis is paramount in detecting population declines before they reach critical levels. We targeted 2 bat species strongly associated with ponderosa pine forests in northern Arizona. Big brown bats and Arizona myotis readily utilize human-made structures and have a cosmopolitan distribution across the ponderosa pine (Pinus ponderosa) ecosystem of northern Arizona (Adams 2003). Between 2005 and 2012 we installed artificial bat roosts at Camp Navajo near Flagstaff, Arizona. We captured bats at these roosting structures and marked them using modified bird bands. We established baseline population characteristics on Camp Navajo by utilizing a 7-year mark-and-recapture data set. We also provide a measure of population status that may be compared across temporal scales within the study area. In essence, this study provides the basis for an early warning system for WNS in Arizona.

STATUS OF RED SQUIRRELS IN GUADALUPE MOUNTAINS NATIONAL PARK, TEXAS

Abstract The Pinaleño Mountains of southeastern Arizona contain the southernmost population of red squirrels (Tamiasciurus hudsonicus) in North America. Red squirrels historically inhabited the Guadalupe Mountains in Trans-Pecos Texas during the Pleistocene and the possibility that red squirrels currently persist has been suggested by several biologists visiting the upper-elevation forests. Herein, we report results of an assessment of small mammals in coniferous forest where we used observational line transects, playback calls, and live trapping to determine status of red squirrels. We surveyed 132 ha of coniferous forest along 8.9 km of transects and observed and found evidence of 10 species of mammals. We detected no evidence of red squirrels inhabiting high-elevation coniferous forest.