Melissa J. Merrick

Characteristics of Mount Graham Red Squirrel Nest Sites in a Mixed Conifer Forest

Abstract The Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is constrained to the Pinaleño Mountains in southeastern Arizona, USA. The populations endangered status and extensive forest damage from insects and fire warrants a better understanding of habitat variables important for nest site selection. We examined characteristics of cavity (n = 91) and drey (n = 38) nests and compared these to random sites (n = 113). Dreys were found primarily in Engelmann spruce (Picea engelmannii) and corkbark fir (Abies lasiocarpa var. arizonica). Cavity nests occurred primarily in aspen (Populus tremuloides) and corkbark fir. Squirrels selected nest sites with higher canopy cover and more corkbark fir, decayed logs, and living trees. Forest management plans emphasizing thinning must consider how altering these habitat characteristics could affect availability and suitability of tree stands for nesting squirrels.

Presence of Guayaquil squirrels on the central coast of Peru: An apparent introduction

No abstract available

Altered natal dispersal at the range periphery: The role of behavior, resources, and maternal condition

Abstract Natal dispersal outcomes are an interplay between environmental conditions and individual phenotypes. Peripheral, isolated populations may experience altered environmental conditions and natal dispersal patterns that differ from populations in contiguous landscapes. We document nonphilopatric, sex‐biased natal dispersal in an endangered small mammal, the Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis), restricted to a single mountain. Other North American red squirrel populations are shown to have sex‐unbiased, philopatric natal dispersal. We ask what environmental and intrinsic factors may be driving this atypical natal dispersal pattern. We test for the influence of proximate factors and ultimate drivers of natal dispersal: habitat fragmentation, local population density, individual behavior traits, inbreeding avoidance, competition for mates, and competition for resources, allowing us to better understand altered natal dispersal patterns at the periphery of a species’ range. A juvenile squirrels body condition and its mothers mass in spring (a reflection of her intrinsic quality and territory quality) contribute to individual behavioral tendencies for movement and exploration. Resources, behavior, and body condition have the strongest influence on natal dispersal distance, but affect males and females differently. Male natal dispersal distance is positively influenced by its mothers spring body mass and individual tendency for movement; female natal dispersal distance is negatively influenced by its mothers spring body mass and positively influenced by individual tendency for movement. An apparent feedback between environmental variables and subsequent juvenile behavioral state contributes to an altered natal dispersal pattern in a peripheral population, highlighting the importance of studying ecological processes at the both range center and periphery of species’ distributions.

Evidence of natal habitat preference induction within one habitat type

Natal habitat preference induction (NHPI) is a mechanism for habitat selection by individuals during natal dispersal. NHPI occurs in wild animal populations, and evidence suggests it may be a common, although little studied, mechanism for post-dispersal habitat selection. Most tests of NHPI examine the influence of distinct, contrasting natal habitat types on post-dispersal habitat selection. We test the hypothesis that NHPI can occur within a single habitat type, an important consideration for habitat specialists. The Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is an endangered forest obligate restricted to a single mountain primarily within mixed-conifer forest. We test for NHPI by comparing intra-individual differences in natal and settlement habitat structure and composition to expected random pairwise differences. Dispersing juveniles appear to select settlement locations that are more similar to natal areas than expected in several forest structure and composition variables that include canopy cover and live basal area. Our results provide support for NHPI as a mechanism for post-dispersal habitat selection in habitat specialists that occupy a single vegetation community type.

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.

Big Cypress fox squirrel ( Sciurus niger avicennia ) ecology and habitat use in a cypress dome swamp-pine forest mosaic

Forested wetlands are in decline, as are many species that are obligate residents. Big Cypress fox squirrels (BCFS; Sciurus niger avicennia) are a threatened endemic to wet pine and cypress forests in southwestern Florida. The region is characterized by development resulting in habitat loss, habitat fragmentation, and hydrological change that influence the quality of these wet forests. Through radiotelemetry and field observations, we examined the ecology and habitat use of BCFS in a natural cypress dome-pine forest mosaic. BCFS selected cypress domes for food and nests throughout the year. Cypress dome habitats were the only habitat type to be used more than available; however, the availability of nearby pine forest was also important. Home ranges were large relative to other tree squirrels, with male home ranges exceeding female ranges. Males overlapped more females than males, while sharing similar food preferences and use patterns with females, suggesting that the sexual dimorphism in home range size is related to mate searching. Roads and oil extraction pads were used less frequently than expected and were incorporated into home ranges less than randomly generated features. The importance of cypress domes within the wet forests and grasslands of Big Cypress National Preserve demonstrates the value of maintaining this delicate mosaic.

Sciurus ignitus (Rodentia: Sciuridae)

Abstract:  Sciurus ignitus (Gray, 1867) is a Neotropical tree squirrel commonly known as the Bolivian squirrel. It is a small-bodied, understory and mid-canopy dweller that occurs within the evergreen lowland and montane tropical rain forests along the eastern slope of the Andes in Peru, Bolivia, and extreme northern Argentina, and the western Amazon Basin in Brazil and Peru between 200 and 2,700 m in elevation. S. ignitus is 1 of 28 species in the genus Sciurus, and 1 of 8 in the subgenus Guerlinguetus. The taxonomic status of this species, as with other small sciurids in Peru and Bolivia, remains ambiguous. S. ignitus is currently listed as “Data Deficient” by the International Union for Conservation of Nature and Natural Resources.

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.

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.