conservation.arizona.edu - Pinaleño Mountains

Edelman, A. J. and J. L. Koprowski. 2007. Communal nesting in asocial Abert's squirrels: the role of social thermoregulation and breeding strategy. Ethology 113: 147-154.

thackerk1 — Tue, 30 Jul 2019 22:49:40 +0000

Authors

Andrew J. Edelman

John L. Koprowski

The social thermoregulation hypothesis states that endothermic species will communally nest to reduce energy expenditures on thermoregulation. The hypothesis predicts that the frequency of communal nesting should increase with decreasing ambient temperature. The potential costs of communal nesting (e.g., increased predation risk, resource competition, cuckoldry, parasite/disease transmission, or infanticide) could decrease the frequency of communal nesting especially for asocial breeding females with dependent offspring. We examined the effects of ambient temperature and seasonal reproductive activities on the probability of communal nesting in Abert's squirrels (Sciurus aberti) in the Pinaleño Mountains, Arizona. Most squirrels nested consistently with the same partner in mixed-sex pairs. The proportion of individuals engaging in communal nesting increased with decreasing ambient temperature as predicted by the social thermoregulation hypothesis. The onset of the breeding season greatly reduced the proportion of individuals communally nesting. The negative relationship between ambient temperature and communal nesting supports the use of communal nesting in Abert's squirrels as a mechanism to reduce thermoregulatory costs during cold conditions. The abrupt drop in the frequency of communal nesting during the breeding season is likely due to female abandonment of this behavior. By avoiding communally nesting during the breeding season, females may prevent males from mating with them outside of mating chases, reduce resource competition, and protect offspring from infanticide, diseases, and parasites. Males may gain additional fitness benefits from nesting with females because familiarity with females increases dominance rank in mating activities.

Additional Information

Communal Nesting in Asocial Abert's Squirrels: the Role of Social Thermoregulation and Breeding Strategy

Date of publication:

2007

Topics

Abert’s squirrel

communal nesting

endothermic

Pinaleño Mountains

Zugmeyer, C. A. and J. L. Koprowski. 2009. Severely insect-damaged forest: A temporary trap for red squirrels? Forest Ecology and Management 257: 464-470.

thackerk1 — Tue, 30 Jul 2019 21:55:53 +0000

Authors

Claire A. Zugmeyer

John L. Koprowski

Recent insect infestations in the spruce-fir forest in the Pinaleño Mountains of southeastern Arizona provided an opportunity to document response to severe forest disturbance and existence of an ecological trap for an endemic montane isolate, the endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis). From September 2003 to December 2005 we assessed habitat selection and home range dynamics, and monitored potential correlates of fitness (body mass, reproduction, survivorship) in red squirrels living in insect-damaged forest, while drawing comparisons to squirrels inhabiting undamaged mixed-conifer forest. Although Mt. Graham red squirrels demonstrate equal- preference for habitat within insect-damaged forests and reproduce as well as individuals in undamaged forest, poor survivorship and reduced potential to reproduce suggest insect-damaged forest may function as an ecological trap. In addition, areas selected within insect-damaged forest had <69% dead trees, suggesting an upper limit to the extent of tree mortality tolerated by red squirrels. Habitat selection and sensitivity to disturbance will influence use of insect-damaged areas by forest-dwelling species. Although insect-damaged forest may retain habitat patches for a few individuals, low survivorship may generate an ecological trap.

Additional Information

Severely insect-damaged forest: A temporary trap for red squirrels?

Date of publication:

2008

Topics

Mount Graham Red Squirrel

isolation

home range

habitat selection

survival

Pinaleño Mountains

Young, P. J., V. L. Greer, and S. K. Six. 2002. Characteristics of Bolus Nests of Red Squirrels in the Pinaleño and White Mountains of Arizona. The Southwestern Naturalist 47: 267-275.

thackerk1 — Tue, 30 Jul 2019 21:51:57 +0000

Authors

Paul J. Young

Vicki L. Greer

Sheri K. Six

Red squirrels (Tamiasciurus hudsonicus) use cavity, bolus, and underground nests for sleeping, protection, and rearing of young. We compared occurrence and structural characteristics of bolus nests at midden sites (area surrounding the central cache) for red squirrels in the Pinaleno Mountains with those in the White Mountains of southeastern Arizona. Bolus nests were more prevalent in the White mountains, possibly as a result of differing habitat structure; forests of the Pinaleno Mountains had significantly (P < 0.05) larger basal area, greater stem densities, and there was less grass on the forest floor than in the White Mountains. Midden sites with more potential cavity nest sites were more likely to have only cavity nests present. Bolus nests were constructed mostly of lichens in the Pinaleno Mountains and of grasses in the White Mountains, whereas most other nest and nest tree characteristics were similar between locations, although nest trees were further from the main cache location at middens in the Pinaleno Mountains.

Additional Information

Characteristics of Bolus Nests of Red Squirrels in the Pinaleno and White Mountains of Arizona

Date of publication:

2002

Topics

red squirrel

nest sights

midden sites

Pinaleño Mountains

cavity nests

bolus nests

underground nests

Merrick, M.J. R.N.Gwinn, R.L. Minor, R.R. Jessen, T.G. Jessen, V.L. Greer, J. L. Koprowski. 2010. Endangered Mount Graham Red Squirrel (Tamiasciurus hudsonicus grahamensis) uses nest following lightning strike. Southwestern Naturalist. 55: 123-124.

thackerk1 — Tue, 23 Jul 2019 23:36:28 +0000

Authors

Melissa J. Merrick

R. Nathan Gwinn

Rebecca L. Minor

Rosa R. Jessen

Timothy G. Jessen

Vicki L. Greer

John L. Koprowski

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 Pinaleńo 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.

Additional Information

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

Date of publication:

2010

Topics

Mount Graham Red Squirrel

fire

behavioral response

Pinaleño Mountains

Merrick, M.J., J.L. Koprowski, R.N.Gwinn, G.H. Palmer, C.A. Zugmeyer. 2011. Surveys to determine the status of red squirrels in Guadalupe Mountains National Park, Texas. Southwestern Naturalist. 56: 24-28.

thackerk1 — Tue, 23 Jul 2019 23:33:49 +0000

Authors

Melissa J. Merrick

John L. Koprowski

R. Nathan Gwinn

Geoffrey H. Palmer

Claire A. Zugmeyer

The Pinaleńo 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.

Additional Information

STATUS OF RED SQUIRRELS IN GUADALUPE MOUNTAINS NATIONAL PARK, TEXAS

Date of publication:

2011

Topics

red squirrel

Pinaleño Mountains

assessment

small mammals

coniferous forest

Circuit theory to estimate natal dispersal routes and functional landscape connectivity for an endangered small mammal.

thackerk1 — Tue, 23 Jul 2019 23:06:39 +0000

Authors

Melissa J. Merrick

John L. Koprowski

Context Natal dispersal links population dynamics to landscape connectivity. Understanding how organisms perceive barriers to movement, or landscape resistance, during natal dispersal is important to conserve and manage populations threatened by fragmentation and habitat loss.

Objectives We aimed to (1) model probability of landscape use by an endangered small mammal (Tamiasciurus hudsonicus grahamensis) in the Pinaleño Mountains, Arizona, USA as a function of forest structure at the population and intra-population level, (2) identify potential natal dispersal pathways between natal and settlement locations based on landscape resistance scenarios, and (3) assess which resistance surface best represented observed exploration, disper- sal, and settlement.

Methods We modeled probability of habitat use via used and available animal locations. We developed three landscape resistance scenarios to represent individual differences in perceived resistance. We used circuit theory to identify potential long-distance dispersal pathways and to assess which resistance scenario best represented observed forest use and settlement.

Results Top probability of forest use models included physical landscape features, forest structure, and burn severity. Composite connectivity models, created from multiple resistance scenarios, identified areas that may promote long distance dispersal move- ments. Connectivity models developed from only natal focal nodes allowed for assessment of resistance scenarios; a non-linear, negative-exponential relationship between probability of use and resistance best represented observed exploration and settlement. Conclusions Circuit theory is a useful tool to identify potential small mammal movement pathways when high temporal resolution movement data are limited, and for assessing how well resistance scenarios represent observed settlement patterns.

Additional Information

Landscape Ecology

Date of publication:

2017

Topics

Arizona

Pinaleño Mountains

point selection function

small mammal

resistance surface

circuitscape

Research Categories

Disturbance Ecology Sky Islands Spatial Ecology Threatened and Endangered Species

Leonard, K. M. and J. L. Koprowski. 2009. Effects of fire on endangered Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis): responses of individuals with known fates. Southwestern Naturalist 55:217-224.

thackerk1 — Tue, 23 Jul 2019 22:33:20 +0000

Authors

Katherine M. Leonard

John L. Koprowski

We studied demography and behavior of endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis) inhabiting areas within and outside low-intensity burns following the Nuttall Fire in the Pinaleńo Mountains, Arizona. Body mass, proportion of individuals in reproductive condition, and distance squirrels traveled to nest did not differ between squirrels within and outside the perimeter of the fire. Within the perimeter, red squirrels had smaller home ranges and shifted territories less frequently and had shorter distances from their previously held territories than squirrels outside the perimeter. Mount Graham red squirrels evolved with patchy, low-intensity fires like those that burned in mixed-conifer forests in the Pinaleńo Mountains and may be able to persist in areas affected by this level of disturbance.

Additional Information

EFFECTS OF FIRE ON ENDANGERED MOUNT GRAHAM RED SQUIRRELS (TAMIASCIURUS HUDSONICUS GRAHAMENSIS): RESPONSES OF INDIVIDUALS WITH KN

Date of publication:

2009

Topics

Mount Graham Red Squirrel

Pinaleño Mountains

body mass

fire

level of disturbance

Koprowski, J. L., K. M. Leonard, C. A. Zugmeyer, and J. L. Jolley. 2006. Direct effects of fire on endangered Mount Graham red squirrels. The Southwestern Naturalist 51(1): 59-63.

thackerk1 — Mon, 22 Jul 2019 23:09:57 +0000

Authors

John L. Koprowski

Katherine M. Leonard

Claire A. Zugmeyer

Julia L. Jolley

Direct mortality of forest wildlife due to fire is rarely documented. In June and July 2004, the Nuttall Complex Fire burned 11,898 ha in the Pinaleño Mountains, southeastern Arizona. Portions of these mountains serve as the only habitat of endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis). Survival of radio-collared red squirrels over a period that included the fire was lower in areas that were burned than on unburned areas; however, the majority of squirrels on our study areas survived the fire. Distance of nests from middens did not differ between pre-fire and post-fire periods for animals in burned or unburned areas, indicating that squirrels did not abandon middens immediately after surviving the effects of fire.

Additional Information

DIRECT EFFECTS OF FIRE ON ENDANGERED MOUNT GRAHAM RED SQUIRRELS

Date of publication:

2006

Topics

Mount Graham Red Squirrel

wildfire

Pinaleño Mountains

Hutton, K. A., J. L. Koprowski, V. L. Greer, M. I. Alanen, C. A. Schauffert and P. J. Young. 2002. Use of Spruce-Fir and Mixed-Conifer Forests by an Introduced Population of Abert's Squirrels (Sciurus Aberti). The Southwestern Naturalist 48: 257-260.

thackerk1 — Mon, 22 Jul 2019 18:45:45 +0000

Authors

Kelly A. Hutton

John L. Koprowski

Vicki L. Greer

Marit I. Alanen

Carol A. Schauffert

Paul J. Young

Abert’s squirrels (Sciurus aberti) are thought to depend on ponderosa pine (Pinus ponderosa) for food sources, cover, and nest sites. Records of Abert’s squirrels using other food sources, forest types, and nest trees are rare. In the 1940s, Abert’s squirrels were introduced to ponderosa pine forests on Mount Graham in the Pinaleño Mountains of southeastern Arizona. Since 1989, while studying Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis), we recorded Abert’s squirrel sightings. In over 41,000 field-hours of studying Mount Graham red squirrels, we documented 498 Abert’s squirrel sightings in both mixed-conifer and spruce-fir forests. Behaviors observed included feeding, collecting nest material, nest building, intraspecific chases, and interactions with the endangered red squirrels in this nontraditional habitat.

Additional Information

USE OF MIXED-CONIFER AND SPRUCE-FIR FORESTS BY AN INTRODUCED POPULATION OF ABERT'S SQUIRRELS (SCIURUS ABERTI)

Date of publication:

2002

Topics

Abert’s squirrel

Pinaleño Mountains

Mount Graham Red Squirrel

mixed-conifer forest

spruce-fir forest

behavioral observations

ponderosa pine

Fitak, R. R., J. L. Koprowski, and M. Culver. 2013. Severe reduction in genetic variation in a montane isolate: the endangered Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis). Conservation Genetics 14:1233-1241.

thackerk1 — Thu, 27 Jun 2019 21:46:27 +0000

Authors

Robert R. Fitak

John L. Koprowski

Melanie Culver

The Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis; MGRS) is endemic to the Pinaleño Mountains of Arizona at the southernmost extent of the species’ range. The MGRS was listed as federally endangered in 1987, and is currently at high risk of extinction due to declining population size and increasing threats. Here we present a genetic assessment of the MGRS using eight nuclear DNA microsatellite markers and a 472 bp fragment of the mitochondrial cytochrome b gene. We analyzed 34 MGRS individuals and an additional 66 red squirrels from the nearby White Mountains, Arizona (T. h. mogollonensis). Both nuclear and mitochondrial DNA analyses revealed an extreme reduction in measures of genetic diversity relative to conspecifics from the White Mountains, suggesting that the MGRS has either experienced multiple bottlenecks, or a single long-term bottleneck. Additionally, we found a high degree of relatedness (mean = 0.75 ± 0.18) between individual MGRS. Our study implies that the MGRS may lack the genetic variation required to respond to a changing environment. This is especially important considering this region of the southwest United States is expected to experience profound effects from global climate change. The reduced genetic variability together with the high relatedness coefficients should be taken into account when constructing a captive population to minimize loss of the remaining genetic variation.

Additional Information

Severe reduction in genetic variation in a montane isolate: the endangered Mount Graham red squirrel (Tamiasciurus hudsonicus gr

Date of publication:

2013

Topics

effective population size

inbreeding

Mount Graham Red Squirrel

bottleneck

Pinaleño Mountains

White Mountains