conservation.arizona.edu - Mount Graham Red Squirrel

Sanderson, H. R. and J. L. Koprowski, editors. 2009. The last refuge of the Mt. Graham red squirrel: ecology of endangerment. University of Arizona Press, Tucson.

thackerk1 — Tue, 30 Jul 2019 23:59:52 +0000

Authors

H. Reed Sanderson

John L. Koprowski

Description unavailable.

Additional Information

The Last Refuge of the Mt. Graham Red Squirrel: Ecology of Endangerment

Date of publication:

2009

Topics

Mount Graham Red Squirrel

Zugmeyer, C. A. 2007. Trailblazers in the forest: response of endangered Mt. Graham red squirrels to severe insect infestation. M.S. Thesis. University of Arizona, Tucson, AZ. 73 pp

thackerk1 — Tue, 30 Jul 2019 22:29:25 +0000

Authors

Claire A. Zugmeyer

I examined habitat selection of middens within insect-damaged forest and compared home range and survival for Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged and healthy forest. Squirrels used habitat in areas with < 69% tree mortality. Basal area, canopy cover, and log volume were greater at middens than random locations. Within midden sites, only greater basal area of live trees distinguished occupied sites from unoccupied sites. Surface temperature at occupied middens tended to be cooler than unoccupied middens. Squirrels living in insect-damaged forest had larger home ranges than in healthy forest. Squirrel body mass and reproductive condition did not differ between forest types, suggesting that insectdamaged forest provided adequate resources. However, squirrels inhabiting insectdamaged forest experienced lower survivorship and 50% fewer potential reproductive events than squirrels in healthy forest, implicating presence of an ecological trap. Preservation of remaining healthy forest is a priority for management of this endangered species.

Additional Information

Trailblazers in the Forest: Response of Endangered Mt. Graham Red Squirrels to Severe Insect Infestation

Date of publication:

2007

Topics

Mount Graham Red Squirrel

habitat selection

insect damage

home range

healthy forest

Zugmeyer, C. A. and J. L. Koprowski. 2007. Avian nestling predation by endangered Mt. Graham red squirrel. The Southwestern Naturalist 52(1): 155-157.

thackerk1 — Tue, 30 Jul 2019 22:19:02 +0000

Authors

Claire A. Zugmeyer

John L. Koprowski

Studies using artificial nests or remote cameras have documented avian predation by red squirrels (Tamiasciurus hudsonicus). Although several direct observations of avian predation events are known in the northern range of the red squirrel distribution, no accounts have been reported in the southern portion. We observed predation upon a hermit thrush (Catharus guttatus) nestling by the Mount Graham red squirrel (T. h. grahamensis), an endangered subspecies living at the southern terminus of the distribution of the red squirrel.

Additional Information

AVIAN NESTLING PREDATION BY ENDANGERED MOUNT GRAHAM RED SQUIRREL

Date of publication:

2007

Topics

red squirrels

predation

hermit thrust

Mount Graham Red Squirrel

artificial nests

Zugmeyer, C. A. and J. L. Koprowski. 2009. Habitat selection is unaltered after severe insect infestation: Concerns for forest-dependent species. Journal of Mammalogy 90: 175-182.

thackerk1 — Tue, 30 Jul 2019 22:07:07 +0000

Authors

Claire A. Zugmeyer

John L. Koprowski

Severe disturbance may alter or eliminate important habitat structure that helps preserve food caches of food- hoarding species. Recent recolonization of an insect-damaged forest by the endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) provided an opportunity to examine habitat selection for midden (cache) sites following disturbance. From September 2003 to December 2005, we examined surface temperature and physical and vegetative characteristics associated with random locations and midden sites in insect-damaged forests. Red squirrel use of midden sites that are similar in structure to those used before insect infestation indicates that insect infestation did not eliminate midden habitat. However, differences between occupied middens and historical middens that are unoccupied reflect the severity of insect infestation tolerated by red squirrels. Occupied middens had ,64% tree mortality, high basal area of live trees, and cooler surface temperatures during snow-free months. Forest areas with greater tree mortality would likely not represent habitat, threatening the persistence of an isolated population. Although conservation efforts can protect remaining habitat, disturbance events continually represent a threat. Habitat loss and predictions of increased disturbance due to climate change highlight the importance of documenting response to disturbance.

Additional Information

HABITAT SELECTION IS UNALTERED AFTER SEVERE INSECT INFESTATION: CONCERNS FOR FOREST-DEPENDENT SPECIES

Date of publication:

2009

Topics

disturbance

Mount Graham Red Squirrel

ecological trap

habitat selection

isolation

midden

larderhoard

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

Wood, D. J. A. 2007. Forest disturbance and the long term population persistence of the Mt. Graham red squirrel: a spatially explicit modeling approach. M. S. Thesis. University of Arizona, Tucson, AZ. 119pp.

thackerk1 — Tue, 30 Jul 2019 21:37:40 +0000

Authors

David J. A. Wood

We combined field data with high-resolution satellite imagery and a spatially explicit population model to predict long-term population dynamics of the endangered Mt. Graham red squirrel (MGRS: Tamiasciurus hudsonicus grahamensis), with the goal of examining effects of disturbance on MGRS population dynamics. We found that modeling MGRS dynamics improved with population specific data. Our results indicate that predation and competition potentially have large, adverse effects on population abundance. Habitat quality analysis indicates much of the spruce-fir forest is degraded to the point that it cannot support MGRS, therefore, the future of the species will rely on management in the mixed conifer zones. Our models predict that future populations will not show the variability exhibited in abundance over the past 20 years, likely due to degradation of spruce-fir forests, and that even low levels of fire and insect disturbance have the potential to drive MGRS population below critical population thresholds.

Additional Information

Forest Disturbance and the Long Term Population Persistence of the Mt. Graham Red Squirrel: A Spatially Explicit Modeling Approa

Date of publication:

2007

Topics

Mount Graham Red Squirrel

population dynamics

predation

competition

Wood, D. J. A., S. Drake, S. P. Rushton, D. Rautenkranz, P. W. Lurz, and J. L. Koprowski. 2007. Fine-scale analysis of Mount Graham red squirrel habitat following disturbance. The Journal of Wildlife Management 71(7): 2357-2364.

thackerk1 — Tue, 30 Jul 2019 21:19:23 +0000

Authors

David J. A. Wood

Sam Drake

Steve P. Rushton

Doug Rautenkranz

Peter W. W. Lurz

John L. Koprowski

Habitat destruction and degradation are major factors in reducing abundance, placing populations and species in jeopardy. Monitoring changes to habitat and identifying locations of habitat for a species, after disturbance, can assist mitigation of the effects of human- caused or -amplified habitat disturbance. Like many areas in the western United States, the Pinalen ̃o Mountains of southeastern Arizona, USA, have suffered catastrophic fire and large-scale insect outbreaks in the last decade. The federally endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is only found in the Pinalen ̃o Mountains, and to assess effects of forest disturbance on habitat we modeled their potential habitat by identifying characteristics of cover surrounding their centrally defended middens. We classified high-spatial resolution satellite imagery into ground cover classes, and we used logistic regression to determine areas used by squirrels. We also used known midden locations in conjunction with slope, elevation, and aspect to create a predictive habitat map. Squirrels selected areas of denser forest with higher seedfall for midden sites. Among active middens, those in the densest and least damaged forests were occupied in more seasons than those in more fragmented and damaged areas. The future conservation of red squirrels and the return of healthy mature forests to the Pinaleño Mountains will rely on preservation of mixed conifer zones of the mountain and active restoration of spruce–fir forests to return them to squirrel habitat. Our ability to evaluate the spectrum of fine- to coarse-scale disturbance effects (individual tree mortality to area wide boundaries of a disturbance) with high-resolution satellite imagery shows the utility of this technique for monitoring future disturbances to habitat of imperiled species. (JOURNAL OF WILDLIFE MANAGEMENT 71(7):2357–2364; 2007)

Additional Information

Fine-scale analysis of Mount Graham red squirrel habitat following disturbance

Date of publication:

2007

Topics

Mount Graham Red Squirrel

forest disturbance

insect damage

catastrophic fire

Schauffert, C. A., J. L. Koprowski, V. L. Greer, M. I. Alanen, K. A. Hutton, and P. J. Young. 2002. Interactions Between Predators and Mt. Graham Red Squirrels (Tamiasciurus hudsonicus grahamensis). The Southwestern Naturalist 47: 498-501.

thackerk1 — Tue, 30 Jul 2019 19:40:34 +0000

Authors

Carol A. Schauffert

John L. Koprowski

Vicki L. Greer

Marit I. Alanen

Kelly A. Hutton

Paul J. Young

Predation in populations of small mammals is a rarely observed event (Pearson, 1985); however, the role of predators in population regulation often is considered to be important. Documentation and assessment of mortality factors are especially critical when considering the population dynamics of threatened or endangered species. Herein, we document interactions of the endangered Mt. Graham red squirrel with potential predators.

Additional Information

nteractions between Predators and Mt. Graham Red Squirrels (Tamiasciurus hudsonicus grahamensis)

Date of publication:

2002

Topics

Mount Graham Red Squirrel

predators

interactions

Rushton, S. P., D. J. A. Wood, P. W. W. Lurz, and J. L. Koprowski. 2006. Modelling the population dynamics of the Mt. Graham red squirrel: Can we predict its future in a changing environment with multiple threats? Biological Conservation 131: 121-131.

thackerk1 — Tue, 30 Jul 2019 18:34:52 +0000

Authors

S.P. Rushton

D.J.A. Wood

P.W.W. Lurz

J.L. Koprowski

The Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis; MGRS) is among the most critically endangered mammals in the United States and is isolated on the periphery of the species’ range, potentially increasing its conservation priority. To investigate potential threats to the population and provide a tool for land managers, we developed a spatially explicit population dynamics model. We tested model predictions using available range-wide data from the literature and field work specific to the MGRS. A general model input data set using mean life history values overpredicted MGRS abundance. However, we found significant correlation with known squirrel abundance using a general data set with curtailed fecundity and survival. A model with MGRS-specific data provided the best fit to observed population size. We investigated potential impacts of two major threats to the MGRS: competition from introduced Abert’s squirrels (Sciurus aberti) and increased levels of predation. Predation and particularly competition could have significant effects on the future population of the MGRS. Careful attention must be used to model the viability of fringe populations as peripheral populations can have a different life history than populations found in the range core

Additional Information

Modelling the population dynamics of the Mt. Graham red squirrel: Can we predict its future in a changing environment with multi

Date of publication:

2006

Topics

conservation

Mount Graham Red Squirrel

introduced species

Abert’s squirrel

Minor, R. L. and J. L. Koprowski. 2015. Seed removal increased by scramble competition with an invasive species. PLoS ONE 10:e0143927. doi:10.1371/journal.pone.0143927

thackerk1 — Tue, 23 Jul 2019 23:40:28 +0000

Authors

Rebecca L. Minor

John L. Koprowski

Competition for seeds has a major influence on the evolution of granivores and the plants on which they rely. The complexity of interactions and coevolutionary relationships vary across forest types. The introduction of non-native granivores has considerable potential to alter seed dispersal dynamics. Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. As biological invasions continue to rise, it is important to understand mechanisms to build up strategies to mitigate the threat. Our field experiment quantified the impact of introduced Abert’s squirrels (Sciurus aberti) on rates of seed removal within the range of critically endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis), which consumes similar foods. In the presence of invasive Abert’s squirrels, the time cones were removed was faster than when the invasive was excluded, accounting for a median removal time of cones available to red and Abert’s squirrels that is 32.8% less than that of cones available only to the rare native red squirrels. Moreover, in the presence of Abert’s squirrels, removal rates are higher at great distance from a territorial red squirrel larderhoard and in more open portions of the forest, which suggests differential patterns of seed dispersal. The impact on food availability as a result of cone removal by Abert’s squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. Furthermore, the magnitude and differential spatial patterns of seed removal suggest that non-native granivores may have impacts on forest regeneration and structure.

Additional Information

Seed Removal Increased by Scramble Competition with an Invasive Species

Date of publication:

2015

Topics

Mount Graham Red Squirrel

Abert’s squirrel

competition

invasive species

seed removal