conservation.arizona.edu - tree squirrels

Wood, D. J. A., J. L. Koprowski, and P. W. W. Lurz. 2007. Tree squirrel introductions: A theoretical approach with population viability analysis. Journal of Mammalogy 88(5): 1271-1279.

thackerk1 — Tue, 30 Jul 2019 21:29:20 +0000

Authors

David J. A. Wood

John L. Koprowski

Peter W. W. Lurz

Reintroduction efforts require knowledge of how many animals are needed for successful establishment. Population viability analysis can be used to predict trajectories of introduced populations and tree squirrels provide an ideal model system to investigate this challenge. Conservation action is needed because more than 80% of species of tree squirrels are of precarious conservation status in some portion of their range. We combined data from closely related species of tree squirrels and used VORTEX to determine how many squirrels are needed to successfully establish populations of 6 species (Sciurus aberti, S. carolinensis, S. niger, S. granatensis, S. vulgaris, and Tamiasciurus hudsonicus). We ran multiple simulations to account for between- patch differences in breeding success (resource availability) and variation between years in different habitats. In the best-case scenarios, populations could be successfully established with fewer than 35 individuals for all species and as few as 15 for a subset of species. Empirical evidence from introductions of tree squirrels supports our simulation results, with 93% of populations of greater than 10 squirrels surviving more than 50 years. With relatively few individuals needed for establishing new squirrel populations, reintroductions are feasible and useful as a buffer for imperiled species.

Additional Information

TREE SQUIRREL INTRODUCTION: A THEORETICAL APPROACH WITH POPULATION VIABILITY ANALYSIS

Date of publication:

2007

Topics

reintroduction

tree squirrels

extinction

VORTEX

Steele, M. A., and J. L. Koprowski. 2001. North American Tree Squirrels. Smithsonian Institution Press: Washington, DC. 224 p.

thackerk1 — Tue, 30 Jul 2019 20:04:43 +0000

Authors

Michael A. Steele

John L. Koprowski

Find summary.

Additional Information

North American Tree Squirrels

Date of publication:

2001

Topics

tree squirrels

gray squirrel

fox squirrel

behavior

Koprowski, J. L. 2002. Handling tree squirrels with a safe and efficient restraint. Wildlife Society Bulletin 30: 101-103.

thackerk1 — Mon, 22 Jul 2019 23:33:17 +0000

Authors

John L. Koprowski

The most desirable handling techniques consider the safety of the study organism and the researcher, maximize efficiency by minimizing handling times, and reduce costs. I detail a handling device for tree squirrels that is safe, efficient, inexpensive, and portable. The restraint has been used to handle >3,500 individuals of 7 species of tree squirrel with a mortality rate of <0.01%. The cloth device enables handling of tree squirrels with minimal mortality in the field.

Additional Information

Handling Tree Squirrels with a Safe and Efficient Restraint

Date of publication:

2002

Topics

handling techniques

tree squirrels

Koprowski, J. L. 2005. The response of tree squirrels to fragmentation: A review and synthesis. Animal Conservation 8: 369-376.

thackerk1 — Mon, 22 Jul 2019 23:29:48 +0000

Authors

John L. Koprowski

Habitat fragmentation is often considered a major threat to biodiversity; however, our understanding of how fragmentation impacts populations is poor. Identifying appropriate models for such studies is difficult. Tree squirrels are dependent on mature forests for food, cover and nests; these are habitats that are being fragmented rapidly and that are easily defined by humans. Squirrels represent excellent models for study of fragmentation. The literature on tree squirrels was reviewed to glean data on density and home-range size in forest fragments. Sufficient data were available on four species (Sciurus carolinensis, S. niger, S. vulgaris, Tamiasciurus hudsonicus). Density was negatively related to fragment size for S. carolinensis and S. niger and marginally so for T. hudsonicus. Sciurus vulgaris did not exhibit this relationship. Home-range size was analyzed for three species of Sciurus and was positively related to forest fragment size for S. carolinensis and S. niger. Again, only S. vulgaris did not to show this relationship. Sciurus vulgaris is rarely found in small forest fragments and is believed to be especially sensitive to fragmentation; other tree squirrels appear to be sensitive to fragmentation in more subtle ways. Home range compaction provides a mechanism by which densities may increase in small fragments. The demographic consequences resultant from the high densities of squirrels found in small woodlots are not known but may explain the forest damage, avian nest predation and reduced diversity often cited to occur in woodland fragments.

Additional Information

The response of tree squirrels to fragmentation: a review and synthesis

Date of publication:

2005

Topics

habitat fragmentation

biodiversity

tree squirrels

home range

density

Koprowski, J. L. 2005. Management and conservation of tree squirrels: The importance of endemism, species richness, and forest condition. USDA Forest Service Proceedings RMRS-P-36: 245-250.

thackerk1 — Mon, 22 Jul 2019 23:19:59 +0000

Authors

John L. Koprowski

Tree squirrels are excellent indicators of forest health yet the taxon is understudied. Most tree squirrels in the Holarctic Region are imperiled with some level of legal protection. The Madrean Archipelago is the epicenter for tree squirrel diversity in North America with 5 endemic species and 2 introduced species. Most species of the region are poorly studied in keeping with an international dearth of data on this taxon; 3 of the 5 native species are the subject of <3 publications. Herein, I review literature on the response of squirrels to forest management from clearcutting to less comprehensive operations. Major threats to squirrel diversity in the Madrean Archipelago’s Sky Islands are the introduction of species, altered fire regimes, and inappropriate application of forestry practices.

Additional Information

Management and Conservation of Tree Squirrels: The Importance of Endemism, Species Richness, and Forest Condition

Date of publication:

2005

Topics

forest health

tree squirrels

endemic species

introduced species

Madrean Archipelago’s Sky Islands

Koprowski, J. L. and R. Nandini. 2008. Global hotspots and knowledge gaps for tree and flying squirrels. Current Science 95: 851-856.

thackerk1 — Mon, 22 Jul 2019 22:59:17 +0000

Authors

John L. Koprowski

R. Nandini

Tree and flying squirrels are important components of forested ecosystems, and are advocated as indicators of forest health. In this global assessment of the distribution, endangerment and scientific knowledge of squirrels, we reveal trends that warrant urgent attention. The tropics, particularly the forests of south and southeast Asia, are hotspots of squirrel diversity; however, this region generates the fewest scientific publications on squirrels. Additionally, the most endangered squirrels occur in tropical countries with high deforestation rates, and flying squirrels are more at risk than tree squirrels. Given the combination of high diversity, extinction risk and lack of knowledge of sciurids in the tropics, we recommend increased effort towards understanding their occurrence and biology in the imperiled tropical forests.

Additional Information

Global hotspots and knowledge gaps for tree and flying squirrels

Date of publication:

2008

Topics

diversity

ecosystem services

species richness

tree squirrels

flying squirrels

sciurids

tropical forests