conservation.arizona.edu - red squirrel

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

Ramos-Lara, N., and J. L. Koprowski. 2015. Spacing behavior of a non-larder-hoarding Tamiasciurus: a study of Mearns's squirrels in xeric coniferous forests. Ethology 121: 196-205.

thackerk1 — Tue, 30 Jul 2019 17:43:48 +0000

Authors

Nicolás Ramos-Lara

John L. Koprowski

In ecosystems with seasonal fluctuations in food supply many species use two strategies to store food: larder hoarding and scatter hoarding. However, because species at different geographic locations may experience distinct environmental conditions, differences in hoarding behavior may occur. Tree squirrels in the genus Tamiasciurus display variation in hoarding behavior. Whereas red (Tamiasciurus hudsonicus) and Douglas’s (Tamiasciurus douglasii) squirrels in mesic coniferous forests defend territories centered around larder hoards maintaining non-overlapping home ranges, red squirrels in deciduous forests defend small scatter-hoarded caches of cones maintaining overlapping home ranges. As in other rodent species, variation in hoarding behavior appears to influence the spacing behavior of red and Douglas’s squirrels. In contrast, Mearns’s squirrels (Tamiasciurus mearnsi) in xeric coniferous forests neither rely on larder hoards nor appear to display territorial behavior. Unfortunately, little is known about the ecology of this southernmost Tamiasciurus. Using radiotelemetry, we estimated home-range size, overlap, and maximum distance traveled from nest to examine the spacing behavior of Mearns’s squirrels. Similar to scatter-hoarding rodents, maximum distance traveled from nest was greater for males during mating season, whereas those of females were similar year round. Although no seasonal differences were detected, male home ranges were three times larger during mating season, whereas those of females were smaller and displayed a minor variation between seasons. Home ranges were overlapped year round but contrary to our expectations, overlap was greater during mating season for both sexes, with no detectable relationship between male home-range size and the number of females overlapped during mating season. Overall, the results appear to support our hypothesis that in the absence of larder hoards, the spacing behavior of Mearns’s squirrels should be different from larder- hoarding congeners and more similar to scatter-hoarding rodents.

Additional Information

Spacing Behavior of a Non-Larder-Hoarding Tamiasciurus: A Study of Mearns’s Squirrels in Xeric Coniferous Forests

Date of publication:

2014

Topics

hoarding behavior

mating system

spacing behavior

tree squirrel

Mearn’s squirrel

red squirrel

Douglas's squirrel

Posthumus, E. E., J. L. Koprowski, and R. J. Steidl. 2015. Red squirrel middens influence abundance but not diversity of other vertebrates. PLoS ONE 10(4):e0123633. doi:10.1371/journal/pone.0123633.

thackerk1 — Wed, 24 Jul 2019 23:22:26 +0000

Authors

Erin E. Posthumus

John L. Koprowski

Robert J. Steidl

Some animals modify the environment in ways that can influence the resources available to other species. Because red squirrels (Tamiasciurus hudsonicus) create large piles of conifer-cone debris (middens) in which they store cones, squirrels concentrate resources that might affect biodiversity locally. To determine whether other animals are attracted to midden sites beyond their affinity for the same resources that attract red squirrels, we assessed associations between middens, mammals, and birds at population and community levels. We surveyed 75 middens where residency rates of red squirrels varied during the previous five years; sampling along this residency gradient permitted us to evaluate the influence of resources at middens beyond the influence of a resident squirrel. At each loca- tion, we quantified vegetation, landscape structure, abundance of conifer cones, and midden structure, and used capture–recapture, distance sampling, and remote cameras to quantify presence, abundance, and species richness of mammals and birds. Red squirrels and the resources they concentrated at middens influenced mammals and birds at the population scale and to a lesser extent at the community scale. At middens with higher residency rates of red squirrels, richness of medium and large mammals increased markedly and species richness of birds increased slightly. After accounting for local forest characteristics, however, only species richness of medium-to-large mammals was associated with a red squirrel being resident during surveys. In areas where red squirrels were resident during surveys or in areas with greater amounts of resources concentrated by red squirrels, abundances of two of four small mammal species and two of four bird species increased. We conclude that the presence of this ecosystem modifier and the resources it concentrates influence abundance of some mammals and birds, which may have implications for maintain- ing biodiversity across the wide geographic range inhabited by red squirrels and other larderhoarding animals.

Additional Information

Red Squirrel Middens Influence Abundance but Not Diversity of Other Vertebrates

Date of publication:

2015

Topics

red squirrel

resources

middens

Mammals

birds

population

community levels

residency

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

Koprowski, J. L., S. R. B. King, and M. J. Merrick. 2008. Expanded home ranges in a peripheral population: space use by endangered Mt. Graham red squirrels. Endangered Species Research, 4:227-232.

thackerk1 — Mon, 22 Jul 2019 23:04:35 +0000

Authors

John L. Koprowski

Sarah R. B. King

Melissa J. Merrick

Peripheral populations are often of increased conservation value; however, knowledge of the ecological and evolutionary consequences of a peripheral location is poor. Spatial dynamics are often interpreted as strategies to maximize access to fitness-limiting resources. Red squirrels Tamiasciurus hudsonicus are territorial in western portions of their range and exhibit overlapping home ranges in eastern forests. Endangered Mt. Graham red squirrels T. hudsonicus grahamensis represent the southernmost extension of the species. We used radiotelemetry to assess space use and interindividual overlap of endangered Mt. Graham red squirrels. Squirrels maintained nearly exclusive 50% core areas; however, 95% ranges overlapped considerably, especially between males and females. Home ranges increased in summer for both males and females and may be related to sex-specific reproductive strategies. Ranges of Mt. Graham red squirrels in this peripheral population were nearly 10 times the size of red squirrels from other locations. The space use of this limital population suggests that resource availability may be substantially different than in other portions of the range.

Additional Information

Expanded home ranges in a peripheral population: space use by endangered Mt. Graham red squirrels

Date of publication:

2008

Topics

limital population

geographic range

Arizona

conservation

Mount Graham Red Squirrel

red squirrel

Functional semelparity drives population dynamics and endangers a peripheral population

thackerk1 — Thu, 27 Jun 2019 22:38:23 +0000

Authors

Emily A. Goldstein

Melissa J. Merrick

John L. Koprowski

Despite increased risk of extinction through stochastic events, peripheral populations are conservation priorities as the distribution of endangered species tends to contract to the periphery of historic ranges rather than toward the core. Trailing-edge populations and mountain isolates, which may become more common as climate change drives range shifts, are an important realm of inquiry and contain important reserves of genetic variation. We use long-term monitoring data from the southernmost population of a widespread species to test the hypothesis that peripheral populations display distinct demographic profiles from core populations. The red squirrel (Tamiasciurus hudsonicus) is predicted to recede from its southern border in response to climate-induced habitat change. We estimate key demographic parameters for this endangered population using survival and reproduction schedules and compare the dynamics to core populations of this and related species. This peripheral population exhibits higher adult mortality, and suffers associated impacts on reproductive output, which results in a demography distinct from core populations and phylogenetically similar species. Poor adult survival, similar to a population that experiences extremely high hunting pressure, has resulted in this normally iteroparous species becoming functionally semelparous at the periphery. Understanding differences in demographic function between peripheral and core populations is key if management strategies are to be effective in supporting continued persistence of at risk populations in the face of range shifts of species or habitats driven by environmental change.

Additional Information

Biological Conservation 205:52-59.

Date of publication:

2016

Topics

sky island

red squirrel

life table

trailing edge

peripheral population

Research Categories

Natural History Population Ecology Sky Islands Threatened and Endangered Species