conservation.arizona.edu - Abert’s squirrel

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

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

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