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

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

conservation.arizona.edu - competition

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.

Authors

Additional Information

Topics

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

Authors

Additional Information

Topics