conservation.arizona.edu - Arizona gray squirrel

Differential response of native Arizona gray squirrels and introduced Abert's squirrels to a mosaic of burn severities

thackerk1 — Mon, 22 Jul 2019 21:22:42 +0000

Authors

Shari L. Ketcham

John L. Koprowski

Donald A. Falk

Disturbance events can alter habitat properties, leading to species displacement, isolation, and/or local extinction. Therefore, understanding the interactions of potential ecological drivers on native and introduced wildlife species post-fire is critical to understand influences on distribution. We studied native Arizona gray squirrels (Sciurus arizonensis), which are believed to favor dense riparian habitat, and introduced Abert’s squirrels (S. aberti), which prefer open ponderosa pine (Pinus ponderosa) forests. We examined how uncommon native Arizona gray squirrels and introduced Abert’s squirrels used areas previously burned by widespread fires more than a decade prior to our study. To determine how past fire may affect squirrel habitat, we examined squirrel use and occupancy within fire altered habitats and used distance sampling to determine squirrel distribution, feeding, and nest use within a mosaic of burn severities. Occupancy and habitat use indicated that introduced Abert’s squirrels readily used post-fire conditions more than native Arizona gray squirrels, likely due to the opening of a dense understory. Arizona gray squirrels remained in unburned riparian areas; therefore, fire affected riparian areas can be directly targeted for management to increase abundance of the native species.

Additional Information

Mammal Study 42:247-258.

Date of publication:

2017

Topics

Arizona gray squirrel

Abert’s squirrels

ponderosa pine

wildfire effects

occupancy

habitat

feeding signs

dreys

Research Categories

Disturbance Ecology Sky Islands Threatened and Endangered Species

Cudworth, N.L., J.L. Koprowski. 2010. Influences of mating strategy on space use of Arizona gray squirrels. Journal of Mammalogy. 91: 1235-1241.

thackerk1 — Mon, 24 Jun 2019 23:37:06 +0000

Authors

Nichole L. Cudworth

John L. Koprowski

Space use frequently differs between sexes and may reflect differences in parental investment and limiting resources. We examined Arizona gray squirrels (Sciurus arizonensis) from April 2007 to December 2008 to determine effects of mating strategy on patterns of home-range size and overlap. Home ranges were large compared to those of congeners, suggesting an environment with low availability and predictability of resources, and differed by sex and season. Females maintained smaller home ranges overlapped more by males than females; overlap by male home ranges increased during the breeding season. Males had larger home ranges that overlapped females more than males; home-range size and overlap of both sexes increased during the breeding season. Additionally, male Arizona gray squirrels appear to respond to the distribution of females by enlarging home ranges to maximize proportion of females overlapped. Consequently, Arizona gray squirrels conform to theoretical predictions, with female space use influenced by access to food and male space use influenced by access to mates.

Additional Information

Influences of mating strategy on space use of Arizona gray squirrels

Date of publication:

2010

Topics

Arizona gray squirrel

mating system

resource limitation

sex differences

reproductive strategies

Cudworth, N.L., J.L. Koprowski. 2011. Importance of scale in nest-site selection in Arizona gray squirrels. Journal of Wildlife Management. 75: 1668–1674

thackerk1 — Mon, 24 Jun 2019 23:02:55 +0000

Authors

Nichole L. Cudworth

John L. Koprowski

Nests provide a place for individuals to rest, raise young, avoid predators, and escape inclement weather; consequently, knowledge of habitat characteristics important to nest placement is critical for managing species of conservation concern. Arizona gray squirrels (Sciurus arizonensis) are endemic to mountains of southwestern United States and northwestern Mexico. We investigated factors influencing nest-site selection at 4 spatial scales (forest-type, nest-site, nest-tree, and within-canopy placement) to provide ecological information and management recommendations for this sensitive species. Nest densities were 2.6 times higher in riparian than pine-oak woodlands. Nest sites had more large trees, snags, logs, and canopy cover and had lower slope. Arizona gray squirrels selected tall trees with more interlocking trees and tended to place nests adjacent to the main trunk. Regardless of scale, Arizona gray squirrels seemed to select nesting areas for their ability to provide protection from predators and the elements as well as access to food. Consequently, maintaining large trees with closed canopies and downed logs should be considered when determining land management plans. ©2011 The Wildlife Society.

Additional Information

Importance of Scale in Nest-Site Selection by Arizona Gray Squirrels

Date of publication:

2011

Topics

Arizona gray squirrel

habitat

drey

Cudworth, N. L., and J. L. Koprowski. 2013. Foraging and reproductive behavior of Arizona gray squirrels (Sciurus arizonensis): impacts of climatic variation. Journal of Mammalogy 94:683-690.

thackerk1 — Mon, 24 Jun 2019 22:57:50 +0000

Authors

Nichole L. Cudworth

John L. Koprowski

Optimal timing of reproduction is critical to ensure adequate conditions for raising young. However, factors influencing timing of reproduction may differ between sexes. Harsh seasonal environments offer unique opportunities to link timing with resource availability and strategies of the sexes. The Arizona gray squirrel (Sciurus arizonensis) inhabits arid forests in which precipitation is highly seasonal and exceptionally variable; however, no data are available on diet or reproduction. We investigated annual variation in foraging and reproductive habits of Arizona gray squirrels to assess responses to extreme seasonality. We found that Arizona gray squirrels have a diverse diet, with consumption of major food items shifting between years. Reproduction also varies between years. Reproductive output was greater in 2008, with more females successfully reproducing and males remaining in reproductive condition for extended periods. Males shifted timing of reproductive behaviors in response to female receptivity, which tracked food availability. This shift likely reflects variation in food production due to precipitation, because rainfall varied greatly, with most years prior to and during our study recording below-average rainfall. With drought conditions and extreme rainfall events predicted to increase with climate change, understanding the relationship between climatic events, phenology of food production, and impacts on reproduction is critical when attempting to manage and conserve species.

Additional Information

Foraging and reproductive behavior of Arizona gray squirrels: impacts of climatic variation

Date of publication:

2013

Topics

Arizona gray squirrel

resource limitation

climate

timing of reproduction

Cudworth, N. L., and J. L. Koprowski. 2014. Survival and mortality of the Arizona gray squirrel (Sciurus arizonensis). The Southwestern Naturalist 59:423-426.

thackerk1 — Thu, 20 Jun 2019 23:28:54 +0000

Authors

Nichole L. Cudworth

John L. Koprowski

Arizona gray squirrels (Sciurus arizonensis) are endemic to the southwestern United States and northwestern Mexico. Despite classification as a species of concern in portions of its range, little is known about Arizona gray squirrels. We investigated survival and causes of mortality for a population of squirrels in the Huachuca Mountains in 2007 and 2008. Adult survival was high and did not differ between sexes, with probability of survival >0.70 one year postcapture. Predation was the most common known cause of mortality; consequently, management plans should account for habitat characteristics that provide protection from predators when managing for Arizona gray squirrels.

Additional Information

Survival and mortality of the Arizona gray squirrel

Date of publication:

2014

Topics

Arizona gray squirrel

survival

causes of mortality

predation