conservation.arizona.edu - home range

Timing of resource availability drives divergent social systems and home range dynamics in ecologically similar tree squirrels

mmerrick — Thu, 25 Jun 2020 23:15:21 +0000

Authors

Maria Vittoria Mazzamuto

Melissa Merrick

Francesco Bisi

John Koprowski

Luc Wauters

Adriano Martinoli

Intraspecific variation in home range size has important implications for the distribution of animals across landscapes and the spatial structuring of population, community, and ecosystem processes. Among species of similar trophic guild and body mass, differences in home range size can reflect extrinsic variables that exert divergent selective forces upon spacing behavior and social organization. We tested predictions about how resource availability and timing influence social system, home range size, and territoriality in two tree squirrel species of similar size and ecological niches but that differ in foraging strategy and social organization. We estimated home range size and intraspecific home range core overlap in the Mt. Graham red squirrel (Tamiasciurus fremonti grahamensis; Arizona USA; MGRS) and the Eurasian red squirrel (Sciurus vulgaris; Alps, Italy; ERS) as functions of species, sex, season, and individual’s body mass. However, body mass did not explain differences found between the two species. We found MGRS home ranges being three times smaller with higher core area exclusivity compared to ERS in all seasons. In fact, territorial MGRS evolved in a system of brief resource pulses and are larder hoarders, whereas ERS experience prolonged resource availability and are non-territorial. Only male MGRSs increased their home range during the breeding season, reflecting interspecific differences in social organization and mating behavior. Male ERS home ranges always overlap with several females to enhance mating success although male and female MGRS maintain nearly exclusive territories throughout the year. Only during spring and summer do males temporarily leave their food-based territory to increase mating opportunities with neighboring estrus females. Home range comparisons between ecologically similar species emphasize the importance of divergent extrinsic factors in shaping variability in body size–home range size scaling relationships. Timing in resource availability influenced the social structure and space use in tree squirrels of similar body size, highlighting how the coevolution of arboreal squirrels with conifer tree species has shaped their natural history.

Additional Information

Frontiers in Ecology and Evolution

Date of publication:

2020

Topics

seed predators

home range

Eurasian red squirrel

Mt. Graham red squirrel

forest ecosystems

Research Categories

Natural History Population Ecology Sky Islands Spatial Ecology Threatened and Endangered Species

Zugmeyer, C. A. 2007. Trailblazers in the forest: response of endangered Mt. Graham red squirrels to severe insect infestation. M.S. Thesis. University of Arizona, Tucson, AZ. 73 pp

thackerk1 — Tue, 30 Jul 2019 22:29:25 +0000

Authors

Claire A. Zugmeyer

I examined habitat selection of middens within insect-damaged forest and compared home range and survival for Mt. Graham red squirrels (Tamiasciurus hudsonicus grahamensis) in insect-damaged and healthy forest. Squirrels used habitat in areas with < 69% tree mortality. Basal area, canopy cover, and log volume were greater at middens than random locations. Within midden sites, only greater basal area of live trees distinguished occupied sites from unoccupied sites. Surface temperature at occupied middens tended to be cooler than unoccupied middens. Squirrels living in insect-damaged forest had larger home ranges than in healthy forest. Squirrel body mass and reproductive condition did not differ between forest types, suggesting that insectdamaged forest provided adequate resources. However, squirrels inhabiting insectdamaged forest experienced lower survivorship and 50% fewer potential reproductive events than squirrels in healthy forest, implicating presence of an ecological trap. Preservation of remaining healthy forest is a priority for management of this endangered species.

Additional Information

Trailblazers in the Forest: Response of Endangered Mt. Graham Red Squirrels to Severe Insect Infestation

Date of publication:

2007

Topics

Mount Graham Red Squirrel

habitat selection

insect damage

home range

healthy forest

Zugmeyer, C. A. and J. L. Koprowski. 2009. Severely insect-damaged forest: A temporary trap for red squirrels? Forest Ecology and Management 257: 464-470.

thackerk1 — Tue, 30 Jul 2019 21:55:53 +0000

Authors

Claire A. Zugmeyer

John L. Koprowski

Recent insect infestations in the spruce-fir forest in the Pinaleño Mountains of southeastern Arizona provided an opportunity to document response to severe forest disturbance and existence of an ecological trap for an endemic montane isolate, the endangered Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis). From September 2003 to December 2005 we assessed habitat selection and home range dynamics, and monitored potential correlates of fitness (body mass, reproduction, survivorship) in red squirrels living in insect-damaged forest, while drawing comparisons to squirrels inhabiting undamaged mixed-conifer forest. Although Mt. Graham red squirrels demonstrate equal- preference for habitat within insect-damaged forests and reproduce as well as individuals in undamaged forest, poor survivorship and reduced potential to reproduce suggest insect-damaged forest may function as an ecological trap. In addition, areas selected within insect-damaged forest had <69% dead trees, suggesting an upper limit to the extent of tree mortality tolerated by red squirrels. Habitat selection and sensitivity to disturbance will influence use of insect-damaged areas by forest-dwelling species. Although insect-damaged forest may retain habitat patches for a few individuals, low survivorship may generate an ecological trap.

Additional Information

Severely insect-damaged forest: A temporary trap for red squirrels?

Date of publication:

2008

Topics

Mount Graham Red Squirrel

isolation

home range

habitat selection

survival

Pinaleño Mountains

White-nosed coatis in Arizona: tropical carnivores in a temperate environment

thackerk1 — Tue, 23 Jul 2019 22:39:56 +0000

Authors

Maureen E. McColgin

John L. Koprowski

Peter M. Waser

Intraspecific variation in ranging and social behavior can be perplexing, but also provides an opportunity to assess which behavioral attributes are labile in the face of geographic variation in resources. White-nosed coatis (Nasua narica) are group-living carnivores of tropical origin that possess an unusual social system. In the resource- rich tropics, larger-bodied males are solitary, whereas females live in groups (“bands”) along with young of both sexes, but leave them to give birth and wean their young. Males often disperse socially, but not spatially. We studied coatis in the Chiricahua National Monument, Arizona, a resource-poor, arid, and highly seasonal landscape. Using live capture and radiotelemetry in conjunction with microsatellite DNA analyses, we found that Chiricahua coatis exhibited the species-typical pattern of solitary males and gregarious females. Young males left their natal bands as yearlings, and some were found as adults within their natal home range. On the other hand, home ranges were expanded greatly. Bands, and some males, focused their movements in areas several km2 in extent over periods of weeks or months but shifted those areas markedly among seasons. Some males followed the typical mammalian pattern of natal dispersal beyond their natal area. Rates of movement were higher and female associations appeared to be more flexible than in the tropics. Adult females sometimes ranged singly, not only around the time of parturition, but also when population density was low and occasionally otherwise. In addition, home range overlap was high among both sexes during some seasons, and female bands sometimes fused for prolonged periods. Core patterns of sociality are constant in both resource-rich tropical and resource- poor temperate populations, but coatis appear to make major adjustments in scale of movement and frequency of association in response to resource variation.

Additional Information

Journal of Mammalogy

Date of publication:

2017

Topics

Arizona

white-nosed coatis

dispersal

home range

social organization

group structure

Research Categories

Behavioral Ecology Natural History Sky Islands Spatial Ecology

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

Edelman, A. J. and J. L. Koprowski. 2006. Seasonal changes in home ranges of Abert's squirrels: Impact of mating season. Canadian Journal of Zoology 84: 404-411.

thackerk1 — Tue, 25 Jun 2019 01:06:09 +0000

Authors

A.J. Edelman

J.L. Koprowski

We compared home ranges of introduced Abert’s squirrels (Sciurus aberti Woodhouse, 1853) in mixed- conifer forests of Arizona during non-mating and mating seasons. Because Abert’s squirrels are reported to depend on ponderosa pine (Pinus ponderosa P. & C. Lawson) forests, the mixed-conifer forest in our study represented a novel habitat. Home-range size, home-range overlap with females, and movement distances increased for males from non-mating to mating seasons. Home-range size and overlap characteristics of females remained consistent between seasons, but movement distances were reduced during the mating season. Males probably increased home-range size, home-range overlap with females, and movement distances during the mating season to maximize contact with scarce females. Home-range size and overlap characteristics of female Abert’s squirrels likely remained stable between seasons because females do not search for mates. Restricted movements by females during the mating season may be due to changes in resource use in preparation for reproduction. Non-mating season home ranges in our study were smaller than home ranges observed in ponderosa pine forest. Abert’s squirrels in mixed-conifer forest may have small home ranges because resource quality is higher than in ponderosa pine forest or competition for space with co-occurring Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis (J.A. Allen, 1894)).

Additional Information

Seasonal changes in home ranges of Abert’s squirrels: impact of mating season

Date of publication:

2006

Topics

Abert’s squirrels

mixed conifer forests

home range

resource quality

sex differences

seasonal changes

mating season

Doumas, S.L., J.L. Koprowski. 2013. Return of fire as a restoration tool: long-term effects of burn severity on habitat use by Mexican fox squirrels. Restoration Ecology 21:133-139.

thackerk1 — Tue, 25 Jun 2019 00:43:39 +0000

Authors

Sandra L. Doumas

John L. Koprowski

After decades of suppression, fire is returning to forests of the western United States through wildfires and prescribed burns. These fires may aid restoration of vegetation structure and processes, which could improve conditions for wildlife species and reduce severe wildfire risk. Understanding response of wildlife species to fires is essential to forest restoration because contemporary fires may not have the same effects as historical fires. Recent fires in the Chiricahua Mountains of southeastern Arizona provided opportunity to investigate long-term effects of burn severity on habitat selection of a native wildlife species. We surveyed burned forest for squirrel feeding sign and related vegetation characteristics to frequency of feeding sign occurrence. We used radio-telemetry within fire- influenced forest to determine home ranges of Mexican fox squirrels, Sciurus nayaritensis chiricahuae, and compared vegetation characteristics within home ranges to random areas available to squirrels throughout burned conifer forest. Squirrels fed in forest with open understory and closed canopy cover. Vegetation within home ranges was characterized by lower understory density, consistent with the effects of low-severity fire, and larger trees than random locations. Our results suggest that return of low-severity fire can help restore habitat for Mexican fox squirrels and other native wildlife species with similar habitat affiliations in forests with a historical regime of frequent, low-severity fire. Our study contributes to an understanding of the role and impact of fire in forest ecosystems and the implications for forest restoration as fire returns to the region.

Additional Information

Return of Fire as a Restoration Tool: Long‐Term Effects of Burn Severity on Habitat Use by Mexican Fox Squirrels

Date of publication:

2012

Topics

Chiricahua fox squirrel

prescribed fire

wildfire

habitat

home range

vegetation

Chen, H. L. and J. L. Koprowski. 2015. Differential effects of roads and traffic on space use and movements of native forest-dependent and introduced edge-tolerant species. PLoS ONE 11:e0148121 doi:10.1371/journal.pone.0148121.

thackerk1 — Thu, 20 Jun 2019 23:06:19 +0000

Authors

Hsiang Ling Chen

John L. Koprowski

Anthropogenic infrastructure such as roads and non-native species are major causes of species endangerment. Understanding animal behavioral responses to roads and traffic provides insight into causes and mechanisms of effects of linear development on wildlife and aids effective mitigation and conservation. We investigated effects of roads and traffic on space use and movements of two forest-dwelling species: endemic, forest-dependent Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis) and introduced, edge-tolerant Abert’s squirrels (Sciurus aberti). To assess the effects of roads on space use and movement patterns, we compared the probability that a squirrel home range included roads and random lines in forests, and assessed effects of traffic intensity on rate of road crossing and movement patterns. Red squirrels avoided areas adjacent to roads and rarely crossed roads. In contrast, Abert’s squirrels were more likely to include roads in their home ranges compared to random lines in forests. Both red squirrels and Abert’s squirrels increased speed when crossing roads, compared to before and after road crossings. Increased hourly traffic volume reduced the rate of road crossings by both species. Behavioral responses of red squirrels to roads and traffic resemble responses to elevated predation risk, including reduced speed near roads and increased tortuosity of movement paths with increased traffic volume. In contrast, Abert’s squirrels appeared little affected by roads and traffic with tortuosity of movement paths reduced as distance to roads decreased. We found that species with similar body size category (<1 kg) but different habitat preference and foraging strategy responded to roads differently and demonstrated that behavior and ecology are important when considering effects of roads on wildlife. Our results indicate that roads restricted movements and space use of a native forest-dependent species while cre- ating habitat preferred by an introduced, edge-tolerant species.

Additional Information

Differential Effects of Roads and Traffic on Space Use and Movements of Native Forest- Dependent and Introduced Edge-Tolerant Sp

Date of publication:

2015

Topics

non-native species

Mount Graham Red Squirrel

Abert’s squirrels

introduced

road impacts

animal behavior

home range

traffic

Blount, S.J., J.L. Koprowski. 2012. Small mammal response to post-fire conditions: case of the endangered Mount Graham red squirrel. Southwestern Naturalist. 57:8-15.

thackerk1 — Thu, 20 Jun 2019 21:50:31 +0000

Authors

Seafha J. Blount

John L. Koprowski

To assess response of Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis) to postfire conditions, we monitored size of home ranges and core areas and characteristics of vegetation at middens in an area of low-intensity burn. For a larger-scale assessment, we monitored mountain-wide occupancy of middens. Although red squirrels selected unburned locations as sites for middens, mean size of home range in a lightly burned area decreased over time, suggesting high availability of resources in lightly burned areas.

Additional Information

Response of the Mount Graham Red Squirrel to Postfire Conditions

Date of publication:

2012

Topics

Mount Graham Red Squirrel

home range

vegetation

middens

burn areas

unburned areas