conservation.arizona.edu - Mt. Graham red squirrel

Foraging Behavior Response of Small Mammals to Different Burn Severities

aburnett93 — Mon, 25 Sep 2023 21:26:18 +0000

Authors

Marina Morandini

Maria Vittoria Mazzamuto

John L. Koprowski

Additional Information

Fire

Date of publication:

2023

Topics

wildfire

wildfire effects

behavior

behavioral response

GUD

predation

Mt. Graham red squirrel

Research Categories

Disturbance Ecology Sky Islands Threatened and Endangered Species

Endemic population response to increasingly severe fire: A cascade of endangerment for the Mt. Graham red squirrel

mmerrick — Thu, 07 Jan 2021 16:50:11 +0000

Authors

Melissa J. Merrick

Marina Morandini

Vicki L. Greer

John L. Koprowski

Drought, past fire suppression, insect invasion, and high-severity fire represent a disturbance cascade characteristic of forests in the western United States. The result is altered forest ecosystems diminished in their function and capacity to support biodiversity. Small habitat specialists are particularly vulnerable to the impacts of disturbances because of their limited movement capacity and high site fidelity. Research suggests that small mammals suffer limited direct mortality from fire but are increasingly vulnerable to local extirpation because of secondary impacts that include habitat loss and reduced food availability, survival, and reproduction. We examine the direct and secondary impacts of increasingly severe fire events on the endangered Mt. Graham red squirrel—a model system to demonstrate how disturbances can threaten the persistence of range-limited species. We document survival, space use, and displacement prior to and following fires and discuss implications for conservation. We suggest that management plans address future threats, including disturbance-related habitat loss.

Additional Information

BioScience

Date of publication:

2021

Topics

Mt. Graham red squirrel

wildfire

disturbance cascade

spatial habitat take

disturbance displacement

Research Categories

Behavioral Ecology Disturbance Ecology Sky Islands Spatial Ecology Threatened and Endangered Species

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

Does caching strategy vary with microclimate in endangered Mt. Graham red squirrels?

mmerrick — Thu, 16 Apr 2020 21:43:52 +0000

Authors

Pereira Mendes, Calebe

Koprowski, John

Food hoarding is a common behavior used by a variety of animals to cope with periods of
low food availability. At the retreating edge of species’ distribution, the stressful environment
and unfavourable climate conditions may impose severe costs on hoarding behavior. Since
relict populations are hotspots for evolution and adaptation, and considering that food hoarding
behavior has a strong evolutionary basis, we decided to evaluate the occurrence of
behavioral variability in the amount of food cached by the endangered Mount Graham red
squirrel (Tamiasciurus fremonti grahamensis). We tested the variation in cache size in
response to microclimate, soil relief, vegetation, food availability and squirrel sex. The number
of pits excavated by squirrels to cache cones was used as a proxy of cache size and
was affected by mountain slope aspect and density of trees. More pits were excavated in
the northeast facing slopes. The density of trees negatively affects the cache volume on
southwest slopes, but not on northeast slopes. The sex of the resident squirrel also affects
the number of pits in the squirrel midden, with males excavating 47% more pits than
females. Males and females also presented different responses to the mountain slope
aspect, with females excavating more pits on northeastern slopes than on southwestern
slopes, whereas male cache size did not vary with the slope aspect. Finally, the squirrel’s
caching behavior did not vary in response to midden microclimate variation, a result with
possible implications for the survival of the Mt Graham red squirrels, given the predicted
temperature increases in the region due to climate change.

Additional Information

PLoS ONE

Date of publication:

2019

Topics

caching

microclimate

Mt. Graham red squirrel

larderhoard

midden

Research Categories

Behavioral Ecology Sky Islands Threatened and Endangered Species