conservation.arizona.edu - Sky Islands

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

Experimental removals reveal dietary niche partitioning facilitates coexistence between native and introduced species

mmerrick — Fri, 12 Jun 2020 18:49:10 +0000

Authors

Jonathan J. Derbridge

John L. Koprowski

1. Niche overlap between native species and ecologically similar invaders can lead to
competitive exclusion of threatened native species, but if two such species also
co‐occur naturally elsewhere, interactions between native and introduced populations
may mirror coevolved niche partitioning that reduces competition and promotes
coexistence.
2. A single, insular population of Fremont’s squirrel (Tamiasciurus fremonti) the Mount
Graham red squirrel (MGRS; T. f. grahamensis) in the Pinaleño Mountains, Arizona,
USA, is critically endangered and resource competition with introduced Abert’s
squirrels (Sciurus aberti) may threaten its long‐term persistence. The species are
naturally synoptic in other mountain sites, and both consume diets comprised primarily
of conifer seeds and fungi.
3. We conducted experimental removals of introduced Abert’s squirrels and used
stable isotope analysis of diets before and after removals, and of diets in naturally
syntopic populations to test the hypothesis that dietary niche partitioning can
facilitate coexistence between native and introduced species. We also developed
a novel approach to determine the influence of fluctuating food availability on
carbon enrichment in consumers.
4. Mount Graham red squirrels and introduced Abert’s squirrels partitioned the dietary
niche similarly to naturally syntopic populations. Removals had no apparent
effect. Diet of MGRS was more closely linked to availability of resources than to
presence of Abert’s squirrels.
5. Flexible dietary niche of introduced Abert’s squirrels may have allowed them to
exploit a resource opportunity in syntopy with MGRS. Variable food production of
MGRS habitat may intensify competition in poor years, and territorial defense
against non‐native Abert’s squirrels likely imposes fitness costs on individual
MGRS. Similarity in our model species’ diets may make MGRS more vulnerable to
competition if climate change eliminates the advantages of larder‐hoarding.
Where introduced populations of ecologically similar species are better adapted

Additional Information

Ecology and Evolution

Date of publication:

2019

Topics

coexistence

diet

introduced species

niche

wildlife ecology

Research Categories

Behavioral Ecology Invasive Species Sky Islands 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

Fire impacts on a forest obligate: western gray squirrel response to burn severity

mmerrick — Thu, 16 Apr 2020 21:22:10 +0000

Authors

Mazzamuto, Maria Vittoria

Mazzella, Maxwell N.

Merrick, Melissa J.

Koprowski, John L.

In the southwestern United States, climate change and climate–fire dynamics are affecting the distribution of natural and managed ecosystems. Forest obligate species on sky islands can experience a restriction in range with the increase of destructive forest fires. Using presence/absence data collected by hair tubes, we identified key habitat features that determine the western gray squirrel (Sciurus griseus) distribution on the sky island of the San Bernardino Mountains (California, USA) and determined post-fire differential use of burn severity in a landscape modified by fire. Gray squirrel presence was related to habitat features important for this species’ ecology and behavior, especially those associated with mature forests. The species was detected in areas with a high percentage of conifers that provide both an important food resource and good branches and cavities for nest sites. Gray squirrels occurred in all burn severities but occurred more in low and high severity sites than unburned sites. These results suggest that the gray squirrel can persist after a wildfire and can take advantage of the post-fire habitat structure if a mosaic of burn severities is maintained in the forest.

Additional Information

Mammalian Biology

Date of publication:

2020

Topics

hair tube

conifers

San Bernardino Mountains

Sciurus griseus

sky island

Research Categories

Disturbance Ecology Natural History Sky Islands Spatial Ecology

Response to fire by a forest specialist in isolated montane forest

mmerrick — Thu, 16 Apr 2020 21:10:54 +0000

Authors

Mazzella, Maxwell N.

Koprowski, John L.

Fire events have increased in scale and severity due to hotter, drier conditions brought on by climate change and fire suppression. Extreme fire events can be detrimental to forest specialists, especially populations at the edge of the species range, where conditions can vary from those within the core of the range. The San Bernardino flying squirrel (Glaucomys oregonensis californicus) is the southernmost subspecies of Humboldt’s flying squirrel and occurs only in the San Bernardino Mountains of southern California after apparent extirpation from the nearby San Jacinto Mountains. We used non-invasive methods to assess how fire affects flying squirrel occupancy. We surveyed for flying squirrels in burned and unburned areas of the San Bernardino Mountains, and measured habitat features to construct occupancy models. Our top models indicated that flying squirrels occupy lower burn severities but could still occur at higher burn severities if canopy cover remained intact, forest duff remained deep, and tree mortality remained low, especially on steeper slopes. Our study illustrates the ability of San Bernardino flying squirrels, and the potential for other flying squirrels, to survive major fire events and maintain their role in the forest ecosystem. Such results are especially important for species management and understanding how parts of an ecosystem can react as fire frequency and severity increases.

Additional Information

Forest Ecology and Management

Date of publication:

2020

Topics

fire

San Bernardino flying squirrel

occupancy modeling

hair tube

non-invasive sampling

Research Categories

Disturbance Ecology Sky Islands Spatial Ecology Threatened and Endangered Species

Phylogeographic and diversification patterns of the white-nosed coati T (Nasua narica): Evidence for south-to-north colonization

thackerk1 — Wed, 24 Jul 2019 00:13:21 +0000

Authors

Sergio F. Nigenda-Morales

Matthew E. Gompper

David Valenzuela

Anna R. Lay

Karen M. Kapheim

Christine Hass

Susan D. Booth-Binczik

Gerald A. Binczik

Ben T. Hirsch

Maureen McColgin

John L. Koprowski

Katherine McFadden

Robert K. Wayne

Klaus-Peter Koepfli

White-nosed coatis (Nasua narica) are widely distributed throughout North, Central, and South America, but the patterns of temporal and spatial diversification that have contributed to this distribution are unknown. In addition, the biogeographic history of procyonid species in the Americas remains contentious. Using sequences from three mitochondrial loci (Cytochrome b, NAHD5 and 16S rRNA; 2201 bp) and genotypes from 11 microsatellite loci, we analyzed genetic diversity to determine phylogeographic patterns, genetic structure, divergence times, and gene flow among Nasua narica populations throughout the majority of the species’ range. We also estimated the ancestral geographic range of N. narica and other procyonid species. We found a high degree of genetic structure and divergence among populations that conform to five evolutionarily significant units. The most southerly distributed population (Panama) branched off much earlier (∼3.8 million years ago) than the northern populations (< 1.2 million years ago). Estimated gene flow among populations was low and mostly northwards and westwards. The phylogeographic patterns within N. narica are associated with geographic barriers and habitat shifts likely caused by Pliocene-Pleistocene climate oscillations. Significantly, our findings suggest the dispersal of N. narica was south-to-north beginning in the Pliocene, not in the opposite direction during the Pleistocene as suggested by the fossil record, and that the most recent common ancestor for coati species was most likely distributed in South or Central America six million years ago. Our study implies the possibility that the diversification of Nasua species, and other extant procyonid lineages, may have occurred in South America.

Additional Information

Molecular Phylogenetics and Evolution

Date of publication:

2018

Topics

Procyonidae

mitochondrial haplotypes

microsatellites

evolutionary history

biogeographical methods White-nosed coatis

Research Categories

Natural History Population Ecology Sky Islands

Evidence of natal habitat preference induction within one habitat type

thackerk1 — Tue, 23 Jul 2019 23:24:14 +0000

Authors

Melissa J. Merrick

John L. Koprowski

Natal habitat preference induction (NHPI) is a mechanism for habitat selection by individuals during natal dispersal. NHPI occurs in wild animal populations, and evidence suggests it may be a common, although little studied, mechanism for post-dispersal habitat selection. Most tests of NHPI examine the influence of distinct, contrasting natal habitat types on post-dispersal habitat selection. We test the hypothesis that NHPI can occur within a single habitat type, an important consideration for habitat specialists. The Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is an endangered forest obligate restricted to a single mountain primarily within mixed-conifer forest. We test for NHPI by comparing intra-individual differences in natal and settlement habitat structure and composition to expected random pairwise differences. Dispersing juveniles appear to select settlement locations that are more similar to natal areas than expected in several forest structure and composition variables that include canopy cover and live basal area. Our results provide support for NHPI as a mechanism for post-dispersal habitat selection in habitat specialists that occupy a single vegetation community type.

Additional Information

Proceedings of the Royal Society B

Date of publication:

2016

Topics

natal dispersal

natal habitat

habitat selection

Arizona

Mount Graham Red Squirrel

behavior

Research Categories

Behavioral Ecology Sky Islands Spatial Ecology Threatened and Endangered Species

Altered natal dispersal at the range periphery: the role of behavior, resources, and maternal condition.

thackerk1 — Tue, 23 Jul 2019 23:22:46 +0000

Authors

Melissa J. Merrick

John L. Koprowski

Natal dispersal outcomes are an interplay between environmental conditions and individual phenotypes. Peripheral, isolated populations may experience altered environmental conditions and natal dispersal patterns that differ from populations in contiguous landscapes. We document nonphilopatric, sex-biased natal dispersal in an endangered small mammal, the Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis), restricted to a single mountain. Other North American red squirrel populations are shown to have sex-unbiased, philopatric natal dispersal. We ask what environmental and intrinsic factors may be driving this atypical natal dispersal pat- tern. We test for the influence of proximate factors and ultimate drivers of natal dispersal: habitat fragmentation, local population density, individual behavior traits, inbreeding avoidance, competition for mates, and competition for resources, allow- ing us to better understand altered natal dispersal patterns at the periphery of a species’ range. A juvenile squirrel’s body condition and its mother’s mass in spring (a reflection of her intrinsic quality and territory quality) contribute to individual behavioral tendencies for movement and exploration. Resources, behavior, and body condition have the strongest influence on natal dispersal distance, but affect males and females differently. Male natal dispersal distance is positively influenced by its moth- er’s spring body mass and individual tendency for movement; female natal dispersal distance is negatively influenced by its mother’s spring body mass and positively influenced by individual tendency for movement. An apparent feedback between environmental variables and subsequent juvenile behavioral state contributes to an altered natal dispersal pattern in a peripheral population, highlighting the importance of studying ecological processes at the both range center and periphery of species’ distributions.

Additional Information

Ecology and Evolution

Date of publication:

2016

Topics

Mount Graham Red Squirrel

behavioral phenotype maternal effects

peripheral population

condition-dependent dispersal

phenotype-dependent dispersal

Research Categories

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