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Ms Proposal on Habitat Preferences of Eastern Spotted
Skunks and Long-tailed Weasels
in Alabama
By Allie Hunter
Introduction (larger theoretical background)
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Meso-carnivores are defined as any carnivore weighing 1-15kg or any predator
that is not the top predator in a system. They account for ~90% of all
carnivores. The scientific literature is deficient in publications on
mammalian meso-carnivores because these species; weasels, raccoons, small
cats, skunks, mongooses, and foxes, often exist in low numbers over large
areas and are very cryptic. This makes getting even natural history data
difficult. We know even less about their community interactions, though
recent studies suggest in some systems they can be keystone species (Gittleman
& Gompper, 2005).
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Animals that have large geographic ranges are in general more resilient in
the face of extinction
(Purvis et al., 2000).
An exception to this rule is found among top-predators, who while wide
spread, exist at extremely low densities and feed at high-trophic levels
(highly carnivorous) (Gittleman et
al. 2001).
However, small omnivorous predators often thrive in situations that are
driving other predators to extinction, such as
foxes (e.g. Vulpes vulpes) and raccoons (Procyon lotor), who
can prosper in human-dominated environments and sustain very high harvest
pressures (Sanderson, 1987; Voight, 1987).
Problem
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Little is known about Eastern spotted skunks and Long-tailed weasels
throughout their range, including Alabama.
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Both of these species appear to be in decline throughout their range and in
Alabama where they are listed as species of conservation concern.
Purpose of Study
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To determine where Eastern spotted skunks and Long-tailed weasels are present
throughout the state of Alabama so that biological and ecological data can be
collected in the future to better manage for these species.
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To see if scat dog surveys are a viable way of determining these species’
distributions.
Literature Review (need info on decline and people effects)
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The locations of scat samples can provide information on animal movements,
home range, habitat, and resource use measures (Wasser
et al., 2004).
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Canids have a very sensitive sense of smell (3 ppm), which enables them to
detect specific multiple (18+) odors (species) at distances over 0.25 mi
(0.4 km) away (Bryson, 1991).
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Scat dogs are the most efficient and accurate way of determining
presence/absence of a species (Long
et al., 2007; Harrison, 2006; Gompper
et al., 2006).
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Habitat preference of eastern spotted skunks is uncertain. Crabb’s (1948)
study in Iowa of an agricultural landscape in the 1940s, when the species
was common, concluded that ESSs were a prairie species that thrived in high
agricultural areas. McCullough and
Fritzell (1984) examined habitat use and home range size of four males in
the Missouri Ozarks and saw a selection for forest habitats rather than open
habitats. Location of four captures in Tennessee, led Reed and Kennedy
(2000) to believe the species to be associated with dense undergrowth.
Mammal reference sources report that wetlands, with the exception of
palmetto thickets, and dense timber stands are avoided and that habitat is
selected to avoid predators (mainly owls) (Hamilton and Whitaker, 1998;
Kinlaw 1995). The most recent study in the Ouachita
Mountains of Arkansas (Lesmeister, et
al., 2009) concluded that the closed canopy and thick understory
provided by young short-leaf pine stands and hardwoods were preferred,
however; there was no prairie or farmland in the study area.
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Long-tailed weasels prefer habitat based on prey diversity. A study of
museum specimens collected in Canada found a preference for late seral
stages and ecotones and a close proximity to water (Gamble, 1981). Gehring
and Seihart’s (2004) study of weasels in an agriculturally fragmented
habitat showed a preference for forest patches and corridors over fields and
edges. Surveys conducted by Richter and Schauber in Illinois (2006) and
Proulx and Randal in Alberta (1993) concluded that weasels have broad
habitat preferences- they were seen and captured in fields, forest, edges,
farmlands, wetlands, and along lakeshores.
Mammal reference sources report that long-tailed weasels can be found in
almost all habitat types with the exceptions of deserts because they require
free-standing in their vicinity (Fagerstone, 1987; Hamilton and Whitaker,
1998)
Questions and Hypotheses
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What are the relative habitat preferences of Eastern Spotted Skunks and
Long-Tailed Weasels? (Have to do for state)
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What effects do anthropological factors like land use (farm, timberland,
recreation), distance to roads, distance to towns, land management practices
(prescribed burn, timber harvest program), and local human population densities
have on skunk and weasel distributions?
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How do the habitat predictions made from presence as determined by scat dog
surveys compare to predictions made by the GAP project and historical road kill
and trapper data?
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Eastern Spotted Skunks will be found throughout the state associated with thick
scrub around residential areas and hardwood bottom lands.
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Long-Tailed Weasels will also be found statewide but in more isolated
populations around low-human impact water bodies in mature hardwood or
hardwood-mix forest.
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Data from the scat dog survey will show greater specificity in distribution for
both species than the GAP data and will have a broader range than the road kill
and trapper data.
Field Sites
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National forest, wildlife management areas, state lands, and some private
lands throughout the state of Alabama including all those surveyed by the
ICP project.
Methods
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Solicit scat over wide geographic range from a variety of individuals (goal
is 20), both sexes, and a range of diets.
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Train dog(s) in manner
similar to that used for narcotic and bomb detection dogs. Dogs will be
selected for specific attributes (e.g., high drive, object orientation,
appropriate temperament) and will be trained to associate the scent of a
single target species’ scat with a reward (i.e., a tennis ball). Dogs will be
trained to indicate; sit or stay at the site of located scat. Once the dog
consistently locates scat from the first target species in field trials, a
second target odor will be introduced. This will take place at Auburn
University’s
Canine Detection Training Center (CDTC) in McClellan, AL 2-3 months prior to the
beginning of the fall field season.
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Scat detection rates and distances will be tested to determine optimal
transect set-up and possible limitations (weather effects, amount of time
the dog can work each day at high accuracy, etc) before the beginning of the
field season.
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Throughout the field season known scats will be placed along transects to
establish likelihood of scat detection.
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Each of the areas to be searched will somehow be divided up into transects
that are ~250m apart. Searched transects will be assigned randomly and the
area searched will be equivalent among the different sites i.e. small sites
will have fewer transects.
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~5-10km will be searched per day with no repetition (or should they be
repeated for future mark-recapture analysis?). Every 100m a GPS location
will be taken along with basic habitat description, percent canopy cover,
percent understory cover and percent fallen debris. If edge, water, or
anthropological factor is visible will be noted with ~distance to.
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When scat is located it will be placed in a plastic bag and labeled. All the
above data will be collected along with data on ~age of scat, species (skunk
or weasel), placement of scat, and if any other animal sign is present.
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A tiny scrapping of the outside of the scat will be preserved in 90% ethanol
for future genetic sampling and then the scat will be frozen.
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Modeling:
Will use an information-theoretic approach involving AIC to determine the
best a priori models for habitat
selection: see Burnham and Anderson, 2002; Kays, Gompper, and Rays, 2008;
Telfer, Griffiths, and Bowman, 2008.
Limitations and Delimitations
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Genetic confirmation of species identity should be unnecessary as long as we are
collecting 7 or more scats in an area. If scats are rare correct species
identity may become an issue (Harrison and Clarke, 2003; Long
et all., 2007).
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Limited to one dog-handler team so limited amount of state will be covered. It
is very possible that skunks and weasels will exist outside searched areas and
habitats.
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Both skunks and weasels show seasonal shifts in habitat use with changing
resources (breeding opportunities and prey) so this study will be limited to
habitat preferences in the fall.
Contributions/ Significance of the Study
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I think this study will add immensely to our knowledge of ESS and
Long-tailed weasels in Alabama. The data collected will show us were at
least some populations of these species are present and will allow us to
determine other areas that might have populations. Once we have known
populations we can begin to conduct more focused ecological and biological
studies including getting density estimates and preferred prey. Hopefully,
the data collected in this study will lead to a better understanding of the
needs of these species allowing for future management and if needed recovery
plans.
Time Frame
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Field work will be conducted in the fall of 2009 and 2010, possibly extending
into other seasons if needed.
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Thesis will be finished by the end of summer term 2011, fall 2011 at the latest.
Funding
Literature Cited
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