Small mammal live-trapping research: 2006 update
by Elizabeth Wallace,
During the summer of 2006, WildMetro staff
and volunteers worked together to conduct 10 different live-trapping surveys
at 4 sites in the greater New York area. We focused on sites that were
rural or suburban to complement our earlier research which targeted more
urban parks. Sites included the Marshlands Conservancy (a Westchester
County Parks Department wildlife sanctuary), the Huyck Preserve, Ward
Pound Ridge Reservation and Great Swamp National Wildlife Refuge. This
research was led by WildMetro Research Director Stefan Ekernas, Research
Coordinator Katherine Mertes, President David Burg, Intern Emily Kaplan,
and a large number of additional devoted staff and volunteers.
These survey sites varied in size from 69
ha at the Marshlands Conservancy to 2,429 ha at the Great Swamp N.R.W.
The Marshlands Conservancy site, located near Rye in Westchester County,
has a diverse array of habitats that include forests, meadows and wetlands.
Our small mammal surveys targeted forest and meadow habitat. Likewise,
surveys at the Huyck Preserve in Rensselaerville, south-west of Albany,
NY, at the Ward Pound Ridge Reservation, and at Great Swamp N.W.R. were
conducted in and meadow habitat.
WildMetro conducted small mammal surveys using
live trapping mark-recapture methods. We placed Sherman traps across a
1 hectare grid with traps set at 15m intervals, for a total of 49 traps
per hectare, to facilitate the capture and identification of small mammal
residents of each site. The most frequently captured species was the white-footed
mouse (Peromyscus leucopus). Although they were most abundant in
forested habitats, white-footed mice were also found in meadows, though
at lower densities. The abundance of white-footed mice was substantially
higher than that of eastern chipmunks and meadow jumping mice (see Figure
1 to right for data from forested habitat at the Huyck Preserve). White-footed
mice made up 90% of the captures at this site, and were typically the
most abundant species captured at each of the forested study sites.
Meadows generally presented a greater diversity
of small mammals than forested habitats. At these sites, we captured meadow
voles (Microtus pennsylvanicus), northern short-tailed shrews (Blarina
brevicauda), meadow jumping mice (Zapus hudsonicus), and eastern
chipmunks (Tamias striatus). These species were all found in the
meadow habitat at Ward Pound Ridge, where white-footed mice were absent
(Figure 2, also to right). In addition to supporting a more diverse community
of small mammals, the relative abundances of each species were also more
even in meadow than in forested habitat.
The data gathered from these surveys enhances
our understanding of the status of small mammal populations along an urbanization
gradient. We found that some species, such as the white-footed mouse,
span the urbanization gradient. These generalist species can persist in
areas of dense human populations and significant landscape alteration.
Other species, such as meadow jumping mice, are more sensitive to increasing
urbanization, and are consequently only found in more remote regions,
such as suburban or rural protected areas. These surveys are an important
contribution towards building our knowledge on how urbanization impacts
Upcoming small mammal research:
In 2007, WildMetro will continue to conduct
research in the New York metropolitan area to further understand changes
in small mammal density, diversity and distribution in response to increasing
urbanization. WildMetro will continue to conduct surveys along the entire
urban-to-rural gradient, particularly focusing on protected areas that
represent the suburban and rural components of the gradient. To this end,
we hope to build on our research at the Huyck Preserve, and Ward Pound
Ridge, and to incorporate additional rural sites. We will also survey
mammal populations at a suite of new sites using a new survey method called
track-tubing. This method consists of tracking animals by looking at species-specific
footprints, and is an efficient way to expand our current knowledge of
small mammal diversity and distribution. (For more information, see T.
Shaos report on WildMetros pilot studies at Marshlands
Conservancy and the New York Botanical Gardens.) WildMetro also aims to
use camera traps to assess patterns of distribution of larger mammals
such as deer, raccoons, foxes, coyotes, weasels etc. Camera traps are
cameras placed in a survey area and equipped with an infrared beam. The
beam acts as a trigger, taking a picture whenever movement is detected,
and the animal is caught on film. Digital images are stored and later
downloaded onto computers for analysis.
Scientific research on the patterns of species
density and diversity can provide important information that contributes
to the management of protected areas. To this end, WildMetro plans to
work directly with several parks in Westchester County to apply ecological
research to adaptive management of the regions natural resources.
We will study the response of small mammal communities to different management
strategies. For an example of an ongoing study on how invasive plant species
removal affects small mammals, see T. Shaos
report on WildMetro research at Marshlands Conservancy.
Scientific research can also be a central
component of environmental education. WildMetro hopes to expand our current
work with local elementary and high schools to develop a research-oriented
educational program. In this program, students would set track tubes near
their schools in order to study small mammal populations. This would contribute
to our growing data on the status of small mammals in urban areas, and
would also encourage the involvement of people with their local environment,
creating durable links between people and nature.
If funds permit, from 2007 to 2009, WildMetro
will conduct a study across 15-20 protected areas spanning the gradient
of urbanization, from rural to urban. We will focus on assessing the responses
of mammals, birds, amphibians and plants to increasing urbanization. This
research will help us identify potential thresholds of urbanization beyond
which fauna and flora are critically impacted, and to determine whether
different species respond similarly to urbanization.
Research supported by
WildMetro research is supported by grants from the National Park Service, the Huyck Preserve, the Westchester County Parks Department, the NYC Department of Parks and Recreation, and the Jamaica Bay Institute. Grant support for future research initiatives is pending from EarthWatch, National Geographic, the Hudson River Foundation and the New York State Biodiversity Research Institute.
Intern Tiffany Shao with mouse