David Magney Environmental Consulting

Large and Small Mammal Surveys

Large and Small Mammal Surveys

Mammal surveys are conducted to determine which species of large and small mammals use a project site.   Large mammals include: cats, bear, deer, elk, raccoon, coyote, foxes, and marine mammals such as seals, porposes, and whales.   Small mammals include: skunk, rabbits, squirrels, rats, mice, voles, etc.

Determining which species are present and what habitats they use is an important component of any biological resources assessment.   A number of mammals are rare, with some being formally listed as threatened or endangered, or as Fully Protected Species (in California).   Knowing how many individuals of each species that live, forage, and/or pass through a site is needed to perform any sort of habitat management or impact assessment.   Mammal surveys can be divided into two basic types, opportunistic observational surveys and trapping surveys.

Most surveys for large mammals consist of walking over a site and noting if any animals are seen or if there are signs of large mammals.   Since most large mammals are afraid of humans, they are rarely observed; however, signs of their presence or use of a site are easily detected by a trained wildlife biologist.   Signs of large mammals typically include
scat, tracks, and eye shine.   The scat and tracks of large mammals are distinctive and fairly easy to identify, for a trained biologist, and are proof of a species' use of a site.   Sometimes, scent stations, track plates, and/or remote cameras are set out to obtain evidence of particular large mammal species that are not easily detected otherwise.   Eye shine can also be a tell-tail sign, as different species have different eye shine characteristics, such as color, but obviously must be done at night with a spotlight or powerful flashlight.

Projects under environmental review, such as a discressionary permit before a planning department in California, must determine if the project would eliminate or block a wildlife movement corridor.   Blocking a wildlife corridor would likely be considered a significant impact, and mitigation required.   Field surveys onsite can be useful in helping determine the importance of a site for wildlife movement, both on the local and regional levels.   Wildlife move along corridors linking core habitat areas, regional movement paths, and along local travel routes, which can be mapped, as illustrated in the linked graphics for each of the underlined words.   Once it is known where large mammal movement corridors exist, informed decisions can be made about the project to minimize or avoid adverse impacts to large mammal movement between important habitats.

Small mammals are detected at a project site in several ways: looking for the tracks, scat, their burrows (for those that live underground), or trapping them.   Most small mammals are very elusive and hard to identify, as suggested by this fleeting glimpse of a small rodent, unless seen up very close.   This is best accomplished by capturing them and examining their toes, teeth, ear length, and hair.   DMEC traps small mammals using Sherman live traps, and releasing the animals unharmed.   Trapping is typically performed in the same locations for three successive nights to allow these cautious animals time to get used to the presence of the traps in their territory.   The traps can be baited with a varity of food types, typically consisting of rolled oats and peanut butter for seed-eating species, such as most species of mice, kangarro rats, and rats (native and exotic).

DMEC staff have conducted mammal surveys for many projects througout the West and elsewhere, and conducted small mammal trapping as several sites, including in Los Angeles County, western Kern County, Orange County, western Riverside County, Ventura County, Mojave Desert, northern Arizona, and New Mexico.   Mr. Magney holds a Scientific Collecting Permit (#801066-05) from the California Department of Fish and Game.

DMEC has the expertise and experience to gather information on small, and large mammals, and determine population densities and distributions on a site.

Go to the link on DMEC's Reports webpage for the project, and DMEC's Projects page for descriptions of projects DMEC has worked on that includes conducting small mammal surveys and assessments, suc as the Lyons Canyon Ranch development project.

This page last updated 20 January 2016
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