Small terrestrial mammals

Most of these species are too cryptic to be observed reliably, and live or kill trapping are the most common survey means. Traps can be obtained from several commercial sources and can be scaled to the size of the animal. Food baits are used to lure animals into traps. If done properly, animals can be captured repeatedly and all segments of the population can be sampled. Direct observation has not been effective, with the exception of those species at the larger end of the range, such as ground squirrels. Radio telemetry units are small enough for most species, but the range of the small units is below the dispersal distance of most rodents and limits their utility in some studies. For species less than 0.4 oz (12 g), most commercial traps are ineffective and radio transmitters are short-lasting due to weight considerations. Pitfall arrays are often used to record a species presence; pitfalls are buckets that are either deep enough that the animal cannot jump out or are partially filled with liquid to kill the animal. Animals are not lured into the buckets with bait, but rather barriers funnel all passing mammals into the buckets.

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