Species list

Species lists can be as complex as a complete mammal survey or as simple as presence/absence of a focal species. Species lists are composed through use of multiple means. Traditional field surveys that use traps, cameras, or transects can be supplemented by sociological techniques such as examination of local markets, discussions with local hunters, and inspecting kitchen remains in villages. When using traps or cameras, they are usually placed in a line to traverse as many habitat types as possible. The distance between the traps would be less than the smallest home range of the animal targeted. The larger the home range, the longer the traps should remain in one spot in order to account for the time it takes an animal to traverse its entire home range. For a rodent, traps might be in place for a few days; for a large predator, a few weeks would be more appropriate.

Researchers use low flying planes to do aerial surveys and to count animals. (Photo by Rudi van Aarde. Reproduced by permission.)

Sociological techniques offer their own challenges, as the barriers to an effective survey tend to be cultural rather than technological or biological. For example, who is interviewed, who does the interview, and even what dialect is used for the interview all affect the survey results. There are strong cultural pressures on the interview process that are difficult to comprehend or anticipate without extensive experience in the target community. Interview methods are effective for relatively large species that are regularly encountered or eaten by local people. Paying a bounty for local hunters to produce specific animals is tempting, but not recommended without consideration of the long-term impact of creating a market for wildlife.

Creating a species list is an open-ended activity; the longer researchers look, the more they find. A species accumulation curve, which graphs the number of new species detected for every additional unit of time or effort, can be used to gauge when a species list is complete. It should be noted that the method used to measure the number of species may only provide the number of species that can be detected.

Beyond the need to do a thorough survey, the most difficult component of a species list is comparability. If lists are to be compared between areas or to lists collected previously, there must be a way to measure the amount of effort used in the survey. Two biologists will not conduct surveys exactly the same way, and differences in lists are always subject to individual protocols.

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