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  • Print publication year: 2003
  • Online publication date: June 2012

6 - Survey and census methods: population distribution and density



A population study of a wild primate typically involves a considerable investment of time and resources (i.e. money, equipment, labour) and it is vital to ensure that such effort is well targeted. When designing your study, a key issue is whether your study objectives genuinely demand an absolute estimate of the population density from either a census (a total count) or a survey (in which density is estimated from statistically valid samples), or whether less information will suffice. Relative estimates of density using data from methods such as ‘catch-per-unit effort’ from trapping or systematic searching do not provide absolute densities but, as long as the sampling methods and other conditions are standardised, can allow reliable comparisons between locations and monitoring of population change over time. Population indices are based on indirect indicators, such as the density of faeces or other characteristic signs, that can be correlated with population density. Such methods may be a more practical alternative to searching for secretive, hard-to-find animals.

In practice, no population survey or census is completely bias free and many studies may find that a reliable relative population estimate or index is more achievable than a reliable absolute estimate of the population size (Bibby et al., 1992; Greenwood, 1996; Krebs, 1999). There is a trade-off between the depth of the data gathered and the number of replicate samples that can be obtained.

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