Mckenzie study center5/5/2023 ![]() The guidance given here on study design issues is particularly applicable to studies of species occurrence and distribution, habitat selection and modelling, metapopulation studies and monitoring programmes.Īs a general concept, the fraction of sampling units in a landscape where a target species is present (occupancy) is of considerable interest in ecology. Failure to do so may compromise the integrity of the study. To make the best use of logistical resources, study objectives must be clearly defined sampling units must be selected, and repeated surveys timed appropriately and a sufficient number of repeated surveys must be conducted. Reliable inferences can only result from quality data. ![]() Our results suggest that for a rare species it is more efficient to survey more sampling units less intensively, while for a common species fewer sampling units should be surveyed more intensively. ![]() We found that an optimal removal design will generally be the most efficient, but we suggest it may be less robust to assumption violations than a standard design. We recommend that sampling units should be surveyed a minimum of three times when detection probability is high (> 0♵ survey −1), unless a removal design is used. Advice on the number of repeat surveys per sampling unit is considered in terms of the variance of the occupancy estimator, for three possible study designs. In this paper we comment on a number of general issues related to designing occupancy studies, including the need for clear objectives that are explicitly linked to science or management, selection of sampling units, timing of repeat surveys and allocation of survey effort. However, practical guidance on the efficient design of occupancy studies has been lacking. ![]() Given that sampling units are surveyed repeatedly within a relatively short timeframe, a number of similar methods have now been developed to provide unbiased occupancy estimates. Yet in many applications the species will not always be detected in a sampling unit even when present, resulting in biased estimates of occupancy. The fraction of sampling units in a landscape where a target species is present (occupancy) is an extensively used concept in ecology. ![]()
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