Multi-scale occupancy estimation and modelling using multiple detection methods
Article first published online: 4 JUL 2008
Journal compilation © 2008 British Ecological Society. No claim to original US government works
Journal of Applied Ecology
Volume 45, Issue 5, pages 1321–1329, October 2008
How to Cite
Nichols, J. D., Bailey, L. L., O’Connell Jr., A. F., Talancy, N. W., Campbell Grant, E. H., Gilbert, A. T., Annand, E. M., Husband, T. P. and Hines, J. E. (2008), Multi-scale occupancy estimation and modelling using multiple detection methods. Journal of Applied Ecology, 45: 1321–1329. doi: 10.1111/j.1365-2664.2008.01509.x
- Issue published online: 29 AUG 2008
- Article first published online: 4 JUL 2008
- Received 15 December 2007; accepted 14 May 2008; Handling Editor: Paul Lukacs
- detection probability;
- Pollock's robust design;
- red salamander;
- striped skunk
- 1Occupancy estimation and modelling based on detection–nondetection data provide an effective way of exploring change in a species’ distribution across time and space in cases where the species is not always detected with certainty. Today, many monitoring programmes target multiple species, or life stages within a species, requiring the use of multiple detection methods. When multiple methods or devices are used at the same sample sites, animals can be detected by more than one method.
- 2We develop occupancy models for multiple detection methods that permit simultaneous use of data from all methods for inference about method-specific detection probabilities. Moreover, the approach permits estimation of occupancy at two spatial scales: the larger scale corresponds to species’ use of a sample unit, whereas the smaller scale corresponds to presence of the species at the local sample station or site.
- 3We apply the models to data collected on two different vertebrate species: striped skunks Mephitis mephitis and red salamanders Pseudotriton ruber. For striped skunks, large-scale occupancy estimates were consistent between two sampling seasons. Small-scale occupancy probabilities were slightly lower in the late winter/spring when skunks tend to conserve energy, and movements are limited to males in search of females for breeding. There was strong evidence of method-specific detection probabilities for skunks. As anticipated, large- and small-scale occupancy areas completely overlapped for red salamanders. The analyses provided weak evidence of method-specific detection probabilities for this species.
- 4Synthesis and applications. Increasingly, many studies are utilizing multiple detection methods at sampling locations. The modelling approach presented here makes efficient use of detections from multiple methods to estimate occupancy probabilities at two spatial scales and to compare detection probabilities associated with different detection methods. The models can be viewed as another variation of Pollock's robust design and may be applicable to a wide variety of scenarios where species occur in an area but are not always near the sampled locations. The estimation approach is likely to be especially useful in multispecies conservation programmes by providing efficient estimates using multiple detection devices and by providing device-specific detection probability estimates for use in survey design.