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Monitoring Approaches – Part III

Ecological Methodology. LEC-06 Althoff. ψ. Monitoring Approaches – Part III. Occupancy Estimation. Fundamental goal: model detection (i.e., ___ = detection probability) and occupancy ( ____ ) Recall: need ________ sampling efforts within the specified timeframe

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Monitoring Approaches – Part III

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  1. Ecological Methodology LEC-06 Althoff ψ Monitoring Approaches – Part III

  2. Occupancy Estimation • Fundamental goal: model detection (i.e., ___ = detection probability) and occupancy (____) • Recall: need ________ sampling efforts within the specified timeframe • In ________ form, the data is collected by one individual, in one habitat type, under uniform weather conditions, with identical presence/influence of other species (plants or animals or both) from survey site to survey site, etc.

  3. Occupancy Estimation….but when not “uniform” sampling/survey conditions: Observers can impact vary in their ability to detect the target species Weather conditions can alter one’s ability to detect species from site to site Habitat: structure and plant species composition can alter detection rates and occupancy Presence (or absence) of other animal species can alter detection rates and occupancy How do we “__________” or “_______” our estimates (i.e., models of occupancy estimation when these Conditions exists…because they will always exist….?

  4. Accounting for / Adjusting for varying situations during surveys: Determine ___________________ These are factors (i.e., effects) that help explain possible _____________ in the raw data--even if densities are equal between two areas. The covariate data can be “__________” to account for the influence of these factors to provide more reliable estimates of occupancy

  5. Example: Mountain Plovers and Burrowing Owls Tipton, H.C., V. J. Dreitz, and P.F. Doherty, Jr. 2008. Occupancy of mountain plover and burrowing owl in Colorado. Journal of Wildlife Management 72(4): 1001-1006. Mountain Plovers: Hypothesized the occupancy would be higher on prairie dog colony and dryland agricultural plots than on grassland plots Burrowing Owls: Hypothesized the occupancy would be higher on active prairie dog colony and non-active plots and grassland and dryland agricultural plots

  6. Field Method Selected plots using an ArcGIS design called spatially balanced sampling (SBS). Surveyed 282 plots: 90 in prairie dog colonies 92 in dryland agriculture 100 in grasslands Each plot was 500m x 500m Each plot was surveyed 2-4 times each (most surveyed). The model used for occupancy accommodates unequal number of surveys Used visual and auditory cues

  7. 500 m Plot layout & travel path for observers 125 m 500 m 125 m 125 m Begin survey

  8. “Suspected” covariate(i.e., factor) • ____________ was a factor that would affect detectability of each species: prairie dog colony vs. grassland vs. dryland agriculture

  9. MOUNTAIN PLOVER

  10. BURROWING OWL Prairie dog colony

  11. Yes…other “factors” matter in occupancy estimation, so adjust accordingly • In this study, habitat type mattered • Higher probability of occupancy for burrowing owls on active vs. inactive prairie dog towns…and both were higher than grassland or dryland ag sites • For mountain plovers, prairie dog towns (active or inactive) had higher probability of occupancy than dryland ag sites, which had slightly higher than grassland sites. • Important info for _________ monitoring protocols and “________” occupancy estimation models !!

  12. Sampling Schemes _________________: incorporating a random, stratified, and/or systematic sampling design to avoid bias ________________ design….cannot with good conscience come up with estimate of precision because __________-based assumptions are usually violated vs.

  13. Probability-based designs (survey “points” = ) Random Stratified Systematic

  14. Convenience sampling design (survey “points”= ) _______ roads, trails, contours of a hill or mountain, etc. Assumes that what is “near” these easy-to-travel routes (i.e., transects?) is the _______ throughout the survey site

  15. Bottomline…. • The past….most sampling efforts were based on “convenience”-based designs. Still used today for various reasons (cheaper, match long-term data sets, etc.) but require _____________________ about how precise the resulting estimates and/or indices are • The future….more and more sampling efforts will be based on probability-based designs because they minimize biased estimates and allow for statistical analysis—usually without violation of major assumptions– to make ____________________ __________. For occupancy estimates that would be ____

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