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Observer error in identifying species using indirect signs: analysis of a river otter track survey technique

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dc.contributor.advisor Packard, Jane M. en_US
dc.creator Evans, Jonah Wy en_US
dc.date.accessioned 2007-09-17T19:35:21Z
dc.date.available 2007-09-17T19:35:21Z
dc.date.created 2003-05 en_US
dc.date.issued 2007-09-17T19:35:21Z
dc.identifier.uri http://hdl.handle.net/1969.1/5853
dc.description.abstract Indirect signs of species presence (e.g., tracks, scats, hairs) are frequently used to detect target species in occupancy, presence/absence, and other wildlife studies. Indirect signs are often more efficient than direct observation of elusive animals, making such signs well suited for long-term and broad-scale monitoring programs. However, error associated with misidentification of indirect signs can be high, and should be measured if meaningful inferences about population parameters are to be made. This study addressed the need for systematic approaches to estimate and minimize variation due to observer error in identifying indirect signs. I reanalyzed data from 4 replicates of a presence/absence survey of northern river otters (Lontra canadensis) that had been conducted by Texas Parks and Wildlife Department (1996-2003). Sixteen observers had recorded tracks at sample points under bridges (n = 250) distributed throughout 27 counties in the Piney-Woods ecoregion of east Texas. My objectives were to 1) determine if observers were a source of bias in the survey, 2) estimate the proportion of error associated with track identification skill, and 3) evaluate the use of an international certification procedure that measured observer tracking skill. The null hypothesis that observers had no effect on the variation in reported sign was rejected. Indeed, binary logistic regression tests indicated that observers were significantly associated with variation in reported track presence. Observers were not randomly distributed among bridge sites, and therefore were significantly correlated with 4 habitat variables that may have influenced heterogeneity in otter occupancy and probability of detection (watershed, vegetation-type, water-type, bridge-area). On average, experienced observers (n = 7) misidentified 44% of otter tracks, with a range of 0% to 100% correct detection. Also, 13% of the tracks of species determined to be 'otter-like' were misidentified as belonging to an otter. During the certification procedure, participants misidentified the tracks of 12 species as otter. Inaccurate identification of indirect signs is a likely source of error in wildlife studies. I recommend that observer skill in identification of indirect signs be measured in order to detect and control for observer bias in wildlife monitoring. en_US
dc.format.extent 3798841 bytes
dc.format.medium electronic en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher Texas A&M University en_US
dc.subject Observer error en_US
dc.subject observer bias en_US
dc.subject river otter en_US
dc.subject Lontra canadensis en_US
dc.subject Lutra lutra en_US
dc.subject animal tracks en_US
dc.subject tracking en_US
dc.subject spoor en_US
dc.subject pugmark en_US
dc.subject presence/absence en_US
dc.subject occupancy en_US
dc.subject index of abundance en_US
dc.title Observer error in identifying species using indirect signs: analysis of a river otter track survey technique en_US
dc.type Book en
dc.type Thesis en
thesis.degree.department Wildlife and Fisheries Sciences en_US
thesis.degree.discipline Wildlife and Fisheries Sciences en_US
thesis.degree.grantor Texas A&M University en_US
thesis.degree.name Master of Science en_US
thesis.degree.level Masters en_US
dc.contributor.committeeMember Higginbotham, Billy J. en_US
dc.contributor.committeeMember Stronza, Amanda en_US
dc.type.genre Electronic Thesis en_US
dc.type.material text en_US
dc.format.digitalOrigin born digital en_US

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