Inter-observer and intra-observer differences in measuring body length: a test in the common lizard, Zootoca vivipara
2011
Authors:
Roitberg, Evgeny SOrlova, Valentina F.
Kuranova, Valentina N.
Bulakhova, Nina A.
Zinenko, Oleksandr
Ljubisavljević, Katarina
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Shamgunova, Regina
Carretero, Miguel Angel
Clasen, Astrid
Fokt, Michael
Boehme, Wolfgang
Document Type:
Article (Published version)
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© 2011 Brill
Metadata
Show full item recordAbstract:
The snout-vent length (SVL), a conventional measure of overall body size in lizards and snakes, is used in a wide variety of ecological, evolutionary, and taxonomical studies. Trends in SVL variation are often analysed using data from several researchers (observers), but possible confounding effects due to inter-observer differences in measurement protocols have never been appropriately examined. This study reports inter-observer biases between eleven herpetologists who measured the same specimens of the Eurasian common lizards (21 adult specimens were examined by eight observers and additional 192 specimens by two observers). Intra-observer bias over time (1.5-15 months between measuring sessions)
was also estimated. In the vast majority of comparisons, mean difference between the first author and another observer varied from −1.0 to +0.8 mm, or from −1.9 to +1.6% if expressed as a percent of the specimen’s SVL value. Some non-regular effects of sex and study sample on the studied bias were revealed, and their possible reasons are discussed. We are advising the researchers who intensively collect SVL and other morphometric data to consider testing intra-observer and inter-observer
biases and to establish etalon samples available for re-examinations.
Keywords:
body size; inter-observer bias; lizards; morphometrics; snout-vent length; Zootoca viviparaSource:
Amphibia-Reptilia, 2011, 32, 4, 477-484Funding / projects:
- Deutsche Forschungsgemeinschaft [RO 4168/1-1]
DOI: 10.1163/156853811X601636
ISSN: 0173-5373