Inter- and intra-researcher variation in measurement of morphometrics on Steller sea lions (Eumetopias jubatus)

Waite, Jason N.; Mellish, Jo‐Ann E.

doi:10.1007/s00300-009-0649-7

Cited by 7 publications

(6 citation statements)

References 20 publications

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“…This is a reminder that some errors could result from variation in direct measurements, as significant differences in inter‐researcher length measurements can occur (e.g. Waite & Mellish, ). CVs of repeat measurements were comparable to other laser photogrammetry studies (1.5–3.7%) (Rowe & Dawson, ; Deakos, ; Webster et al ., ) but were slightly higher than CVs for repeat physical measurements of adult dolphins (0.705%) (Read et al ., ).…”

Section: Discussionmentioning

confidence: 99%

Laser photogrammetry reveals variation in growth and early survival in free‐ranging bottlenose dolphins

Cheney

Wells

Barton

et al. 2017

Animal Conservation

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Growth and body condition can be used as indices of health and fitness, but are difficult to collect for populations of conservation concern where individuals cannot be captured. We incorporated a laser photogrammetry system into boat-based photo-identification surveys that underpin individual-based studies of cetacean populations. These data were integrated with >25 years of observations from a temperate bottlenose dolphin population in Scotland to investigate the influence of sex on growth patterns, effects of birth order on calf size and the longer term consequences of variation in early growth. Field measurements of the distance from the blowhole to the dorsal fin were made in multiple years from 87 dolphins that had been followed from birth, ranging in age from newborn to 26 years. These estimates were validated against direct measurements of 12 individuals that had previously been captured and released in Florida and two study individuals that subsequently stranded. Using relationships derived from other stranded individuals, age-specific body lengths were used to produce growth curves that were based entirely on remote observations. Multilevel regression growth curve analyses suggested males and females showed similar patterns of growth, unlike bottlenose dolphins in sub-tropical areas, and growth was best described by a Richards' growth curve. Newborn length was unrelated to sex; however, females' first calves were shorter than subsequent calves. Sample sizes remain small, yet there was evidence of fitness consequences of variation in calf length; calves that died in their first winter were significantly shorter than those that survived. The incorporation of this simple-to-use and inexpensive method into individual-based photo-identification studies provides new opportunities to non-invasively investigate drivers of variation in growth and the demographic consequences of variation in early growth in cetaceans from protected populations.

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Section: Discussionmentioning

confidence: 99%

Laser photogrammetry reveals variation in growth and early survival in free‐ranging bottlenose dolphins

Cheney

Wells

Barton

et al. 2017

Animal Conservation

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“…The difference between the interobserver rates could be because two observers measured animals using the remote method during a single field season, whereas several researchers performed physical measurements over several field seasons from 1972 to 2014. Waite and Mellish [2009] emphasize that interobserver error rates in physical measurements are rarely compared with error rates in photogrammetry. In their study comparing these two measurement methods in sea lions, they found no significant differences between interobserver rates [Waite & Mellish, 2009].…”

Section: Comparison and Critiquementioning

confidence: 99%

Testing parallel laser image scaling for remotely measuring body dimensions on mantled howling monkeys (Alouatta palliata)

Barrickman

Schreier

Glander

2015

American J Primatol

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Body size is a fundamental variable for many studies in primate biology. However, obtaining body dimensions of wild primates through live capture is difficult and costly, so developing an alternative inexpensive and non-invasive method is crucial. Parallel laser image scaling for remotely measuring body size has been used with some success in marine and terrestrial animals, but only one arboreal primate. We further tested the efficacy of this method on the arboreal mantled howling monkey (Alouatta palliata) in La Pacifica, Costa Rica. We calculated interobserver error, as well as the method's repeatability when measuring the same animal on different occasions. We also compared measurements obtained physically through live capture with measurements obtained remotely using parallel laser image scaling. Our results show that the different types of error for the remote technique are minimal and comparable with the error rates observed in physical methods, with the exception of some dimensions that vary depending on the animals' posture. We conclude that parallel laser image scaling can be used to remotely obtain body dimensions if careful consideration is given to factors such as species-specific morphology and postural habits.

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“…For example, when the only phenotypic characteristics to use for distinguishing 2 photographs include color hue or saturation, these differences can be difficult for humans to see. As noted by other authors, using trained and qualified users may decrease the false acceptance rate (Huffard et al , Schofield et al , Waite and Mellish ), but we suggest that users use a test data set of known individuals to estimate false acceptance rate before using results from our approach to estimate population parameters. Users could test their false acceptance error by taking ≥2 photographs of the same individual, removing the background or other distinguishing characteristics within the photographs using photograph manipulation software, and testing their ability to match them among photographs of different individuals.…”

Section: Discussionmentioning

confidence: 62%

Likelihood‐based photograph identification: Application with photographs of free‐ranging bison

Merkle

Fortin

2013

Wildl. Soc. Bull.

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Using photographs to identify individual animals and monitor populations is becoming more common. However, photographic identification methods where measurements of morphological traits (e.g., horn length) are compared have received little attention. We present an approach for aiding with the identification of individual animals from photographs. The approach incorporates measurement data, metadata from photographs, and multiple sources of error, and calculates a matching score between pairs of photographs using a likelihood‐based algorithm. We tested and identified the false‐rejection error rate using 91 photographs, representing 33 known free‐ranging bison (Bison bison), and 117 simulated data sets with varying numbers of unique individuals, morphological measurements, and photograph error. We then used the approach to estimate the adult population size of bison in Prince Albert National Park, Canada, in 2011. For bison, the false‐rejection rate of our approach was 0.055. Using a Huggins closed population model with misidentification, we estimated 103 (95% CI = 82–130) and 46 (95% CI = 37–58) adult female and male bison, respectively. After incorporating field‐based calf‐ and juvenile‐to‐female ratios, we estimated 202 (95% CI = 171.6–231.4) bison. We found this estimate to be plausible using 2 minimum‐count aerial surveys conducted in March 2011 and 2012 for comparison. With our approach, researchers and managers can build capture histories of individuals, which can be used for studies of population dynamics and habitat selection. This approach can incorporate any morphological measurements extracted from photographs (e.g., coat color), making it robust to a variety of species and study systems. © 2013 The Wildlife Society.

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Inter- and intra-researcher variation in measurement of morphometrics on Steller sea lions (Eumetopias jubatus)

Cited by 7 publications

References 20 publications

Laser photogrammetry reveals variation in growth and early survival in free‐ranging bottlenose dolphins

Laser photogrammetry reveals variation in growth and early survival in free‐ranging bottlenose dolphins

Testing parallel laser image scaling for remotely measuring body dimensions on mantled howling monkeys (Alouatta palliata)

Likelihood‐based photograph identification: Application with photographs of free‐ranging bison

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