Parallel Lasers for Remote Measurements of Morphological Traits

Bergeron, Patrick

doi:10.2193/2006-290

Cited by 54 publications

(102 citation statements)

References 18 publications

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“…Finally, to have a precise measurement, it is important that parallel orientation of the lasers be preserved. Like the apparatus designed by Bergeron [2007], the distance between our two lasers was adjustable with small screws. Although the small screws allowed adjustments, as the lasers were not fixed permanently at 4 cm, they could inadvertently move during fieldwork, thus great care was taken to ensure that the lasers were immobilized and regularly calibrated.…”

Section: Discussionmentioning

confidence: 99%

“…Like Bergeron [2007], we designed an L-shaped aluminum frame to hold a camera and two laser pointers, with the lasers separated by a known distance of 4 cm (Fig. 1a).…”

Section: Laser Apparatus and Techniquementioning

confidence: 99%

“…When it was not clear that the target was positioned perpendicular to either the lasers or the ground (e.g. if the tail was bent), the longest calculated length was considered the most accurate estimate, as any deviation from the perpendicular would always decrease the inferred length of a morphologic feature [Bergeron, 2007].…”

Section: Validationmentioning

confidence: 99%

“…Remotely projected parallel lasers have been used to measure the physical traits of marine and terrestrial animals [Bergeron, 2007;Durban & Parsons, 2006]. The method is based on the principle that parallel lasers project light that is equidistant regardless of the distance from the origin.…”

Section: Introductionmentioning

confidence: 99%

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Measuring physical traits of primates remotely: the use of parallel lasers

Rothman

Chapman

Twinomugisha

et al. 2008

American J Primatol

117

104

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Physical traits, such as body size, and processes like growth can be used as indices of primate health and can add to our understanding of life history and behavior. Accurately measuring physical traits in the wild can be challenging because capture is difficult, disrupts animals, and may cause injury. To measure physical traits of arboreal primates remotely, we adapted a parallel laser technique that has been used with terrestrial and marine mammals. Two parallel lasers separated by a known distance (4 cm) and mounted onto a digital camera are projected onto an animal. When a photograph is taken, the laser projections on the target provide a scale bar. We validated the technique for measuring the physical traits of identifiable red colobus monkeys (Procolobus rufomitratus) in Kibale National Park, Uganda. First, we photographed the tails of monkeys with laser projections and compared these with measurements previously obtained when the animals were captured. Second, we manually measured the distance between two markers placed on tree branches at similar heights to those used by monkeys, and compared them with the measurements obtained through digital photographs of the markers with parallel laser projections. The mean tail length of the monkeys via manual measurements was 63.3+/-4.4 cm, and via remote measurements was 63.0+/-4.1 cm. The mean distance between the markers on tree branches via manual measurements was 13.8+/-3.59 cm, and via remote measurements was 13.9+/-3.58 cm. The mean error using parallel lasers was 1.7% in both cases. Although the needed precision will depend on the question asked, our results suggest that sufficiently precise measurements of physical traits or substrates of arboreal primates can be obtained remotely using parallel lasers.

show abstract

Section: Discussionmentioning

confidence: 99%

“…Like Bergeron [2007], we designed an L-shaped aluminum frame to hold a camera and two laser pointers, with the lasers separated by a known distance of 4 cm (Fig. 1a).…”

Section: Laser Apparatus and Techniquementioning

confidence: 99%

Section: Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Measuring physical traits of primates remotely: the use of parallel lasers

Rothman

Chapman

Twinomugisha

et al. 2008

American J Primatol

117

104

View full text Add to dashboard Cite

show abstract

“…This means that one has to measure the proboscis on live, wild, elephant seal males, during their natural behavior, and, in particular, when they vocalize. In principle, the study of morphology of wild animals can be carried out using photogrammetry, that is, by taking standardized photographs in which a metric scale is included in the photograph frame, such as, for instance, by using parallel lasers (Bergeron, ). Photogrammetry is a non‐invasive method that is now frequently used in field studies because it permits to estimate body size of wild animals without capturing and/or sedating them (Berger, ), but the use of photogrammetry to study morphology of wild animals is definitely less frequent (Breuer, Robbins, & Boesch, ), and its application to soft tissues in naturally behaving individuals is even rarer (Sonnweber et al., ).…”

Section: Introductionmentioning

confidence: 99%

“Nose-metrics” of wild southern elephant seal (Mirounga leonina) males using image analysis and geometric morphometrics

Galimberti

Sanvito

Vinesi

et al. 2019

J Zool Syst Evol Res

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The elephant seal (genus Mirounga) proboscis is a textbook example of an exaggerated secondary sexual trait, whose function is debated. The proboscis can be related to sexual status advertising, emission of aggressive vocalizations, and/or female mating choice. The study of the proboscis is complicated, because it is a soft trait that needs to be studied when males vocalize and it is thus expanded. Here, we combined field stimulation experiments, 2D photogrammetry, and geometric morphometrics, to study the proboscis of wild elephant seals in natural conditions. The goal of our study was twofold: (a) to demonstrate that photogrammetry and geometric morphometrics can be effectively applied in the field to wild, large, non‐sedated mammals; (b) to study the proboscis shape development during maturation. We found that it is possible to accurately estimate the proboscis size and shape using photographs of vocalizing males taken in the field. Moreover, we showed that mature and non‐mature males differ not only in proboscis size but also in its shape, a difference that is largely allometric and can have important effects on the frequency structure and individual signature of male vocalizations. These results open new avenues for future research on this enigmatic structure, its function in aggressive displays and potential role in sexual selection, and also exemplify a very promising approach, that could be applied in field studies of other large mammals.

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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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Parallel Lasers for Remote Measurements of Morphological Traits

Cited by 54 publications

References 18 publications

Measuring physical traits of primates remotely: the use of parallel lasers

Measuring physical traits of primates remotely: the use of parallel lasers

“Nose-metrics” of wild southern elephant seal (Mirounga leonina) males using image analysis and geometric morphometrics

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

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