The ability to accurately measure morphological characteristics of wild primates in the field is ... more The ability to accurately measure morphological characteristics of wild primates in the field is challenging, yet critical for understanding fundamental aspects of their biology and behavior. Recent studies have shown that digital photogrammetry can be used to non-invasively measure morphological traits of wild primates, as it allows for the determination of geometric properties of objects remotely from photographic images. We report here on a rare opportunity to test this methodology by comparing measurements obtained directly from living great apes to those obtained from photographs. We test the accuracy and precision of two independent photogrammetric techniques, employing the use of parallel lasers and a distance meter, respectively, for obtaining measurements of static objects and captive western lowland gorillas (Gorilla gorilla gorilla) (n = 4) at Zoo Atlanta. For static objects, the mean percent error between corresponding measurements collected by the same observer directly...
Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically d... more Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically distinguishable from those living in eastern central Africa (Gorilla beringei). Genomic analyses show eastern gorillas experienced a significant reduction in population size during the Pleistocene subsequent to geographical isolation from their western counterparts. However, how these results relate more specifically to the recent biogeographical and evolutionary history of eastern gorillas remains poorly understood. Here we show that two rare morphological traits are present in the hands and feet of both eastern gorilla subspecies at strikingly high frequencies (>60% in G. b. graueri; 28% in G. b. beringei) in comparison with western gorillas (<1%). The intrageneric distribution of these rare traits suggests that they became common among eastern gorillas after diverging from their western relatives during the early to middle Pleistocene. The extremely high frequencies observed among grauer gorillas—which currently occupy a geographic range more than ten times the size of that of mountain gorillas—imply that grauers originated relatively recently from a small founding population of eastern gorillas. Current paleoenvironmental, geological, and biogeo-graphical evidence supports the hypothesis that a small group of eastern gorillas likely dispersed westward from the Virungas into present-day grauer range in the highlands just north of Lake Kivu, either immediately before or directly after the Younger Dryas interval. We propose that as the lowland forests of central Africa expanded rapidly during the early Holocene, they became connected with the expanding highland forests along the Albertine Rift and enabled the descendants of this small group to widely disperse. The descendant populations significantly expanded their geographic range and population numbers relative to the gorillas of the Virunga Mountains and the Bwindi-Impenetrable Forest, ultimately resulting in the grauer gorilla subspecies recognized today. This founder-effect hypothesis offers some optimism for modern conservation efforts to save critically endangered eastern gorillas from extinction. Am J Phys Anthropol 159:S4
The ability to accurately measure morphological characteristics of wild primates in the field is ... more The ability to accurately measure morphological characteristics of wild primates in the field is challenging, yet critical for understanding fundamental aspects of their biology and behavior. Recent studies have shown that digital photogrammetry can be used to non-invasively measure morphological traits of wild primates, as it allows for the determination of geometric properties of objects remotely from photographic images. We report here on a rare opportunity to test this methodology by comparing measurements obtained directly from living great apes to those obtained from photographs. We test the accuracy and precision of two independent photogrammetric techniques, employing the use of parallel lasers and a distance meter, respectively, for obtaining measurements of static objects and captive western lowland gorillas (Gorilla gorilla gorilla) (n = 4) at Zoo Atlanta. For static objects, the mean percent error between corresponding measurements collected by the same observer directly...
Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically d... more Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically distinguishable from those living in eastern central Africa (Gorilla beringei). Genomic analyses show eastern gorillas experienced a significant reduction in population size during the Pleistocene subsequent to geographical isolation from their western counterparts. However, how these results relate more specifically to the recent biogeographical and evolutionary history of eastern gorillas remains poorly understood. Here we show that two rare morphological traits are present in the hands and feet of both eastern gorilla subspecies at strikingly high frequencies (>60% in G. b. graueri; 28% in G. b. beringei) in comparison with western gorillas (<1%). The intrageneric distribution of these rare traits suggests that they became common among eastern gorillas after diverging from their western relatives during the early to middle Pleistocene. The extremely high frequencies observed among grauer gorillas—which currently occupy a geographic range more than ten times the size of that of mountain gorillas—imply that grauers originated relatively recently from a small founding population of eastern gorillas. Current paleoenvironmental, geological, and biogeo-graphical evidence supports the hypothesis that a small group of eastern gorillas likely dispersed westward from the Virungas into present-day grauer range in the highlands just north of Lake Kivu, either immediately before or directly after the Younger Dryas interval. We propose that as the lowland forests of central Africa expanded rapidly during the early Holocene, they became connected with the expanding highland forests along the Albertine Rift and enabled the descendants of this small group to widely disperse. The descendant populations significantly expanded their geographic range and population numbers relative to the gorillas of the Virunga Mountains and the Bwindi-Impenetrable Forest, ultimately resulting in the grauer gorilla subspecies recognized today. This founder-effect hypothesis offers some optimism for modern conservation efforts to save critically endangered eastern gorillas from extinction. Am J Phys Anthropol 159:S4
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