Photographic identification in reptiles: a matter of scales (original) (raw)
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The numerical encoding of scale morphology highly improves photographic identification in lizards
2006
Photographic identification is a promising marking technique alternative to the toe-clipping, but is time consuming, particularly when a large number of individuals is involved. For this reason several authors had frequently preferred the toe-clipping. In this study we analysed the black spot pattern of ventral scales of wall lizards (Podarcis muralis) and we showed that photographic identification is an effective method for recognizing individuals, and the error of this technique is much less than that of the toe-clipping arising from natural toe loss. Moreover, the numerically encoding of the black spot pattern may radically reduce the time needed to compare the pictures of large samples of individuals, solving one of the more important obstacle against the use of photographic identification.
Sex identification of juvenile sand lizards, Lacerta agilisusing digital images
Amphibia-Reptilia, 2015
Sexing neonate animals is necessary for many evolutionary and ecological studies. Yet non-invasive sex identification of neonate reptiles is often problematic because these do not exhibit salient differences in colouration and body proportions. We examined digital images of the ventral body surface in 214 adult or subadult individuals (95 males + 119 females), 59 juveniles (29 + 30), and 156 hatchlings of the Eurasian sand lizard, Lacerta agilis. Two quantitative traits, the number of transverse rows of ventral scales and the width/length ratio of the anal plate, which are easily recordable from digital images and show no substantial correlation with body size, exhibit pronounced sexual dimorphism. A discriminant function derived from these two characters allows correct identification of the sex in 90% of juvenile individuals when males and females of older stages are used as reference samples. Also, we introduce a new qualitative trait, namely the presence/absence of the skin hyperaemia behind cloaca in hatchlings, and provide indirect evidence that this trait is likely to be strongly associated with sex.
Photographic identification of individuals of a free-ranging, small terrestrial vertebrate
Ecology and evolution, 2016
Recognition of individuals within an animal population is central to a range of estimates about population structure and dynamics. However, traditional methods of distinguishing individuals, by some form of physical marking, often rely on capture and handling which may affect aspects of normal behavior. Photographic identification has been used as a less-invasive alternative, but limitations in both manual and computer-automated recognition of individuals are particularly problematic for smaller taxa (<500 g). In this study, we explored the use of photographic identification for individuals of a free-ranging, small terrestrial reptile using (a) independent observers, and (b) automated matching with the Interactive Individual Identification System (I(3)S Pattern) computer algorithm. We tested the technique on individuals of an Australian skink in the Egernia group, Slater's skink Liopholis slateri, whose natural history and varied scale markings make it a potentially suitable ...
Biological Journal of the Linnean Society
Geometric morphometrics is a better tool to evaluate the variation of shape than 'traditional' morphometrics. In reptiles, it outperforms morphometrics based on linear measurements and scalation. In an earlier study, two-dimensional outline-based geometric morphometrics in six species of rock lizards (Darevskia) showed that their shapes reflected the species divergence pattern. This allowed us to separate species from different clades, but we could not distinguish closely related species within a clade. We hypothesized that three-dimensional (3D) head shape data would be sufficiently discriminative to identify closely related species. To test this hypothesis, we compared head shapes of three closely related species of the 'rudis' clade, Darevskia portschinskii, Darevskia valentini and Darevskia rudis, with the last species treated as two distinct groups (D. r. obscura vs. D. r. rudis), using 3D landmark data. The 3D analysis isolated the species of the 'rudis' clade from each other and even separated individuals from populations that showed a genetic introgression pattern. The analysis showed that D. r. obscura is morphologically as distinct from D. r. rudis as from the other nominal species. For this reason, we suggest elevating the status of D. r. obscura to species level, i.e. Darevskia obscura Lantz & Cyrén, 1936.
A reference database of reptile images
bioRxiv (Cold Spring Harbor Laboratory), 2024
While there are millions of reptile images available online, they are not well organized and not easily findable, accessible, interoperable, or reproducible (FAIR). More importantly, they are not standardized and thus hardly comparable. Here we present a reference database of more than 14,000 standardized images of 1,045 reptile species (969 lizard and 76 snake species), that are based on preserved specimens in 20 different collections, including 533 type species of genera and type specimens of 72 species. All images were taken with standardized views, including dorsal and ventral body shots as well as dorsal, ventral, and lateral views of the heads and other body parts. Although only 11 out of the 20 collections are cross-referenced in Vertnet, some others are indexed in GBIF, and this fraction will certainly grow in the near future. The utility of this and similar image collections will further grow with additional material and further cross-referencing, e.g., to DNA sequence databases or citizen science projects. The images are searchable and freely available on Morphobank.org (Project 5121) and on Figshare.com.
The use of digital images for the individual identification of amphibians
2005
Mark-recapture techniques are widely used in amphibian demographical studies (Beausoleil et al., 2004; Donnely et al., 1994; Schmidt, 2003). A variety of marking techniques are available for adult amphibians, with permanent or temporary marks, either date-specific or individual specific. Long-term studies, including monitoring, require permanent marks, that ideally should be individualspecific.
Evaluation of a photographic technique for estimating body size in lizards from a distance
2012
Body size is often an important factor in understanding an animal's ecology. In squamates, snout-to-vent length (SVL) is a primary metric for quantifying body size. Measuring SVL typically requires capture and handling of animals, which may be difficult due to a species' behavior or its presence in complex habitat. Here, we evaluated an alternative to the capture, handling, and direct measurement of lizards via the use of paired photographs of animals in situ and with a ruler positioned in place of the lizard. Paired digital images were processed using the freely available image analysis software ImageJ. We found that snout-to-hindlimb length (SHL) measured directly on an animal was highly correlated with its SVL. In turn, SHL estimated from images was highly correlated with SHL measured directly on the animals and had an average error of 19.4 ± 16.2% (1 SD) compared with measurements made on the animals themselves. Estimates of total length from images were also highly correlated with total length measurements made directly on the animals and had an average error of 14.8 ± 12.9% (1 SD). There was no correlation between image measurement error and the distance from which photographs were made. Our results identify that the use of digital photographs and image analyses can in some cases eliminate the need to capture and handle lizards to quantify body size.
Microgeographic variation of colour morph frequency and biometry of common wall lizards
Journal of Zoology, 2007
The throat and belly of both sexes of the common wall lizard Podarcis muralis exhibit a polymorphic coloration with three morphs (white, yellow and red). We documented the occurrence of this polymorphism in 11 populations of northern Italy, and investigated the morphometric features of the three morphs in both sexes. The white morph was more frequent (56.6%), while yellow and red morphs accounted for 28.7 and 14.7% of the lizards, respectively. Moreover, the red morphotype was more frequent among males while the white one was more frequent among females. The occurrence of the three morphs varied microgeographically from populations with a higher proportion of white individuals to those where all morphs were more equally represented. The comparisons of morphometry between morphs did not reveal any significant difference among males, while snout–vent length and head height in females increased from the white-throated to the yellow-throated morph, and from the yellow-throated morph to the red-throated one. Possible functions of this polymorphic coloration are discussed.
An inventory of online reptile images
Zootaxa
No central online repository exists for the collection of animal images; hence it remains unclear how extensively species have been illustrated in the published literature or online. Here we compiled a list of more than 8000 reptile species (out of 11,341) that have photos in one of six popular online repositories, namely iNaturalist (6,349 species), the Reptile Database (5,144), Flickr (4,386), CalPhotos (3,071), Wikimedia (2,952), and Herpmapper (2,571). These sites have compiled over one million reptile photos, with some species represented by tens of thousands of images. Despite the number of images, many species have only one or a few images. This suggests that a considerable fraction of morphological and geographic variation is under documented or difficult to access. We highlight prominent gaps in amphisbaenians, lizards, and snakes, with geographic hotspots for species without images in Central Africa, Pacific Islands, and the Andes Mountains. We present a list of ~3,000 spe...