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Variations between distinct natural markings of freckled hawkfish (Paracirrhites forsteri) could allow in situ identification of individuals from underwater photography. Receiver operating characteristic analysis was used to assess the ability of the Interactive Individual Identification System (I3S) software to assist in discriminating between images of P. forsteri individuals. This study's results show the high discriminant ability of I3S to differentiate between unlike individuals and identify images of the same individual. The ability to use automatic computer‐aided assistance in the study of this species will enable future research to explore behaviour and movements of individuals in the wild. [ABSTRACT FROM AUTHOR]

Background. The smalleye stingray (Megatrygon microps) is a large and rare dasyatid ray, patchily distributed across the Indo-West Pacific. Free-swimming individuals have regularly been recorded in Southern Mozambican coastal waters utilizing different inshore environments. Distinctive features of the species include latitudinal rows of white spots on the dorsal surface of their pectoral disc. Methods. This study aimed to determine if the natural spot patterns on M. microps are sufficiently unique and stable to use in photo-identification studies of wild populations. Research dive logs were combined with opportunistic photographs from local dive centers and recreational divers to create a photographic database from the Inhambane Province coastline. Results. Seventy different individuals were identified over a 15-year period, all exhibiting uniquely identifiable patterns. Stingrays were easily identifiable over a period of six years with multiple re-sightings of the same individuals recorded. Analysis of encounters across the Inhambane coastline revealed that individual rays regularly use inshore reefs along a 350 km stretch of coastline. Fifteen stingrays were re-sighted during the study period, including one showing a 400 km return movement between Tofo Beach and the Bazaruto Archipelago, which is the longest distance traveled by a dasyatid ray on record. Several presumably pregnant females have also been recorded in the Bazaruto Archipelago National Park. [ABSTRACT FROM AUTHOR]

Pelage patterns, colouration and other biometric traits are perceived to be uniform in the Neotropical giant anteater (Myrmecophaga tridactyla), a conception precluding the identification of individuals, which is essential for field research on the little known aspects of the species’ ecology and behaviour. Here we present a new, non-invasive technique of matrix photo-identification to identify individual giant anteaters by their natural markings. In a long-term field study in the Brazilian Pantanal, photographs of 475 giant anteater observations (396 = direct sightings, 79 = camera traps) were captured from 2010 to 2015 and considered for our analysis. Photographs were stored in a catalogue and coded in a computerised identification table, with biometric traits being categorised and described for each observed individual in a matrix. In 71% of all photographed giant anteaters, differences in pelage marking patterns, as well as other characteristics such as ear shape and scars, allowed individual recognition. We ensured consistency of the method by conducting a double-blind verification by an experienced researcher and naïve volunteers. This simple, non-invasive method can push the level of information about life history and population structure of giant anteaters, as it applies to a large array of study designs. It can thus enhance future studies, be integrated in ongoing research projects or supply additional information out of older data sets. It is applicable to expand data collection and raise awareness in local communities, and potentially for participatory citizen science methods. Altogether these are important cornerstones for conservation actions on the species which is listed as ‘Vulnerable’ on the International Union for Conservation of Nature Red List of Threatened Species. [ABSTRACT FROM AUTHOR]

Long-term studies often rely on natural markings for individual identification across time. The primary method for identification in small cetaceans relies on dorsal fin shape, scars, and other natural markings. However, dorsal fin markings can vary substantially over time and the dorsal fin can become unrecognizable after an encounter with a boat or shark. Although dorsal fins have the advantage in that they always break the water surface when the cetacean breathes, other physical features, such as body scars and pigmentation patterns can supplement. The goal of this study was to explore the use of dorso-lateral pigment patterns to identify wild bottlenose dolphins. We employed photographic pigment matching tests to determine if pigmentation patterns showed (1) longitudinal consistency and (2) bilateral symmetry using a 30 yr photographic database of bottlenose dolphins ( Tursiops aduncus). We compared experienced dolphin researchers and inexperienced undergraduate student subjects in their ability to accurately match images. Both experienced and inexperienced subjects correctly matched dolphin individuals at a rate significantly above chance, even though they only had 10 s to make the match. These results demonstrate that pigment patterns can be used to reliably identify individual wild bottlenose dolphins, and likely other small cetacean species at other sites. [ABSTRACT FROM AUTHOR]

Photographic capture-mark-recapture (CMR) permits individual recognition whilst avoiding many of the concerns involved with marking animals. However, the construction of capture histories from photographs is a time-consuming process. Furthermore, matching accuracy is determined based on subjective judgements of the person carrying out the matching, which can lead to errors in the resulting datasets - particularly in long-term projects where multiple observers match images. We asked 63 volunteers to carry out two photographic-matching exercises using a database of known individuals of the yellow-bellied toad (Bombina variegata). From these exercises, we quantified the matching accuracy of volunteers in terms of false-acceptance and false-rejection rates. Not only were error rates greatly reduced with the use of photographic-matching software, but variation in error rates among volunteers was also lowered. Furthermore, the use of matching software led to substantial increases in matching speeds and an 87% reduction in the false-rejection rate. As even small error rates have the potential to bias CMR analyses, these results suggest that computer software could substantially reduce errors in CMR datasets. The time-savings and reduction in variance among observers suggest that such methods could be particularly beneficial in long-term CMR projects where a large number of images may be matched by multiple observers. [ABSTRACT FROM AUTHOR]

Using photos of captive Andean bears of known age and pedigree, and photos of wild Andean bear cubs

Risso's dolphins are known for the persistency of their natural markings, possibly due to the loss of pigment during the healing process of skin wounds. Nonetheless, the actual longevity and reliability of each mark type has never been assessed. In this paper, we used photographs to investigate the etiology of skin marks in the species, analyze their distribution and temporal variability, and discuss implications for photo identification. Nineteen mark types were described on the dorsal fin of Risso's dolphin, including 2 new to the literature: the snakelike mark and the protruding fat. Longevity of skin marks ranged from 6 years for the protruding fat to several decades for scrapes and dots. Persistent and reliable marks were notch, tooth-rake, and thick single and parallel scrapes. Mark change was sufficiently low that all mark types could be used for photo identification, provided that backlit or underexposed images were discarded as photographs taken under suboptimal light conditions proved to be unreliable. Finally, mark distribution and variability were unequal between age classes; juveniles were less marked and showed a higher rate of mark change than older individuals so that, even if they possessed enough notches to be classified as reliably marked, they could be confidently matched over a time interval of up to 3 years. [ABSTRACT FROM AUTHOR]

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 (I3S 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 candidate for photo-identification. From 'photographic captures' of skink head profiles, we designed a multi-choice key based on alternate character states and tested the abilities of observers - with or without experience in wildlife survey - to identify individuals using categorized test photos. We also used the I3S Pattern algorithm to match the same set of test photos against a database of 30 individuals. Experienced observers identified a significantly higher proportion of photos correctly (74%) than those with no experience (63%) while the I3S software correctly matched 67% as the first ranked match and 83% of images in the top five ranks. This study is one of the first to investigate photo identification with a free-ranging small vertebrate. The method demonstrated here has the potential to be applied to the developing field of camera-traps for wildlife survey and thus a wide range of survey and monitoring applications. [ABSTRACT FROM AUTHOR]

Changes of body coloration have not been described in manta rays (genus Manta) so far; therefore, their natural body coloration is used to distinguish species and their ventral spot markings are used to identify individuals worldwide to estimate their population size or seasonal migration. The present study describes the first evidence of rapid coloration changes of manta rays based on observations of captive individuals. Body coloration changes were observed most intensely on the dorsal surface and on the head, which occurred within minutes prior to feeding and during intense social interactions. The coloration intensity drastically changed for the white markings of the shoulder bars, the chevron-shaped marking on the back, the dorsal side of fin tips, the area around the eyes, the upper margin of mouth, and the inner side of cephalic fins. Three out of five of the captive specimens have been identified as a putative third manta ray species, and detailed description about their rapid coloration changes is provided. The present observational study confirms the ability of manta rays to rapidly change body coloration during exposure to certain environmental stimuli. Understanding the dynamics of these rapid coloration changes is essential for accurate species identification and to perhaps gain insight into more advanced forms of communication. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 180-193. [ABSTRACT FROM AUTHOR]

Recently we started implementing a highly efficient, non-invasive method of direct individual marking (i.e., typifying) in a population study of the fire salamander, Salamandra salamandra. Our technique is based on the unique alphanumeric code for every individual, generated upon the numbers of openings of repellent/toxic skin glands in the yellow areas of the selected regions of the body. This code was proved reliable in the sample of 159 individuals from two separate populations and enabled easy and quick recognition of recaptured animals. The proposed method is inexpensive, easily applicable in the field, involves minimum stress for the animals and does not affect their behaviour and the possibility of repeated captures of "marked" (i.e., coded) individuals. It is particularly suitable for dense populations. [ABSTRACT FROM AUTHOR]

We estimated sex- and age-specific apparent survival of harbor seals (Phoca vitulina richardii) born at Tugidak Island, Alaska, from 2000 to 2007 using mark-recapture models and photographs of ventral pelage markings to identify individuals. Estimates of annual apparent survival (1 - (mortality + emigration)) of females were from 0.05 to 0.10 higher than those of males and were 0.820 for weaning (~1 month) to 1 year, 0.865 for 1-3 years, and 0.929 at 3-7 years. Annual survival of males was 0.717, 0.782, and 0.879 for the same ages. Highest mortality occurred preweaning, with cumulative mortality to 4 weeks of age of 0.259, indicating this is the most vulnerable period for Tugidak harbor seals. Estimates of survival, not biased by misidentification, required that an individual had at least 2 good-quality, matching photographs in the photograph library. The number of photographs available for matching improved resighting probabilities from 0.43 for seals with 2 photographs to 0.69 for seals with 8 photographs, but this heterogeneity did not affect survival estimates. Survival estimates based on photograph-identification data were nearly identical to those based on resightings of flipper-tagged seals using mark-recapture models with a preliminary double-tag-loss estimate of 2.5% per year. Photograph identification of natural pelage markings provides a viable method for estimating vital rates of harbor seals even at large haul-outs (> 1,000 animals) and may be useful for populations of conservation concern that require low disturbance of animals or where capturing sufficient numbers of seals for artificial marking is not feasible. [ABSTRACT FROM AUTHOR]

The narwhal is a hunted species for which we have many knowledge gaps. Photo-identification, which uses photographs of natural markings to identify individuals, is widely used in cetacean studies and can address a broad range of biological questions. However, it has not been developed for narwhals. The marks used for other cetaceans are inappropriate for this species either because narwhals lack the body part on which these marks are found or because the marks are known to change with time. We investigated the marks apparent in photographs of narwhals. Nicks and notches on the dorsal ridge are the mark types most promising for photo-identification. They are found on 91%–98% of the individuals, thus allowing the identification of a large part of the population. They can be used to differentiate between individuals, in part because they are variable in their location, numbers, shape, and size. Although our results suggest that nicks and notches are relatively stable over time, rates of change should be formally measured to assess the probability of photographic matches over multiple years. However, we are confident that these marks can be used in studies spanning at least a field season. [ABSTRACT FROM AUTHOR]

Monitoring the dynamics and status of populations of harbor seals (Phoca vitulina richardii) requires efficient methods for estimating population parameters from mark--resight data. We used a test set of photographs from 182 individuals identified by flipper tags, scars, or unique pelage markings to test whether individuals could be identified accurately by their ventral pelage markings; to document efficiency and misidentification error rate associated with a computer-assisted photograph-matching system; and to test for bias in mark-recapture survival estimates resulting from misidentification errors. Pelage patterns of seals that were not of dark-intermediate or intermediate color phase were unique and stable from birth until 6-8 years, and from year to year as adults. The computer-assisted system greatly improved efficiency of photograph matching: 93.3% of good photographs and 69.9% of all photographs ranked 1st, and 95.2% of good photographs ranked in the top 0.3% of the ordered list for visual checking. Additional visual matching error averaged <3.0% for good photographs, and overall misidentification error rate was low at 1.8%, due to the availability of multiple photographs for matching. Inclusion of poor-quality photographs reduced ranking success by ~20% and increased additional visual matching error up to 20%. Bias in survival estimates was -7.0% for a misidentification rate of 8.8%, but was ≤1.1% for misidentification rates of <2.7%, achieved by restricting data to only good photos. Our study suggests that estimation of misidentification error rate, inclusion of only high-quality photographs, or use of models that account for misidentification error, are required to prevent bias in mark-recapture survival estimates when using data from natural-marking studies. [ABSTRACT FROM AUTHOR]

Using photos of captive Andean bears of known age and pedigree, and photos of wild Andean bear cubs <6 months old, we evaluated the degree to which visual information may be used to estimate bears' ages and assess their kinship. We demonstrate that the ages of Andean bear cubs ≤6 months old may be estimated from their size relative to their mothers with an average error of <0.01 ± 13.2 days (SD; n = 14), and that ages of adults ≥10 years old may be estimated from the proportion of their nose that is pink with an average error of <0.01 ± 3.5 years (n = 41). We also show that similarity among the bears' natural markings, as perceived by humans, is not associated with pedigree kinship among the bears (R (2) < 0.001, N = 1,043, p = 0.499). Thus, researchers may use photos of wild Andean bears to estimate the ages of young cubs and older adults, but not to infer their kinship. Given that camera trap photos are one of the most readily available sources of information on large cryptic mammals, we suggest that similar methods be tested for use in other poorly understood species.