Mark-recapture Techniques Research Articles

A Mark-Recapture Approach to Estimating Item Pool Compromise.

Testing organizations routinely investigate if secure exam material has been compromised and is consequently invalid for scoring and inclusion on future assessments. Beyond identifying individual compromised items, knowing the degree to which a form is compromised can inform decisions on whether the form can no longer be administered or when an item pool is compromised to such an extent that serious action on a broad scale must be taken to ensure the validity of score interpretations. Previous research on estimating the population of item compromise is sparse; however, this is a more generally long-studied problem in ecological research. In this note, we exemplify the utility of the mark-recapture technique to estimate the population of compromised items, first through a brief demonstration to introduce the fundamental concepts and then a more realistic scenario to illustrate applicability to large-scale testing programs. An effective use of this technique would be to longitudinally track changes in the estimated population to inform operational test security strategies. Many variations on mark-recapture exist and interpretation of the estimated population depends on several factors. Thus, this note is only meant to introduce the concept of mark-recapture as a useful application to evaluate a testing organization's compromise mitigation procedures.

Population Size and Spatial Distribution of the Mexican Blind Cavefish (Astyanax) within the Caves

The most studied cavefish in the world is Astyanax mexicanus, and the most frequently used specimens in research come from the Pachón cave in Northeast Mexico. A recent study using the capture–mark–recapture technique revealed that the Pachón population size is only in the hundreds of individuals, not in the thousands. This result raises serious concerns about their long-term survival and highlights the need to accurately estimate the population size of other Astyanax caves. In our study, we used a well-established, non-invasive method for estimating population size: the transect sampling method, which counts the abundance of organisms along a line at regular intervals. We used the 310 m long Sabinos Cave’s Pool #1 for measurements and estimated a population of 1142 individuals. Most importantly, we found that cavefish are not distributed uniformly: 68% of the individuals were clustered under a bat roost. To corroborate this observation, we used drones to explore submerged galleries inaccessible to scientists. Results from the Toro/Calera Cave system confirmed that most galleries were essentially void of cavefish, except for in those few areas with high amounts of nutrients. Scientists visiting the most studied Astyanax localities (Pachón, Sabinos, Tinaja, and Chica) experience what appear to be high-density populations of about 10 fish/m2, possibly because the pool they visit happens to be under bat roosts. Our study shows that one cannot extrapolate the density at these localities to the rest of the habitat, where densities might be two orders of magnitude lower. Future studies should consider that the apparent high density at visited sites is overrepresenting the total population size when calculating the number of fish specimens to be captured.

Population size and movement ecology of intertidal gastropods on rocky shores and seawalls in Singapore

ABSTRACTIncreasing coastal development and global warming have resulted in large-scale habitat changes, with artificial coastal structures replacing extensive tracts of natural shores. In Singapore, for example, more than 63% of the natural coastline has been replaced by seawalls. Multiple studies from both temperate and tropical regions have compared species diversity supported by these artificial structures with natural rocky shores. Few, however, have estimated and compared the population size and movement of common intertidal species between these two habitat types. Using mark–recapture techniques, this study investigated: (1) the population size of three common gastropod genera (Nerita spp., Trochus spp. and Turbo spp.) and (2) differences in displacement of Nerita spp. and Trochus spp., two common species found on natural rocky shores and seawalls in Singapore. The results of our mark–recapture surveys indicated that seawalls supported large densities of Nerita spp.—more than 50 times greater than that on adjacent rocky shores. The mark–recapture data also revealed that movement of the gastropod species differed between the two habitats, with individuals on seawalls generally travelling longer distances.

Population parameters and heterogeneity in survival rates of Indo-Pacific humpback dolphins in a heavily urbanized coastal region of southeast China: implications for conservation

The Pearl River Delta (PRD) region on the southeast coast of China is among the largest and most populated metropolitan regions of the world, subjecting the Indo-Pacific humpback dolphins (Sousa chinensis) inhabiting coastal waters of this region – apparently the largest population of this species – to intense anthropogenic pressure. In this 5-year study (2011-2015), we applied mark-recapture techniques to quantify population parameters of humpback dolphins in the main body of the extensive estuarine system of the Pearl River, the Lingding Bay (LB), the most urbanized and industrialized part of PRD. The super-population size was estimated at 928 individuals (95% CI=823-1046), which however over-represents the latest number of extant animals. Annual estimates fluctuated between 708 and 750 dolphins, and likely reflect most accurately the latest/current number of humpback dolphins in waters of LB. Both the overall and annual estimates generated by our study are considerably lower than previously published abundance estimates. Apparent survival rates were generally low, estimated at 0.943 (SE = 0.008, 95% CI = 0.929-0.958) and 0.815 (SE = 0.025, 95% CI = 0.766-0.866) for adults and juveniles, respectively. In conjunction with limited recruitment, they may have led to a substantial decline in population numbers over the past two decades. Notably, dolphins exhibited heterogeneous apparent survival rates across the complex anthropogenic seascape of LB. Adult individuals that use Hong Kong waters as their primary habitat exhibited 6.2% higher survival rates than those in other parts of LB. This difference tripled (19.2%) for juveniles, a likely expression of their susceptibility to environmental and/or anthropogenic stresses. We suggest that the difference in survival is largely due to heterogeneous anthropogenic stressors that vary spatially across the estuary, among which habitat loss, pollution, and declining prey resources appear to be the primary threats. Based on our latest findings, we call for a strategic conservation planning with the highest priority given to preserve the remaining key dolphin habitats in Hong Kong waters, and to quantify and mitigate the impacts of major stressor(s) in Guangdong (mainland China) waters. Given the encroachment of ever-more-intense human activities on the coastal habitats of humpback dolphins, understanding their demographic response and the underlying mechanisms of the population processes may prove instrumental in the formulation of a conservation management strategy that can secure their continuous survival.

Let's wait for the evening: nocturnal copulation in a tropical damselfly Phylolestes ethelae (Odonata, Synlestidae)

Sexual selection is one of the main causes of the diversity of reproductive behaviours observed intra- and interspecifically. Here we study the reproductive behaviour of a unique species, Phylolestes ethelae, the only member of the family Synlestidae (Odonata) found in America. Our hypothesis was that the phylogenetic uniqueness of this species and the fact that it lives on an island would produce novel behaviours worth protecting as they are a part of the biodiversity. Between 2017 and 2019 we studied a population of P. ethelae in the National Park Armando Bermúdez in the Dominican Republic by means of mark-recapture techniques and focal observations. The survival rate was estimated as 0.953 ± 0.012 (SE), which translates into an expected lifespan of 20.6 days. We found that some males showed high site fidelity but very little activity, and territorial disputes were almost inexistent. Females, on the other hand, were rarely observed on the river, and were found mainly on the nearby paths and forest. We recorded 28 tandems and observed a total of 17 copulations, lasting an average of 18.6 min. Examination of sperm volumes in females interrupted during copulation indicated that males removed most of the sperm from the female bursa copulatrix during stage I of copula, but they could not remove sperm from the paired spermathecae. The duration of precopulatory tandem was highly variable (from 3 min to 7.8 h). In some cases, copulation was observed shortly (3 min) after tandem formation, mainly during the morning. However, some pairs formed during the morning, remained in tandem for several hours, and mated late, after dusk. Females laid eggs not accompanied by the male. Mating after the main peak of activity might be a strategy which protects sperm investment because females laying eggs after dusk are unlikely to be mated again that day. Further studies are needed to decipher phenotypic correlates of the males that mate after dusk.

Release the hens: a study on the complexities of guinea fowl as tick control.

Established tick control strategies often involve methods that can be damaging to existing environmental conditions or natural host ecology. To find more environmentally friendly methods, biological controls, like predators of ticks, have been suggested. There are natural predators of ticks, but most are generalists and not expected to control tick populations. Helmeted guinea fowl (Numida meleagris (L.) (Galliformes: Numididae)) have been suggested to be biological controls of ticks, and therefore, tick-borne pathogens, but their potential role as hosts for ticks complicates the relationship. A study was conducted to assess whether guinea fowl reduces the abundance of lone star ticks, Amblyomma americanum (L.) (Acari: Ixodidae), or whether they are hosts of ticks. Using mark-recapture techniques, painted lone star ticks were placed into 3 different treatments: penned, excluded, and free range. The recapture rates of painted ticks were compared. There was a significant difference between excluded and free-range treatments, but not between excluded and penned or between free range and penned. To investigate the role of guinea fowl as hosts of ticks, coop floors were examined for engorged ticks. Engorged lone star nymphs that had fed on guinea fowl were found. Lastly, ticks collected were tested to identify the potential reduction in risk of tick-borne pathogens. This study found no evidence that guinea fowl are an effective biological control of lone star ticks or tick-borne pathogens, but they are hosts of lone star nymphs. Future studies are needed to assess the complex ecology of a biological control of ticks that is also a host.

Population parameters and conservation implications for one of the world's rarest marine fishes, the red handfish (Thymichthys politus).

Population estimates are required for effective conservation of many rare marine species, but can be difficult to obtain. The critically endangered red handfish (Thymichthys politus) is a coastal anglerfish known only from two fragmented populations in southeast Tasmania, Australia. It is at a high risk of extinction due to low numbers, loss of habitat, and the impacts of climate change. To aid conservation efforts, we provide the first empirical population size estimates of red handfish and investigate other important aspects of the species' life history, such as growth, habitat association, and movement. We surveyed both red handfish local populations via underwater visual census on scuba over 3 years and used photographic mark-recapture techniques to estimate biological parameters. In 2020, the local adult population size was estimated to be 94 (95% confidence interval [CI] 40-231) adults at one site, and 7 (95% CI 5-10) at the other site, suggesting an estimated global population of 101 adults. Movement of individuals was extremely limited at 48.5 m (± 77.7 S.D.) per year. We also found evidence of declining fish density, a declining proportion of juveniles, and increasing average fish size during the study. These results provide a serious warning that red handfish are likely sliding toward extinction, and highlight the urgent need to expand efforts for ex situ captive breeding to bolster numbers in the wild and maintain captive insurance populations, and to protect vital habitat to safeguard the species' ongoing survival in the wild.

An Authentic Demonstration of the Mark–Recapture Technique Using Ant Colonies

The mark–recapture technique paired with the Lincoln–Peterson index is a commonly used method of estimating the size of animal populations in ecological research. However, this technique is difficult to emulate in an educational setting due to the logistical constraints inherent to the process of capturing and marking live animals. As a result, most lessons on mark–recapture use captive animals or inanimate objects as the focal population. This approach may give students an inaccurate understanding of the potential applications and limitations of the mark–recapture technique. Here, we describe an authentic application of the mark–recapture technique that allows students to gain hands-on experience with the method on naturally occurring ant colonies, a ubiquitous animal system. By participating in this lesson, students will directly engage with the mark–recapture technique to estimate the number of individuals within ant colonies and will learn about the natural history of ants in the process.

Population size and residency patterns of northern bottlenose whales (Hyperoodon ampullatus) using the Gully, Nova Scotia

A population of northern bottlenose whales (Hyperoodon ampullatus) uses the Gully, a submarine canyon off the coast of Nova Scotia, Canada. Eleven years of photo-identification records has permitted estimation of population size using mark-recapture techniques. The population estimate was small (133 individuals, 95% CI = 111-166 from left side identifications; 127 individuals, 95% CI = 106-160 from right side identifications). The population was not closed, with the combined mortality, mark change and emigration rate estimated at 13% per year for left side identifications (95% CI = 9-17) and 14% for right side identifications (95% CI = 10-18). There was no significant increase or decrease in the population size between 1988-1999 (change in population size: left side: –0.13% per year, 95% CI = -3.4 to 3.9; right side: –0.43% per year, 95% CI = -4.5 to 3.1). The sex ratio was roughly 1:1, with equal numbers of sub-adult and mature males. Over the summer field season, individuals emigrated from, and re-immigrated into the Gully, spending an average of 20 days within the Gully before leaving (left side identifications 19 days, SE = 17; right side identifications 23 days, SE = 10). Approximately 34% of the population was present in the Gully at any time. Individuals of all age and sex classes displayed similar residency patterns although there were annual differences as individuals spent less time in the Gully in 1996 than in 1990 and 1997. Sighting rates were similar in all years with extensive fieldwork, indicating little variability in the number of whales in the Gully each summer. Accurate estimates of population size and residency patterns will be useful in determining the regulations and required coverage for a marine protected area in the Gully.

Whale shark abundance forecast: The interannual hotspot effect

Abstract Each year, whale sharks (Rhincodon typus) aggregate in the northern Gulf of California at Bahia de los Angeles, a small coastal village that recently developed whale shark swimming as economic activity during the summer and autumn. Since the number of animals using the bay fluctuates annually, we aimed to predict it 1 month before each whale shark season. We based our modelling approach on the hypothesis that interannual warming conditions would spatially restrict whale shark habitats, triggering larger aggregations in areas that remain productive. We photo‐identified whale sharks while surface feeding in Bahia de los Angeles during a 13‐year period, which allowed us to estimate a local abundance index per year through mark–recapture techniques. Then, we fitted these abundances as a function of several competing model structures, based on means of sea surface temperature and chlorophyll‐a, as well as their interannual anomalies from the linear trend, during spring, within the best‐known range of the species in the northern Gulf of California. The results of the ecological model showed that whale sharks visit Bahia de los Angeles in larger numbers during extreme warming conditions, with relatively high surface chlorophyll‐a concentrations, which was especially evident during the 2014–2016 northeast Pacific Marine Heatwave and El Niño. Presumably, the overall reduction in surface productivity associated with these events forced whale sharks to restrict their summer–autumn habitat to productivity hotspots, including Bahia de los Angeles. Our model allowed us to predict the number of animals visiting the site before each season starts, which has crucial proactive management implications, such as allowing authorities to regulate the ecotourism effort dynamically to reduce the probability of ship strikes and/or excessive stress to the animals. We propose an abundance baseline from the prediction for neutral interannual conditions. Synthesis and applications. We recommend local authorities apply the model described in this study during the late spring of each year to obtain predictions of the upcoming whale shark abundance and establish the maximum ecotourism effort allowed accordingly.

Bycatch of the Indo-Pacific bottlenose dolphin (Tursiops aduncus) in gillnet fisheries off Amakusa-Shimoshima Island, Japan

A year-round resident population of the Indo-Pacific bottlenose dolphin (Tursiops aduncus) inhabits the waters off Amakusa-Shimoshima Island (32°25′N, 130°05´E), in Japan. The effect of bycatch in gillnet fisheries on the Amakusa population was examined. Population size in 2007 and 2008 was estimated at 230 individuals (CV = 2.5%) and 216 individuals (CV = 2.1%), respectively, based on a mark-recapture technique. The magnitude of bycatch was evaluated by analysing interview surveys (263 gillnetters) during these two years. Minimum numbers of dolphin bycatch were 12 individuals in 2007 and 14 individuals in 2008. Most of the dolphins, which were captured by bottom-set gillnets, were considered to be Indo-Pacific bottlenose dolphins for the following reasons: (1) two individuals were identified based on DNA analysis; (2) only Tursiops sp. and finless porpoises were found in the sighting survey by ferry boats, and fishermen can distinguish between the two; and (3) the seasonal and spatial distribution of bycatch corresponded well to habitat use patterns of the Amakusa population. If the US potential biological removal (PBR) approach is used it estimates two individuals per year, which is much lower than the minimum bycatch numbers of 12–14 individuals per year (5.2–6.5% of abundance estimates). Reducing bycatch mortality caused by bottom-set gillnets is essential for the effective conservation of Indo-Pacific bottlenose dolphins in Amakusa, Japan.

Mark-recapture of microorganisms.

Fundamental questions in ecology and evolution require the quantitative tracking of individuals across space and time. For more than a century, mark-recapture techniques have been used to estimate demographic events and population dynamics of animal and plant species. Recent developments in molecular barcoding allow for the monitoring of microorganisms while meeting many of the key assumptions of traditional mark-recapture studies. Beyond applications related to the biosecurity of human pathogens, molecular barcoding is emerging as a cost-effective, versatile, and scalable tool to quantify species interactions, biogeographic ranges, and evolutionary dynamics in simple and complex communities. Although there are logistical and ethical issues related to the release of barcoded organisms, mark-recapture provides opportunities to test theory and better understand the evolutionary ecology of microorganisms in the wild.

Plastron color patterns allow for individual photo-identification in two different chelonian species

Natural marks have increasingly been used as a tool for individual identification in capture–mark–recapture techniques. Photo-identification is a noninvasive alternative to traditional marking techniques, allowing individual recognition of species through time and space. We tested the APHIS (Automatic Photo Identification Suite) software as a software capable of identifying individuals of Hermann’s Tortoise ( Testudo hermanni Gmelin, 1789) and European Pond Turtle ( Emys orbicularis (Linneaus, 1758)) in different populations during capture–release sessions in the field based on plastron color patterns, since they can be used as natural marks for identification. For this individual identification, spot pattern matching (SPM) and image template matching (ITM) procedures were tested, achieving 100% success of individuals recognized in both procedures and visually verified by comparing the images. However, the ITM procedure was more efficient at recognizing recaptures than SPM because ITM allowed faster recapture verification, since most of the matches were directly placed in the first position on the candidate list. Previous studies used photo-identification on freshwater or sea turtles but never with terrestrial tortoise species. Consequently, it was corroborated that APHIS is a competent and efficient software considering photo-identification of T. hermanni and E. orbicularis, and that it can be applied to close species with similar and unique individual color patterns in their plastron.

Effect of Season on Analysis of Growth in a Population of the Western Lesser Siren, Siren intermedia nettingi, in Northwestern Louisiana

We analyzed growth in a population of Siren intermedia nettingi, Western Lesser Siren, from northwestern Louisiana using a mark–recapture technique employing PIT tags from January 1992 through March 1998. Traps were monitored for eight consecutive trap nights for all four seasons from 1992 to 1996, January and December winter trapping sessions in 1997, and late February through early March in 1998. A total of 1,004 siren captures included 575 original captures and 429 recaptures. A total of 223 sirens were recaptured at least once for a recapture rate of 38.7%. Thirty-five of the original sirens captured were recaptured in the same season and year and were not used in the analyses. Therefore, we had a usable recapture rate of 32.7%. Based on captures, bites by conspecifics, and presence of juveniles in the study pond, we concluded that sirens in this population were most active in autumn and winter and presumably had a winter breeding season. Males grew faster and reached larger sizes than females due to the large energy investment of females that produced ova and the importance of male agonistic behavior toward other male and female conspecifics. The greatest growth occurred in the spring, despite increased activity in autumn and winter. Sirens were least active in the summer. Growth was inversely proportional to size and smaller sirens grew at a faster rate than larger ones.

CameratrapR: An R package for estimating animal density using camera trapping data

1.Camera trapping plays an important role in wildlife surveys, and provides valuable information for estimation of population density. While mark-recapture techniques can estimate population density for species that can be individually recognized or marked, there are no robust methods to estimate density of species that cannot be individually identified.2.We developed a new approach to estimate population density based on the simulation of individual movement within the camera grid. Simulated animals followed a correlated random walk with the movement parameters of segment length, angular deflection, movement distance and home-range size derived from empirical movement paths. Movement was simulated under a series of population densities. We used the Random Forest algorithm to determine the population density with the highest likelihood of matching the camera trap data. We developed an R package, cameratrapR, to conduct simulations and estimate population density.3.Compared with line transect surveys and the random encounter model, cameratrapR provides more reliable estimates of wildlife density with narrower confidence intervals. Functions are provided to visualize movement paths, derive movement parameters, and plot camera trapping results.4.The package allows researchers to estimate population sizes/densities of animals that cannot be individually identified and cameras are deployed in a grid pattern.

Large, old trees define the vertical, horizontal, and seasonal distributions of a poison frog.

In tropical forests, large, old trees (LOTs) can be considered keystone structures for provisioning unique habitats such as decaying wood, roots, cavities, and epiphytes, including those that hold water (phytotelmata). These habitats may also be stratified in vertical space, for example, root structures occur at ground level and below, whereas epiphytes occur above-ground. Canopy habitat is utilized by a diversity of amphibians, but canopy habitat may only be viable in the wet season when epiphytes and surfaces are sufficiently saturated. Here, we examine how the provisioning of microhabitats and structures by LOTs influence the horizontal, vertical, and seasonal distribution patterns of phytotelmata-breeding poison frogs. We conducted ground-to-canopy surveys over 4years, constituting 6 seasons, in Panama and used mark-recapture techniques on a population of the yellow-bellied poison frog, Andinobates fulguritus. We found that A. fulguritus migrated vertically, tracking seasonal rainfall, and displayed strong philopatry to individual trees. Furthermore, A. fulguritus almost exclusively inhabited the largest trees at the study location, which provided disproportionately high-quality microhabitats and epiphytes compared to other trees. LOTs, and specifically Anacardium excelsum at our site, appear to serve as keystone structures with high conservation value due to their provisioning of unique habitats. We conclude that the distribution of A. fulguritus is defined vertically by the stratification of arboreal microhabitat resources, horizontally by the presence of LOTs providing the resources, and temporally by the seasonal viability of the resources.

Seasonal variation of non-volant small mammals in Gibe Sheleko national park, Southwestern Ethiopia

The species composition and abundance of small mammals can vary within space and time. The main objective of this study was to assess seasonal variation of non-volant small mammals from randomly selected Acacia woodland, bushland, farmland, grassland, riverine forest and wooded grassland habitats in Gibe Sheleko National Park, southwestern Ethiopia. Data were collected using 49 Sharman live traps in 70 x 70 m sized square girds from December, 2018 to August, 2020. Capture mark recapture technique was applied to estimate population size of the existing small mammals and the data were analyzed using a chi-square test. A total of 1160 individual small mammals belonging to 10 species and 2 families were recorded. Three non-captured species: Hystrix cristata, Xerus rutilus and Tachyoryctes splendens were also identified. There was a significant (χ2= 31.12, df = 1, P < 0.05) difference in the total abundance of small mammals between seasons. Of the total individuals captured, 675(58.19%) were trapped during the wet season while 485(41.81%) individuals were during the dry season. Significant seasonal variation was also observed in the total abundance of both sexes, i e. males (χ2= 11.99, df = 1, P < 0.05) and females (χ2= 20.24, df = 1, P < 0.05). Among age groups, significant statistical seasonal variation was shown in adults (χ2=15.14, df = 1, P < 0.05) and young (χ2=44.61, df = 1, P < 0.05) but not significant in sub-adults (χ2=0.75, df = 1, P >0.05). The identified small mammals exhibited seasonal changes in their abundance associated with changes in climatic and environmental conditions. However, a long-term and annual based study is required to see the overall dynamics of existing small mammals.

Fluid Nest Membership Drives Variable Relatedness in Groups of a Facultatively Social Bee

Kin selection theory has dominated our understanding of the evolution of group living. However, many animal groups form among non-relatives, which gain no indirect fitness benefits from cooperating with nestmates. In this study, we characterized the relatedness and inter-nest migration behavior of the facultatively social carpenter bee, Xylocopa sonorina. Nesting constraints due to costly nest construction in this species give rise to intense intraspecific competition over access to existing nests. We used mark-recapture techniques to characterize patterns of dispersal and nest relocation within a nesting aggregation of spatially clustered nests. Two-thirds of bees relocated at least once during the reproductive season, likely to seek reproductive opportunities in another nest. This fluid nest membership creates opportunities for association among non-relatives. To assess the effects of this dynamic nesting behavior on group relatedness, we used microsatellite analysis to estimate relative relatedness within and between nests in the aggregation. We found that relatedness was variable across sampling years, but that in many cases nestmates were no more related to one another than they were to non-nestmate bees in the population. Together, these results suggest that group composition in X. sonorina may result from strategies to maximize direct fitness. This study supports the hypothesis that factors beyond kinship, such as ecological constraints, are likely to drive group formation in this species.

Comments on the distribution and population estimation of Neurergus derjugini (Urodela, Salamandridae) in western Iran

Basic knowledge of population status is effective for the conservation of many species, especially threatened and endangered species. In this study, we used the Mark-recapture technique (Linconln-Petersen method) as an established method for estimating population in wildlife surveys. Population surveys of critically endangered newts conducted for Neurergus derjugini in the streams of Kurdistan and Kermanshah Provinces, western Iran, at Sarvabad, Marivan, Baneh, Saghez and Nosoud. The study consists of estimating population size by sampling annually for two consecutive years (2018-2019) with each annual sampling consisting of several surveys between May-August. The species has a restricted distribution, occurring at high mountain streams. Our results also reject the occurrence of this species in Sarvabad and Awraman stream habitats and water ecosystems as was stated by former researchers. Distribution information of this species was updated in the region, and all known records are mapped. The results showed that Miri Sour (Marivan) with 1591-1568 and Asnabad (Marivan) with 14-18 specimens as estimated populations were found as most and less populated and suitable habitats respectively.

Efficiency of photo identification of inguinal color patterns of Pithecopus gonzagai (Anura: Phyllomedusidae) from northeastern Brazil

Animal monitoring research involving mark-recapture techniques increasingly requires non-invasive methods of individual identification. The photographic identification method (PIM) is an excellent tool for this purpose and has been applied successfully to many taxa. However, the utility of PIM is a function of species-specific features that are judged suitable for a given target-species. Herein, the suitability of inguinal color patterns for photo identification of individuals of Pithecopus gonzagai are evaluated by comparing two widely used computer-assisted photographic matching programs (I³S and Wild.ID). Both programs accurately identified more than 70% of individuals in the top 20 potential matching photographs. Wild.ID was slightly better than I³S in matching efficiency and has a faster processing time. Thus, PIM is useful to identify individual P. gonzagai; however, before implementing the technique in animal-monitoring studies of other taxa, one must evaluate the suitability PIM for the target species and calibrate the relative efficiency of the software programs in identifying individuals.