Scat Surveys Research Articles

Wolves: A Primer for Ranchers

Author(s): Williams, John; Johnson, Douglas E.; Clark, Patrick E.; Larson, Larry L.; Roland, Tyanne J. | Abstract: Ranch management has become more complex since wolves were reintroduced into Idaho and Wyoming in 1996. In wolf areas, livestock have experienced increased death loss and greater stress. Increased livestock aggressiveness has been observed, especially toward working dogs, making handling livestock more difficult. Additionally ranchers have reported a loss of body condition, lower conception rates, increased time and expense for management. Our study was designed to investigate the effect of wolf presence on cattle behavior, landscape use patterns, and resource selection by comparing high wolf density areas against low wolf density areas. This study also generated baseline information on cattle spatial behavior before wolves were on the landscape. A Before-After/Control-Impact Paired (BACIP) experimental design was used. Control study areas in Idaho (3) have high wolf presence while Impact study areas in Oregon (3) started with no wolf presence, and are shifting to elevated wolf presence. Paired Idaho and Oregon areas have similar topography, vegetation composition, wild ungulate prey bases, and livestock management. Cows are tracked at 5-minute intervals using GPS collars (10 per area) throughout the grazing season. Wolf presence is monitored by GPS, trail cameras, and scat surveys. Ten GPS-collared cattle in an Idaho study area encountered a GPS-collared wolf 783 times at less than 500 meters during 137 days in the 2009 grazing season. At 100 meters there were 53 encounters; 52 at night. Tests of naive and experienced cattle exposed to a simulated wolf encounter found increased excitability and fear-related physiological stress responses in cows previously exposed to wolves. This was shown through increased cortisol levels, body temperature, and temperament scores. Cattle presence near occupied houses doesn’t offer protection from wolves. Data shows wolves within 500m of occupied houses 588 times during 198 days of tracking. Many confirmed depredations on this site were also close to houses.

Range-Wide Snow Leopard Phylogeography Supports Three Subspecies.

The snow leopard, Panthera uncia, is an elusive high-altitude specialist that inhabits vast, inaccessible habitat across Asia. We conducted the first range-wide genetic assessment of snow leopards based on noninvasive scat surveys. Thirty-three microsatellites were genotyped and a total of 683 bp of mitochondrial DNA sequenced in 70 individuals. Snow leopards exhibited low genetic diversity at microsatellites (AN = 5.8, HO = 0.433, HE = 0.568), virtually no mtDNA variation, and underwent a bottleneck in the Holocene (∼8000 years ago) coinciding with increased temperatures, precipitation, and upward treeline shift in the Tibetan Plateau. Multiple analyses supported 3 primary genetic clusters: (1) Northern (the Altai region), (2) Central (core Himalaya and Tibetan Plateau), and (3) Western (Tian Shan, Pamir, trans-Himalaya regions). Accordingly, we recognize 3 subspecies, Panthera uncia irbis (Northern group), Panthera uncia uncia (Western group), and Panthera uncia uncioides (Central group) based upon genetic distinctness, low levels of admixture, unambiguous population assignment, and geographic separation. The patterns of variation were consistent with desert-basin "barrier effects" of the Gobi isolating the northern subspecies (Mongolia), and the trans-Himalaya dividing the central (Qinghai, Tibet, Bhutan, and Nepal) and western subspecies (India, Pakistan, Tajikistan, and Kyrgyzstan). Hierarchical Bayesian clustering analysis revealed additional subdivision into a minimum of 6 proposed management units: western Mongolia, southern Mongolia, Tian Shan, Pamir-Himalaya, Tibet-Himalaya, and Qinghai, with spatial autocorrelation suggesting potential connectivity by dispersing individuals up to ∼400 km. We provide a foundation for global conservation of snow leopard subspecies, and set the stage for in-depth landscape genetics and genomic studies.

Meso-scale studies on the penetration and retention of diluted bitumen in different types of shorelines, Northern British Columbia, Canada

ABSTRACT 2017-210 Compared to conventional oil, diluted bitumen (dilbit) spills in the environment could be challenging due to the rapid increase in density, viscosity and adhesion properties associated with accelerated weathering. To enhance the response in case of an accidental dilbit spill in the marine environment, a Research & Development program has been developed by the Emergencies Science and Technology Section (ESTS) of Environment and Climate Change Canada (ECCC) as a part of the Federal Government’s Enhancing Marine Safety Strategy. One of the goals of this project was to develop science-based decision support for a dilbit spill to the shorelines of northern British Columbia (BC). In response to this objective, the contractor Coastal and Ocean Resources Inc. has conducted a meso-scale Diluted Bitumen Sediment Interactions Experiments (Bit_EX) to evaluate the potential of penetration and retention of dilbit in different types of sediments. In total, two dilbits, Access Western Blend (AWB) and Cold Lake Blend (CLB) at three weathered states (0%, 17% and 26% mass loss), were tested against seven types of sediments (from coarse sand to very large pebble). The adhesion of dilbit on bare cobbles and on cobbles covered with barnacles and seaweed (fucus) was also tested for different time of exposure. Results showed that unweathered (or fresh) dilbit has its maximum penetration and retention in coarse sand or granule whereas moderately weathered dilbit has maximum penetration and retention in small pebbles or larger sediment sizes. Heavily weathered dilbits have very limited penetration in finer sediments but are expected to penetrate and have high retention in permeable coarse sediments. Moreover, we have observed that dilbit adherence could be enhanced with longer drying time. In northern BC, the bedrock platforms with thin overlays of various types of sediment, from sand to boulders, are common and presents a complex case for treatment. Because dilbit characteristics change rapidly, early SCAT survey data combined with rapid decision and operational response in the initial stages of the spill could reduce dilbit retention and adhesion. The Bit_EX also suggests that existing techniques for protection and cleanup of conventional oil on shorelines could be applicable or can be adjusted for dilbit spills. This experiment provides information suitable to a first response guide for protecting and cleaning shorelines in case of bitumen spills in northern BC.

OIL BEHAVIOUR AND THE RESPONSE TO A SUNKEN OIL SPILL OF SLURRY IN QUINTERO BAY, CHILE

ABSTRACT Slurry oils are one of the few groups of oils that have a density greater than full salinity seawater. Slurry spills at sea are rare, but when they do occur, the response can be difficult, with low final recovery rates. Oil spill response planning and recovery techniques have been refined over many years and the research and development of most methods has been underpinned by the principle that oil floats on water. This recent case study provides an example of the behavior of a slurry spill and the subsequent response operations. A leak of an API gravity 4° slurry occurred from a submarine pipeline in Quintero Bay, Chile, on 14th May 2016. The oil sank to the adjacent sea bed and covered an area of approximately 10,000 m2 in water depths of 18–22 m. The initial response involved over 20 dry-suit divers with surface air to recover the oil with vacuum hoses. These were then supplemented by four diver-operated vacuum dredges. Fortunately weak bottom currents did not redistribute the oil; nevertheless “sea bed booms” were deployed around the perimeter to prevent migration. These “booms” were initially a screen mesh that was later supplemented by sturdier metal frame screens deployed around the zone of the sunken oil in a zigzag configuration. Baseline benthic sediment samples were collected from the adjacent unaffected area and subsequently from the treatment area after completion of operations. A benthic SCUBA SCAT survey using a track-line positioning system was conducted to systematically document the distribution of the oil and post-treatment systematic ROV survey ensured that the end-point oiling conditions had been achieved.

Strong inference from transect sign surveys: combining spatial autocorrelation and misclassification occupancy models to quantify the detectability of a recovering carnivore

Monitoring of species using surveys of ambiguous signs and assuming 100% detectability produces potentially biased occupancy estimates. Novel analytical tools have been developed that correct for bias arising from imperfect detectability, species misidentification and spatial autocorrelation between detection survey replicates that can affect transect surveys. To date they have been applied individually, but their combined value is unclear.The recovery of carnivores such as the European pine marten Martes martes potentially has far reaching, but largely unknown, implications for ecosystem restoration. Analysis of the species' distribution has as yet been crude and hence unsuited for informing management. We aimed to assess the validity of standard scat surveys to provide recommendations to increase inference from future surveys.We employed spatially replicated scat surveys along forest paths in NE Scotland, genetic verification of scat provenance and occupancy modelling techniques to quantify pine marten detectability and variation therein. Detectability for 1 km and 1.5 km transects, comparable to standard protocols, was estimated to be 0.35 and 0.58 respectively, highlighting the importance of accounting for imperfect detectability. Detection probabilities decreased with vegetation cover and increased with path width. Models accounting for spatial autocorrelation between adjacent transect segments suggested that segments of ≥ 400 m could be analysed as spatial replicates with negligible bias. As is the norm, not all scats yielded DNA to genetically verify they were produced by pine marten. This was accounted for through the use of ‘miss‐classification occupancy models’ which allowed the use of unverified scats, increasing detection probabilities while accounting for the probability of unverified scats being false positive detections.This study exemplifies that robust inference on species occupancy is achievable through careful consideration of sampling design and the application of readily available analytical techniques. Adopting best‐practice need not increase monitoring costs and can even increase cost‐efficiency.

Quantifying and correcting for scat removal in noninvasive carnivore scat surveys

Scat surveys are commonly used to monitor wildlife populations. For carnivores, surveys are typically conducted along roads and trails. Scats available for detection may not reflect scats deposited and variation in disappearance may bias results. Previous research has investigated natural decay and deterioration, but scats deposited along roads or trails are likely influenced to a greater degree by anthropogenic disturbance in some systems. We used experimental plots to evaluate variation in scat removal for two model carnivores, coyote Canis latrans and kit fox Vulpes macrotis, along roads in the Great Basin Desert, USA. Using parametric survival regression, we predicted scat survival and developed persistence‐rate correction factors, which were applied to results from relative abundance scat surveys conducted along 15 transects. Kit fox scats disappeared more rapidly than coyote scats, with 3.3% and 10.6%, respectively, persisting through 42 days. At 14 days, 90.8‐41.7% of scats had been removed across road types. Survival models indicated species, road type, scat position and daily traffic were important predictors of scat persistence. Applying persistence‐rate correction factors to scat survey results altered the inferred relative abundances. Across seasons, mean corrected:uncorrected relative abundance ratios ranged from 1.0–91.2 for coyotes and 1.3–139.3 for kit foxes, with higher mean ratios being influenced by high corrected relative abundances on roads with high traffic volumes. Understanding scat removal rates and patterns can improve inferences from surveys. Persistence‐rate correction factors can be used to reduce bias in indices of abundance, but caution should be used when removal rates are high. Knowledge of spatial variation in persistence can elucidate concerns of false‐positives and false‐negatives in occupancy and capture—recapture studies. Considering the disparity in scat removal between species and among road types and positions, we recommend practitioners quantify and consider variation in removal when interpreting scat survey results.

Spatial Capture–Recapture: A Promising Method for Analyzing Data Collected Using Artificial Cover Objects

Abstract Spatial capture–recapture (SCR) is a relatively recent development in ecological statistics that provides a spatial context for estimating abundance and space use patterns, and improves inference about absolute population density. SCR has been applied to individual encounter data collected noninvasively using methods such as camera traps, hair snares, and scat surveys. Despite the widespread use of capture-based surveys to monitor amphibians and reptiles, there are few applications of SCR in the herpetological literature. We demonstrate the utility of the application of SCR for studies of reptiles and amphibians by analyzing capture–recapture data from Red-Backed Salamanders, Plethodon cinereus, collected using artificial cover boards. Using SCR to analyze spatial encounter histories of marked individuals, we found evidence that density differed little among four sites within the same forest (on average, 1.59 salamanders/m2) and that salamander detection probability peaked in early October (Julia...

Comparing direct and indirect methods to estimate detection rates and site use of a cryptic semi-aquatic carnivore

Monitoring animal populations can be challenging, particularly when working with species that are cryptic, rare, or occur at low densities. The northern river otter (Lontra canadensis) is a cryptic, semi-aquatic carnivore that has been intensively studied in recent decades, yet much of what is known about its ecology is a result of studies that have employed indirect methods of detection and monitoring. These indirect methods, such as latrine or other sign surveys, have been the primary approach used for studying distribution, abundance, and habitat use of otters, with minimal representation of direct methods. In this study, we compared direct (camera traps) and indirect (scat count surveys) methods of evaluating detection probabilities and site use patterns of otters at latrines. We found that the direct method produced a significantly greater monthly detection probability than the indirect method and that camera surveys resulted in fewer occurrences of false negatives than scat surveys. However, the number of scats deposited at a site was positively correlated with number of visits by otters at a site (Tau-b=0.675). Thus, while cameras outperformed scat counts in terms of detection, the two methods were comparable in determining intensity of site use. We conclude that, depending on the parameter of interest, scat counts may be an acceptable surrogate for more direct methods of monitoring otters and other cryptic species. We caution, however, that in the absence of comparative methodological data, direct methods such as camera trapping should be preferred when making inferences about animal distribution, abundance, or habitat use.

Climate Tolerances and Habitat Requirements Jointly Shape the Elevational Distribution of the American Pika (Ochotona princeps), with Implications for Climate Change Effects.

Some of the most compelling examples of ecological responses to climate change are elevational range shifts of individual species, which have been observed throughout the world. A growing body of evidence, however, suggests substantial mediation of simple range shifts due to climate change by other limiting factors. Understanding limiting factors for a species within different contexts, therefore, is critical for predicting responses to climate change. The American pika (Ochotona princeps) is an ideal species for investigating distributions in relation to climate because of their unusual and well-understood natural history as well as observed shifts to higher elevation in parts of their range. We tested three hypotheses for the climatic or habitat characteristics that may limit pika presence and abundance: summer heat, winter snowpack, and forage availability. We performed these tests using an index of pika abundance gathered in a region where environmental influences on pika distribution have not been well-characterized. We estimated relative pika abundance via scat surveys and quantified climatic and habitat characteristics across two North-Central Rocky Mountain Ranges, the Wind River and Bighorn ranges in Wyoming, USA. Pika scat density was highest at mid-elevations and increased linearly with forage availability in both ranges. Scat density also increased with temperatures conducive to forage plant growth, and showed a unimodal relationship with the number of days below -5°C, which is modulated by insulating snowpack. Our results provide support for both the forage availability and winter snowpack hypotheses. Especially in montane systems, considering the context-dependent nature of climate effects across regions and elevations as well as interactions between climatic and other critical habitat characteristics, will be essential for predicting future species distributions.

Evaluating the reliability of field identification and morphometric classifications for carnivore scats confirmed with genetic analysis

ABSTRACTScat surveys are commonly used to monitor carnivore populations. Scats of sympatric carnivores can be difficult to differentiate and field‐based identification can be misleading. We evaluated the success of field‐based species identification for scats of 2 sympatric carnivores—coyotes (Canis latrans) and kit foxes (Vulpes macrotis). We conducted scat surveys in the Great Basin desert of Utah, USA, during the winter and summer of 2013, and we detected 1,680 carnivore scats. We classified scats based on field identification, recorded morphometric measurements, and collected fecal DNA samples for molecular species identification. We subsequently evaluated the classification success of field identification and the predictive power of 2 nonparametric classification techniques—k‐nearest neighbors and classification trees—based on scat measurements. Overall, 12.2% of scats were misclassified by field identification, but misclassifications were not equitable between species. Only 7.1% of the scats identified as coyote with field identification were misclassified, compared with 22.9% of scats identified as kit fox. Results from both k‐nearest neighbor and classification‐tree analyses suggest that morphometric measurements provided an objective alternative to field identification that improved classification of rarer species. Overall misclassification rates for k‐nearest neighbor and classification‐tree analyses were 11.7% and 7.5%, respectively. Using classification trees, misclassification was reduced for kit foxes (8.5%) and remained similar for coyotes (7.2%), relative to field identification. Although molecular techniques provide unambiguous species identification, classification approaches may offer a cost‐effective alternative. We recommend that monitoring programs employing scat surveys utilize molecular species identification to develop training data sets and evaluate the accuracy of field‐based and statistical classification approaches. © 2015 The Wildlife Society.

Estimating population density from presence-absence data using a spatially explicit model

Presence–absence (detection/non-detection) data are routinely collected in wildlife studies where identification of individuals is impossible or impractical and where the detection method may be able to detect only the presence of an individual rather than a count (e.g., track or scat surveys). Estimating population density from presence–absence data usually is assumed to be difficult or impossible unless certain restrictive assumptions are made or supplementary information is collected. Recently, Chandler and Royle (2013) presented an extension of a spatially explicit capture–recapture model that estimates population density from spatially replicated counts in unmarked populations. We extended the model of Chandler and Royle (2013) to situations where only presence–absence data can be collected. The model assumes that individuals can be detected at multiple sample units, producing spatially correlated detections. A spatially explicit model of the detection process is then fit to the correlated detection data using Bayesian methods. We report on the performance of the model using simulation and illustrate its use with a practical example estimating the abundance and density of red foxes (Vulpes vulpes) from remote camera surveys in the Grampians National Park in southeastern Australia. Results from simulations suggest the model produces unbiased estimates of density if device spacing is less than the radial length of a typical home range and the number of encounter occasions is high (i.e., at least 10). Application of the model to camera detection data from foxes in the Grampians National Park resulted in an estimated density of 0.22 foxes/km2 (95% CI: 0.16–0.53). For this dataset, precision of the density and detection parameter estimates were increased by the use of an informative prior distribution for the home-range-scale parameter. The current model should apply widely to a range of sampling situations that result in spatially correlated detection/non-detection data such as bait take, scat surveys, tracking stations, and chew cards, to name a few. © 2015 The Wildlife Society.

Accuracy and efficiency of detection dogs: a powerful new tool for koala conservation and management.

Accurate data on presence/absence and spatial distribution for fauna species is key to their conservation. Collecting such data, however, can be time consuming, laborious and costly, in particular for fauna species characterised by low densities, large home ranges, cryptic or elusive behaviour. For such species, including koalas (Phascolarctos cinereus), indicators of species presence can be a useful shortcut: faecal pellets (scats), for instance, are widely used. Scat surveys are not without their difficulties and often contain a high false negative rate. We used experimental and field-based trials to investigate the accuracy and efficiency of the first dog specifically trained for koala scats. The detection dog consistently out-performed human-only teams. Off-leash, the dog detection rate was 100%. The dog was also 19 times more efficient than current scat survey methods and 153% more accurate (the dog found koala scats where the human-only team did not). This clearly demonstrates that the use of detection dogs decreases false negatives and survey time, thus allowing for a significant improvement in the quality and quantity of data collection. Given these unequivocal results, we argue that to improve koala conservation, detection dog surveys for koala scats could in the future replace human-only teams.

Effects of predation risk on elk (Cervus elaphus) landscape use in a wolf (Canis lupus) dominated system

Food acquisition and predation avoidance are key drivers of herbivore behaviour. We investigated the interaction of top-down (predator) and bottom-up (food, fire, thermal) effects by measuring the relationship between wolf (Canis lupus L., 1758) predation risk perceived by elk (Cervus elaphus L., 1758) and elk landscape use. We conducted fecal pellet and wolf scat surveys in three valleys with three wolf population levels (Saint Mary: low; Waterton: moderate; North Fork: high). In the North Fork, 90% of quaking aspen (Populus tremuloides Michx.) stands burned recently; the other valleys had no fire. We created predictive models of elk pellet density that incorporated bottom-up and top-down variables. All valleys had a high elk pellet density (≥10 per 100 m2). Wolf scat density was similar where there was no fire, but one order of magnitude greater in burned areas. Elk pellet density was lower in the North Fork, a predation-related response. In all valleys, site-specific elk density declined as impediments to detecting or escaping wolves increased, and elk avoided aspen, except for North Fork unburned areas. Models that best predicted elk density contained bottom-up and top-down effects. At local scales, high predation risk negatively influence elk occurrence, suggesting that even with minimal wolf exposure elk avoid risky sites.

Inferring the Distribution and Demography of an Invasive Species from Sighting Data: The Red Fox Incursion into Tasmania

A recent study has inferred that the red fox (Vulpes vulpes) is now widespread in Tasmania as of 2010, based on the extraction of fox DNA from predator scats. Heuristically, this inference appears at first glance to be at odds with the lack of recent confirmed discoveries of either road-killed foxes—the last of which occurred in 2006, or hunter killed foxes—the most recent in 2001. This paper demonstrates a method to codify this heuristic analysis and produce inferences consistent with assumptions and data. It does this by formalising the analysis in a transparent and repeatable manner to make inference on the past, present and future distribution of an invasive species. It utilizes Approximate Bayesian Computation to make inferences. Importantly, the method is able to inform management of invasive species within realistic time frames, and can be applied widely. We illustrate the technique using the Tasmanian fox data. Based on the pattern of carcass discoveries of foxes in Tasmania, we infer that the population of foxes in Tasmania is most likely extinct, or restricted in distribution and demographically weak as of 2013. It is possible, though unlikely, that that population is widespread and/or demographically robust. This inference is largely at odds with the inference from the predator scat survey data. Our results suggest the chances of successfully eradicating the introduced red fox population in Tasmania may be significantly higher than previously thought.

Habitat requirements of Eurasian pine marten Martes martes in a Mediterranean environment

Evaluating presence and habitat requirements of small carnivores is essential for their conservation. The Eurasian pine marten Martes martes, often described as a habitat specialist associated primarily with forest habitats, has been recently found to live even in patchily wooded country and in shrublands. We evaluated the environmental factors that determine the distribution of the pine marten in a Mediterranean landscape on the island of Sardinia (central Italy). Camera trapping sessions and scat surveys were carried out to assess the presence of the species, then a potential distribution model was developed using ecological niche factor analysis (ENFA), which requires only presence data. The pine marten selected highest altitudes, shrublands, rocky areas, and woodlands, and avoided urban areas and arable lands. Our results indicate that pine marten distribution in our study area is constrained by these variables. The ENFA analysis provided important clues about the distribution range of M. martes and its preferential environmental conditions, updating knowledge of its ecological requirements in Italy.

Genetic inference as a method for modelling occurrence: A viable alternative to visual surveys

Management and conservation require a comprehensive understanding of species distributions and habitat requirements. Reliable species occurrence data are critical in the face of climate change and other anthropogenic activity, but are often difficult to obtain, particularly for wide ranging species. This directly affects ecological models of occurrence and habitat suitability and, in turn, conservation and management decisions. We used generalized linear mixed-effects models to identify ecological determinants of occurrence for four macropod species (across a region of tropical northern Australia) using a non-invasive genetic scat approach with and without additional observation records from visual surveys. We show that genetically derived occurrence data, alone, can be used to develop informative ecological models that describe the inter-specific habitat requirements of macropods. Furthermore, we show that genetic scat surveys of macropods are cheaper and less time consuming to conduct, and tend to provide more occurrence records (and less false absences) than visual surveys. We conclude that indirect surveys using molecular approaches have an important role to play in modelling species' occurrence, and developing future management practices and guidelines to aid species conservation.

Faecal particle size and tooth wear of the koala (Phascolarctos cinereus)

We used computer-aided image analysis of leaf fragment particles found in faecal pellets of 45 koalas, representing the range of tooth wear in this species, to investigate how tooth wear in the koala influences faecal particle sizes. Although the range of sizes of particles produced did not vary between koalas across different tooth wear classes, with all koalas producing small, medium and large particles, koalas with advanced tooth wear produced a greater proportion of larger particles. This observation may prove useful for demographic population analyses based on scat surveys since the broad age class of individual koalas can be estimated from faecal pellet analysis. Older koalas produced faecal pellets containing a higher proportion of the largest-sized particle sizes (those greater than 0.59 mm2) than either young or mature koalas but there was no difference detected between mature and young koalas.

Monitoring European wildcat Felis silvestris populations using scat surveys in central Spain: are population trends related to wild rabbit dynamics or to landscape features?

Accurate data on the European wildcat Felis silvestris population trends are scarce for most of its range, despite this information being essential in assessing the threat status of the species. Moreover, ecological correlates of these population trends have never been evaluated. The aim of this study was to describe population trends of the European wildcat in a central region of Spain during the period 1997 to 2005 on both regional and local scales. Putative associations with several landscape features and wild rabbit population trajectories were also examined. Analyses were based on temporal variations of abundance indexes calculated for both species, which were derived from the respective frequencies of occurrence of scats along linear transects. Moreover, we propose monitoring wildcat populations across their range using scat surveys. Results showed that wildcat populations remained stable between the two survey periods considered, and variations in wildcat abundances were not associated with either habitat features or changes in rabbit abundances. Moreover, results suggested that wildcat predation does not limit the growth capacity of rabbit populations. We propose standardized scat surveys as the most efficient methodology for monitoring wildcat populations across European regions. Problems with genetic analyses for correctly identifying carnivore scats are noted, which indicate that the best complementary method for monitoring wildcats is probably camera trapping (especially where hybridization is suspected). Furthermore, results showed that controlling wildcats to protect the rabbit populations is not justified.

Combining camera-trapping and noninvasive genetic data in a spatial capture–recapture framework improves density estimates for the jaguar

Abundance and density are key pieces of information for questions related to ecology and conservation. These quantities, however, are difficult to obtain for rare and elusive species, where even intensive sampling effort can yield sparse data. Here, we combine data from camera-trapping and noninvasive genetic sampling (scat surveys) of a jaguar population in the Caatinga of northeastern Brazil, where the species is threatened and little studied. We analyze data of both survey types separately and jointly in the framework of spatial capture–recapture. Density estimates were 1.45 (±0.46) for the camera-trap data alone, 2.03 (±0.77) for the genetic data alone, and 1.57 (±0.43) and 2.45 (±0.70) for the two methods, respectively, in the joint analysis. Density and other parameters were estimated more precisely in the joint model. Particularly the differences in movement between males and females were estimated much more precisely when combining both data sources, especially compared to the genetic data set alone. When compared to a previous non-spatial capture–recapture approach, present density estimates were more precise, demonstrating the superior statistical performance of spatial over non-spatial capture recapture models. The ability to combine different surveys into a single analysis with shared parameter allows for more precise population estimates, while at the same time enabling researchers to employ complementary survey techniques in the study of little known species.

Road use by the Iriomote Cat (Prionailurus bengalensis iriomotensis) on Iriomote-Jima Island in Relation to its Herpetile Prey

The Iriomote cat is an endangered subspecies (CR on the Japanese Red List) found only on Iriomote-jima Island in the Ryukyu Archipelago, Japan. One of the main factors threatening the Iriomote cat is the main paved road that contributes to traffic mortality of this wildcat and also alters its preferred lowland habitats with abundant prey. One of the reasons why the Iriomote cat appears on the road may be due to the presence of prey; therefore, we investigated road use by this wildcat in relation to its prey. In 2009, scat surveys were conducted to assess road use by the Iriomote cat, and prey surveys were undertaken in the morning and at night, mainly targeting terrestrial frogs and reptiles. To analyse the importance of factors related to road use by the Iriomote cat, the influences of prey density along road types, habitat types, presence or absence of road construction activities, and survey regions on number of scats were examined using nested generalised linear models (GLM), assuming Poisson error and a log-link function. Diurnal lizard density was strongly correlated with scat along roads, and the density of road-killed Fejervarya sakishimensis was positively correlated with scat presence along roads.