Mark-recapture Models Research Articles

Life history patterns, individual heterogeneity, and density dependence in breeding common goldeneyes of the northern boreal forest

Life history patterns and their associated tradeoffs influence population dynamics, as they determine how individuals allocate resources among competing demographic traits. Here we examined life history strategies in common goldeneyes Bucephala clangula (hereafter goldeneye), a cavity‐nesting sea duck, in the northern boreal forest of interior Alaska, USA. We used multistate capture–mark–recapture models to estimate adult survival, breeding probability, first‐year survival, and recruitment probability using a long‐term nest box study (1997–2010). We detected annual variation in adult survival, which varied from 0.74 ± 0.12 (SE) to 0.93 ± 0.06. In contrast, breeding probability remained relatively high and invariant (0.84 ± 0.11) and was positively related to individual nest success the year prior. Nonbreeding individuals in one year were more likely to remain a nonbreeder, than attempt to breed the following year. First‐year survival decreased with smaller residual duckling mass and larger brood sizes. Probability of recruitment into the breeding population conditioned on survival was constant during the study (0.96 ± 0.06), and did not vary among ages 2–5 yr‐old. Overall, goldeneyes exhibited high, but somewhat variable, adult survival, and high breeding and recruitment probabilities, which is consistent with observed patterns in bet‐hedging species that breed annually in high quality breeding environments, but whose reproductive output is often influenced by stochastic events. Demographic estimates from this study are among the first for goldeneyes within Alaska. Life history patterns are known to vary geographically, therefore, we recommend further examination of life history patterns within the distribution of goldeneyes.

Mark-recapture models identify imminent extinction of Yaqui catfish Ictalurus pricei in the United States

Data describing population abundance, survival, and recruitment informs species conservation status and conservation actions. Acquiring these data remains challenging for rare and endangered species, especially freshwater fish, with ~37% threatened or extinct. The absence of data risks inaction, ineptness and ignorance that can contaminate conservation decisions to the species detriment. The solution is obvious: ensure credible data underpin species conservation. We focus on Yaqui catfish (Ictalurus pricei), an endangered, freshwater endemic to the Sonoran desert (Arizona, US and Sonora, Mexico). Our method incorporates mark-recapture data, coupled with hierarchical Bayesian state-space formulations of the Cormack-Jolly Seber models and Jolly-Seber models, to quantify species growth, survival probability, recruitment probability, abundance and trends for the US population. Yaqui catfish growth matched other Ictalurid species. Population recruitment is essentially zero (<0.01%) and annual survival high (>70–75%). Overall, the US Yaqui catfish population declined by 15% per year (λ=0.85). Remaining catfish represent remnants of stocked progeny from the 1990s (age of 19–21years), with US extinction predicted by 2018. A pulse of conservation activity followed by 20years of unsuccessful management resulted in the US population collapsing while habitat degradation and introgression from non-native fish threaten most populations in Mexico. Now approaching global extinction, saving Yaqui catfish requires collaboration between Mexican and US biologists to establish species status in Mexico, hatchery cultivation, habitat protection, habitat restoration and appropriate monitoring. Work herein springboards recent conservation efforts to secure this species.

Mark-recapture vs. line-transect abundance estimates of a coastal dolphin population: a case study of Tursiops truncatus from Laguna, southern Brazil

Cetacean populations in coastal habitats are increasingly threatened by multiple anthropogenic impacts. Monitoring these populations to obtain robust estimates of abundance and detect trends over time is critical to achieve conservation goals. Here, we conducted a pilot study to evaluate the effectiveness of two commonly used abundance estimation methods: mark-recapture and distance sampling line-transect. Surveys were conducted to estimate the abundance of bottlenose dolphins in Laguna, southern Brazil. We implemented power-analysis models and compared both techniques in terms of cost, time and effectiveness to detect trends over a five-year period. Mark-recapture models were analyzed in MARK and resulted in an abundance of 50 individuals (CI = 39-64) with a coefficient of variation (CV) of 0.13. The line-transect models were implemented using the program DISTANCE and resulted in an estimate of 62 individuals (CI = 38-103), with a CV of 0.24. Comparing both approaches, mark-recapture resulted 1.30 time more expensive than line-transect for a single season of effort, but was twice as effective in terms of precision. As a consequence, the probability of detecting a 5% trend during a five-year period is 2.08 times higher with mark recapture. Conversely, the final cost to detect a trend with distance sampling is 1.19 time higher but considering six more years of effort. These results highlight the importance of selecting a-priori sampling design techniques that include developing pilot studies that evaluate the bias, precision and accuracy of estimates while considering costs involved. Considering the small population size estimated herein, the sensitivity of both approaches for detecting trends is not sufficient because the original population would be markedly reduced by the time a declining trend was detected. Thus, a precautionary approach is still imperative, even when robust estimates are obtained.

First estimate of common bottlenose dolphin (Tursiops truncatus) (Cetacea, Delphinidae) abundance off Uruguayan Atlantic coast

The common bottlenose dolphin Tursiops truncatus is often observed throughout the oceanic coast of Uruguay. Historically, its distribution was wider, including the estuary of the Río de la Plata, but currently its occurrence seems to be restricted mainly to the Uruguayan Atlantic coast (Rocha Department). Conflicting interests and tradeoffs between conservation and development are being generated in Uruguay. On one hand, the establishment of protected areas, responsible tourism and sustainable fisheries are promoted, while on the other hand, foreign exploitation of natural resources and development of mega-infrastructure in coastal zone are facilitated. In this work, we provide the first estimate of bottlenose dolphin’s abundance along the Uruguayan Atlantic coast. These results can be used as baseline information for monitoring population trends and guiding conservation actions for bottlenose dolphins in Uruguay. Mark-recapture models were applied to data of photoidentified animals with long-lasting natural marks. Total population size estimates of 63 individuals (95% CI = 54–74) and 61 (95% CI = 53–73) were obtained from closed and open population models, respectively. Although the estimates are within the range of values obtained for other coastal bottlenose dolphin populations in the Southwest Atlantic Ocean, as well as other regions of the world, it is lower than the values reported for populations inhabiting open habitats. This small population is probably vulnerable to non-natural removals, environmental and demographic stochasticity. Therefore, precautionary actions are recommended given the planned development for this coastal region.

Hard choices in assessing survival past dams — a comparison of single- and paired-release strategies

Mark–recapture models are widely used to estimate survival of salmon smolts migrating past dams. Paired releases have been used to improve estimate accuracy by removing components of mortality not attributable to the dam. This method is accompanied by reduced precision because (i) sample size is reduced relative to a single, large release; and (ii) variance calculations inflate error. We modeled an idealized system with a single dam to assess trade-offs between accuracy and precision and compared methods using root mean squared error (RMSE). Simulations were run under predefined conditions (dam mortality, background mortality, detection probability, and sample size) to determine scenarios when the paired release was preferable to a single release. We demonstrate that a paired-release design provides a theoretical advantage over a single-release design only at large sample sizes and high probabilities of detection. At release numbers typical of many survival studies, paired release can result in overestimation of dam survival. Failures to meet model assumptions of a paired release may result in further overestimation of dam-related survival. Under most conditions, a single-release strategy was preferable.

Applying citizen-science data and mark–recapture models to estimate numbers of migrant Golden Eagles in an Important Bird Area in eastern North America

ABSTRACT Estimates of population abundance are important to wildlife management and conservation. However, it can be difficult to characterize the numbers of broadly distributed, low-density, and elusive bird species. Although Golden Eagles (Aquila chrysaetos) are rare, difficult to detect, and broadly distributed, they are concentrated during their autumn migration at monitoring sites in eastern North America. We used hawk-count data collected by citizen scientists in a virtual mark–recapture modeling analysis to estimate the numbers of Golden Eagles that migrate in autumn along Kittatinny Ridge, an Important Bird Area in Pennsylvania, USA. In order to evaluate the sensitivity of our abundance estimates to variation in eagle capture histories, we applied candidate models to 8 different sets of capture histories, constructed with or without age-class information and using known mean flight speeds ± 1, 2, 4, or 6 SE for eagles to travel between hawk-count sites. Although some abundance estimates were produ...

Variable vital rates and the risk of population declines in Adélie penguins from the Antarctic Peninsula region

AbstractPredicting population responses in changing environments is an important task for ecologists. In polar regions, climate warming, loss of sea ice, and more frequent anomalous events suggest that further reductions in ice‐dependent animal populations are likely. We assess the risk of near‐term (30‐year) depletion of an Adélie penguin (Pygoscelis adeliae) population with a stochastic matrix model parameterized with 30 yr (1982–2011) of data from the Copacabana colony on King George Island, Antarctica. The model was fitted to nest census data by estimating correction factors for survival rates estimated from a multi‐state mark–recapture model. We modeled future survival and fecundity scenarios during the projection period (2012–2041) based on a two‐state Markov chain that randomly assigned survival rates and reproductive success from their respective historical distributions to represent “good” and “poor” years. Monte Carlo simulation was used to estimate population trajectories across a range of progressively worse survival conditions. The results suggest that, given historical distributions of survival and reproductive success, a limited scope for recovery of the population is present, commensurate with recent stabilization in population size at the study site. However, our projections mainly suggest that the Adélie penguin population will decline if the frequency of years with poor survival remains at, or increases above, its 30‐year mean. The risk of local depletion within 30 yr, defined according to International Union for Conservation of Nature categories for endangered and critically endangered species, was 33% for &gt;90% declines, but near 100% for 50% declines given status‐quo conditions. As survival conditions worsen, the risk of substantive depletions rose rapidly. Given expectations of further environmental and ecosystem changes in the northern Antarctic Peninsula region, continued declines in Adélie penguin population size at the northern extent of their range should be expected.

Survival of Steller sea lion (Eumetopias jubatus) pups during the first months of life at the Forrester Island complex, Alaska

Mark–recapture models and a sample of 607 Steller sea lion (SSL, Eumetopias jubatus) pups born to individually marked, known-aged females were used to estimate pup survival probabilities from birth to approximately 2 months of age over 8 years (2007–2014) at the Forrester Island complex, the largest rookery in Alaska. Survival of pups was lowest (0.846/week) early in the season when pupping areas were less dense than after the time of maximum counts of adults (≥ 18 June, 0.972/week). Survival was lowest in the first 2 weeks of life and then consistently high after 2 weeks of age. After including age effects, survival was lowest for pups born < 9 June and for pups of 5–7-year-old mothers than 8–20-year-old mothers. Compared to average survival over 6 other years, pup survival to 3 weeks of age was ∼20% lower in 2010, due to a prolonged storm during the middle of the active pupping period, and in 2013, for unknown reasons but not storm-related. Average survival to 3 weeks of age was 0.79, suggesting neonatal mortality was significant and likely important to population dynamics at this stable rookery and in shaping reproductive strategies of females. To prevent disturbance of very young pups and their mothers, SSL pups are first marked for long-term mark–recapture studies at approximately 3 weeks of age throughout their range. When the high neonatal mortality rate observed in this study was ignored, the positively biased model-based population trend estimate (2.3%/year) was triple the estimate produced when the 1st-year survival estimate included neonatal mortality (0.7%/year).

Accurate recapture identification for genetic mark-recapture studies with error-tolerant likelihood-based match calling and sample clustering.

Error-tolerant likelihood-based match calling presents a promising technique to accurately identify recapture events in genetic mark–recapture studies by combining probabilities of latent genotypes and probabilities of observed genotypes, which may contain genotyping errors. Combined with clustering algorithms to group samples into sets of recaptures based upon pairwise match calls, these tools can be used to reconstruct accurate capture histories for mark–recapture modelling. Here, we assess the performance of a recently introduced error-tolerant likelihood-based match-calling model and sample clustering algorithm for genetic mark–recapture studies. We assessed both biallelic (i.e. single nucleotide polymorphisms; SNP) and multiallelic (i.e. microsatellite; MSAT) markers using a combination of simulation analyses and case study data on Pacific walrus (Odobenus rosmarus divergens) and fishers (Pekania pennanti). A novel two-stage clustering approach is demonstrated for genetic mark–recapture applications. First, repeat captures within a sampling occasion are identified. Subsequently, recaptures across sampling occasions are identified. The likelihood-based matching protocol performed well in simulation trials, demonstrating utility for use in a wide range of genetic mark–recapture studies. Moderately sized SNP (64+) and MSAT (10–15) panels produced accurate match calls for recaptures and accurate non-match calls for samples from closely related individuals in the face of low to moderate genotyping error. Furthermore, matching performance remained stable or increased as the number of genetic markers increased, genotyping error notwithstanding.

Juvenile survival, recruitment, population size, and effects of avian pox virus in Laysan Albatross (Phoebastria immutabilis) on Oahu, Hawaii, USA

ABSTRACT Understanding population dynamics and determining conservation priorities in long-lived species with delayed breeding often is hampered by lack of information about younger age classes. Obtaining accurate estimates of juvenile survival and recruitment can be difficult because young individuals are infrequently observed. We used mark–recapture models to estimate age-specific survival, recruitment, population size, and encounter probability of Laysan Albatrosses (Phoebastria immutabilis) using a 14-yr dataset from Oahu, Hawaii, USA. We also measured the long-term effect of avian pox virus (Poxvirus avium) on the survival and recruitment of albatrosses infected as nestlings. Survival of juvenile albatrosses during the first year after fledging was 0.757 ± 0.042. We were able to estimate juvenile survival, the first such estimate in any long-lived seabird, because our high search effort revealed that some birds began visiting the natal colony at the age of 1 yr. The survival of prebreeders increased ...

Resilience to agricultural habitat fragmentation in an arboreal marsupial

The impact of habitat fragmentation on arboreal mammals is poorly understood and potentially greater than for ground-dwelling mammals. We investigated the influence of landscape fragmentation on a generalist arboreal marsupial, the koomal (Trichosurus vulpecula hypoleucus), a geographically isolated subspecies of the common brushtail possum endemic to south-western Australia. Since European settlement this taxon has undergone a significant reduction in range and population. We describe a year-long trapping study, incorporating radio-tracking, of a koomal population in a fragmented agricultural landscape to determine how agriculture and habitat fragmentation affect populations. In all, 61 free-ranging individuals were captured. Mark–recapture modelling estimated the population of 28.8 per trapping event with a total population size of 69 individuals having been present in the test landscape during the course of the study. Population demographics were comparable with populations found in relatively continuous landscapes. Mean home-range size was 8.8 ha of remnant vegetation for males and 7.9 ha for females. Home ranges usually incorporated several patches. Utilisation of shrublands, wetlands, and areas infested with Phytophthora dieback was not observed. Individuals required access to a selection of suitable denning trees and distances between patches &lt;100 m did not appear to impair movement, with gaps &lt;400 m regularly crossed.

Informing conservation strategies for the endangered Atlantic sturgeon using acoustic telemetry and multi‐state mark–recapture models

Summary Causes of non‐intentional mortality may pose conservation challenges for long‐lived, migratory species. Recovery attempts for Atlantic sturgeon Acipenser oxyrinchus oxyrinchus populations in the USA have mainly involved closures of targeted fishing, but bycatch mortality from fisheries targeting other species remains a significant obstacle. Natural and fishing mortality levels are highly uncertain and difficult to separate, but quantifying spatial and temporal patterns of movements and total mortality can directly inform management policies regarding fishing activity that affects sturgeon. Subadult sturgeon were tagged with acoustic transmitters to track their movements with receivers deployed in active fishing areas within the New York Bight. Multi‐state mark–recapture models were used to quantify seasonal patterns in survival and migration while accounting for detection probabilities of tagged fish. Movement patterns of sturgeon were highly variable among seasons along the Long Island Coast, with frequent south‐westward movements during the increase in sea surface temperature in spring. North‐eastward movements were most pronounced during winter, when temperatures were lowest. Sturgeon were less common along coastal Long Island during summer. Larger fish transitioned among strata more frequently, but also had slightly lower survival than smaller fish, which may result from selectivity for larger individuals caught incidentally in bottom trawl or gillnet fisheries. Weekly total mortality rates, including both natural and fishing mortality, averaged 0·24%. Highest weekly survival rates were observed during periods of decreasing sea surface temperature in autumn and winter, while lowest survival was observed during periods of increasing temperature in spring and summer while sturgeon migrated through areas of known bycatch. Policy implications. Movement and survival patterns of Atlantic sturgeon suggest that late spring, coinciding with periods of ocean bycatch in fisheries along the coast of Long Island, is a particularly sensitive period for Atlantic sturgeon. Conservation efforts could target these few weeks using real‐time observations from acoustic telemetry and remote sensing technologies to implement in‐season fishery closures, thereby reducing incidental mortality of Atlantic sturgeon. Such bycatch management measures would aid in recovery attempts of a long‐lived, migratory population with endangered status.

A field test of the effects of body composition analysis by quantitative magnetic resonance on songbird stopover behaviour

Quantitative magnetic resonance (QMR) is a non-invasive technology used to measure body composition. It has great potential to advance the study of energetics and fuel use of migratory birds. However, there is concern that exposure to a strong magnetic field during QMR analysis could affect magnetite-based geomagnetic senses of migratory songbirds which may be important for orientation and navigation. We used radiotelemetry and capture-mark-recapture analysis to test for effects of QMR analysis on stopover duration and departure orientation. There was no evidence from radiotelemetry data that QMR analysis influenced minimum stopover duration or departure orientation of Black-throated Blue Warblers (Setophaga caerulescens) in the spring or fall, or Magnolia Warblers (Setophaga magnolia) in the spring. Capture-mark-recapture analysis of White-throated Sparrow (Zonotrichia albicollis) ringing data showed no effects of QMR on transiency or recapture probability, but a slight increase in estimated stopover duration (days) in the fall. Our study provides evidence that stopover duration and departure orientation of migrating songbirds are not significantly affected by QMR analysis with the exception of fall stopover duration estimates from mark-recapture models, and that QMR is a safe technique for the study of birds in the field.

Use ofAtlanticForest protected areas by free‐ranging dogs: estimating abundance and persistence of use

AbstractWorldwide, domestic dogs (Canis familiaris) are one of the most common carnivoran species in natural areas and their populations are still increasing. Dogs have been shown to impact wildlife populations negatively, and their occurrence can alter the abundance, behavior, and activity patterns of native species. However, little is known about abundance and density of the free‐ranging dogs that use protected areas. Here, we used camera trap data with an open‐robust design mark–recapture model to estimate the number of dogs that used protected areas in Brazilian Atlantic Forest. We estimated the time period these dogs used the protected areas, and explored factors that influenced the probability of continued use (e.g., season, mammal richness, proportion of forest), while accounting for variation in detection probability. Dogs in the studied system were categorized as rural free‐ranging, and their abundance varied widely across protected areas (0–73 individuals). Dogs used protected areas near human houses for longer periods (e.g., &gt;50% of sampling occasions) compared to more distant areas. We found no evidence that their probability of continued use varied with season or mammal richness. Dog detection probability decreased linearly among occasions, possibly due to the owners confining their dogs after becoming aware of our presence. Comparing our estimates to those for native carnivoran, we found that dogs were three to 85 times more abundant than ocelots (Leopardus pardalis), two to 25 times more abundant than puma (Puma concolor), and approximately five times more abundant than the crab‐eating fox (Cerdocyon thous). Combining camera trapping data with modern mark–recapture methods provides important demographic information on free‐ranging dogs that can guide management strategies to directly control dogs' abundance and ranging behavior.

Comparing estimates of population change from occupancy and mark–recapture models for a territorial species

AbstractMonitoring studies often use marked animals to estimate population abundance at small spatial scales. However, at smaller scales, occupancy sampling, which uses detection/nondetection data, may be useful where sites are approximately territories, and occupancy dynamics should be strongly correlated with population dynamics. Occupancy monitoring has advantages in that it is less expensive and invasive, and marked animals are not needed. Here, we used empirical data to determine whether and when change in occupancy is a good proxy for population change for a territorial species. As part of this overall goal, we also compared maximum‐likelihood estimates using a model‐averaging approach with a Bayesian MCMC approach. We used field data collected from 1993 to 2013 on three study areas for California spotted owls (Strix occidentalis occidentalis), a territorial species. Although correlations for trajectories of realized population change (Δt) between territory occupancy and Pradel models were moderate to high for Bayesian MCMC‐based estimates and high for model‐averaged estimates, magnitudes of the trajectories were different with the Pradel model reporting greater magnitudes of change. For the two areas showing a decline, Δt for the Pradel model was approximately 20–30% lower than for the occupancy model, and 25% higher in the area showing an increase. These differences can arise because the occupancy model is less sensitive, in that if two owls share a territory, the loss of one may be reflected in survival and, consequently in Δt by the Pradel model, but because the territory remains occupied it is not reflected by the occupancy model. Bayesian MCMC‐based and model‐averaged estimates of Δt were in close agreement in pattern (correlation ≥0.74) and magnitude (relative differences of last Δt were ≤5%) for both occupancy and mark–resight models. Results from the Pradel model may lead to conservation actions necessary to avoid high extinction or extirpation risk for small populations, while results from the territory occupancy model may result in status quo management. We found both Bayesian MCMC‐based and model‐averaged estimates of Δt robust approaches to evaluate population trends. However, we recommend the Bayesian MCMC approach for estimating risk (e.g., probability of declines) for retrospective analyses.

Mark-recapture estimation of mortality and migration rates for sea trout (Salmo trutta) in the northern Baltic sea

Knowledge of current fishing mortality rates is an important prerequisite for formulating management plans for the recovery of threatened stocks. We present a method for estimating migration and fishing mortality rates for anadromous fishes that combines tag return data from commercial and recreational fisheries with expert opinion in a Bayesian framework. By integrating diverse sources of information and allowing for missing data, this approach may be particularly applicable in data-limited situations.Wild populations of anadromous sea trout (Salmo trutta) in the northern Baltic Sea have undergone severe declines, with the loss of many populations. The contribution of fisheries to this decline has not been quantified, but is thought to be significant. We apply the Bayesian mark-recapture model to two reared sea trout stocks from the Finnish Isojoki and Lestijoki Rivers. Over the study period (1987–2012), the total harvest rate was estimated to average 0.82 y–1 for the Isojoki River stock and 0.74 y−1 for the Lestijoki River stock. Recreational gillnet fishing at sea was estimated to be the most important source of fishing mortality for both stocks, particularly during the 1980s and 1990s. Our results indicate a high probability of unsustainable levels of fishing mortality for both stocks, and illustrate the importance of considering the effect of recreational fisheries on fish population dynamics.

Benefits of Prescribed Flows for Salmon Smolt Survival Enhancement Vary Longitudinally in a Highly Managed River System

The influence of streamflow on survival of emigrating juvenile Pacific salmonids Oncorhynchus spp. (smolts) is a major concern for water managers throughout the northeast Pacific Rim. However, few studies have quantified flow effects on smolt survival, and available information does not indicate a consistent flow–survival relationship within the typical range of flows under management control. In the Yakima Basin, Washington, the potential effects of streamflow alterations on smolt survival have been debated for over 20 years. Using a series of controlled flow releases from upper basin reservoirs and radiotelemetry, we quantified the relationship between flow and yearling Chinook salmon smolt survival in the 208 km reach between Roza Dam and the Yakima River mouth. A multistate mark–recapture model accounted for weekly variation in flow conditions experienced by tagged fish in four discrete river segments. Smolt survival was significantly associated with streamflow in the Roza Reach [river kilometre (rkm) 208–189] and marginally associated with streamflow in the Sunnyside Reach (rkm 169–77). However, smolt survival was not significantly associated with flow in the Naches and Prosser Reaches (rkm 189–169 and rkm 77–3). This discrepancy indicates potential differences in underlying flow-related survival mechanisms, such as predation or passage impediments. Our results clarify trade-offs between flow augmentation for fisheries enhancement and other beneficial uses, and our study design provides a framework for resolving uncertainties about streamflow effects on migratory fish survival in other river systems. Copyright © 2016 John Wiley & Sons, Ltd.

A recipe for postfledging survival in great tits Parus major: be large and be early (but not too much).

Survival of juveniles during the postfledging period can be markedly low, which may have major consequences on avian population dynamics. Knowing which factors operating during the nesting phase affect postfledging survival is crucial to understand avian breeding strategies. We aimed to obtain a robust set of predictors of postfledging local survival using the great tit (Parus major) as a model species. We used mark–recapture models to analyze the effect of hatching date, temperatures experienced during the nestling period, fledging size and body mass on first‐year postfledging survival probability of great tit juveniles. We used data from 5192 nestlings of first clutches ringed between 1993 and 2010. Mean first‐year postfledging survival probability was 15.2%, and it was lower for smaller individuals, as well as for those born in either very early or late broods. Our results stress the importance of choosing an optimum hatching period, and raising large chicks to increase first‐year local survival probability in the studied population.

A noninvasive method to detect Mexican wolves and estimate abundance

Monitoring wolf abundance is important for recovery efforts of Mexican wolves (Canis lupus baileyi) in the Blue Range Wolf Recovery Area in Arizona and New Mexico, USA. Although radiotelemetry has been a reliable method, collaring and tracking wolves in an expanding population will be prohibitively expensive and alternative methods to estimate abundance will become necessary. We applied 10 canid microsatellite loci to 235 Mexican wolf samples, 48 coyote (C. latrans) samples, and 14 domestic dog (C. lupus familiaris) samples to identify alleles that provide reliable separation of these species. We then evaluated an approach for prescreening, noninvasively collected DNA obtained from fecal samples to identify Mexican wolves. We generated complete genotypes for only those samples identified as probable Mexican wolves. We used these genotypes to estimate mark–recapture population estimates of Mexican wolves and compared these to known numbers of wolves in the study area. We collected fecal samples during 3 sampling periods in 2007–2008 and used Huggins-type mark–recapture models to estimate Mexican wolf abundance. We were able to generate abundance estimates with 95% confidence for 2 of 3 sampling periods. We estimated abundance to be 10 (95% CI = 6–34) during one sampling period when the known abundance was 10 and we estimated abundance to be 9 (95% CI = 6–30) during the other sampling period when the known abundance was 10. The application of this noninvasive method to estimate Mexican wolf abundance provides an alternative monitoring tool that could be useful for long-term monitoring of this and other recovering populations. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Demographic shifts related to mycoheterotrophy and their fitness impacts in two Cephalanthera species

Evolutionary losses of photosynthesis in terrestrial plants all originate in photosynthetic ancestors. The adaptive context under which this transition happens has remained elusive because of the rarity of plants in which both photosynthetic and non-photosynthetic forms exist as a polymorphism. Here, we report on demographic patterns in photosynthetic ("green") and nonphotosynthetic ("albino") individuals within populations of two such species, Cephalanthera damasonium and C. longifolia, which also acquire nutrition from their mycorrhizal hosts (partial mycoheterotrophy). We hypothesized that demographic shifts in albinos relative to greens would include compensatory patterns with respect to fitness, such that maladaptive changes to survival or reproduction would be adaptively countered by changes to other parameters, such as growth probabilities. We tracked individuals in two populations of C. damasonium for 3 yr, and in one population of C. longifolia for 14 yr. We then analyzed vital rates for both phenotypes using general linear mixed models (GLMMs) and multi-state capture mark-recapture models (CMR), and used these models to develop size-classified, function-based population projection matrices. We estimated fitness as the deterministic population growth rate (λ) for each phenotype, and explored the impact of shifts in demographic patterns to albinism via life table response experiments (LTREs). Mortality differed between greens and albinos, but not similarly across species. Albinos generally sprouted less than greens, and flowered more when small but less at other times. Albinos typically had a higher probability of fruiting, although their lower flower numbers yielded lower numbers of fruits overall. Fitness did not differ significantly among phenotypes. Thus, we did not find significant evidence that albinism is adaptive or maladaptive; however, if in fact it is the latter, then we did find evidence of incomplete compensation for declines in survival and reproduction from growth transitions, particularly to small flowering size classes in C. damasonium, and to large vegetative size classes in C. longifolia. These patterns indicate some support for the idea that albinism may lead to the speciation of mycoheterotrophic plants.