The contrasting effects of short‐ and long‐term habitat drainage on the population dynamics of freshwater turtles in a human‐dominated landscape

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Estimating preharvest density,adult sex ratio,and fecundity of white‐tailed deer using noninvasive sampling techniques

Adult sex ratio and fecundity (juveniles per female) are key population parameters in sustainable wildlife management, but inferring these requires abundance estimates of at least three age/sex classes of the population (male and female adults and juveniles). Prior to harvest, we used an array of 36 wildlife camera traps during 2 and 3 weeks in the early autumn of 2016 and 2017, respectively. We recorded white‐tailed deer adult males, adult females, and fawns from the pictures. Simultaneously, we collected fecal DNA (fDNA) from 92 20 m × 20 m plots placed in 23 clusters of four plots between the camera traps. We identified individuals from fDNA samples with microsatellite markers and estimated the total sex ratio and population density using spatial capture–recapture (SCR). The fDNA‐SCR analysis concluded equal sex ratio in the first year and female bias in the second year, and no difference in space use between sexes (fawns and adults combined). Camera information was analyzed in a spatial capture (SC) framework assuming an informative prior for animals’ space use, either (a) as estimated by fDNA‐SCR (same for all age/sex classes), (b) as assumed from the literature (space use of adult males larger than adult females and fawns), or (c) by inferring adult male space use from individually identified males from the camera pictures. These various SC approaches produced plausible inferences on fecundity, but also inferred total density to be lower than the estimate provided by fDNA‐SCR in one of the study years. SC approaches where adult male and female were allowed to differ in their space use suggested the population had a female‐biased adult sex ratio. In conclusion, SC approaches allowed estimating the preharvest population parameters of interest and provided conservative density estimates.     

Local site differences in survival and parasitism of periwinkles (Littorina sitkana Philippi, 1846)

The periwinkle, Littorina sitkana, is found throughout the intertidal zone, often in isolated subpopulations. The majority of trematode parasites use snails as intermediate hosts, and decreased survivorship is often observed in snails infected with trematodes. Sampling L. sitkana from four sites in Barkley Sound, British Columbia, Canada, we test the effects of parasitic infection on snail survival using maximum likelihood and Bayesian approaches using the software MARK and WinBUGS. We found that survival of periwinkles and trematode community composition differed among sites, but survival and trematode prevalence were uncorrelated. WinBUGS performed better than MARK in two ways: (1) by allowing the use of information on known mortality, thus preventing survival overestimation; and (2) by giving more stable estimates while testing the effect of body size on snail survival. Our results suggest that snail survival depends heavily on local environmental factors that may vary greatly within a small geographical region. These findings are important because the majority of experimental studies on survival are done on snails from a single location.     

A Comparison of Population Size Estimators under the Truncated Count Model With and Without Allowance for Contaminations

The purpose of the study is to estimate the population size under a homogeneous truncated count model and under model contaminations via the Horvitz‐Thompson approach on the basis of a count capture‐recapture experiment. The proposed estimator is based on a mixture of zero‐truncated Poisson distributions. The benefit of using the proposed model is statistical inference of the long‐tailed or skewed distributions and the concavity of the likelihood function with strong results available on the nonparametric maximum likelihood estimator (NPMLE). The results of comparisons, for finding the appropriate estimator among McKendrick's, Mantel‐Haenszel's, Zelterman's, Chao's, the maximum likelihood, and the proposed methods in a simulation study, reveal that under model contaminations the proposed estimator provides the best choice according to its smallest bias and smallest mean square error for a situation of sufficiently large population sizes and the further results show that the proposed estimator performs well even for a homogeneous situation. The empirical examples, containing the cholera epidemic in India based on homogeneity and the heroin user data in Bangkok 2002 based on heterogeneity, are fitted with an excellent goodness‐of‐fit of the models and the confidence interval estimations may also be of considerable interest. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Parameter Redundancy in Multistate Capture‐Recapture Models

Multistate capture‐recapture models are a powerful tool to address a variety of biological questions concerning dispersal and/or individual variability in wild animal populations. However, biologically meaningful models are often over‐parameterized and consequently some parameters cannot be estimated separately. Identifying which quantities are separately estimable is crucial for proper model selection based upon likelihood tests or information criteria and for the interpretation of the estimates obtained. We show how to investigate parameter redundancy in multistate capture‐recapture models, based on formal methods initially proposed by Catchpole and his associates for exponential family distributions (Catchpole, Freeman and Morgan, 1996. Journal of the Royal Statistical Society Series B 58, 763–774). We apply their approach to three models of increasing complexity.     

Homing precision of roach Rutilus rutilus in Lake Arungen,Norway

Synopsis The present study tests the precision of repeat homing of roach, Rutilus rutilus, to two tributaries of a small Norwegian Lake, Årungen. A sample of 19 959 spawners was tagged or marked in the spawning area. After spawning the roach intermingled with other spawning demes in the lake. The year after marking, 2515 (12.6%) roach were recaptured during spawning in the five tributaries, 340 (13.5) of these were strayers. This straying is considerably larger than found in comparable autumn spawning species, but approximately the same as reported for other spring spawning species. The recapture rate was lower for females than for males, probably due to increased female mortality induced by the tagging manipulation.     

Are badgers ‘Under The Weather’? Direct and indirect impacts of climate variation on European badger (Meles meles) population dynamics

Weather conditions, and how they in turn define and characterize regional climatic conditions, are a primary limit on global species diversity and distribution, and increasing variability in global and regional climates have significant implications for species and habitat conservation. A Capture–Mark–Recapture study revealed that badger (Meles meles) life history parameters interact in complicated ways with annual variability in the seasonality of temperature and rainfall, both in absolute and in phenological terms. A strong predictive relationship was observed between survival and both temperature and late‐summer rainfall. This link at the population dynamics level was related to individual body‐weight increases observed between summer and autumn. In addition, fecundity was correlated with spring rainfall and temperature. We investigated and confirmed that relationships were consistent with observed variation in the intensity of a parasitic infection. Finally, fecundity during any given year correlated with conditions in the preceding autumn. Badger survival also correlated with late winter weather conditions. This period is critical for badgers insofar as it coincides with their peak involvement in road traffic accidents (RTAs). RTA rate during this period was linked strongly to temperature, underlining the intricate ways in which a changing climate might interact with anthropogenic agents to influence species' population processes. Equinoctial conditions produced significant population driver effects. That is, while summers will always be relatively warm compared with winters, spring and autumn weather can be more variable and functionally delimit the ‘productive’ vs. nonproductive period of the year in terms of badger behavioural and physiological cycles. This study highlights how appropriately informed conservation strategies, mindful of trends in climatic conditions, will become ever‐more essential to ensure the survival of many species globally.     

Field evaluation by RNA/DNA ratios on post-release nutritional status of released and wild Japanese flounder Paralichthys olivaceus juveniles

A large-scale juvenile Japanese flounder (Paralichthys olivaceus) release-recapture experiment was undertaken to find the optimal release season by evaluating the nutritional status of released fish at different seasons during which food abundance was significantly different. Forty thousand fish were released at depths of 1.5 m for early-release (May 29, 1997) and 2 m for late-release (July 2, 1997) (42.1±3.5 and 40.9±4.2 mm body length, respectively) in an experimental field, Wakasa Bay, the Sea of Japan. Samples were taken, after the releases, at Wada beach at intervals of 1, 2, 3, 6, 10, 16 and 30 days after release (DAR), including pre-surveys before each release. Released fish recaptured from the two different release groups totaled 764; 467 from the early-release group (ER) and 297 from the late-release group (LR). A total of 1956 wild flounder juveniles were simultaneously collected (1041 ER, 915 LR). ER fish were subject to higher food availability and were exposed to less pressure from predation by smaller wild juvenile flounder. RNA/DNA ratios in ER juveniles were significantly higher than those of LR fish during all samples. Especially, RNA/DNA ratios in ER juveniles were higher than in wild juveniles from 3 to 50 DAR. In the LR group, the nutritional status of juveniles was relatively low in shallower water. These findings corresponded well with feeding incidence examined by coworkers. Mass release of hatchery-reared juveniles apparently reduced RNA/DNA ratio of the wild juveniles right after releasing. The present study showed that earlier release of hatchery-reared juvenile Japanese flounder with higher RNA/DNA ratio could increase the possibilities of survival right after release in the nursery ground, and that RNA/DNA ratio appeared to be a good tool in evaluating nutritional status of released juveniles as well as wild juveniles in Japanese flounder.     

Demographic versus genetic dispersal measures

Quantifying dispersal, a fundamental biological process, is far from simple. Here, both direct and indirect methods were employed to estimate dispersal in an endangered butterfly species. A high and significant correlation between the dispersal patterns, generated by an inverse power function fitted to capture-mark-recapture (CMR) data on the one hand, and population genetic analyses on the other hand, was observed. Stepping-stone type movements were detected by both methods, evidence for the importance of connectivity in the studied metapopulation. These results are particularly relevant to those population and conservation biology studies where quantifying dispersal is essential for the elaboration of successful management actions.     

Reduction of Banana Weevil Populations Using Different Formulations of the Entomopathogenic Fungus Beauveria bassiana

One of the major constraints for banana production in Uganda is the banana weevil, Cosmopolites sordidus (Germar), (Coleoptera: Curculionidae). Investigations were carried out to evaluate the efficacy of maize, soil-based and oil formulations of an indigenous isolate of Beauveria bassiana for the control of the banana weevil. Weekly trapping of weevils over a 9-month monitoring period showed significant reduction in unmarked and marked weevil population in B. bassiana treated plots. Application of maize formulation at 2 ×10 15 conidia ha -1 proved most effective, reducing the weevil populations by 63-72% within 8 weeks after a single application. The soil based formulation at 2 ×10 14 conidia ha -1 was intermediate while the oil formulation at 6 ×10 15 conidial ha -1 was least effective. Trapping efficiency declined in B. bassiana treated and untreated banana plots but was greatest in the latter.