Effectiveness of plastic matrix lures and traps against Bactrocera dorsalis and Bactrocera cucurbitae in Hawaii

Trapping trials were conducted in two locations on the island of Hawaii with plastic‐matrix formulations of methyl eugenol (ME) (1‐2‐dimethoxy‐4‐allylbenzene) and cuelure (CL) [4‐(p‐acetoxyphenyl)‐2‐butanone] in traps with or without a toxicant (2, 2‐dichlorovinyl dimethyl phosphate, DDVP) against wild fly populations of oriental fruit fly, Bactrocera dorsalis (Hendel) and melon fly, Bactrocera cucurbitae (Coquillett) respectively. Both 5 g disks and 10 g cones of ME and 2 g plugs of CL caught flies for >9 months which varied relative to the population fluctuations. In all of these trials a one‐way entrance design trap caught more flies than the toxicant‐baited trap. The similar‐sized entrance holes (0.70 cm) of the latter may have slowed the dispersal of the toxicant vapour, thus causing flies to be repelled or killed outside the entrance to the trap when DDVP vapour was evolving at a maximum rate. The effect decreased as the toxicant aged. One‐way entrance traps are appropriate where toxicant traps are not allowed (e.g. organic farms), present a health hazard (e.g. yards with children), or would need to be replaced more frequently than lures. The results of these studies are discussed in relation to areawide fruit fly suppression programs where large populations of these flies are persistent, as well as to detection programs in areas where fruit flies have not established.     

Two modified Breder traps for quantitative studies of tropical amphidromous migration

Amphidromy is a life cycle of fauna found throughout the tropics and subtropics, including representatives from three phyla. Amphidromy involves a life cycle of oceanic larval development, with postlarval migration into streams where growth and reproduction take place. With increasing industrial and urban development in tropical regions, demands for freshwater are continuously growing, resulting in the construction of dams and diversions that break the freshwater continuum necessary for the amphidromous life cycle; thus, jeopardizing many populations of native and endemic tropical stream fauna. Because of this, more quantitative studies are needed to better understand this unique life cycle, which heretofore, has been relatively little studied compared to tropical terrestrial communities. As such, new and quantitative methods are needed to study the immature stages (e.g., postlarvae) associated with amphidromy. In this paper, we introduce two modifications of the original Breder trap that have been designed specifically for standardized, quantitative monitoring of amphidromous postlarval migration. In addition, the two modified traps can be used in a variety of stream settings from natural bed substrates to modified channels with little heterogeneity. The first modification is made of acrylic, with a flat bottom useful in channelized streams or streams with relatively flat, unnatural benthic substrate (e.g., concrete). The second modification is an affordable trap made from polyvinylchloride (PVC) compression couplings, to be used in streams with natural benthic substrates, particularly those with large, embedded and immovable boulders and bedrock outcrops. Both traps were designed for continuous water flow through the traps, providing the necessary rheotactic cue for migrating amphidromous postlarvae, and ameliorating deficiencies of earlier traps not intended for tropical amphidromous fauna. We also make recommendations for standardized use of these traps to facilitate data comparisons among studies.     

Two modified Breder traps for quantitative studies of tropical amphidromous migration

Amphidromy is a life cycle of fauna found throughout the tropics and subtropics, including representatives from three phyla. Amphidromy involves a life cycle of oceanic larval development, with postlarval migration into streams where growth and reproduction take place. With increasing industrial and urban development in tropical regions, demands for freshwater are continuously growing, resulting in the construction of dams and diversions that break the freshwater continuum necessary for the amphidromous life cycle; thus, jeopardizing many populations of native and endemic tropical stream fauna. Because of this, more quantitative studies are needed to better understand this unique life cycle, which heretofore, has been relatively little studied compared to tropical terrestrial communities. As such, new and quantitative methods are needed to study the immature stages (e.g., postlarvae) associated with amphidromy. In this paper, we introduce two modifications of the original Breder trap that have been designed specifically for standardized, quantitative monitoring of amphidromous postlarval migration. In addition, the two modified traps can be used in a variety of stream settings from natural bed substrates to modified channels with little heterogeneity. The first modification is made of acrylic, with a flat bottom useful in channelized streams or streams with relatively flat, unnatural benthic substrate (e.g., concrete). The second modification is an affordable trap made from polyvinylchloride (PVC) compression couplings, to be used in streams with natural benthic substrates, particularly those with large, embedded and immovable boulders and bedrock outcrops. Both traps were designed for continuous water flow through the traps, providing the necessary rheotactic cue for migrating amphidromous postlarvae, and ameliorating deficiencies of earlier traps not intended for tropical amphidromous fauna. We also make recommendations for standardized use of these traps to facilitate data comparisons among studies.     

Influence of spatial and temporal heterogeneities on the estimation of demographic parameters in a continuous population using individual microsatellite data

Drift and migration disequilibrium are very common in animal and plant populations. Yet their impact on methods of estimation of demographic parameters was rarely evaluated especially in complex realistic population models. The effect of such disequilibria on the estimation of demographic parameters depends on the population model, the statistics, and the genetic markers used. Here we considered the estimation of the product Dsigma2 from individual microsatellite data, where D is the density of adults and sigma2 the average squared axial parent-offspring distance in a continuous population evolving under isolation by distance. A coalescence-based simulation algorithm was used to study the effect on Dsigma2 estimation of temporal and spatial fluctuations of demographic parameters. Estimation of present-time Dsigma2 values was found to be robust to temporal changes in dispersal, to density reduction, and to spatial expansions with constant density, even for relatively recent changes (i.e., a few tens of generations ago). By contrast, density increase in the recent past gave Dsigma2 estimations biased largely toward past demographic parameters values. The method was also robust to spatial heterogeneity in density and estimated local demographic parameters when the density is homogenous around the sampling area (e.g., on a surface that equals four times the sampling area). Hence, in the limit of the situations studied in this article, and with the exception of the case of density increase, temporal and spatial fluctuations of demographic parameters appear to have a limited influence on the estimation of local and present-time demographic parameters with the method studied.     

Forms of density regulation and (quasi-) stationary distributions of population sizes in birds

The theta-logistic model of density regulation is an especially flexible class of density regulation models where different forms of non-linear density regulation can be expressed by only one parameter, θ. Estimating the parameters of the theta-logistic model is, however, challenging. This is mainly due to the need for information concerning population growth at low densities as well as data on fluctuations around the carrying capacity K in order to estimate the strength of density regulation. Here we estimate parameters of the theta-logistic model for 28 populations of three species of birds that have grown from very small population sizes followed by a period of fluctuations around K. We then use these parameters to estimate the quasi-stationary distribution of population size. There were often large uncertainties in these parameters specifying the form of density regulation that were generally independent of the duration of the study period. In contrast, precision in the estimates of environmental variance increased with the length of the time series. In most of the populations, a large proportion of the probability density of the (quasi-) stationary distribution of population sizes was located at intermediate population sizes relative to K. Thus, we suggest that the (quasi-) stationary distribution of population sizes represents a useful summary statistic that in many cases provides a more robust characterisation of basic population dynamics (e.g. range of variation in population fluctuations or proportion of time spent close to K) than can be obtained from analyses of single model parameters.     

Short-term growth responses and associated wood density fluctuations in variously irrigated Eucalyptus globulus

Cambial growth and wood properties respond to fluctuating environmental conditions. Understanding the nature of these responses is crucial to understanding their cumulative effect on the wood quality characteristics of a forest stand. This paper reports on a study conducted over a period of 3? years in continuously irrigated, alternately irrigated and non-irrigated Eucalyptus globulus, in which changes in wood density occurring in response to short-term growth responses were examined. The study showed that continuous irrigation led to the production of wood with significantly more homogenous density than was the case in situations, where trees experienced large fluctuations in temporal water availability. Although the trees which were not irrigated had the highest wood density overall, trees in which growth was relatively continuous tended to produce the largest volumes of wood with relatively high density, compared to trees in which periodic growth responses were caused by intermittent irrigation, in which wood density was actually reduced. This was largely due to more growth days in summer under the conditions of higher radiation, and a reduction in the number of growth events leading to the production of disproportionately large amounts of low density wood. Soil water deficits contributed to density variation in all treatments, but the effect of energy limitations became more important in continuously irrigated trees.     

Optimising the capacity of field trials to detect the effect of genetically modified maize on non‐target organisms through longitudinal sampling

To assess risks of cultivation of genetically modified crops (GMCs) on non‐target arthropods (NTAs), field tests are necessary to verify laboratory results and in situations where exposure pathways are very complex and cannot be reproduced in the laboratory. A central concern in the design of field trials for this purpose is whether the tests are capable of detecting differences in the abundance or activity of NTAs in a treated crop in comparison with a non‐treated comparator plot. The detection capacity of a trial depends on the abundance and variability of the taxon, the values assumed for type I (α) and II (β) errors, and the characteristics of the trial and statistical design. To determine the optimal trial layout and statistical analysis, 20 field trials carried out in Spain from 2000 to 2009 to assess risks of GMCs on NTAs were examined with α and β set at 0.05 and 0.20, respectively. In this article we aim to determine the optimal number of sampling dates during a season, or longitudinal samples, in the design of field trials for assessing effects of GM maize on NTAs, and the ones that contribute most to achieving detectable treatment effects (d_c) less than 50% of the mean of the control. Detection capacities are a function of the number of individual samples taken during the season but a high number of samples is rarely justified because gains of repeated sampling can be relatively low. These gains depend primarily on field tests relative experimental variability in individual samplings (i.e. experimental variability relative to the mean of the control in each sampling date) which in turn depends on the sampling method (visual counts, pitfall traps or yellow sticky traps) and the density (or abundance) of the taxon in question. Taxa showing more density (or abundance) have less relative experimental variability. The smaller the experimental variability, the lower the profit of increasing the number of sampling dates. Sticky traps have a good effect detection capacity and need very few sampling dates, whereas visual counts and pitfall traps have a poorer effect detection capacity and need more individual samples to achieve d_c values lower than 50%. In maize field trials, it is recommended to concentrate sampling efforts in certain growth stages; the optimal ones for achieving an acceptable detection capacity are variable but, in general, samples in the first half of the season render better detection capacity than samples in the second half.     

How Small is too Small? Camera Trap Survey Areas and Density Estimates for Ocelots in the Bolivian Chaco

Studies on carnivores, which are generally difficult to observe directly because they are elusive and nocturnal, are carried out through indirect methods, e.g. , camera trapping and radiotracking. The first method has been used to estimate population densities of species that can be differentiated as individuals using unique pelage patterns. However, the use of capture–recapture methodology has raised doubts regarding the estimation of the sampling area around the camera traps, which is obtained using maximum distances traveled by individuals photographed at two or more different locations. In this paper, the results from camera traps are compared with a radiotracking study carried out simultaneously with ocelots ( Leopardus pardalis ) to confirm whether maximum distances observed in camera traps coincide with ranging patterns determined from radio telemetry, and in turn whether the sampling areas estimated from camera traps are appropriate for estimating density. Mean maximum distance moved was 2880 m according to camera trap records during a 60-d survey period while, with radiotracking, the maximum distance moved was 3176 m during the same period. The difference is not significant, and the sampling areas estimated with camera traps to assess ocelot density are reliable. However, if the area covered by cameras is reduced to less than three to four times average home range for the target species, then density estimates from camera trapping are exaggerated because of the reduced observed distances and the fact that multiple individuals can overlap in relatively small areas.     

Effect of aerosol surface lubricants on the abundance and richness of selected forest insects captured in multiple-funnel and panel traps

Survey and detection programs for native and exotic forest insects frequently rely on traps baited with odorants, which mediate the orientation of target taxa (e.g., the southern pine beetle, Dendroctonusfrontalis Zimmermann) toward a resource (e.g., host material, mates). The influence of trap design on the capture efficiency of baited traps has received far less empirical attention than odorants, despite concerns that intercept traps currently used operationally have poor capture efficiencies for some target taxa (e.g., large woodborers). Several studies have recently demonstrated that treating traps with a surface lubricant to make them "slippery" can increase their capture efficiency; however, previously tested products can be expensive and their application time-consuming. The purpose of this study was to evaluate the effect of alternate, easier to apply aerosol lubricants on trap capture efficiency of selected forest insects. Aerosol formulations of Teflon and silicone lubricants increased both panel and multiple-funnel trap capture efficiencies. Multiple-funnel traps treated with either aerosol lubricant captured significantly more Monochamus spp. and Acanthocinus obsoletus (Olivier) than untreated traps. Similarly, treated panel traps captured significantly more Xylotrechus sagittatus (Germar), Ips calligraphus (Germar), Pissodes nemorensis (Germar), Monochamus spp., A. obsoletus, Thanasimus dubius (F.), and Ibalia leucospoides (Hochenwarth) than untreated traps. This study demonstrates that treating multiple-funnel and panel traps with an aerosol dry film lubricant can increase their capture efficiencies for large woodborers (e.g., Cerambycidae) as well as bark beetles, a weevil, a woodwasp parasitoid and a bark beetle natural enemy (Coleoptera: Cleridae).     

Ecology of small rodents in Africa

This account considers progress in research on small rodent ecology since about 1970. While some ecological survey has been undertaken throughout much of the continent, the main research thrust has involved the detailed examination of population processes in a range of habitats from deserts to tropical rain forests. The deserts and semi-arid regions support a range of species with some better adapted to these harsh conditions than others. The adaptations manifest themselves in different life history strategies e.g., opportunistic with high turnover species, or low turnover-low reproduction species, in their physiology e.g., adaption to water retention, and in their behaviour e.g., avoiding heat of day. Long term studies show large numerical fluctuations with a quick response by some species to favourable conditions caused by relatively high precipitation. In the savanna and grasslands, studies have centred on population dynamics, the relationship between food and breeding, reproductive and life history strategies and the determination of niche. These have been approached through the study of groups of species in particular localities as well as by the examination of individual species. In these habitats populations are more stable and less erratic than in semi-arid regions. Perturbations, particularly fire, can have various effects on the numbers and species composition of the disturbed area. In the tropical rain forest population fluctuations are modest and may take up to 2–3 years to pass from a peak to a trough and back again. Breeding typically extends over much of the year with, apparently, the greatest number of rodents occurring on the ground surface. Bush and temporary farms derived as a result of forest modification support more animals (and often more species) than forest. The niches occupied by forest rodents are poorly understood and very little is known of the ecology within the canopy. In most localities a small number of species are abundant and the remainder much less frequent.     

Potential for mountaintop boulder fields to buffer species against extreme heat stress under climate change

Species may circumvent or minimize some impacts resulting from climate change by utilizing microhabitats that buffer against extreme events (e.g., heat waves). Boulder field habitats are considered to have functioned as important refugia for rainforest fauna during historical climate fluctuations. However, quantitative data on microhabitat buffering potential in these habitats is lacking. We characterized temperature buffering over small distances (i.e., depths) within an exposed and forested boulder field on a tropical mountain. We demonstrate that temperatures are cooler and become more stable at increasing depths within boulder fields. The magnitude of difference is most pronounced in exposed situations where temperatures within boulder fields can be as much as 10°C lower than near surface conditions. Our data provide a first step toward building models that more realistically predict exposure to heat stress for fauna that utilize rocky habitats.     

What happens if density increases? Conservation implications of population influx into refuges

Sudden catastrophic events like fires, hurricanes, tsunamis, landslides and deforestation increase population densities in habitat fragments, as fleeing animals encroach into these refuges. Such sudden overcrowding will trigger transient fluctuations in population size in the refuges, which may expose refuge populations to an increased risk of extinction. Until recently, detailed information about the operation of density dependence in stage-structured populations, and tools for quantifying the effects of transient dynamics, have not been available, so that exploring the extinction risk of such transient fluctuations has been intractable. Here, we use such recently developed tools to show that extinction triggered by overcrowding can threaten populations in refuges. Apart from situations where density dependence acts on survival, our results indicate that short-lived species may be more at risk than longer-lived species. Because dynamics in local populations may be critical for the preservation of metapopulations and rare species, we argue that this aspect warrants further attention from conservation biologists.     

Interactions between habitat heterogeneity and food affect reproductive output in a top predator

1. Habitat heterogeneity has important repercussions for species abundance, demography and life-history patterns. While habitat effects have been more thoroughly studied in top-down situations (e.g. in association with predation), their role in bottom-up situations (e.g. in association with food abundance) has been less explored and the underlying mechanism(s) behind the ecological patterns have not commonly been identified. 2. With material from 1993 to 2003, we test the hypothesis that the reproduction of Finnish northern goshawks Accipiter gentilis (L.) is bottom-up limited by habitat composition, especially in situations where the density of their main prey (grouse) is low. Special emphasis was placed on identifying the mechanism(s) behind potential habitat effects. 3. While laying date and large-scale variation in the main prey density (but not habitat composition) were related to the number of eggs goshawks laid, small-scale differences in alternative prey density between different territories later influenced how many young were fledged via the mechanism of habitat-dependent partial-brood loss. As a result of this mechanism, a difference in nestling condition also arose between goshawk territories with differing habitat compositions. 4. As the relative proportions of different landscape elements in a given landscape is a function of large-scale differences in geomorphology and land use, this means that the reproductive performance of goshawks as averaged over larger scales can be understood correctly only in respect to the fact that habitat gradients differ across landscapes. 5. In addition to being one of the first papers identifying the mechanism of partial brood loss as being primarily responsible for the habitat-specific differences in the production of young, this study further illustrates the need to identify small-scale mechanisms to correctly understand the large-scale patterns of reproductive performance in territorial species. The repercussions of the observed habitat effect for local population development are discussed.     

Driving reservoir models with oscillations: a solution to the extreme structural sensitivity of chaotic networks

A large body of experimental and theoretical work on neural coding suggests that the information stored in brain circuits is represented by time-varying patterns of neural activity. Reservoir computing, where the activity of a recurrently connected pool of neurons is read by one or more units that provide an output response, successfully exploits this type of neural activity. However, the question of system robustness to small structural perturbations, such as failing neurons and synapses, has been largely overlooked. This contrasts with well-studied dynamical perturbations that lead to divergent network activity in the presence of chaos, as is the case for many reservoir networks. Here, we distinguish between two types of structural network perturbations, namely local (e.g., individual synaptic or neuronal failure) and global (e.g., network-wide fluctuations). Surprisingly, we show that while global perturbations have a limited impact on the ability of reservoir models to perform various tasks, local perturbations can produce drastic effects. To address this limitation, we introduce a new architecture where the reservoir is driven by a layer of oscillators that generate stable and repeatable trajectories. This model outperforms previous implementations while being resistant to relatively large local and global perturbations. This finding has implications for the design of reservoir models that capture the capacity of brain circuits to perform cognitively and behaviorally relevant tasks while remaining robust to various forms of perturbations. Further, our work proposes a novel role for neuronal oscillations found in cortical circuits, where they may serve as a collection of inputs from which a network can robustly generate complex dynamics and implement rich computations.     

A targeted maximum likelihood estimator of a causal effect on a bounded continuous outcome

Targeted maximum likelihood estimation of a parameter of a data generating distribution, known to be an element of a semi-parametric model, involves constructing a parametric model through an initial density estimator with parameter ? representing an amount of fluctuation of the initial density estimator, where the score of this fluctuation model at ? = 0 equals the efficient influence curve/canonical gradient. The latter constraint can be satisfied by many parametric fluctuation models since it represents only a local constraint of its behavior at zero fluctuation. However, it is very important that the fluctuations stay within the semi-parametric model for the observed data distribution, even if the parameter can be defined on fluctuations that fall outside the assumed observed data model. In particular, in the context of sparse data, by which we mean situations where the Fisher information is low, a violation of this property can heavily affect the performance of the estimator. This paper presents a fluctuation approach that guarantees the fluctuated density estimator remains inside the bounds of the data model. We demonstrate this in the context of estimation of a causal effect of a binary treatment on a continuous outcome that is bounded. It results in a targeted maximum likelihood estimator that inherently respects known bounds, and consequently is more robust in sparse data situations than the targeted MLE using a naive fluctuation model. When an estimation procedure incorporates weights, observations having large weights relative to the rest heavily influence the point estimate and inflate the variance. Truncating these weights is a common approach to reducing the variance, but it can also introduce bias into the estimate. We present an alternative targeted maximum likelihood estimation (TMLE) approach that dampens the effect of these heavily weighted observations. As a substitution estimator, TMLE respects the global constraints of the observed data model. For example, when outcomes are binary, a fluctuation of an initial density estimate on the logit scale constrains predicted probabilities to be between 0 and 1. This inherent enforcement of bounds has been extended to continuous outcomes. Simulation study results indicate that this approach is on a par with, and many times superior to, fluctuating on the linear scale, and in particular is more robust when there is sparsity in the data.     

Network and graph analyses of folding free energy surfaces

Protein folding is governed by a complex free energy surface whose entropic contributions are relevant because of the large number of degrees of freedom involved. Such complexity, in particular the conformational heterogeneity of the denatured state, is hidden in projections onto one or two order parameters (e.g. fraction of native contacts and/or radius of gyration), which usually results in relatively smooth surfaces. Recent approaches borrowed from network and graph theory have yielded quantitative unprojected representations of the free energy surfaces of a beta-hairpin and a three-stranded beta-sheet peptide using equilibrium folding-unfolding molecular dynamics simulations. Interestingly, the network and graph analyses of these structured peptides have revealed a very heterogeneous denatured state ensemble. It includes high-enthalpy, high-entropy conformations with fluctuating non-native secondary structure, as well as low-enthalpy, low-entropy traps.     

Dyadic associations reveal clan size and social network structure in the fission–fusion society of spotted hyaenas

Estimating the size and dynamics of populations is of paramount importance in ecology. In species with uniquely marked individuals, capture–recapture methods can be used to establish population size and to explore associations between individuals. However, very few studies have used cameras traps to focus on group composition in social carnivores, despite being of particular interest in species characterised by “fission–fusion” formation of sub-groups. Here, we provide estimates of (a) population size, (b) density, (c) clan size, (d) association patterns and (e) social network structure in spotted hyaenas (Crocuta crocuta) based on images from camera traps deployed at waterholes on Ongava Game Reserve (northern Namibia). In a 15 week study period, we identified 32 individuals. Dyadic associations and the resulting social network showed that all but two hyaenas associated directly or indirectly with each other, indicating the presence of one clan of at least 30 individuals, resulting in a density of 8.1 hyaenas/100 km². We found a very high variability in the tendency of individuals to associate with others. This study confirms a highly dynamic fission–fusion society in spotted hyaenas. We argue that camera traps can provide relevant insights into large carnivore social network structure where associations between individuals are difficult to observe directly.     

Population dynamics of the whitefly,Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), in Java,Indonesia, with special reference to spatio-temporal changes in the quantity of food resources

Six monitoring plots were established in the northern part of West Java, Indonesia, to clarify the factors that influence population fluctuations of the whitefly,Bemisia tabaci. Yellow sticky traps were used to monitor adult populations. To examine the relationship between the population fluctuations and the quantity of food resources, the quantity of food resources ofB. tabaci (i.e. soybean and mung bean) was also investigated routinely in each subdistrict where the experimental plot was located. The maximum number of adults per trap in each sowing season showed a similar noticeable seasonal trend in all experimental plots. Climatic factors did not have a major role to play in population fluctuations. The number of adults per trap in each experimental plot tended to increase when the quantity of food resources in each subdistrict increased. The changes of the quantity of food resources seemed to influence the population fluctuations. It is suggested that the operation of regulatory processes in population density is influenced largely by both the distance between habitat patches and the amplitude of temporal fluctuations of the quantity of food resources. An explanation for why the time lag between fluctuations of the quantity of food resources and the number of individuals ofB. tabaci occurred is discussed. Based on their flight ability and intrinsic rate of natural increase,B. tabaci is considered not to be a serious pest in the environment where the host plants are grown discontinuously in time and space.     

Determining the efficacy of camera traps,live capture traps,and detection dogs for locating cryptic small mammal species

Metal box (e.g., Elliott, Sherman) traps and remote cameras are two of the most commonly employed methods presently used to survey terrestrial mammals. However, their relative efficacy at accurately detecting cryptic small mammals has not been adequately assessed. The present study therefore compared the effectiveness of metal box (Elliott) traps and vertically oriented, close range, white flash camera traps in detecting small mammals occurring in the Scenic Rim of eastern Australia. We also conducted a preliminary survey to determine effectiveness of a conservation detection dog (CDD) for identifying presence of a threatened carnivorous marsupial, Antechinus arktos, in present‐day and historical locations, using camera traps to corroborate detections. 200 Elliott traps and 20 white flash camera traps were set for four deployments per method, across a site where the target small mammals, including A. arktos, are known to occur. Camera traps produced higher detection probabilities than Elliott traps for all four species. Thus, vertically mounted white flash cameras were preferable for detecting the presence of cryptic small mammals in our survey. The CDD, which had been trained to detect A. arktos scat, indicated in total 31 times when deployed in the field survey area, with subsequent camera trap deployments specifically corroborating A. arktos presence at 100% (3) indication locations. Importantly, the dog indicated twice within Border Ranges National Park, where historical (1980s–1990s) specimen‐based records indicate the species was present, but extensive Elliott and camera trapping over the last 5–10 years have resulted in zero A. arktos captures. Camera traps subsequently corroborated A. arktos presence at these sites. This demonstrates that detection dogs can be a highly effective means of locating threatened, cryptic species, especially when traditional methods are unable to detect low‐density mammal populations.     

Aseasonality in the abundance and life history of an ecologically dominant freshwater crab in the Rift Valley, Kenya

1. Freshwater crabs appear to show at least two alternative life history patterns, which differ in the timing of seasonal reproduction. Reproduction occurs during low flow among temperate lotic species, but during high water levels among wetland species. Crab biomass is often very high and both strategies would lead to spatial and temporal pulses in density and biomass. The life history and reproductive strategy adopted by tropical lotic species is poorly known, however, despite their importance in community and ecosystem dynamics. 2. In this study, we determined annual patterns of life history, density and biomass of a lotic freshwater crab in a small headwater stream in the East African highlands where it maintains high biomass. This crab is an as yet undescribed species of Potamonautes, here referred to as the Chinga crab. 3. Crabs were sampled non‐destructively for 15 months using baited traps and benthic sampling with a Surber sampler. At the end of the study, an intensive hand search was carried out. Each method was biased towards different size classes of crabs and the efficiency of both long‐term methods varied according to water levels in the stream. The intensive search was more effective than benthic sampling, but failed to record the large individuals caught by baited traps. 4. Population density and biomass remained constantly high throughout the study period. Reproduction, as evidenced by the presence of ovigerous females and small free‐living juveniles, also showed no seasonality. As a consequence, the population size structure (size‐frequency distribution) of crabs remained constant throughout the year. 5. The Chinga crab illustrates a third life history pattern, with no clear breeding season, and this may be common among tropical species. This is probably a consequence of the non‐seasonal nature of its habitat: temperature varied little throughout the year and rainfall fluctuations were relatively small. This strategy allows the species to maintain high biomass without seasonal pulses and, perhaps, to dominate community and ecosystem processes.