Extraordinary Sex Ratios: Cultural Effects on Ecological Consequences

We model sex-structured population dynamics to analyze pairwise competition between groups differing both genetically and culturally. A sex-ratio allele is expressed in the heterogametic sex only, so that assumptions of Fisher's analysis do not apply. Sex-ratio evolution drives cultural evolution of a group-associated trait governing mortality in the homogametic sex. The two-sex dynamics under resource limitation induces a strong Allee effect that depends on both sex ratio and cultural trait values. We describe the resulting threshold, separating extinction from positive growth, as a function of female and male densities. When initial conditions avoid extinction due to the Allee effect, different sex ratios cannot coexist; in our model, greater female allocation always invades and excludes a lesser allocation. But the culturally transmitted trait interacts with the sex ratio to determine the ecological consequences of successful invasion. The invading female allocation may permit population persistence at self-regulated equilibrium. For this case, the resident culture may be excluded, or may coexist with the invader culture. That is, a single sex-ratio allele in females and a cultural dimorphism in male mortality can persist; a low-mortality resident trait is maintained by father-to-son cultural transmission. Otherwise, the successfully invading female allocation excludes the resident allele and culture, and then drives the population to extinction via a shortage of males. Finally, we show that the results obtained under homogeneous mixing hold, with caveats, in a spatially explicit model with local mating and diffusive dispersal in both sexes.Comment: final version, reflecting changes in response to referees' comment

Scavenging of an Elk, Cervus elaphus, Carcass by Multiple Cougars, Puma concolor, in Southeastern Alberta

We report the confirmed or suspected scavenging by six different Cougars, Puma concolor, on an Elk (Cervus elaphus) carcass, from January to April 2009, near Cypress Hills Interprovincial Park in southeastern Alberta, Canada. Visitations by Cougars were captured by a camera trap focused on the carcass; we were able to tentatively identify 6 individual Cougars by the presence of radio-collars, ear sizes and tail characteristics. Our photos are the first published event of >2 Cougars feeding on the same carcass

Visual Marking of Ground Nests Might Attract Corvids

For ground-nesting birds such as waterfowl, estimating nest survival is a crucial step in assessing population dynamics, and marking nests facilitates continuous monitoring. A conventional method for marking ground nests is to use an inconspicuous rod at the nest bowl and a wooden lathe 10 m away. Nests are visually marked to allow for greater efficiency when revisiting nests and to facilitate subsequent nest searching sessions. Anecdotal evidence suggests that common ravens (Corvus corax) and American crows (C. brachyrhynchos) might learn to recognize these nest markers, resulting in artificially inflated rates of nest predation. In 2017 in central Alberta, Canada, we compared fates of nests marked with the conventional lathe-rod combination versus only a rod. We also tested the prevalence of corvid predation of marked nests in areas with and without high observations of corvid activity, using data from a study of dabbling duck (Anas spp.) nest survival. Our results suggest that marking nests with a lathe can increase predation by corvids and that nests marked with a rod only were more likely to hatch. Evaluation and use of alternate nest-marking methods would be beneficial for future studies of ground-nesting birds in areas where corvids are common. Our work highlights the importance of re-evaluating the efficacy of well-established field methods

Integrated Step Selection Analysis: Bridgingthe Gap Between Resource Selection and Animal Movement

A resource selection function is a model of the likelihood that an available spatial unit will be used by an animal, given its resource value. But how do we appropriately define availability? Step selection analysis deals with this problem at the scale of the observed positional data, by matching each ‘used step’ (connecting two consecutive observed positions of the animal) with a set of ‘available steps’ randomly sampled from a distribution of observed steps or their characteristics. Here we present a simple extension to this approach, termed integrated step selection analysis (iSSA), which relaxes the implicit assumption that observed movement attributes (i.e. velocities and their temporal autocorrelations) are independent of resource selection. Instead, iSSA relies on simultaneously estimating movement and resource selection parameters, thus allowing simple likelihood‐based inference of resource selection within a mechanistic movement model. We provide theoretical underpinning of iSSA, as well as practical guidelines to its implementation. Using computer simulations, we evaluate the inferential and predictive capacity of iSSA compared to currently used methods. Our work demonstrates the utility of iSSA as a general, flexible and user‐friendly approach for both evaluating a variety of ecological hypotheses, and predicting future ecological patterns

Prey Behavior, Age-Dependent Vulnerability, and Predation Rates

Variation in the temporal pattern of vulnerability can provide important insights into predator-prey relationships and the evolution of antipredator behavior. We illustrate these points with a system that has coyotes (Canis latrans) as a predator and two species of congeneric deer (Odocoileus spp.) as prey. The deer employ different antipredator tactics (aggressive defense vs. flight) that result in contrasting patterns of age-dependent vulnerability in their probability of being captured when encountered by coyotes.We use longterm survival data and a simple mathematical model to show that (1) species differences in age-dependent vulnerability are reflected in seasonal predation rates and (2) seasonal variation in prey vulnerability and predator hunt activity, which can be associated with the availability of alternative prey, interact to shape seasonal and annual predation rates for each prey species. Shifting hunt activity from summer to winter, or vice versa, alleviated annual mortality on one species and focused it on the other. Our results indicate that seasonal variation in prey vulnerability and hunt activity interact to influence the impact that a predator has on any particular type of prey. Furthermore, these results indicate that seasonal variation in predation pressure is an important selection pressure shaping prey defenses

Quantifying tropical wetlands using field surveys, spatial statistics and remote sensing

Tropical wetlands support high biodiversity and ecological services, but in most areas they suffer from a paucity of baseline data to support management. We demonstrate how modern technology can be used to develop ecological baseline data including, landuse/landcover, water depth, water quality, lake-level fluctuation, and normalized difference vegetation index (NDVI). For the first time we quantified and mapped these metrics for the Paya Indah Wetlands, Malaysia using the new high-spatial-resolution World View 2 imagery. Landuse/landcover classifications were validated by field visits and visual interpretation of the imagery. NDVI was extracted based on red and near infra-red 2 bands. Topo to Raster method was used for interpolation of water depths. Annual mean of a water-quality index and annual water-level fluctuation of lakes were interpolated across lakes using the inverse-distance weighting method. Qualitative and quantitative accuracy assessment of classification (75 % overall accuracy, user’s accuracies ranged from 60 % to 90 % and producer’s accuracy ranged from 60 % to 97 %) was promising and clearly illustrated that World View 2 imagery can yield fast and reasonably precise identification of ecosystem characteristics for ecological baselines

Response of the Agile Antechinus to Habitat Edge, Configuration and Condition in Fragmented Forest

Habitat fragmentation and degradation seriously threaten native animal communities. We studied the response of a small marsupial, the agile antechinus Antechinus agilis, to several environmental variables in anthropogenically fragmented Eucalyptus forest in south-east Australia. Agile antechinus were captured more in microhabitats dominated by woody debris than in other microhabitats. Relative abundances of both sexes were positively correlated with fragment core area. Male and female mass-size residuals were smaller in larger fragments. A health status indicator, haemoglobin-haematocrit residuals (HHR), did not vary as a function of any environmental variable in females, but male HHR indicated better health where sites' microhabitats were dominated by shrubs, woody debris and trees other than Eucalyptus. Females were trapped less often in edge than interior fragment habitat and their physiological stress level, indicated by the neutrophil/lymphocyte ratio in peripheral blood, was higher where fragments had a greater proportion of edge habitat. The latter trend was potentially due to lymphopoenia resulting from stress hormone-mediated leukocyte trafficking. Using multiple indicators of population condition and health status facilitates a comprehensive examination of the effects of anthropogenic disturbances, such as habitat fragmentation and degradation, on native vertebrates. Male agile antechinus' health responded negatively to habitat degradation, whilst females responded negatively to the proportion of edge habitat. The health and condition indicators used could be employed to identify conservation strategies that would make habitat fragments less stressful for this or similar native, small mammals

Humans Strengthen Bottom-Up Effects and Weaken Trophic Cascades in a Terrestrial Food Web

Ongoing debate about whether food webs are primarily regulated by predators or by primary plant productivity, cast as top-down and bottom-up effects, respectively, may becoming superfluous. Given that most of the world\u27s ecosystems are human dominated we broadened this dichotomy by considering human effects in a terrestrial food-web. We studied a multiple human-use landscape in southwest Alberta, Canada, as opposed to protected areas where previous terrestrial food-web studies have been conducted. We used structural equation models (SEMs) to assess the strength and direction of relationships between the density and distribution of: (1) humans, measured using a density index; (2) wolves (Canis lupus), elk (Cervus elpahus) and domestic cattle (Bos taurus), measured using resource selection functions, and; (3) forage quality, quantity and utilization (measured at vegetation sampling plots). Relationships were evaluated by taking advantage of temporal and spatial variation in human density, including day versus night, and two landscapes with the highest and lowest human density in the study area. Here we show that forage-mediated effects of humans had primacy over predator-mediated effects in the food web. In our parsimonious SEM, occurrence of humans was most correlated with occurrence of forage (beta = 0.637, p \u3c 0.0001). Elk and cattle distribution were correlated with forage (elk day: beta = 0.400, p \u3c 0.0001; elk night: beta = 0.369, p \u3c 0.0001; cattle day: beta = 0.403, p \u3c 0.0001; cattle, night: beta = 0.436, p \u3c 0.0001), and the distribution of elk or cattle and wolves were positively correlated during daytime (elk: beta = 0.293, p \u3c 0.0001, cattle: beta = 0.303, p \u3c 0.0001) and night-time (elk: beta = 0.460, p \u3c 0.0001, cattle: beta = 0.482, p \u3c 0.0001). Our results contrast with research conducted in protected areas that suggested human effects in the food web are primarily predator-mediated. Instead, human influence on vegetation may strengthen bottom-up predominance and weaken top-down trophic cascades in ecosystems. We suggest that human influences on ecosystems may usurp top-down and bottom-up effects