Animal Population Dynamics Research Articles

Rainfall trends and variation in the Maasai Mara ecosystem and their implications for animal population and biodiversity dynamics.

Rainfall exerts a controlling influence on the availability and quality of vegetation and surface water for herbivores in African terrestrial ecosystems. We analyse temporal trends and variation in rainfall in the Maasai Mara ecosystem of East Africa and infer their implications for animal population and biodiversity dynamics. The data originated from 15 rain gauges in the Mara region (1965–2015) and one station in Narok Town (1913–2015), in Kenya’s Narok County. This is the first comprehensive and most detailed analysis of changes in rainfall in the region of its kind. Our results do not support the current predictions of the International Panel of Climate Change (IPCC) of very likely increases of rainfall over parts of Eastern Africa. The dry season rainfall component increased during 1935–2015 but annual rainfall decreased during 1962–2015 in Narok Town. Monthly rainfall was more stable and higher in the Mara than in Narok Town, likely because the Mara lies closer to the high-precipitation areas along the shores of Lake Victoria. Predominantly deterministic and persistent inter-annual cycles and extremely stable seasonal rainfall oscillations characterize rainfall in the Mara and Narok regions. The frequency of severe droughts increased and floods intensified in the Mara but droughts became less frequent and less severe in Narok Town. The timings of extreme droughts and floods coincided with significant periodicity in rainfall oscillations, implicating strong influences of global atmospheric and oceanic circulation patterns on regional rainfall variability. These changing rainfall patterns have implications for animal population dynamics. The increase in dry season rainfall during 1935–2015 possibly counterbalanced the impacts of resource scarcity generated by the declining annual rainfall during 1965–2015 in Narok Town. However, the increasing rainfall extremes in the Mara can be expected to create conditions conducive to outbreaks of infectious animal diseases and reduced vegetation quality for herbivores, particularly when droughts and floods persist over multiple years. The more extreme wet season rainfall may also alter herbivore space use, including migration patterns.

Why are demographic Allee effects so rarely seen in social animals?

Allee effects in group-living species are common, but little is known about the way in which Allee effects at the group-level scale up to influence population dynamics. Most notably, it remains unclear whether component Allee effects within groups (where some component of fitness in small groups decreases with decreasing group size) will translate into a population-level demographic Allee effect (where per capita fitness in small populations decreases with decreasing overall population size). The African wild dog (Lycaon pictus) is an obligate cooperative breeder that lives in packs and has a multitude of group-level component Allee effects. With the African wild dog as a case study, we use models to determine the effect that group structure has on the population dynamics of social animals and, specifically, whether Allee effects operating at the group level lead to a demographic Allee effect at the population level. We developed a suite of models to analyse the population dynamics of group-living species, as well as comparable "packless" models lacking group structure. By comparing these models, we can identify how Allee effects within groups influence population-level dynamics. Our results show that group structure buffers populations against a demographic Allee effect, because mechanisms affecting birth and mortality are more strongly influenced by group size than population size. We find that interactions between groups are vital in determining the relationship between density dependence within groups and density dependence at the population level. As sufficiently large groups provide protection against positive density dependence, even at low overall population sizes, our results have conservation implications for group-living species, as they suggest group size is a necessary population feature to consider in efforts to manage population size. Furthermore, we provide novel insight regarding the role that dispersal and pack size variation play in the buffering nature of social structure in groups subject to Allee effects.

Bounding reproductive rates in state‐space models for animal population dynamics

AbstractTime‐series models applied in the study of animal population dynamics commonly assume linearity on the log‐scale, leading to log‐normally distributed rates of increase. While this is often computationally convenient, in particular when performing statistical inference in the presence of observation error, it may lead to unrealistic predictions for animals with a limited reproduction. We introduce a model that includes an explicit bound on the reproductive rate of an individual, and apply this to a population time series of ungulates in Kruger National Park, South Africa. Due to observational error, the year‐to‐year increases in animal counts occasionally exceeded the maximal reproductive rate of the animals. In such cases, the traditional unbounded model showed a tendency of overfitting data, leading to unrealistic predictions of the underlying population increase. An observed increase above the maximal reproductive rate also provides empirical confirmation that observation error exists. The model with an explicit bound was able to utilize this in order to separate observational error from population process noise, which the traditional unbounded model was unable to do. We conclude that enforcing a strict upper bound on the reproductive rate of an animal population model may lead to more realistic statistical inference than commonly applied log‐linear models when an explicit bound on reproductive rate is known. We further conclude that introducing a bound on reproduction can greatly assist in separating observational error and population process noise for slow life histories, or more generally, when the rate of sampling is high compared to reproductive rates.

Bayesian spatiotemporal dynamic models for regional dynamics of avian populations

The spatiotemporal dynamics of multiple animal populations may exhibit the hierarchical dynamic patterns including regional common trends or spatial synchrony and local variability. Environmental drivers such as climatic variability, operating on large spatial scales, have been proposed to be a driver of the spatial synchrony of avian and mammalian populations (i.e., the Moran effect). On the other hand, demographic responses to heterogeneous, local environments may result in substantial local population variability (i.e., variance across multiple populations). This study used the Bayesian hierarchical spatiotemporal dynamic model to determine the spatiotemporal dynamic patterns of 27 eastern wild turkey (Meleagris gallopavo silvestris) populations scattered across Mississippi, USA, from 1994 to 2005. The regional effects of seasonal climate and relative amount of forest in habitats were also evaluated to test the Moran effect. Twenty seven wild turkey populations had a spatial synchrony with the strength and spatial scale similar to those of other avian populations in North America. Warming spring or spring-autumn climate appeared to reduce wild turkey relative abundance; however, winter climate did not influence the dynamics of wild turkey populations in Mississippi. Average proportion of forest affected the average relative abundance of wild turkeys in a nonlinear manner, with its positive effects switching to a lessened constant effect beyond the threshold of 60% forest cover. However, regional climatic variability was unlikely to synchronize wild turkey populations in Mississippi. This study proposed a hypothesis concerning regional habitat quality degradation, which may cause regional population declines and synchronize the dynamics of animal populations.

‘Mathematical exercise’ on a solvable stochastic control model for animal migration

Animal migration is a mass biological phenomenon indispensable for comprehension and assessment of food-webs. So far, theoretical models to describe decision-making processes inherent in the animal migration have not been well established, which is the motivation of this research. It is natural to formulate the animal migration based on a stochastic control theory, which can describe system dynamics and its optimization in stochastic environment. To address this issue, a conceptual stochastic control model for the decision-making processes in animal migration is introduced and mathematically analysed. Its novelty is mathematical simplicity and the new theoretical, stochastic control viewpoint. Stochastic differential equations govern the animal population dynamics with gradual and radical migrations from the current habitat toward the next one. The population decides the occurrences, magnitudes, and timings of the migrations, so that a heuristic performance index is maximised. I derive a variational inequality that governs the maximised performance index and is exactly solvable. Its free boundaries govern the gradual and radical migrations. Despite the model simplicity, the exact solution is consistent with the empirical observation results of fish migration, implying its potential applicability to animal migration. The present model can be used for assessing fish migration. References S. Bauer and B. J. Hoye. Migratory animals couple biodiversity and ecosystem functioning worldwide. Science, 344, 2014. Article No. 1242552. N. E. Leonaerd. Multi-agent system dynamics: Bifurcation and behavior of animal groups. Annual Reviews in Control, 38(2):171–183, 2014. A. M. Oberman. Convergent difference schemes for degenerate elliptic and parabolic equations: Hamilton–jacobi equations and free boundary problems. SIAM Journal on Numerical Analysis, 44(2):879–895, 2006. B. \T1\O ksendal. Stochastic Differential Equations. Springer Berlin Heidelberg, 2003. B. \T1\O ksendal and A. Sulem. Applied Stochastic Control of Jump Diffusions. Springer Berlin Heidelberg, 2007. Y. Yaegashi, H. Yoshioka, K. Unami, and M. Fujihara. An optimal management strategy for stochastic population dynamics of released \(plecoglossus\) \(altivelis\) in rivers. International Journal of Modeling, Simulation, and Scientific Computing, 8(2), 207. Article No. 1750039. H. Yoshioka, T. Shirai, and D. Tagami. Viscosity solutions of a mathematical model for upstream migration of potamodromous fish. In Proceedings of 12th SDEWES Conference, October 4-8, 2017, Dubrovnik, Croatia, 2017. In press.

Habitat degradation and trout stocking can reinforce the impact of flash floods on headwater specialist Alpine bullhead Cottus poecilopus - A case study from the Carpathian Mountains

In freshwater streams, flooding is a typical source of natural disturbance that plays a key role in the dynamics of animal populations and communities. However, habitat degradation and fish stocking might increase the severity of its impact. We tested the effects of a flash flood on the abundance of three size classes of headwater dwelling Alpine bullhead, Cottus poecilopus, in the streams of the Carpathian Mountains in the Czech Republic, that are stocked with hatchery-reared brown trout, Salmo trutta. We showed that the overall abundance of Alpine bullhead was highest at the sites with the least degraded habitat (i.e., natural habitat) and we caught almost no Alpine bullhead at the sites with the most degraded habitat. The flash flood had a strong negative effect on the abundance of the largest individuals of Alpine bullhead. Abundance of small and medium size Alpine bullhead was negatively affected by the abundance of adult stocked brown trout before as well as after the flash flood. However, negative effect of adult brown trout abundance on abundance of large Alpine bullhead was not significant before the flash flood, and it became significant after the flash flood. This could indicate an accumulation of negative impacts of trout stocking and flash flood on this size class. Overall, our results suggest that stocking of hatchery trout and habitat degradation can reinforce the impact of flash floods on the population of Alpine bullhead in the streams of the Carpathian Mountains.

Predator arrival elicits differential dispersal, change in age structure and reproductive performance in a prey population

Predators are an important ecological and evolutionary force shaping prey population dynamics. Ecologists have extensively assessed the lethal effects of invasive predators on prey populations. However, the role of non-lethal effects, such as physiological stress or behavioural responses like dispersal, has been comparatively overlooked and their potential population effects remain obscure. Over the last 23 years, we developed a mark-recapture program for the Audouin’s gull and an intensive carnivore monitoring program to assess how the appearance and invasion of the study site by carnivores affects population dynamics. We evaluate changes in turnover of discrete breeding patches within the colony, age structure and breeding performance. Once carnivores entered the colony, the number of occupied patches increased, indicating a higher patch turnover. Breeders responded by moving to areas less accessible to carnivores. More importantly, the presence of carnivores caused differential (and density-independent) breeding dispersal: experienced, better-performing breeders were more likely to leave the colony than younger breeders. This differential dispersal modified the age structure and reduced the reproductive performance of the population. Our results confirm the importance experience in the study of populations. The role of differential dispersal for animal population dynamics might be more important than previously thought, especially under scenarios of global change.

Survival and cause‐specific mortality of elk Cervus canadensis in Kentucky, USA

Wildlife management relies heavily on high quality field data to analyze and predictively model animal population dynamics, evaluate population viability, and ultimately inform management decisions. During 2011–2015, we conducted a study to investigate survival and cause‐specific mortality of male and female elk Cervus canadensis in a harvested population in southeastern Kentucky, USA, which was established via reintroduction a decade prior. Preliminary male elk survival data led state wildlife managers to modify hunting zone boundaries and establish several areas with limited hunter access mid‐way (2013) through our study to attempt to improve male survival and prevent overharvest. Thus, we also investigated the effectiveness of limiting hunter access for improving male elk survival in one of these regulated areas. We captured and radio‐monitored 237 (F91:M146) elk, of which 155 (65.4%) died by the conclusion of our study; harvest‐related deaths were the leading causes of mortality for both sexes (85.2%; 132/155). Estimated mean annual female and male survival rates were 0.67 (95% CI = 0.53–0.81) and 0.57 (95% CI = 0.45–0.71), respectively. Results from Cox proportional hazards regression models indicated that females < 2 years‐of‐age (HR≤2yoa = 3.84, p = 0.004) and males ≥ 5 years‐of‐age (HR5yoa = 1.83, p = 0.01; HR≥6yoa = 2.26, p = 0.004) had significantly higher hazards of dying compared to other sex‐specific age classes. Support also existed for variation in female survival by herd. The establishment of areas that limited hunter access did not affect male elk survival, as estimates were similar pre and post‐implementation. Given the probability of mortality from harvest was consistently much higher for both sexes relative to other causes, we suggest that reducing overall harvest permits likely would be the most effective management action for improving elk survival and reducing the potential of overharvest of this population.

Understanding animal social structure: exponential random graph models in animal behaviour research

The social environment is a pervasive influence on the ecological and evolutionary dynamics of animal populations. Recently, social network analysis has provided an increasingly powerful and diverse toolset to enable animal behaviour researchers to quantify the social environment of animals and the impact that it has on ecological and evolutionary processes. However, there is considerable scope for improving these methods further. We outline an approach specifically designed to model the formation of network links, exponential random graph models (ERGMs), which have great potential for modelling animal social structure. ERGMs are generative models that treat network topology as a response variable. This makes them ideal for answering questions related directly to how and why social associations or interactions occur, from the modelling of population level transmission, through within-group behavioural dynamics to social evolutionary processes. We discuss how ERGMs have been used to study animal behaviour previously, and how recent developments in the ERGM framework can increase the scope of their use further. We also highlight the strengths and weaknesses of this approach relative to more conventional methods, and provide some guidance on the situations and research areas in which they can be used appropriately. ERGMs have the potential to be an important part of an animal behaviour researcher's toolkit and fully integrating them into the field should enhance our ability to understand what shapes animal social interactions, and identify the underlying processes that lead to the social structure of animal populations.

Lianas reduce community‐level canopy tree reproduction in a Panamanian forest

AbstractLianas are a key component of tropical forests, where they compete intensely with trees, reducing tree recruitment, growth and survival. One of the most important potential outcomes of liana competition is the reduction of tree reproduction; however, no previous study has experimentally determined the effects of lianas on tree reproduction beyond a single tree species.We used a large‐scale liana removal experiment to quantify the effect of lianas on community‐level canopy and understorey tree and palm reproduction. In 2011, we removed lianas from eight 6,400‐m2plots (eight plots served as controls) and surveyed understorey tree reproduction in 2012, canopy tree and palm reproduction in 2013, and a second census of all plants in 2016.We found that lianas significantly reduced canopy tree community flowering and fruiting after liana removal. Two years after liana removal, the number of canopy trees with fruits was 173% higher, fruiting individuals had 50% more of their canopy covered by fruits and the number of tree species with fruits was 169% higher than in control plots where lianas were present. Five years after liana removal, the number of canopy trees with fruits was 150% higher, fruiting individuals had 31% more of their canopy covered by fruits and the number of tree species with fruits was 109% higher than in unmanipulated control plots.Liana removal had only a slight positive effect on palms and on understorey tree flower and fruit production, even though understorey light levels had increased 20% following liana cutting.Synthesis. Our findings provide the first experimental demonstration that competition from lianas significantly reduces community‐level canopy tree reproduction. Reduced reproduction increases canopy tree seed and dispersal limitations, and may interfere with deterministic mechanisms thought to maintain tropical canopy tree species diversity, as well as reduce food availability to many animal species. Because lianas are increasing in abundance in many neotropical forests, the effects of lianas on tree reproduction will likely increase, and if the effects of lianas on tree reproduction vary with tree species identity, lianas ultimately could have a destabilizing effect on both tree and animal population dynamics.

A hierarchical model for estimating the spatial distribution and abundance of animals detected by continuous-time recorders.

MotivationSeveral spatial capture-recapture (SCR) models have been developed to estimate animal abundance by analyzing the detections of individuals in a spatial array of traps. Most of these models do not use the actual dates and times of detection, even though this information is readily available when using continuous-time recorders, such as microphones or motion-activated cameras. Instead most SCR models either partition the period of trap operation into a set of subjectively chosen discrete intervals and ignore multiple detections of the same individual within each interval, or they simply use the frequency of detections during the period of trap operation and ignore the observed times of detection. Both practices make inefficient use of potentially important information in the data.Model and data analysisWe developed a hierarchical SCR model to estimate the spatial distribution and abundance of animals detected with continuous-time recorders. Our model includes two kinds of point processes: a spatial process to specify the distribution of latent activity centers of individuals within the region of sampling and a temporal process to specify temporal patterns in the detections of individuals. We illustrated this SCR model by analyzing spatial and temporal patterns evident in the camera-trap detections of tigers living in and around the Nagarahole Tiger Reserve in India. We also conducted a simulation study to examine the performance of our model when analyzing data sets of greater complexity than the tiger data.BenefitsOur approach provides three important benefits: First, it exploits all of the information in SCR data obtained using continuous-time recorders. Second, it is sufficiently versatile to allow the effects of both space use and behavior of animals to be specified as functions of covariates that vary over space and time. Third, it allows both the spatial distribution and abundance of individuals to be estimated, effectively providing a species distribution model, even in cases where spatial covariates of abundance are unknown or unavailable. We illustrated these benefits in the analysis of our data, which allowed us to quantify differences between nocturnal and diurnal activities of tigers and to estimate their spatial distribution and abundance across the study area. Our continuous-time SCR model allows an analyst to specify many of the ecological processes thought to be involved in the distribution, movement, and behavior of animals detected in a spatial trapping array of continuous-time recorders. We plan to extend this model to estimate the population dynamics of animals detected during multiple years of SCR surveys.

A scoping review of published research on the population dynamics and control practices of companion animals

Companion animal population dynamics is a global, diverse issue that can affect society in multiple ways, including impacts on public health, environmental destruction and shelter management. The purpose of this scoping review was to use structured and transparent methods to identify all published research investigating companion animal population dynamics and/or control practices. A comprehensive search strategy was implemented using five online databases (i.e., PubMed, CAB Direct, Agricola, PsycINFO, and Scopus) and resulted in the identification of 7810 unique citations. These citations were screened for relevance by two independent reviewers. Of these, 1410 were initially deemed relevant. Full articles were procured and 931 articles (456 primary research and 475 reviews) were confirmed relevant and important data extracted. Most of the included articles were published in the United States (395, 42.4%) and 218 articles (23.4%) were published between 2012 and 2015. The majority of the articles investigated or discussed control practices (758, 81.4%), more specifically different reproduction control practices (597, 64.1%), or euthanasia (345, 37.1%) methods The quantity of research in these areas offers future opportunities for systematic review and meta-analysis.

The impact of invasive knotweed species (Reynoutria spp.) on the environment: review and research perspectives

I conducted an exhaustive literature review on Japanese knotweeds s.l. (including Reynoutria japonica, R. sachalinensis and R. ×bohemica), especially on the effects of these invasive plants on biodiversity and ecological processes or the chemical and physical characteristics of invaded habitats. A total of 44 studies have been published, the earliest in 2005, in peer-reviewed journals. Most studies were conducted in Europe, the others in the USA. Invasive knotweeds have major negative impacts on native plants, while the abundant litter produced and the deep rhizome system alter soil chemistry to the benefit of the invaders. However, the effects of knotweeds on other groups of species vary, with a combination of losers (soil bacteria, most arthropods and gastropods, some frogs and birds) and winners (most fungi, detritivorous arthropods, aquatic shredders, a few birds). This literature review highlights significant knowledge gaps of the effects of knotweeds on biodiversity (vertebrates) and ecological processes (ecohydrology). To what extent knotweed invasions have an impact on the population dynamics of native plants and animals on a regional to national scale remains to be verified. Although there is some evidence that knotweed invasions have negative effects on the environment, the research to date remains modest and a more extensive effort is needed to better define the environmental impacts of these plant invaders.

Quantifying micro-environmental variation in tropical rainforest understory at landscape scale by combining airborne LiDAR scanning and a sensor network

We combined aerial LiDAR and ground sensors to map the spatial variation in micro-environmental variables of the tropical forest understory. We show that these metrics depend on forest type and proximity to canopy gaps. Our study has implications for the study of natural forest regeneration. Light impacts seedling dynamics and animals, either directly or through their effect on air temperature and relative humidity. However, the micro-environment of tropical forest understories is heterogeneous. We explored whether aerial laser scanning (LiDAR) can describe short-scale micro-environmental variables. We also studied the determinants of their spatial and intra-annual variation. We used a small-footprint LiDAR coverage combined with data obtained from 47 environmental sensors monitoring continuously understory light, moisture and temperature during 1 year over the area. We developed and tested two models relating micro-environmental conditions to LiDAR metrics. We found that a volume-based model predicts empirical light fluxes better than a model based on the proportion of the LiDAR signal reaching the ground. Understory field sensors measured an average daily light flux between 2.9 and 4.7% of full sunlight. Relative seasonal variation was comparable in the understory and in clearings. In canopy gaps, light flux was 4.3 times higher, maximal temperature 15% higher and minimal relative humidity 25% lower than in the forest understory. We found consistent micro-environmental differences among forest types. LiDAR coverage improves the fine-scale description of micro-environmental variables of tropical forest understories. This opens avenues for modelling the distribution and dynamics of animal and plant populations.

Long-Form Science

[ILLUSTRATION OMITTED] Using an extended text in an upper-level science course is not a revolutionary idea. For example, many advanced biology teachers have been teaching Rebecca Skloot's The Immortal Life of Henrietta Lacks (2010), a book examining ethical issues in medical research. Indeed, a diverse selection of science nonfiction texts is suitable for a high school course, ranging from Michael Pollan's Omnivore's Dilemma (2007) to Deborah Blum's The Poisoner's Handbook (2010). Introducing a novel or nonfiction book into the curriculum can reward both teacher and student, offering deep immersion into science content, but may seem daunting to many teachers, especially with little training in literacy instruction. Nevertheless, the Next Generation Science Standards (NGSS Lead States 2013) and Common Core State Standards (NGAC and CCSSO 2010) emphasize teaching of informational texts in content-based courses (see box, p. 31). This article offers strategies for teaching extended texts in the science classroom. Part 1: Before reading Choosing a text An extended text must lend itself to course goals and inspire relevant discussion (Calmer and Straits 2014). Consider, as an example, the book Zoo Story by Thomas French (2010). The author draws on six years of work experience at the Lowry Park Zoo in Tampa to address zoos' responsibilities to animals, employees, and patrons. Describing the lives of specific animals, French blends his scientific understanding of animal behavior, ecosystem and population dynamics, and biodiversity with an empathic portrayal of lives and relationships, echoing unifying themes appropriate for a course on general biology or zoology. [ILLUSTRATION OMITTED] French unravels the depth and complexity of a modern zoo as a journalist, not a scientist. He approaches scientific subject matter with a style of writing that is accessible to a general reader, useful for students preparing to become scientifically literate citizens. Fisher and Frey (2012) define worthy texts as those that allow readers to reflect on themselves and their actions; invite them in the worlds of others; understand the biological, social, or physical world; or solve problems that are timely and important. Zoo Story fits these criteria by allowing readers to reflect on the various dimensions of zoos, including their history as institutions, their intentions to conserve biological diversity, and the ethical and social problems they pose. Each student should have access to a copy of an extended text (Calmer and Straits 2014), which can be expensive. My school district opted to buy a classroom set of Zoo Story books for my zoology course instead of a traditional textbook. Some students bought their own copies. Used copies can be relatively inexpensive, and reading assignments can be staggered so the class can get by on fewer copies, rather than the entire class reading simultaneously. Introducing the text I introduce the text at the start of the course, months before it is assigned, in part to address misconceptions about zoology. Many students expect a zoo-ology course to focus on zoo animals. I explain that the course name is derived from the Greek zoia (animals) and encompasses the entire animal kingdom. We won't address charismatic megafauna until later in the course, looking first at the major invertebrate phyla, as is traditional for zoology curricula. Introducing Zoo Story early on offers the promise of in-depth discussion of elephants, tigers, and chimpanzees later on. When it's time to assign the text, I reintroduce it by showing ecologist Carl Safina's 2015 TED Talk (see On the web). His provocative and controversial central question, What are animals thinking and feeling? leads to the driving question central to Zoo Story: What are humans' responsibilities to protect animal species? After viewing the TED video, students discuss their own interactions with domestic animals, native wild fauna, and captive animals. …

Effects of predation risk on behavior, hormone levels, and reproductive success of plateau pikas

AbstractPredation is a strong selective force that affects animal population dynamics either through direct killing or predation risk effects. Although recent empirical research has shown that the non‐consumptive effect of predator risk on prey dynamics can be as large (or even larger) as direct effects, little is known about the strength of predation risk effects in wild populations or the physiological mechanisms that mediate them. Here, we test both the predator‐sensitive food hypothesis and predation‐stress hypothesis in a single system by investigating activity budgets, stress/sex hormone levels, and demography of plateau pikas (Ochotona curzoniae) and their predators in Haibei Alpine Meadow Ecosystem Research Station of the Chinese Academy of Science. During the study period (2009 and 2010), plateau pikas experienced various predation pressures due to many predators being poisoned in 2010. In the year of high predator numbers, pikas spent more time on vigilant duty and less time foraging and they also showed higher plasma corticosterone levels and lower plasma estradiol and testosterone levels. Reproductive success and male with developed testes also reduced in the year of higher predation risk. In general, our results support both the predator‐sensitive food and predation‐stress hypothesis. Predator‐induced risk affects prey reproduction by changes in feeding patterns and stress physiology.

Cultural turnover among Galápagos sperm whales.

While populations may wax and wane, it is rare for an entire population to be replaced by a completely different set of individuals. We document the large-scale relocation of cultural groups of sperm whale off the Galápagos Islands, in which two sympatric vocal clans were entirely replaced by two different ones. Between 1985 and 1999, whales from two clans (called Regular and Plus-One) defined by cultural dialects in coda vocalizations were repeatedly photo-identified off Galápagos. Their occurrence in the area declined through the 1990s; by 2000, none remained. We reassessed Galápagos sperm whales in 2013–2014, identifying 463 new females. However, re-sighting rates were low, with no matches with the Galápagos 1985–1999 population, suggesting an eastward shift to coastal areas. Their vocal repertoires matched those of two other clans (called Short and Four-Plus) found across the Pacific but previously rare or absent around Galápagos. The mechanisms behind this cultural turnover may include large-scale environmental regime shifts favouring clan-specific foraging strategies, and a response to heavy whaling in the region involving redistribution of surviving whales into high-quality habitats. The fall and rise of sperm whale cultures off Galápagos reflect the structuring of the Pacific population into large, enduring clans with dynamic ranges. Long-lasting clan membership illustrates how culture can be bound up in the structure and dynamics of animal populations and so how tracking cultural traits can reveal large-scale population shifts.

Forecasting climate change impacts on plant populations over large spatial extents

AbstractPlant population models are powerful tools for predicting climate change impacts in one location, but are difficult to apply at landscape scales. We overcome this limitation by taking advantage of two recent advances: remotely sensed, species‐specific estimates of plant cover and statistical models developed for spatiotemporal dynamics of animal populations. Using computationally efficient model reparameterizations, we fit a spatiotemporal population model to a 28‐year time series of sagebrush (Artemisia spp.) percent cover over a 2.5 × 5 km landscape in southwestern Wyoming while formally accounting for spatial autocorrelation. We include interannual variation in precipitation and temperature as covariates in the model to investigate how climate affects the cover of sagebrush. We then use the model to forecast the future abundance of sagebrush at the landscape scale under projected climate change, generating spatially explicit estimates of sagebrush population trajectories that have, until now, been impossible to produce at this scale. Our broadscale and long‐term predictions are rooted in small‐scale and short‐term population dynamics and provide an alternative to predictions offered by species distribution models that do not include population dynamics. Our approach, which combines several existing techniques in a novel way, demonstrates the use of remote sensing data to model population responses to environmental change that play out at spatial scales far greater than the traditional field study plot.

Patterns of population dynamics of Eurasian beaver (Castor fiber L.) after reintroduction into nature reserves of the European part of Russia

This paper presents the results of analysis of the population dynamics of Eurasian beaver after its reintroduction into the Lapland, Darvinsky, Central-Forest, Prioksko-Terrasnyi, Oksky, and Khopersky natural reserves that are located in European Russia in the northern, southern and central parts of the beaver range. The paper analyzes the effectiveness of a discrete time model that includes a feedback between animals and their food resources for the quantitative description of the population dynamics in the optimal, suboptimal, and pessimal habitats. It is shown that the beaver population dynamics demonstrates four grows types (patterns): the eruptive type (Lapland Reserve); single-stage type with a quasi-periodic oscillation (Prioksko-Terrasnyi Reserve), multi-stage type with quasi-periodic oscillations (Darvinsky, Central-Forest, and Khopersky reserves) and the logistic curve of population growth with periodic oscillations around it (Oksky Reserve). The biotic and abiotic factors that determine these types of animal population dynamics are discussed.

Life on the beach for a sand crab (Emerita rathbunae) (Decapoda, Hippidae): parasite-induced mortality of females in populations of the Pacific sand crab caused by Microphallus nicolli (Microphallidae)

Parasites, by definition, can affect mortality of their host, making parasitism an important biotic determinant of animal population dynamics and community structure. Reduction in the number of larger, reproductive age females in populations of the Pacific sand crab, Emerita rathbunae (Decapoda, Hippidae), was observed in studies of the helminth community of this host. The aim of this study was to determine if high abundance of the metacercaria of the trematode, Microphallus nicolli (Microphallidae), causes mortality in this host. Females of E. rathbunae were collected from four sandy beaches in Guerrero State, Mexico, and helminths were collected from each crab. An analysis of variance (Anova) was applied to these data in order to identify differences in abundance between sizes of crabs, and an analysis of covariance (Ancova) was applied to identify differences in the abundance of metacercariae between locations. Parasite-related mortality was inferred by a decrease in abundance in older hosts. Linear and polynomial regressions of mean abundance of helminths (log x+1 transformed data) vs. cephalothorax length of crabs were significant for the four populations of E. rathbunae, indicating increased mortality of older, more heavily infected female crabs and resultant removal from the population. Encapsulation and melanization of cysts by crabs was observed, indicating that an immune response by crabs also killed a portion of the cysts from subsequent exposures. Mortality of hosts through behavioral modification favoring transmission of highly infected crabs was suggested as the driving force behind this process.