Animal Population Dynamics Research Articles

Habitat management decisions for conservation: a conceptual framework

The focus of this selection of papers is the linkage of habitat and population dynamics for the purpose of conservation. We thus provide a general framework for making conservation decisions, emphasizing how knowledge of habitat–population linkages fits into this framework. We begin by describing structured decision-making (SDM) as a general approach to making conservation decisions. SDM requires the development of the following elements: objectives, actions, model(s), monitoring, and decision algorithm. We then describe adaptive resource management (ARM), a specific type of SDM developed for recurrent decisions characterized by potentially resolvable uncertainty. Many different classes of actions can be used to influence animal population dynamics, and modification of habitat is one class of action that is frequently used. Habitat management requires models for predicting responses of the managed system to management actions, and these models are based on our knowledge of habitat–population linkages. Frequently, these models are decomposed into two submodels: one used to predict habitat changes expected to result from management actions and another used to predict population responses to habitat changes. This latter modeling focuses generally on the influence of habitat change on vital rates governing the dynamics of population state variables (variables such as population size or density that describe the status or health of a population). Specific recommendations depend on 1) the vital rates and state variable(s) being considered, 2) the relative spatial scales of animal movement and habitat measurement, and 3) the relative temporal scales of habitat change and vital rate estimation. Finally, we present an example of an ARM program for habitat management, highlighting the role of habitat-linked population modeling in this effort.

Integrating big data analytics in the study of animal population dynamics

Integrating big data analytics in the study of animal population dynamics

Negative binomial approach: A useful application for the study of Echinococcus granulosus

Cystic Echinococcosis is a parasitic disease caused by the larvae of Echinococcus granulosus. The transmission of E. granulosus is affected by environmental changes and anthropogenic factors, which are in turn influenced by changes in the spatial and population dynamics of animals. The deterministic model can be extended stochastically to address the low prevalence rate, which is often observed in small mammal host populations, and to account for complex processes that reflect the highly widespread disease reservoirs and non-random mixing, such as the heterogeneous contact patterns of susceptible hosts with infectious materials. In this study, a mathematical model based on a set of differential equations that define the continuous transition between different classes was used is not regulated by host. The findings indicate that each protoscolex has an equal chance of developing into a worm and creating a dispersed population. Empirical modeling can be used to represent the frequency distribution of the number of parasites in each host using the negative binomial distribution.

Modeling slough crayfish populations in response to hydrologic variability

Understanding and predicting animal population dynamics as a function of hydrologic variation is critical for the management of freshwater ecosystems. Crayfish are important fauna supported by the hydro-dynamic freshwater wetlands of the Everglades. We modeled the complex relationships between slough crayfish ( Procambarus fallax) population densities and hydrologic conditions using a spatially and temporally extensive 21-year dataset. We applied linear mixed–effect models, a classification and regression tree (CART), and random forest (RF) algorithms to develop predictions and eco-hydrologic interpretations. The RF model demonstrated the greatest predictive ability ( R2 = 0.56) followed by linear mixed–effect models ( R2 = 0.45) and the regression tree ( R2 = 0.29). Primary effects of hydrologic terms were similar among models, but the RF model identified important nonlinear and threshold relationships. Lower average depths (appr. 30–60 cm) over the year prior to the sample, in conjunction with relatively long periods of inundation, and more recent depths >30 cm, were associated with greater crayfish densities. The three methods revealed consistent understanding of crayfish eco-hydrologic relations and provide insight for natural resource management.

Do wolves control their own numbers? Understanding and updating the long debate

The population dynamics of animals involve a complex interplay between intrinsic and extrinsic factors. Intrinsic regulation, characterized as population self‐regulation, encompasses mechanisms that moderate growth rates before reaching maximum food‐dependent densities. Conversely, extrinsically regulated populations are constrained by environmental variables such as food availability, predation, and disease. What regulates wolf populations has been debated for decades, with most publications concluding that wolves are extrinsically regulated, despite evidence of intrinsic mechanisms. This paper summarizes one perspective from a debate at the 'Wolves Across Borders' conference in Stockholm, Sweden in May 2023. Since this paper is a summary of a public debate, the paper is neither a review nor research paper, rather a research history and a recommendation on how the long‐term disagreement might be resolved. Wolf population regulation is likely an interplay between both intrinsic and extrinsic factors which is best studied longitudinally by monitoring one population through time.

Low temperature induces a significant decrease in auditory sensitivity of Xenopus laevis

ABSTRACT Temperature is a critical factor in shaping the physiological and metabolic processes of animals, notably impacting their auditory systems. Particularly, ectotherms face heightened vulnerability to temperature fluctuations. To comprehend the impact of rapid temperature changes on the auditory sensitivity of ectotherms, we measured the auditory sensitivity of Xenopus laevis at 10°C, 20°C, and 30°C respectively, using the auditory brainstem response. Our results reveal a significant decrease in auditory sensitivity of X. laevis at 10°C, with auditory thresholds markedly higher than those observed at 20°C and 30°C. Conversely, as the test temperature increased from 20°C to 30°C, their hearing sensitivity did not decline but tended to become more sensitive. In conclusion, our results suggest that rapid temperature changes have a discernible impact on the hearing sensitivity of X. laevis, particularly at low temperatures. These rapid environmental temperature changes significantly impact the sensory capabilities and courtship behaviours of animals, thereby influencing their population dynamics. Hence, revealing the consequences of rapid temperature fluctuations on sensory sensitivity in ectotherms is crucial for understanding the repercussions of climate change on animal population dynamics. These insights have profound implications for both environmental management and animal conservation.

An agent architecture for expressive spatial knowledge and reasoning in land use modeling and simulations

This paper presents a new cognitive agent design approach integrating spatial knowledge representation and reasoning in agent-based modeling dedicated to land use simulations. A deep motivation for our agent-centric contribution is the ever-increasing development of spatially explicit agent simulation platforms. We build on this technological evolution and topology theory to endow the agent with human’s spatial representation and reasoning following a Belief–Desire–Intention architecture. A pilot implementation of the methodology with simulation experiments on a hunting model was carried out in GAMA platform to assess agent performances. Simulations display a consistent trend of animal population dynamics and also confirm a high model sensitivity to the integration of spatial knowledge and reasoning in agent-based models of human actor. These results demonstrate a successful implementation and the importance of spatial dimension in the expressive power and the validity of agent-based models. Future research efforts should therefore emphasize on designing human knowledge representation and incorporating learning abilities to improve models efficiency.

Resource diversity mitigates the effects of intraspecific competition in co-occurring cryptic nematode species

Intraspecific competition and resource diversity are considered major drivers of niche differentiation, which are expected to promote population niche expansion by driving individuals to feed on alternative resources and/or by enhancing individual diet specialization. Nevertheless, experimental studies on the interaction effects of both factors on animal behavior and population dynamics remain scant. Here, we investigate how resource diversity alters the impact of intraspecific competition on resource preference and fitness of three co-occurring cryptic species of the marine nematode complex Litoditis marina (Pm I, Pm III and Pm IV). For each cryptic species, two competition regimes (‘low nematode density’ and ‘high nematode density’) were established in microcosms with varying resource diversity (E. coli, low-, medium- and high-diversity food). Our results show differences in resource preference and population fitness depending on intraspecific competition and resource diversity, but the response also varied considerably between cryptic species. Pm III did not exhibit resource preference under low intraspecific competition, but preferred the two most diverse food sources under high intraspecific competition. Pm IV also showed preference for medium-diversity food under high competition, whereas no resource preference was observed in Pm I regardless of competition regimes and resource diversity. Nevertheless, all cryptic species exhibited enhanced adult population growth on a more diverse food source under stronger intraspecific competition. These results indicate that resource diversity can alleviate intraspecific competition and affect niche diversification, which may impact diversity maintenance in ecological communities.

Ecological traits predict population trends of urban birds in Europe

The population dynamics of urban animals has been so far remarkably understudied. At the same time, urban species’ population trends can provide important information on the consequences of environmental changes in cities. We modelled long-term population trends of 93 bird species breeding in urban areas in 16 European countries as a function of species’ traits, characterising variability in their urbanization and ecology. We found that: (i) earlier colonisers have more negative population trends than recent colonisers; (ii) more urbanized open habitat species had more positive population trends than less urbanized open habitat species; (iii) highly urbanized birds breeding above the ground had more negative trends than highly urbanized ground breeders. These patterns can be explained by several processes occurring in cities as well as outside city borders. Namely, (i) pre-industrial colonisers might struggle to persist in rapidly changing urban areas, limiting their foraging and breeding opportunities of the birds. (ii) Open habitats are under pressure of intensive agricultural exploitation in rural areas, which may negatively affect populations of less urbanized birds. In contrast, urban areas do not experience such pressure keeping the trends of urbanized open habitat species more positive. (iii) Differences in population trends between highly urbanized ground and above-ground breeders suggest that the latter may lose their breeding opportunities in modern buildings that do not provide suitable breeding sites. Our results indicate that even once successful, city dwellers may not keep pace with changes in urban areas, but these areas may also provide suitable habitats for biodiversity.

МОДЕЛЬНЫЙ АНАЛИЗ ДЕМОГРАФИЧЕСКИХ ПРОЦЕССОВ В ПОПУЛЯЦИЯХ ПУШНЫХ ОХОТНИЧЬИХ ЖИВОТНЫХ (НА ПРИМЕРЕ ЕВРЕЙСКОЙ АВТОНОМНОЙ ОБЛАСТИ)

Among biological resources, hunting animals, including fur-bearing species, take a special place. The study of such populations dynamics is a crucial stage in fur harvesting planning and organizing. This work aims to describe and analyze by mathematical modeling methods the dynamics of fur-bearing animal populations inhabiting the Jewish Autonomous region. We consider the populations whose newborn individuals reach maturity by the next breeding season, for example, squirrel, white hare, Manchurian hare, raccoon dog, and weasel. The study is based on the discrete-time model of population dynamics with a simple stage structure. To take into account density-dependent regulation of population growth in the model, birth or survival rates of the immature class are represented by exponential functions of the total population size. To estimate the model parameters, we propose the use of data corresponding to the total population size. The obtained point estimates, based on this approach, are demonstrated to be within the range of biologically meaningful parameter values and exhibit the population dynamics similar to those observed in nature. Specifically, according to the model estimates, squirrel and hare populations are characterized by unstable dynamics with sharp annual fluctuations. In general, the proposed approach for parameter estimation allows for analyzing and modeling the age composition of the animal population, as well as determining demographic parameters that characterize the animal population dynamics based on the total population size data.

Integrating human behavior into structured population models

Human behavior shapes modern ecosystems but is difficult to parse into parameters for ecological models. We used Bayesian models of human behavior, a stage-structured population model, and a novel mortality integration approach to ask how human decisions affect animal population dynamics and conservation outcomes in the context of recreational fishing. Walleye (Sander vitreus) are a broadcast-spawning freshwater fish with large, slow-maturing females and small, fast-maturing males. We observed that simpler and less restrictive fishing regulations outperformed more complex and stricter regulations at conserving equilibrium adult female abundance and overall population abundance while still facilitating large harvests. This outcome was possible because angler behavior within the least restrictive regulation concentrated harvest on juveniles and adult males. Our findings indicate that, counter to intuitive expectations, moderate regulations can acheive conservation objectives when we account for the interaction of regulatory policy, human behavior, and animal life history. We suggest that integrating models of human behavior with models of animal life history and population dynamics will provide essential insights for conservation in ecosystems increasingly shaped by human decisions.

Predicting human-wildlife interaction in urban environments through agent-based models

Synurbic species adapt to global urbanization by increasingly inhabiting urban environments, where social and ecological factors, such as anthropogenic food resources and habitat alterations, promote close human-wildlife interactions. Ineffective management of these interactions can result in conflicts, altered animal population dynamics, and increased public and private expenditures. This study presents the Barcelona wild boar (BCNWB)-prototype model, a spatially explicit, incremental agent-based simulation that captures interactions between citizens and wild boar (Sus scrofa) agents in fine-scale GIS-based scenarios in Barcelona. Developed using GAMA software, the model's results were analyzed with QGIS and R software. The model aims to simulate the dynamics of the social-ecological system underlying the urban ecosystem use by synurbic wild boars and their interactions with humans in the (peri)urban area of Barcelona, Spain.The BCNWB-prototype model demonstrated high accuracy in predicting the magnitude and location of wild boar movements (multiple-resolution-goodness-of-fit = 0.73) compared to reported wild boar presences in Barcelona. The model also forecasted 115 attack events and 1,442 direct feeding events during a one-year simulation period, as compared to the actual 150 attacks and 1,858 feeding events reported annually. The model’s strong performance highlights its potential as a predictive tool for identifying priority areas for human-wild boar interactions and conflicts. Additionally, the model could be employed to assess the cost-effectiveness of management strategies and evaluate the spread, transmission risks, and public health implications of pathogens carried by wild boars.

Age-specific impacts of vegetation functional traits on gastrointestinal nematode parasite burdens in a large herbivore.

Gastrointestinal nematode (GIN) parasites play an important role in the ecological dynamics of many animal populations. Recent studies suggest that fine-scale spatial variation in GIN infection dynamics is important in wildlife systems, but the environmental drivers underlying this variation remain poorly understood. We used data from over two decades of GIN parasite egg counts, host space use, and spatial vegetation data from a long-term study of Soay sheep on St Kilda to test how spatial autocorrelation and vegetation in an individual's home range predict parasite burden across three age groups. We developed a novel approach to quantify the plant functional traits present in a home range to describe the quality of vegetation present. Effects of vegetation and space varied between age classes. In immature lambs, strongyle parasite faecal egg counts (FEC) were spatially structured, being highest in the north and south of our study area. Independent of host body weight and spatial autocorrelation, plant functional traits predicted parasite egg counts. Higher egg counts were associated with more digestible and preferred plant functional traits, suggesting the association could be driven by host density and habitat preference. In contrast, we found no evidence that parasite FEC were related to plant functional traits in the host home range in yearlings or adult sheep. Adult FEC were spatially structured, with highest burdens in the north-east of our study area, while yearling FEC showed no evidence of spatial structuring. Parasite burdens in immature individuals appear more readily influenced by fine-scale spatial variation in the environment, highlighting the importance of such heterogeneity for our understanding of wildlife epidemiology and health. Our findings support the importance of fine-scale environmental variation for wildlife disease ecology and provides new evidence that such effects may vary across demographic groups within a population.

Effects of temperature on azamethiphos sensitivity profile of Caligus rogercresseyi

It is well known that the biology of Caligus rogercresseyi is strongly affected by environmental conditions such as temperature. However, little is known if these variables can affect antiparasitic sensitivity. In this context, the aim of the study was to determine how temperature and light can induce changes in the parasite sensitivity profile to azamethiphos. Temperatures of 9, 12, 15, and 17 °C and two light conditions were evaluated through sensitivity evaluation in vitro bioassays. Parasites were exposed to an azamethiphos concentration gradient of 0, 3, 10, 30, 100, and 300 ppb. A range of temperature between 12 °C and 15 °C did not significantly change the sensitivity profile of the parasite. Moreover, light conditions did not induce significant changes in the sensitivity profile either. However, the temperature of 9 °C induced higher effective concentrations (EC50) than the rest of the temperatures, but also lower affectation and mortality of the parasite. This evidence suggested that sensitivity to azamethiphos decreases with temperature, regardless of the light conditions. These results are considered relevant since strong variations of environmental conditions (like temperature) among seasons and geographical areas could impact salmon–parasite interactions, but also the effectiveness of the treatments applied in the salmon industry. Even more, in a climate change context, for which temperature is considered one of the main variables, it is expected that important changes occur in the biology, metabolism, and population dynamics of parasites, fish, and marine animals, being these changes a matter of concern in the future sustainability of aquaculture.

Integrated analysis shows how the effects of extreme flooding events propagate through fish communities to impact amphibians.

Research Highlight: Davis, C. L., Walls, S. C., Barichivich, W. J., Brown, M. E., & Miller, D. A. (2022). Disentangling direct and indirect effects of extreme events on coastal wetland communities. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.13874. Catastrophic events such as floods, hurricanes, winter storms, droughts and wildfires increasingly touch our lives either directly or indirectly. These events draw our attention to the seriousness of changes in climate not only to human well-being but also to the integrity of ecological systems upon which we depend. Understanding the impacts of extreme events on ecological systems requires the ability to characterize the cascading effects of environmental changes on the environments in which organisms live and the altered biological interactions produced. This scientific ambition represents no small challenge for the study of animal communities, which are typically difficult to census as well as dynamic in time and space. Davis et al. (2022) in a recent study in the Journal of Animal Ecology examined the amphibian and fish communities found in depressional coastal wetlands to better understand how they respond to major rainfall and flooding events. Data from the U.S. Geological Survey's Amphibian Research and Monitoring Initiative provided an 8-year record of observations as well as environmental measurements. For this study, the authors integrated techniques for assessing the dynamics of animal populations with a Bayesian implementation of structural equation modelling. Using their integrated methodological approach permitted the authors to reveal the direct and indirect effects of extreme weather events on co-occurring amphibian and fish communities while accounting for observational uncertainty and temporal variation in population-level processes. Their findings indicate that the most prominent effects of flooding on the amphibian community were caused by changes in the fish community that led to increased predation and resource competition. In their conclusions, the authors emphasize the importance of understanding networks of abiotic and biotic effects if we are to predict and mitigate the influence of extreme weather events.

What's hot and why?

What's hot and why?

Time-series forecasting offers novel quantitative measure to assess loud sound event in an urban park with restored prairie

Soundscape ecology and ecoacoustics study the spatiotemporal dynamics of a soundscape and how the dynamics reflect and influence ecological processes in the environment. Soundscape analysis methods employ acoustic recording units (ARUs) that collect acoustic data in study areas over time. Analyzing these data includes computation of several acoustic diversity indices developed to quantify species abundance, richness, or habitat condition through digital audio processing and algorithm adaptations for within-group populations. However, the success of specific indices is often dependent on habitat type and biota richness present and analyzing these data can be challenging due to temporal pseudo-replication. Time-series analytical methods address the inherent problems of temporal autocorrelation for soundscape analyses challenges. Animal population dynamics fluctuate in a variety of ways due to changes in habitat or natural patterns of a landscape and chronic noise exposure, with soundscape phenology patterns evident in terrestrial and aquatic environments. Historical phenological soundscape patterns have been used to predict expected soundscape patterns in long-term studies but limited work has explored how forecasting can quantify changes in short-term studies. We evaluate how forecasting from an acoustic index can be used to quantify change in an acoustic community response to a loud, acute noise. We found that the acoustic community of a Midwestern restored prairie had decreased acoustic community activity after a loud sound event (LSE), a Civil War Reenactment, mainly driven by observed changes in the bird community and quantified using two methods: an automated acoustic index and species richness. Time-series forecasting maybe considered an underutilized tool in analyzing acoustic data whose experimental design can be flawed with temporal autocorrelation. Forecasting using auto ARIMA with acoustic indices could benefit decision makers who consider ecological questions at different time scales.

Gut Microbiota is Associated with Aging-Related Processes of a Small Mammal Species under High-Density Crowding Stress.

Humans and animals frequently encounter high-density crowding stress, which may accelerate their aging processes; however, the roles of gut microbiota in the regulation of aging-related processes under high-density crowding stress remain unclear. In the present study, it is found that high housing density remarkably increases the stress hormone (corticosterone), accelerates aging-related processes as indicated by telomere length (in brain and liver cells) and DNA damage or inflammation (as revealed by tumor necrosis factor-α and interleukin-10levels), and reduces the lifespan of Brandt's vole (Lasiopodomys brandtii). Fecal microbiota transplantation from donor voles of habitats with different housing densities induces similar changes in aging-related processes in recipient voles. The elimination of high housing density or butyric acid administration delays the appearance of aging-related markers in the brain and liver cells of voles housed at high-density. This study suggests that gut microorganisms may play a significant role in regulating the density-dependent aging-related processes and subsequent population dynamics of animals, and can be used as potential targets for alleviating stress-related aging in humans exposed to high-density crowding stress.

Sequential analysis of δ15 N in guard hair suggests late gestation is the most critical period for muskox calf recruitment.

Analysis of stable isotopes in tissue and excreta may provide information about animal diets and their nutritional state. As body condition may have a major influence on reproduction, linking stable isotope values to animal demographic rates may help unravel the drivers behind animal population dynamics. We performed sequential analysis of δ15 N values in guard hair from 21 muskoxen (Ovibos moschatus) from Zackenberg in high arctic Greenland. We were able to reconstruct the dietary history for the population over a 5-year period with contrasting environmental conditions. We examined the linkage between guard hair δ15 N values in 12 three-month periods and muskox calf recruitment to detect critical periods for muskox reproduction. Finally, we conducted similar analyses of the correlation between environmental conditions (snow depth and air temperature) and calf recruitment. δ15 N values exhibited a clear seasonal pattern with high levels in summer and low levels in winter. However, large inter-annual variation was found in winter values, suggesting varying levels of catabolism depending on snow conditions. In particular δ15 N values during January-March were linked to muskox recruitment rates, with higher values coinciding with lower calf recruitment. δ15 N values were a better predictor of muskox recruitment rates than environmental conditions. Although environmental conditions may ultimately determine the dietary δ15 N signal in muskox guard hairs, muskox calf recruitment was more strongly correlated with δ15 N values than ambient snow and temperature. The period January-March, corresponding to late gestation, appears particularly critical for muskox reproduction.

Winter mortality of a passerine bird increases following hotter summers and during winters with higher maximum temperatures.

Climate change may influence animal population dynamics through reproduction and mortality. However, attributing changes in mortality to specific climate variables is challenging because the exact time of death is usually unknown in the wild. Here, we investigated climate effects on adult mortality in Australian superb fairy-wrens (Malurus cyaneus). Over a 27-year period, mortality outside the breeding season nearly doubled. This nonbreeding season mortality increased with lower minimum (night-time) and higher maximum (day-time) winter temperatures and with higher summer heat wave intensity. Fine-scale analysis showed that higher mortality in a given week was associated with higher maxima 2 weeks prior and lower minima in the current fortnight, indicating costs of temperature drops. Increases in summer heat waves and in winter maximum temperatures collectively explained 62.6% of the increase in mortality over the study period. Our results suggest that warming climate in both summer and winter can adversely affect survival, with potentially substantial population consequences.