Assessing behaviour states of a forest carnivore in a road-dominated landscape using Hidden Markov Models

Seasonal movement behavior of domestic goats in response to environmental variability and time of day using Hidden Markov Models

BACKGROUND

Current research on livestock movement ecology focuses on quantifying the factors that trigger alterations in movement behavior and understanding hidden mechanisms. Modern tracking technologies and robust statistical analysis models deliver new opportunities for investigating how individual animals cope with the joint effect of biotic and abiotic factors at different time scales.

METHODS

We applied multivariate Hidden Markov Models (HMMs) to characterize the fine-scale movement behavior (30-second intervals) of GPS-tracked domestic Zhongwei goats (Capra aegagrus hircus) for 124 days and analyzed the combined influence of biotic and abiotic factors and specific time of day on their seasonal movement behavioral transition in a predator-free, semi-arid mountain grassland in China.

RESULTS

We classified the behaviors of goats into two states: foraging (low step length, varied turning angle) and travelling (long step lengths, small turning angles). The terrain slopes had the most impact on their movement behavioral transition in the full year, spring, autumn, and winter. However, in the summer with hotter temperatures, the specific time of day explains their movement behavior most. Forage resources indicated by the Normalized Difference Vegetation Index (NDVI), and terrain ruggedness measured by the Vector Ruggedness Measure (VRM), had less impact on their behavior transitions compared to terrain slope and specific time of day. Elevation and solar radiation could not explain their movement behavior in different seasons, nor could NDVI in winter or VRM in spring and autumn. Across different seasons, the probability of foraging behavior increased with the later times of day, steeper terrain slopes, and higher NDVI, while it decreased with increasing VRM. The impact of NDVI on the probability of foraging behavior was largest during the early onset of vegetation growth in spring, and lowest in winter coinciding with a lower availability of food resources. The movement speed was lower, and the daily foraging percentage was higher in spring and winter due to lower food resources and shorter daylight hours. In contrast, movement speed was higher, and the daily foraging percentage was lower in summer and autumn with more food resources and longer daylight hours. The percentage of time allocated to foraging increases hourly from 9:00 am to 8:00 pm across various seasons.

CONCLUSIONS

HMMs were found to be useful for disentangling the movement behavior of goats. Our approach provides new insights into the seasonal and daily behavioral strategies of goats. Results demonstrate that in the mountain region, terrain slopes and specific times of the day more effectively trigger domestic goat behavioral transition from one state to the next compared with biotic factors, represented herein by NDVI, across different seasons. The early onset of vegetation growth and a shorter period of available high-quality forage in spring, significantly influenced goat behavioral transitions. Overall, these results are important for designing appropriate grazing management strategies that satisfy the ecological and socioeconomic demands of semi-arid grassland ecosystems.

Examination of head versus body heading may help clarify the extent to which animal movement pathways are structured by environmental cues?

Understanding the processes that determine how animals allocate time to space is a major challenge, although it is acknowledged that summed animal movement pathways over time must define space-time use. The critical question is then, what processes structure these pathways? Following the idea that turns within pathways might be based on environmentally determined decisions, we equipped Arabian oryx with head- and body-mounted tags to determine how they orientated their heads - which we posit is indicative of them assessing the environment - in relation to their movement paths, to investigate the role of environment scanning in path tortuosity. After simulating predators to verify that oryx look directly at objects of interest, we recorded that, during routine movement, > 60% of all turns in the animals' paths, before being executed, were preceded by a change in head heading that was not immediately mirrored by the body heading: The path turn angle (as indicated by the body heading) correlated with a prior change in head heading (with head heading being mirrored by subsequent turns in the path) twenty-one times more than when path turns occurred due to the animals adopting a body heading that went in the opposite direction to the change in head heading. Although we could not determine what the objects of interest were, and therefore the proposed reasons for turning, we suggest that this reflects the use of cephalic senses to detect advantageous environmental features (e.g. food) or to detect detrimental features (e.g. predators). The results of our pilot study suggest how turns might emerge in animal pathways and we propose that examination of points of inflection in highly resolved animal paths could represent decisions in landscapes and their examination could enhance our understanding of how animal pathways are structured.

Behavioral-dependent recursive movements and implications for resource selection

Within home ranges, animals repeatedly visit certain areas. Recursive movement patterns are widespread throughout the animal kingdom, but are rarely considered when developing resource selection models. We examined how behavioral state-dependent recursive movements influenced reource selection of eastern wild turkey (Meleagris gallopavo silvestris) broods as they aged from day 1 to 28. Because broods become more plastic in behaviors once they begin roosting off the ground, we separated data into broods that were ground roosting (1-13 days) and tree roosting (14-28 days). We used Hidden Markov Models to identify 2 behavioral states (restricted and mobile). We extracted state-specific recursive movements based on states and specific step lengths, which we integrated into a step selection analysis to evaluate resource selection. We found that in a restricted state, ground roosting broods spent less time in areas of mixed pine-hardwoods and more time in areas with greater vegetation density. Tree roosting broods revisited areas closer to shrub/scrub landcover types, and areas with greater vegetation density. Tree roosting broods also spent less time near mixed pine-hardwoods, while spending more time in areas with greater vegetation density. We found that in a mobile state, ground roosting broods revisited areas closer to secondary roads and mixed pine-hardwoods, but farther from hardwoods. Tree roosting broods revisited areas farther from secondary roads and with greater vegetation density. Tree roosting broods also spent more time in areas closer to pine. Resource selection varied depending on behavioral state and recursive movements. However, revisitation and residence time impacted selection in both ground and tree roosting broods. Our findings highlight the need to consider how behaviors can influence movement decisions and ultimately resource selection.

Movement and behavioral states of common carp (Cyprinus carpio) in response to a behavioral deterrent in a navigational lock

BACKGROUND

Freshwater ecosystems are some of the most affected by biological invasions due, in part, to the introduction of invasive carp worldwide. Where carp have become established, management programs often seek to limit further range expansion into new areas by reducing their movement through interconnected rivers and waterways. Lock and dams are important locations for non-physical deterrents, such as carbon dioxide (CO₂), to reduce unwanted fish passage without disrupting human use. The purpose of this study was to evaluate the behavioral responses of common carp (Cyprinus carpio) to non-physical deterrents within a navigation structure on the Fox River, Wisconsin. Acoustic telemetry combined with hidden Markov models (HMMs) was used to analyze variation in carp responses to treatments. Outcomes may inform CO₂ effectiveness at preventing invasive carp movement through movement pinch-points.

METHODS

Carbon dioxide (CO₂) was recently registered as a pesticide in the United States for use as a deterrent to invasive carp movement. As a part of a multi-component study to test a large-scale CO₂ delivery system within a navigation lock, we characterized the influence of elevated CO₂ and forced water circulation in the lock chamber on carp movements and behavior. Through time-to-event analyses, we described the responses of acoustic-tagged carp to experimental treatments including (1) CO₂ injection in water with forced water circulation, (2) forced water circulation without CO₂ and (3) no forced water circulation or CO₂. We then used hidden Markov models (HMMs) to define fine-scale carp movement and evaluate the relationships between carp behavioral states and CO₂ concentration, forced water circulation, and temperature.

RESULTS

Forced water circulation with and without CO₂ injection were effective at expelling carp from the lock chamber relative to null treatments where no stimulus was applied. A portion of carp exposed to forced water circulation with CO₂ transitioned from an exploratory to an encamped behavioral state with shorter step-lengths and a unimodal distribution in turning angles, resulting in some carp remaining in the lock chamber. Whereas carp exposed to forced water circulation only remained primarily in an exploratory behavioral state, resulting in all carp exiting the lock chamber.

CONCLUSION

Our findings illustrate the potential of forced water circulation, alone, as a non-physical deterrent and the efficacy of CO₂ injection with forced water circulation in expelling carp from a navigation lock. Results demonstrate how acoustic telemetry and HMMs in an experimental context can describe fish behavior and inform management strategies.

Ecological Solutions for Linear Infrastructure Networks: The key to green infrastructure development

Collapse