Animal Population Spatial Analysis - The Elk of Bannf Nationa Park
Introduction
What is Spatial Ecology and Why It Matters
Spatial ecology examines how ecological processes are shaped by spatial patterns and environmental variation. It helps explain species distributions, movement behaviour, and ecosystem functions (Fletcher 2018). The field integrates both endogenous processes—such as dispersal, population growth, and behaviour—and exogenous factors like habitat structure and human disturbance (Ovaskainen et al. 2017; Massol et al. 2011). Together, these dynamics shape how species interact with their environment across spatial and temporal scales (Nathan et al. 2008).
Technological advances such as GPS telemetry, remote sensing, and spatial analysis tools (e.g., RStudio and QGIS) have allowed ecologists to collect and analyse high-resolution spatial data. These tools support a Lagrangian approach, allowing individual-based movement analysis at fine spatial and temporal scales (Nathan et al. 2008). As a result, ecologists can estimate home ranges, evaluate resource selection, identify behavioural responses to environmental stimuli, and model movement patterns over time with exceptional precision (Seidel et al. 2018).
Spatial ecology is essential for conservation management. It provides key insights into species’ space use and habitat needs, helps identify and protect movement corridors in fragmented landscapes, and supports adaptive responses to anthropogenic and climate-driven pressures. Through understanding the dynamics of habitat selection, home range variability, and movement behaviour, conservation decisions can be based on robust ecological evidence.
Context and Aims
Elk (Cervus elaphus), also known as wapiti in North America, are large-bodied, social ungulates (hoofed mammal) that are native to forested and mountainous regions of the Northern Hemisphere. In North America they are primarily found in the Rocky Mountains. In our study area, in and around Banff National Park, Alberta, Canada, Cervus elaphus serves as a keystone species influencing plan communities, predator-prey dynamics, and nutrient cycling (Hobbs 2006; Ripple and Larsen 2001).
Cervus elaphus, from here on referred to as “elk”, have strong seasonal patterns driven by resource availability, climate, and risk avoidance. In their mountainous habitats they usually migrate between lower-elevation winter ranges and higher-elevation summer ranges (Hebblewhite, Merrill, and McDermid 2008). Elk prefer open meadows for foraging and forested areas for refuge and for resting and rutting (Mark S. Boyce et al. 2003; Ciuti, Muhly, et al. 2012).
Elk exhibit crepuscular activity (active during dawn and dusk), but studies have shown that they easily shift their behavioural patterns to avoid areas of high human use and activity (Ciuti, Muhly, et al. 2012). In areas with active elk hunting, such as our study area, elk have been shown to change their use of space and movement behaviour and some populations have shown to avoid humans and have selection for wariness, especially among females (Thurfjell, Ciuti, and Boyce 2017a).
This study uses spatial ecology tools to assess movement data from 16 elk in and around Banff National Park, Alberta, Canada. This elk population is exposed to seasonal environmental change and anthropogenic pressure, especially from hunting in autumn. Understanding their spatial ecology under such pressures is critical for developing effective conservation strategies.
The study aims to analyse elk spatial behaviour using a combination of home range estimation, resource selection modelling, and movement behaviour analysis. The research applies multiple spatial methodologies—including Minimum Convex Polygon (MCP), Kernel Density Estimation (KDE), Autocorrelated KDE (AKDE), Resource Selection Functions (RSFs), Step Selection Functions (SSFs), and Hidden Markov Models (HMMs)—to examine how elk respond to seasonal variation, habitat structure, and anthropogenic influence.
The main research questions being explored in this study:
RQ1: Home Range Estimation – How do elk home range sizes vary across individuals and seasons, and how do different estimation methods (MCP, KDE, AKDE) influence the interpretation of spatial usage under hunting pressure?
RQ2: Resource Selection – How does elk (Cervus elaphus) resource selection vary across seasons, and are these patterns influenced by sex and age under hunting pressure?
RQ3: Movement Behaviour – How does elk movement behaviour vary across seasons and landscapes, and to what extent do step-based movement patterns and behavioural state transitions reflect responses to environmental and anthropogenic pressures?
Objectives
Estimate seasonal home range sizes using MCP, KDE, and AKDE, and evaluate inter-individual and seasonal variation
Model habitat selection using RSFs, considering terrain, vegetation, roads, and demographic variables
Characterise movement using SSFs and HMMs, exploring behavioural changes under hunting pressure
Integrate methods to inform conservation strategies for elk movement, habitat, and space-use models to inform conservation strategies for elk and other large herbivores
Methods
Home Range Estimation
Spatial Use vs Home Range:
Home range literature differentiates between space use and home range, both of which help to understand how animals interact with their environment:
Space Use:
- Describes where an animal spends its time, often visualised through utilisation distributions (UDs) or density maps. Spatial use is usually analysed over shorter time periods (weeks or days) and is used for assessing habitat use and behavioural responses to both endo- (dispersal, population growth, and behaviour) and exogenous factors (habitat and human disturbance).
Home Range:
- Refers to the area an animal uses to satisfy its “life-history” requirements (foraging, resting, breeding) over longer periods, such as seasons or a year (Burt 1943).
Estimation Methods:
- MCP: Encloses all points in the smallest convex polygon around all known locations (Mohr 1947). However, it is very sensitive to outliers, and does not account for physical boundaries, such as lakes, rivers, and inhabitable areas within the landscape, and can be ineffective at calculating home range estimations with small sample sizes (Noonan et al. 2019; Mukomberanwa et al. 2024). Regardless of these limitations, MCP was still used a baseline data set for comparison between the other methods.
- KDE: Uses density of locations to estimate a utilisation distribution, which is the probability of where an animal is to be found within the space based on the pattern of its GPS locations. It is useful for identifying core use areas (Worton 1989). assumes that the GPS locations are independent and identically distributed (IID), whereas the ecological reality is that the data is usually nearly always autocorrelated (C. H. Fleming et al. 2015).
It is best to think of autocorrelation as “momentum”. The animals don’t teleport from one location to the next. They move gradually, so their recent locations usually influence where they go next! The more clustered the locations are in space and time, the more similar they tend to be! (Silva et al. 2021)
- AKDE: Improves KDE by accounting for the autocorrelation in the data. This autocorrelation within KDE estimates is what causes most estimates to be biased and underestimate home ranges (Hansteen, Andreassen, and Ims 1997). It better represents true home ranges from irregularly sampled GPS data (C. H. Fleming et al. 2015; Silva et al. 2021).
AKDE was chosen over dBBMM due to elk data containing inconsistent fix intervals (~120 minutes) and anomalies, which limited dBBMM performance. Hansteen et al., (Hansteen, Andreassen, and Ims 1997) explains that with increasing time intervals the degree of autocorrelation will decrease as the sample size decreases.
Implementation
Telemetry data was cleaned, seasonally split (pre-hunting and hunting), and analysed by individuals. MCP, KDE, and AKDE home ranges were calculated using R packages adehabitatHR and ctmm, with contours at 50%, 75%, and 95% to represent core to total space use. AKDE, which accounts for autocorrelation and sampling frequency (Christen H. Fleming and Calabrese 2017), provided refined seasonal range estimates. This multi-method approach enabled comparison of spatial responses to hunting pressure across individuals.
You can explore the different methods of home range methodologies and their outputs in Figure 1