Concepts and Synthesis |
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Corresponding author: Leonna Szangolies ( szangolies@uni-potsdam.de ) Academic editor: Orr Spiegel
© 2025 Leonna Szangolies, Florian Jeltsch, Lewis G. Halsey, Cara A. Gallagher.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Szangolies L, Jeltsch F, Halsey LG, Gallagher CA (2025) From metabolism to coexistence: Understanding animal movement and community dynamics through energy. Individual-based Ecology 1: e151741. https://doi.org/10.3897/ibe.1.151741
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To counteract ongoing biodiversity loss due to global change, we need a deeper understanding of when and how species coexist. Recent work has begun to uncover mechanistic links between species coexistence and the movement of individual animals, revealing how individual behaviour can shape community dynamics. This movement behaviour is both motivated by and constrains an animal’s energy state, which in turn drives organism fitness and species interactions, for example by minimizing energy costs or maximizing energy intake. Advancing our understanding of individual energetic mechanisms can therefore reveal key drivers of coexistence. Here, we propose a conceptual framework linking animal energetics, movement behaviour and coexistence to explore how energy fluxes drive movement, mediate species interactions and shape community dynamics, extending former theories that address subsets of these relationships. Energetics is an important process influencing whether, how, where and when animals move, and underpins both equalizing (e.g., similar energy balances among species) and stabilizing (e.g., energy costs that limit large populations) mechanisms of coexistence. By synthesizing insights from community ecology, movement ecology and ecophysiology, we highlight how the integration of these fields reveals a fundamental set of interconnected mechanisms shaping species coexistence. We advocate for this mechanistic framework to improve our understanding of diversity dynamics and predictions of the impacts of environmental change on coexistence and biodiversity. We call for the development of interdisciplinary methods to test predictions evolving in this area and provide examples of how this framework can be applied to advance understanding across varied ecological systems.
Animal movement energetics, biodiversity conservation, community theory, energy dynamics, equalizing and stabilizing mechanisms, individual-based ecology
Understanding when and how species coexist is one of the great challenges in ecology (
Other concepts seek to explain species coexistence by the physiology and metabolic rates of individuals. For example, the metabolic theory of ecology (MTE,
Empirical findings indeed suggest that individual energetics can act as stabilizing or equalizing mechanisms for coexistence. For instance, differences in energy-related foraging strategies between bumblebees (Bombus spp.) and honeybees (Apis mellifera) lead to resource partitioning and reduced interspecific competition, supporting stable coexistence (
Energetics encompasses both the energy available in the landscape and an individual’s energy demands and reserves. Optimal foraging theories have long been used to predict how animals move to maximize their energy intake (
In this article, we aim to describe the mechanistic triangle of interactions among animal energetics, movement behaviour and species coexistence (Fig.
We present a framework that positions individual energetics as a mechanistic basis for species interactions and coexistence, and energy budgets as the central currency driving movement decisions, from routine foraging to long-distance relocation (Fig.
| Energy balance: The relationship between energy intake and energy expenditure ( |
| Energy expenditure: The total amount of energy used by an individual over a given period, such as a day ( |
| Energy budget: The total amount of energy acquired by an individual and then allocated across various biological processes, including maintenance and survival, growth, reproduction, and movement ( |
| Biodiversity: The variety of life across all levels of biological organization, including diversity within species (e.g., phenotypic variation), between species, and across ecosystems ( |
| Coexistence: The pattern in which different species occur in the same place while maintaining stable populations over time ( |
| Co-occurrence: The presence of multiple species at the same location, which may occur randomly, but can lead to coexistence under certain conditions ( |
| Coexistence mechanisms: Processes that enable competing species to coexist. Modern coexistence theory proposes two mechanisms: Equalizing mechanisms, which reduce fitness differences, and stabilizing mechanisms, which increase intraspecific competition relative to interspecific competition ( |
| Community assembly: Processes that determine the identity and relative abundance of species which coexist in an environment ( |
| Community composition or community structure: The relative frequencies and identities of co-occurring species. |
| Community dynamics: Changes in community composition or structure over time. |
| Metacommunity: Concept describing a larger-scale regional species pool that is a set of communities, and is maintained through different mechanisms, for example, dispersal ( |
| Movement ecology paradigm: Conceptual framework in movement ecology which focuses on how internal state, motion capacity, and navigation capacity of individuals are influenced by external factors to produce emergent movement paths ( |
| Movement behaviour: Emergent dynamics of spatial relocation of individuals that can be evolved and species-specific or plastic in response to environmental conditions. |
Conceptual framework linking energy budget theory with the movement ecology framework at the level of the individual animal, and integrating concepts from metacommunity theory, community assembly and coexistence theory at the community level. Movement (in light teal) and energetics (in dark teal) scale up to the community level (in purple) through resource and process links affecting the environment (R-P-generated external factors), as well as through direct links between energy budgets, metacommunity processes and coexistence mechanisms. Square boxes depict processes, rounded shapes represent patterns, and arrows indicate links of processes and patterns. This framework is adapted and extended from
As animals move through their habitats, they acquire energy through foraging, which is ingested, digested and stored. Simultaneously, they expend energy on life processes, collectively termed “field metabolic rate” or daily “energy expenditure” (
Whether movement responses arise from short-term behavioural plasticity or from evolved reaction norms, the internal energetic state acts as a key integrator linking environmental conditions to movement effort. For example, individuals may behaviourally suppress activity in response to acute energy stress (e.g.,
Animals must balance their energy investment among movement, maintenance, growth and reproduction (
At the population level, individual movement scales up to species-level mobility, shaping how individuals of different species interact with each other and their environment. These interactions are central to “metacommunity” and community-level processes (Fig.
These filters are themselves modulated by energetics. For example, reaching a new habitat patch depends not just on distance, but on the animal’s ability to allocate energy to travel without compromising survival. Once there, environmental conditions, such as temperature, can constrain metabolic rates and foraging efficiency. Biotic interactions, including competition and predation, are themselves also energy-mediated: the ability to outcompete others or withstand aggression depends on energy intake, storage and use.
Within this biotic filter, coexistence theory identifies two key mechanisms: “stabilizing mechanisms”, which reduce niche overlap, and “equalizing mechanisms”, which minimize fitness differences (
To illustrate the interactions, trade-offs and feedbacks within this framework, consider an animal foraging to meet its energy needs. If local food sources are insufficient, energy balance declines prompting movement to new areas. This relocation incurs energy costs and must be weighed against the probability of finding richer patches. As energy stores are depleted, the animal’s ability to reach distant patches is constrained (dispersal limitation). Even when a new patch is reached, survival still depends on abiotic suitability (e.g., temperature; environmental filtering) and on biotic interactions. If co-occurring individuals use different resources (niche partitioning) or if they can achieve similar energetic outcomes and maintain comparable fitness levels (fitness similarity), coexistence is possible. These interactions, in turn, alter future energy access for all individuals, completing a feedback loop. Upon death, the animal’s stored energy becomes available to others via scavenging or decomposition, further linking energy flows across trophic levels.
By integrating energetics, movement and coexistence within a single framework, we offer a mechanistic lens to understand how individual-level processes scale up to shape community dynamics. In the sections that follow, we examine each of these links in detail (1. Coexistence and Movement, 2. Coexistence and Energetics, 3. Movement and Energetics), highlighting theory and empirical work that illuminates how energy and movement jointly govern the structure and persistence of communities.
There are several mechanisms by which the movement of individual animals influences species coexistence. These mechanisms span all types of movement, including dispersal, migration and daily foraging (
Beyond these direct effects, movement can also have mobile link effects, where animals transport nutrients, other organisms, propagules or genes (
Recent research has further expanded our understanding of movement-coexistence linkages, revealing insights such as the role of individual personalities in mediating species coexistence (
Animal coexistence is fundamentally shaped by individual physiology and energetics (
The two key mechanisms that govern species coexistence identified by modern coexistence theory can both be contextualized through the lens of animal energetics (Fig.
Conceptual visualization of how energetics may act as stabilizing or equalizing mechanisms in the context of species coexistence. When one species has a much higher energy balance, it may outcompete other species, so a stabilizing mechanism would be a reduction of energy balance with increasing abundance (A). This could occur as a result of increases in energy invested into intraspecific competition (e.g. fighting, searching for nesting sites, stress, infections) or reductions in energy intake due to intraspecific resource competition (B, C). When species have similar energy balances (incoming versus outgoing energy), they are likely to coexist due to comparable fitness (D). Similar energy balance may result even with different levels of energy intake and costs (E), and similarity in total energy costs may arise despite differences in energy allocation to metabolic processes (F).
Second, equalizing mechanisms reduce fitness differences among different species (
While similarity in energy balance can foster coexistence, dissimilarity can disrupt it. Species with higher energy intake or greater efficiency may gain a competitive advantage, potentially outcompeting others. In systems initially in balance, shifts in energy dynamics, such as the introduction of new resources, can reduce opportunities for coexistence. For example, human-made garbage dumps provide abundant food for some species, boosting their energy intake leading to larger group sizes. These species often continue to exploit other resources, increasing competition with other species that do not consume garbage and intensifying predation pressure on prey, ultimately threatening coexistence (
Despite these disruptive effects, energetics offer a powerful lens for understanding and fostering coexistence. In the following sections, we explore empirical examples and propose energetically mediated pathways that may support species coexistence.
Mechanisms that elevate intraspecific over interspecific competition can stabilize coexistence by inducing negative density dependence in energy balance (Fig.
In the field, an increase in intraspecific over interspecific competition can arise from highly specialized energetic niches (
Ontogenetic niche shifts—changes in trophic niche across life stages—offer another path to stabilization. When a dominant competitor’s energy and nutrient demands vary substantially over its lifespan, direct interspecific competition can be reduced through trophic resource partitioning. This, in turn, can promote coexistence, as observed in two coexisting fish species: the Trinidadian guppy (Poecilia reticulata) and the killifish (Rivulus hartii) (
Additionally, energy-saving strategies under resource limitation or in harsh environments can foster coexistence by reducing the need for direct competition. In the Yukon, such strategies may support the coexistence of snowshoe hares (Lepus americanus) and squirrels (Tamiasciurus hudsonicus) (
Building on this, the theory of the maximum power principle posits that species with the highest metabolic rate dominate in competitive experiments and that similarly, when the summed metabolic rate of a diverse community surpasses that of a single species, coexistence may result (
Equalizing mechanisms reduce average fitness differences between species, thereby slowing exclusion and allowing coexistence to persist even in the absence of strong niche partitioning (
This principle aligns with the ‘equal fitness paradigm’, which posits that trade-offs between survival and production lead to balanced fitness outcomes across species (
Equalized fitness can arise from trade-offs between reproductive output and somatic growth (Fig.
However, environmental context can influence which energy allocation strategies are advantageous. In highly seasonal environments, fast life-history strategies may be more successful. For example,
Several energy-based equalizing mechanisms are closely tied to movement, linking activity patterns to energy balance and the potential for species coexistence. A prominent example is contrasting foraging modes (
A similar equalizing mechanism at a broader scale involves differences between migratory and resident strategies. Migratory species invest in large-scale movement, often to access more abundant resources, while resident species avoid these costs but may face lower resource availability (
Similarly,
Overall, these examples demonstrate how animals with different life-history and behavioral strategies can maintain similar fitness levels by balancing energy expenditure and intake in ways that support coexistence.
The relationship between energetics and movement (Fig.
Integrating individual energy budgets (A) with movement decisions (B) and their effects on population and community dynamics. An animal acquires energy from its environment through foraging movements (light teal arrows), then allocates ingested energy to digestion, maintenance, locomotion, growth, and reproduction. The resulting balance and reserves define its internal state, which in turn drives decisions about whether, how, when and where to move. Movement paths both determine future energy intake, by selecting patches with particular food availability, and incur locomotion costs that trade off against other metabolic demands. Arrow thickness in the “Energy use” panel provides an illustrative snapshot of potential allocation among processes, and light teal arrows highlight the feedback loop between movement and energy balance. Positive energy balance allows storage of surplus reserves for later use. Changes in energetics and movement behavior shape individual fitness, influence population trajectories (dark blue), and ultimately drive local community structure (purple) through competition for resources and shifts in species’ habitat occupancy. This schematic emphasizes the key pathways by which energy fluxes and movement interact to mediate species interactions and govern coexistence under variable environmental conditions.
Energy serves as both a motivator for and a cost of movement. Foraging movements provide energy but incur costs associated with locating, obtaining and digesting resources (Fig.
Examples of how energetics shape decisions about whether to move (A), how to move (B), and when and where to move (C). In Sierra Nevada bighorn sheep (Ovis canadensis sierrae), individuals with higher energy reserves remain at high elevations to conserve energy (A1), while those with lower reserves migrate to access better forage, despite increased predation risk (A2) (
Yet, as previously noted, in some contexts conserving energy by reducing activity may be more beneficial than seeking food (
Conversely, increased movement is often necessary to prepare for future energy demands, such as in prehibernation hyperphagia (
Thermoregulation also shapes movement behavior. Increased movement can help offset hypothermia (
Internal energy state is thus central to movement decisions (Fig.
The decision to move or stay is shaped by the balance between energy reserves, physiological needs, and environmental risks. From routine foraging to long-distance dispersal, these decisions reflect dynamic thresholds: animals may delay leaving shelter until energy stores fall below a certain level, shorten foraging bouts under scarcity or increase movement to prepare for future energetic demands (
The energetic costs and benefits of movement depend on how animals navigate their environments (‘motion capacity’, Fig.
Species capable of multiple movement modes often face trade-offs. For example, in starlings (Sturnus vulgaris), experimental studies have shown that individuals switch between walking and flying, weighing locomotion costs against foraging efficiency to maximize net energy gain per unit time (
Different movement types reflect varying strategies for energy management. Station-keeping and home ranging movements allow animals to remain near stable resources, but even routine movements can be costly (
Migration for many species is driven by predictable, seasonal shifts in energy availability (
Expanding niche theory to include how animals move, and at what energetic cost, also offers insight into species coexistence. Movement efficiency influences how far individuals can travel to access resources and how frequently they must move to meet energy demands. For example, species that glide or drift may traverse larger areas with minimal cost, while those using short, intense bursts of activity may be constrained to high-quality, localized patches. These differences can reduce spatial and temporal overlap, even among species with similar resource needs, thus easing competition.
An animal’s decisions about when and where to move are shaped by its energetic state and by current or anticipated resource availability (‘navigation capacity’ in Fig.
Seasonal movements are often timed through a combination of external cues (e.g., photoperiod, temperature) and internal mechanisms (e.g., fuel stores, corticosterone levels, circannual rhythms, e.g.,
Hence, the paths animals follow and how they distribute themselves in space reflect a balance between energy gain and the costs of moving through heterogeneous terrain, vegetation, and microclimates. (
Decisions about when and where to move, such as ‘surfing green waves’, shifting to thermal refuges or timing migrations, do more than optimize individual energy budgets. They shape spatiotemporal overlap among species, filtering competitive and facilitative interactions. By navigating energy landscapes, animals self-organize into distinct niches: some gain a competitive edge by tracking resource peaks, while others reduce overlap by shifting in time or space. These energetically informed strategies not only reflect how animals balance energy gain and expenditure across dynamic environments, but also influence how communities are structured.
Our framework relies on explicit, bidirectional coupling of energy balance and movement decisions, and embeds this coupling within the stabilizing–equalizing framework of coexistence theory. When an animal’s energy reserves rise or fall, its movement-rules, governing when, where and how to forage or disperse, change accordingly. Those shifts alter resource use patterns (niche differences) and set energetic limits on survival and reproduction (fitness differences). In turn, this reshapes the filters: dispersal, environmental, biotic, and abiotic; that determine which species can establish and persist in a given landscape. By tracing these pathways explicitly, we can generate concrete, testable predictions about when and how species coexist - predictions that lie beyond the reach of theories focused on energy, movement or coexistence in isolation.
We build on existing theories in several ways. The MTE and the Maximum Entropy Theory of Ecology emphasize energetic constraints across scales, while EPOLS theory links life history variation to energy use and movement (
While the full integration of all framework components is particularly novel and promising for future studies, even applying selected combinations of its elements can improve predictions about certain aspects of species coexistence. Hence, different parts of the framework may be considered depending upon the research focus. Nonetheless, maintaining a holistic view that fully integrates energetics, movement and coexistence offers a mechanistic and predictive lens for understanding how individual-level dynamics scale up to shape community structure.
Operationalizing this framework requires linking individual energetics to behavior and interactions of individuals and species under realistic conditions. While tools for measuring movement, physiology, and community structure exist, integrating them remains a challenge. In the following we outline how three complementary approaches—controlled experiments, field-based methods, and mechanistic simulation modeling—can complement one another to test predictions and refine the framework.
Controlled experiments can be used to quantify the energy costs of movement or test fitness outcomes under standardized conditions. Treadmill studies, for example, can incorporate environmental complexity (e.g., slope, temperature) and biotic interactions (e.g., predators or competitors) using visual or other stimuli (e.g.,
Field-based methods are essential for capturing energy use in ecologically realistic contexts. Multi-sensor technologies recording accelerometry, heart rate and temperature, among other metrics, allow estimation of field metabolic rates (
Mechanistic simulation models are essential for bridging biological scales, from individual energetics and behavior to population and community dynamics (
By combining the different approaches, we can overcome existing limitations and unlock a deeper understanding of how energetics shapes, and is shaped by, movement and community dynamics. For example, conducting parallel experimental or field studies alongside model development can allow for the targeted measurement of parameters needed to inform models and to test model-derived predictions in real-world scenarios. By encouraging collaboration between physiologists, movement ecologists, community ecologists, and ecological modellers, we aim to inspire innovative approaches that integrate physiological and behavioral measurements into multi-species analyses. Advancing this interdisciplinary effort will help answer pressing ecological questions and enhance our understanding of community biodiversity dynamics in the face of environmental perturbations and global change.
In the following, we highlight several illustrative testable predictions that emerge from our framework, describing how they are embedded within its structure and offering approaches for their evaluation. These predictions underscore the importance of jointly considering movement, energy and coexistence processes to understand how energy-mediated movement dynamics shape the assembly and persistence of communities in a warming, increasingly variable world.
Prediction 1. Under resource scarcity, individuals that flexibly switch between intensive foraging and energy-saving modes will persist longer than inflexible individuals, driving movement patterns that reshape competitive interactions and community composition.
In the presented framework, reduced energy intake leads to a negative energy balance, depleting reserves and altering the individual’s internal state. This shift can trigger a behavioral transition from high-effort foraging to energy-saving modes. Species with this flexibility may down-regulate motion capacity under scarcity, minimizing locomotion costs and preserving energy stores. In contrast, inflexible species that maintain high movement rates under low returns may quickly exhaust their reserves, leading to higher mortality or competitive disadvantage. When resources remain accessible but patchily distributed, such persistent movement may confer short-term advantages, but under ongoing scarcity, it becomes maladaptive. By modulating movement effort according to energetic state, flexible species reduce costly encounters in the biotic and abiotic filter, reducing competition and potentially stabilizing coexistence.
This prediction is supported by studies showing non-monotonic movement responses to hunger in species such as griffon vultures (
To test this prediction, controlled manipulations of resource availability in semi-natural environments could be paired with fine-scale monitoring of movement (e.g., GPS, accelerometry), metabolic rates (e.g., heart rate loggers, doubly labeled water) and fitness outcomes (e.g., survival, reproduction). Comparative studies across species or phenotypes with varying capacities for energy conservation would reveal how state-dependent movement plasticity shapes persistence and community dynamics under resource limitation. As droughts intensify and food pulses become more erratic, species capable of shifting between high-effort foraging and low-effort conservation modes may be better equipped to track ephemeral resources and survive prolonged lean periods.
Prediction 2. In environments with fluctuating energy availability, individuals with higher energy demands or lower tolerance to deficits will move away from depleted patches more rapidly, leading to shifts in community composition.
Individuals continuously assess local energy intake relative to their internal reserves. In our framework, as energy returns decline, an individual nearing an energetic threshold may abandon its current patch in search of better conditions. Moreover, consistent with Optimal Foraging Theory and the marginal value theorem (
Empirical work already supports components of this mechanism. For instance,
This prediction could be tested by tracking sympatric species with differing energetic demands in a shared, fluctuating landscape. In a semi-arid system with predictable dry-season declines, individuals from two or more species, which differ in metabolic rate, body size or physiological flexibility, could be fitted with GPS and energy-use sensors (e.g., accelerometers, heart rate loggers), while habitat monitoring (e.g., remote sensing) tracks resource availability. Linking movement with energy status and local conditions could reveal species-specific thresholds for patch departure. For example, if one species reliably departs sooner as conditions deteriorate it would indicate lower tolerance to declines and highlight how energetic traits shape patch abandonment. Long-term data could show how these differences influence community persistence and spatial sorting, particularly across years with contrasting rainfall. Semi-arid systems may be especially vulnerable to global change, as climate-driven drought and land-use-induced degradation make energy resources increasingly patchy and unpredictable. In response, species with high demands or narrow tolerances may face repeated, costly relocations, leading to fragmentation or local extinction, while more tolerant species may persist through bottlenecks and benefit from reduced competition. Understanding these dynamics can illuminate drivers of biodiversity shifts under increasing environmental volatility.
Prediction 3. Interference competition among sympatric species will intensify as their metabolic niches increasingly overlap.
Classic niche theory holds that the degree of resource-use overlap governs the intensity of interspecific competition, traditionally focusing on diet, habitat, and time (
Support for this prediction comes from studies showing that similarity in energetics can intensify antagonism, for instance, bacteria more strongly inhibit metabolically similar competitors (
To test this prediction, spatially explicit individual-based models (e.g.,
Global change is reshaping energy landscapes. Land use change, droughts, heatwaves, resource pulses, and invasions increasingly alter not just resource availability, but the energetic costs of acquiring them. Species must continually adjust their movement strategies and interactions to track a shifting energetic terrain. The proposed framework offers a perspective for anticipating how these adjustments propagate across different scales.
Energetic mismatches may accelerate species turnover by filtering out individuals that cannot meet metabolic demands. Interaction networks may reorganize as movement patterns change, producing novel spatial and temporal overlaps, and previously unobserved assemblages. These transitions are likely to not be gradual. Thresholds may be crossed when energetic constraints are breached, triggering abrupt shifts in movement, competition or coexistence outcomes.
Addressing these challenges requires integrating across scales, from individual traits and behaviors to population and community dynamics. Trait-based approaches remain valuable but must be paired with process-based models that capture how energy fluxes and movement strategies respond to environmental variability. Embedding these processes within coexistence theory can help build a more mechanistic and predictive ecology of biodiversity under change.
The authors have declared that no competing interests exist.
No ethical statement was reported.
No use of AI was reported.
This work was supported by a grant to L.S, F.J., and C.A.G. from the German Research Foundation (DFG) in the framework of the BioMove Research Training Group (DFG-GRK 2118/1).
Conceptualization: LS, CAG. Funding acquisition: FJ. Investigation: CAG, LS. Visualization: LS, CAG. Writing - original draft: LS, CAG. Writing - review and editing: FJ, LGH.
Leonna Szangolies https://orcid.org/0000-0003-0266-1163
Florian Jeltsch https://orcid.org/0000-0002-4670-6469
Lewis G. Halsey https://orcid.org/0000-0002-0786-7585
Cara A. Gallagher https://orcid.org/0000-0001-7094-1752
All of the data that support the findings of this study are available in the main text.