Modelling Toxin-Induced Intraspecific Personality Variation in Predator-Prey Dynamics

arXiv:2610.30431 · q-bio.PE · Submitted 2026-10-21 · Read on arXiv

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Introduction to the show: ident: Genomics Radio. Generated commentary on the latest computational biology and genomics papers.

Ines: We're looking at the paper: "Modelling Toxin-Induced Intraspecific Personality Variation in Predator-Prey Dynamics".

Marcus: Here's the gist of the paper. The gist: Toxin-induced personality variation can qualitatively change predator-prey dynamics.

Ines: Model Formulation The study extends a toxin-dependent predator-prey model by incorporating personality variation in both prey and predators, where prey personality affects birth and growth, and predator personality affects the functional response of the predator.

Marcus: The model is parameterized for rainbow trout and aquatic insect prey exposed to methylmercury.

Ines: The system involves biomass densities for prey (x) and predator (y), along with their respective toxin concentrations (U and V).

Paper summary: Ines: So, summarizing the main point from "Modelling Toxin-Induced Intraspecific Personality Variation in Predator-Prey Dynamics", we see that incorporating personality variation into both prey and predator populations, driven by toxin body burden, fundamentally alters the long-term behavior of these systems.

Marcus: The authors parameterized this for rainbow trout and aquatic insect prey exposed to methylmercury, and their numerical results show that the effects of prey personality and predator personality are distinct. Prey personality acts to promote stable coexistence, while predator personality tends to increase biomass fluctuations and cause persistent oscillations.

Yuki: And the mathematical analysis confirmed this by showing that increasing the prey personality contrast can reduce oscillation amplitudes, whereas increasing the predator personality contrast actually destabilizes the system by amplifying those oscillations.

Ines: The paper is interested in how these behavioral traits influence birth, growth, and functional responses, which are then modulated by environmental toxins. They use numerical simulations and a quasi-steady-state approximation to analyze the resulting dynamics.

Marcus: The authors also used that mathematical framework to classify all possible equilibrium structures based on the toxin level and those personality contrasts between the species. This gives a classification for what can happen, like extinction or coexistence, depending on where you are in that parameter space.

Yuki: What this means for us is that population dynamics under toxic stress aren't just about mortality rates; they are also about how the individuals within those populations are behaving differently based on their personality.

Ines: It suggests we need to consider these behavioral shifts when we try to predict how ecosystems will respond to persistent environmental stressors like methylmercury, especially at low and intermediate concentrations where these effects are most relevant.

Conclusion: Ines: So, to wrap up this paper titled "Modelling Toxin-Induced Intraspecific Personality Variation in Predator-Prey Dynamics," it’s about how personality traits in both the prey and the predator change when they're exposed to toxins like methylmercury.

Marcus: Right, so it looks at how that changes population dynamics, specifically for rainbow trout and aquatic insects. The authors are looking at how personality variation impacts birth, growth in the prey, and foraging behavior in the predator.

Yuki: From a population genetics angle, they’re connecting these individual traits to how populations behave over time under chemical stress. It’s about seeing if these behavioral differences matter when a whole system is changing its chemistry.

Ines: The main thing is that prey personality tends to stabilize things, reducing biomass fluctuations and helping coexistence. But the predator personality can actually make things worse, leading to more wild oscillations in population sizes.

Marcus: That’s the key finding, because it shows that you can have two different effects depending on which species you look at. It's not just one toxin effect; it's a complex interaction between what the prey is doing and what the predator is doing.

Yuki: And this suggests that if we only looked at mortality rates, we’d miss this whole layer of behavioral complexity that could dictate whether a population crashes or keeps going.

Ines: Exactly. The paper also looks at different scenarios, like when personality is only in the prey versus when it's in both species, and how the toxin level shifts those outcomes.

Marcus: It’s a pretty big picture study because it gives us a framework to think about how environmental stressors can interact with internal animal traits to change ecological outcomes.

Yuki: And that opens up questions about how much of this behavioral plasticity we are actually seeing in the wild populations right now versus what the model predicts.

Jingyi Jin, Tian Xu Wang, Hao Wang

University of Alberta

q-bio.PE

Submitted: 2026-10-21

Updated: 2026-10-21

Comments: 38 pages, 5 figures. Submitted to Journal of Theoretical Biology

License: http://creativecommons.org/licenses/by-nc-nd/4.0/

The gist: The gist: Toxin-induced personality variation can qualitatively change predator-prey dynamics.

Key concepts

Prey Personality
This refers to the boldness or shyness of prey individuals, which is influenced by toxins. In this model, prey personality determines birth rates and growth. Bolder individuals may have different foraging behaviors that impact their survival and reproduction under toxic stress.
Predator Personality
This describes the boldness or shyness of predators, which also changes due to toxins. Predator personality dictates how effectively they hunt prey (the functional response). This affects the predator's ability to consume prey and influences population dynamics through fluctuations in biomass.
Biomass Fluctuations
This refers to the ups and downs in the total weight or number of individuals in a population over time. The study found that predator personality can increase these fluctuations, leading to unstable cycles, whereas prey personality helps reduce these swings for a more stable ecosystem.
Toxin-Dependent Personality
This means an animal's boldness or shyness is not fixed but changes based on the level of environmental toxins it absorbs. The proportion of bold versus shy individuals in both prey and predators shifts depending on the toxin concentration, linking environmental stress directly to behavioral traits.

Summary

The gist: Toxin-induced personality variation can qualitatively change predator-prey dynamics.

Model Formulation

The study extends a toxin-dependent predator-prey model by incorporating personality variation in both prey and predators, where prey personality affects birth and growth, and predator personality affects the functional response of the predator. The model is parameterized for rainbow trout and aquatic insect prey exposed to methylmercury. The system involves biomass densities for prey (x) and predator (y), along with their respective toxin concentrations (U and V).

The model equations describe the dynamics of prey biomass, predator biomass, and the toxin concentrations in both species. The prey growth rate b(u, x, γ1(u)) depends on the proportion of bold individuals through B(u), which incorporates the bold-shy composition. Similarly, the predation function p(x, γ2(v)) is personality-dependent, defined as p(x, γ2(v)) = γ2(v)p1(x) + (1 − γ2(v)) p2(x), where p1 and p2 are functional responses for bold and shy predators.

Effects of Personality on Dynamics

Numerical simulations show that prey and predator personality have different effects on population dynamics. Specifically, prey personality tends to reduce biomass fluctuations and promote stable coexistence. In contrast, predator personality can increase biomass fluctuations and lead to persistent population oscillations. These effects are mainly observed at low and intermediate toxin concentrations that are environmentally relevant to freshwater ecosystems.

The paper compares four scenarios differing in whether personality variation is present in the prey, the predator, or both species. When personality is absent from both prey and predators, persistent oscillations occur at low toxin concentrations before transitioning to a stable coexistence equilibrium. Including personality only in the predator population causes the system to exhibit two separate oscillatory intervals at very low toxin concentrations. When personality is included in both species, an intermediate oscillatory interval occurs, and this interval is followed by another stable coexistence regime before transitioning to a prey-only state at sufficiently high toxin concentrations.

Mathematical Analysis

The model is reduced to a two-dimensional system using a quasi-steady-state approximation. This reduction establishes the positivity and boundedness of the reduced system and identifies a positively invariant region. The equilibrium structure depends jointly on the toxin level T, the prey and predator personality contrasts.

The existence classification determines whether there is extinction, prey-only, and positive coexistence equilibria. For a fixed toxin level T, the prey personality contrast ρα determines whether the prey can persist. The predator personality contrast ρµ determines the number of positive coexistence equilibria.

Personality Contrasts and Stability

The relative personality contrast for predators is defined as ρµ:= µ1 − µ2 / 2¯µ, where µ¯:= µ1 + µ2 / 2. The relative personality contrast for prey is defined as ρα:= α11 − α12 / 2¯α, where α¯:= α11 + α12 / 2.

Increasing the prey personality contrast ρα decreases the oscillation amplitudes and promotes stability, whereas increasing the predator personality contrast ρµ destabilizes the system by generating and amplifying oscillations. This suggests that differences in prey birth and growth suppress oscillations, while differences in predator foraging generate them.

The local stability classification is determined numerically from the eigenvalues of the corresponding Jacobian matrices. The results show that personality variation can qualitatively change predator-prey dynamics, with effects mainly observed at low and moderate toxin concentrations.

Conclusion

Overall, toxin-induced personality variation can qualitatively change predator-prey dynamics. The model suggests that the presence of personality in prey and predators can substantially reshape the toxin-dependent long-term dynamics of the predator-prey system. Future work could consider time- and space-dependent toxin exposure, alternative personality response functions, and personality-dependent metabolism. The research demonstrates that personality can change population dynamics before direct toxic effects cause population loss.

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Modelling Toxin-Induced Intraspecific Personality

Variation in Predator-Prey Dynamics

Jingyi Jin, Tian Xu Wang, Hao Wang October 23, 2026

Abstract

Personality traits, such as boldness and shyness, can affect interspecific interactions through differences in individual behaviour. Environmental toxins may also alter these traits. However, few predator-prey models have considered animal personality. In this study, we extend a toxin-dependent predator-prey model by incorporating personality variation in both prey and predators. Prey personality affects birth and growth, whereas predator personality affects the predator functional response. The model is parameterized for rainbow trout and aquatic insect prey exposed to methylmercury. Numerical results show that prey and predator personality have different effects on population dynamics. Prey personality tends to reduce biomass fluctuations and promote stable coexistence. In contrast, predator personality can increase biomass fluctuations and lead to persistent population oscillations.

Keywords Environmental toxins, personality traits, predator-prey dynamics MSC Classification 92C15, 34A12, 34D20.

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associated with the boldness-shyness continuum. Activity level is an important dimension of animal personality and reflects consistent differences among individuals in how actively they move, forage, and feed (R’eale et al. 2007). Bolder individuals are often more active and exploratory and may exhibit greater foraging activity and food intake, whereas shyer individuals tend to be less active (Biro and Stamps 2008). For example, in three-spined sticklebacks (Gasterosteus aculeatus), bolder individuals consumed considerably more food than shyer individuals, even after differences in body size were taken into account (Jolles et al. 2016). These behavioural differences can subsequently influence growth and reproductive performance.

Although these personality traits are generally consistent, they can also show substantial plasticity and be shaped by environmental stressors. Toxic contaminants are an important class of environmental stressors and are widely present in aquatic ecosystems.

How it works

The study incorporates toxin-induced changes into the bold-shy composition of both prey and predator populations, where the proportions depend on toxin body burden. Prey personality affects birth and growth, while predator personality affects the predator functional response.

The model is parameterized for rainbow trout and aquatic insect prey exposed to methylmercury. The functions for prey birth and growth b(u, x, γ1(u)) depend on the bold-shy composition of the prey population <ref:

Improvements for AI systems

  1. Positivity and Boundedness Check: The improved AI system can verify that solutions of system (5.14) remain in a bounded region Omega based on Theorem 5.1, ensuring the model maintains biologically meaningful population densities throughout simulation time t greater than zero.

  2. Equilibrium Existence Classification: The AI can determine the number of candidate coexistence equilibria (E0,1, E0,2, E1) by checking the conditions derived in Table 5.1 based on toxin level T and personality contrasts ra and rho mu.

  3. Stability Mapping based on Personality Contrasts: The system can map local stability regimes (stable extinction, prey-only persistence, coexistence) in the parameter space defined by toxin level T, prey personality contrast ra, and predator personality contrast rho mu.

  4. Prey Personality Effect Quantification: The AI can quantify how increasing the prey personality contrast ra affects long-term dynamics; it can show that increasing ρα promotes extinction when shy prey are the majority but promotes persistence when bold prey are the majority.

  5. Predator Personality Effect Quantification: The AI can determine whether predator personality contrast rho mu leads to zero, one, or two positive coexistence equilibria and identify parameter regions corresponding to locally stable extinction, prey-only persistence, coexistence, and bistability.

Abstract

Personality traits, such as boldness and shyness, can affect interspecific interactions through differences in individual behaviour. Environmental toxins may also alter these traits. However, few predator-prey models have considered animal personality. In this study, we extend a toxin-dependent predator-prey model by incorporating personality variation in both prey and predators. Prey personality affects birth and growth, whereas predator personality affects the predator functional response. The model is parameterized for rainbow trout and aquatic insect prey exposed to methylmercury. Numerical results show that prey and predator personality have different effects on population dynamics. Prey personality tends to reduce biomass fluctuations and promote stable coexistence. In contrast, predator personality can increase biomass fluctuations and lead to persistent population oscillations. These effects are mainly observed at low and intermediate toxin concentrations that are environmentally relevant to freshwater ecosystems. Using a quasi-steady-state approximation, we reduce the model to a two-dimensional system and study its positivity, boundedness, and the existence of equilibria. The equilibrium structure depends jointly on the toxin level and the prey and predator personality contrasts. Based on this existence classification, we numerically investigate the local stability of all feasible equilibria and identify parameter regions corresponding to locally stable extinction, prey-only persistence, coexistence, and bistability. Overall, toxin-induced personality variation can qualitatively change predator-prey dynamics.

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