Introduction

The study of animal personalities has received much attention in recent years. This emerging field has shown that consistent behavioural differences among individuals are common in animals (Réale et al. 2007). These differences are sometimes correlated across different behavioural contexts, forming behavioural syndromes (Sih, Bell & Johnson 2004; Sih et al. 2004). Behavioural differences have important implications for ecological and evolutionary dynamics since they affect individual fitness and can have cascading effects on animal communities by shaping the magnitude and direction of species interactions (Sih et al. 2012; Wolf & Weissing 2012). In addition, behavioural differences provide a framework to study how individuals cope with increasing anthropogenic activities (Sih et al. 2010). Human‐induced environmental changes challenge species to respond adaptively to those novel conditions. The effects of these changes may vary depending on the behavioural phenotype being considered. Some personality types perform better in human‐disturbed environments (Martin & Réale 2008; Madden & Whiteside 2013), and the overall architecture of behavioural syndromes can differ between populations with varying degrees of anthropogenic pressures (Miranda et al. 2013; Royauté, Buddle & Vincent 2014). In addition, certain classes of anthropogenic changes (e.g. urban noise, pollutants) may amplify or attenuate behavioural and physiological variation (Killen et al. 2013).

Pesticides used in agriculture are important stressors for animals. These compounds are often wide‐spectrum and are linked to declines in populations of seed dispersers (Krebs et al. 1999; Donald, Green & Heath 2001), pollinators (Brittain et al. 2010) and biocontrol agents (Geiger et al. 2010). Most pesticides degrade rapidly after spraying, and organisms are frequently exposed to pesticide residues, which cause changes in physiology and behaviour, rather than to doses causing direct mortality (reviewed in Desneux, Decourtye & Delpuech 2007).

While our knowledge of the effects of sublethal exposure to pesticides on behaviour has increased rapidly, individual differences remain poorly accounted for in ecotoxicological assays (Montiglio & Royauté 2014). Current practices tend to report shifts in average behaviour post‐exposure rather than focusing on how behavioural expression of individuals may change through pre‐ and post‐exposure phases. Stated another way, current studies ignore potential effects that may be due to personality differences. Most studies focus on unique traits rather than using the multidimensional approach favoured by behavioural syndrome studies.

Studying how personality differences and correlations among personality traits vary under exposure to pesticides addresses a significant gap in our knowledge of the consequences of pesticide exposure on non‐targeted organisms. It is important to understand if differences in aggressive, bold or exploratory behaviours remain consistent when individuals are exposed to pesticide stress. These effects can be particularly relevant for predator species with regulating effects on the population dynamics of prey species. In an agroecological context, certain behavioural phenotypes may participate more actively in biocontrol (e.g. active and voracious individuals) and a decoupling of these differences through pesticide exposure may limit their contribution to pest control.

Spiders (Araneae) are an ideal taxon to study the interaction between behavioural variation and pesticide exposure. Spiders are abundant in many agroecosystems and provide important pest regulation services (Carter & Rypstra 1995). They are sensitive to pesticides (Pekar 2012) and their personality traits and behavioural syndromes are well‐documented (Pruitt & Riechert 2012). We used the jumping spider Eris militaris (Araneae: Salticidae) as a model taxon in this research. This species is commonly found in apple orchards and is easily reared under laboratory conditions. Previous work indicated differences in syndrome structure when comparing insecticide‐free and insecticide‐exposed populations, most notably regarding the strength of an activity‐voracity syndrome (Royauté, Buddle & Vincent 2014). Here, we expand on this work by testing how direct exposure to an insecticide can impact personality traits and their syndromes. We focus on traits related to activity and prey capture behaviours because these traits are frequently correlated in spiders with important consequences for individuals’ survival and fitness (Pruitt, Riechert & Jones 2008; Pruitt & Krauel 2010).

Our objective was to test whether sublethal exposure to an organophosphate insecticide can alter personality, either by affecting the consistency of behavioural traits or by affecting the strength of correlation between traits. We tested several hypotheses by which sublethal exposure to insecticides is expected to alter the expression of personality traits and their correlations. First, insecticidal exposure may affect patterns of repeatability, a measure of the extent of personality differences (Fig. 1a). Such differences may occur because (i) insecticide‐exposed individuals become more similar (collapse of behavioural differences hypothesis); (ii) personality differences are amplified after insecticidal exposure (amplification of behavioural differences hypothesis); or (iii) each individual becomes more variable after exposure (variability increase hypothesis). Second, insecticidal exposure may affect patterns of correlation between behavioural traits and either reduce (syndrome collapse hypothesis) or amplify (syndrome amplification hypothesis) the magnitude of behavioural correlations (Fig 1b).