My research is focused on two main fields of interests: 1) Evolutionary and ecological consequences of predator-prey interactions. 2) Causes and consequences of behavioural types (BT), animal personalities and behavioural syndromes (BS).
1) Evolutionary and ecological consequences of predator-prey interactions.
Predator-prey interactions have long been acknowledged as important determinants in prey population dynamics and can have major impacts on entire ecosystems. Earlier, predators were thought to affect prey mainly through direct removal of prey from the prey population. However, it has become more and more apparent that predators also invoke strong indirect effects on their potential prey by inducing behavioural and morphological adjustments as well as physiological stress. These indirect effects have the potential to be as important, or even more important, than the direct effect of predation.
Most organisms live their lives under the threat of predation, and while some organisms experience the same predator regime their entire lives, others are subjected to several different predator regimes during a life cycle. Striking examples of the latter are organisms that undergo metamorphosis from a larval stage in one environment (e.g. aquatic) to an adult stage in a different environment (e.g. terrestrial). In such case both predator community and the organism itself changes dramatically from pre-metamorphosis to post-metamorphosis. It has been suggested that metamorphosis can represent a way of escaping high predation pressure in the larval environment.
In my studies of predator-prey interactions I have mainly used odonate larvae as prey and perch as predators. Special fields of interest are behavioural anti-predator responses and the effects thereof, behavioural syndromes and the effects of chemical cues associated with predators.
2) Causes and consequences of behavioural types (BT), animal personalities and behavioural syndromes (BS)
Individual organisms continuously react to their environment in order to maximize their fitness, but interestingly, individuals often differ in their reaction towards the same stimuli. This variation is often not just noise around an optimal strategy, and reactions to different stimuli are frequently structured in 'behavioural syndromes', comparable to how humans differ in personality. A behavioural syndrome exists if, even as individuals alter their behaviour depending on the situation, behaviours are consistent across contexts. For instance, individuals that are aggressive usually also take more risks in exploring novel environments and in the presence of predators. Interestingly, BS may be associated with constrained behavioral plasticity that results in suboptimal behavior in certain situations. For example, if boldness and aggression are positively correlated, it means that aggressive individuals that are successful in environments where high levels of aggression are favored (e.g. during competition for food or mates) may spillover to do poorly in situations when high levels of aggression are disadvantageous (e.g. in the presence of predators). The notion that behavioral carryovers happen and that they can explain suboptimal behavior has been invoked to explain inappropriate risk taking in prey (Sih et al. 2003), excessive sexual cannibalism (Arnqvist & Henriksson 1997, Johnson & Sih 2005) inappropriate aggressiveness (Duckworth 2006) and poor parental care (Wingfield et al. 1990, Ketterson & Nolan 1999). Interestingly, some deeper, more fundamental questions about BS and BTs are only beginning to be investigated. Notably, we are only beginning to ask why the phenomenon exists at all? A major defining part of a BS is within-individual consistency in behavior (e.g., a tendency for a given individual to exhibit a bold BT even as the environment changes). A fundamental question is why does this occur at all? If having a BT can include behavioral carryovers that results in suboptimal behavior, why should individuals exhibit a BT? Why not exhibit optimal plasticity in response to all environmental situations, with no discernible BT? Along similar lines, we are only beginning to ask why particular suites of behaviors are correlated? Why should boldness and aggressiveness be correlated? Note that consistent BTs and behavioral correlations are not ubiquitous. Some studies have found that individuals do not maintain consistent BTs over time, or over multiple contexts; that is, BTs are sometimes stable, but sometimes not stable. Similarly, a particular behavioral correlation (e.g., between boldness and aggressiveness) sometimes occurs, but not always. While positive phenotypic and genetic correlations between aggressiveness and risk-taking often have been reported, recent population comparisons in three-spined stickleback now show that the association between these traits differs between populations, with the 'aggressiveness-boldness' syndrome only existing in populations with high predation pressure (Bell and Sih 2007, Dingemanse et al. 2007). These findings illustrate that environmental factors affect phenotypic correlations between components of 'animal personality'. An important challenge is thus to explain this variation in the stability of BTs and BS.