HUMAN ACTIVITIES MAKE EXPLORATORY INDIVIDUALS CHANGE HABITATS
Proactive individuals are generally more active, explore more and are more likely to disperse (Table 1). Consequently, in situations where HIREC reduces habitat quality, proactive animals can be expected to be the first individuals to leave. This has been previously observed in crabs, where bold individuals were the first to disperse when habitat quality was reduced (Belgrad & Griffen 2018). While studies conducted in the wild are still lacking, some laboratory tests have shown that bold individuals work harder to escape threatening situations. Bolder fish have more attempts to escape laboratory-induced hypoxia (Brelinet al. 2005), or tend to avoid the hypoxic environment (Ferrariet al. 2016). Bold individuals are also better at avoiding or escaping fishing gear (Diaz Pauli & Sih 2017), which could be related to their higher anaerobic capacities (Table 1) (Killen et al.2015).
While leaving a non-suitable habitat might lead to a superior fitness outcome for bold individuals of a given population, this implies that they are subsequently able to successfully find suitable habitat. This is not necessarily an easy task in the context of HIREC, which is often characterized by overall habitat degradation and increases in the presence of ecological traps (Robertson et al. 2013).
Previous studies have also found inter-individual differences within a population in the propensity to disperse. Indeed, populations are likely comprised of individuals that differ in consistent ways; dispersers are bold, aggressive and asocial while joiners are rather shy, slow-explorers and social (Cote et al. 2010a). Harrison et al. (Harrison et al. 2015) also recently differentiated ‘resident’ from ‘mobile’ individuals. Mobile individuals tend to explore more, be more active and be less site-specific, and thus, they resemble proactive individuals. In this sense, less socially embedded yearling female marmots (Marmota flaviventer ) are also more likely to disperse (Blumstein et al. 2009), and in the month preceding dispersal these marmots upregulate a suite of specific genes, many of which are associated with migration (Armenta et al. 2018). Consequently, in many cases mobile (or proactive) individuals are more prone to change habitats in stressful situations related to HIREC (Fig. 1.1) and this may have evolutionary consequences.