Toward the emergence of a new coping style in predator
free-areas
The presence of predators is a key driver that influences the structure
of behavioral syndromes (Réale & Festa-Bianchet 2003; Smith &
Blumstein 2012). Thus, by extirpating predators, or protecting prey from
predation risk, correlations between personality traits may become
decoupled (Bell 2005; Bell and Sih, 2007) with a series of cascading
effects on the underlying physiology. The sudden elimination of
predators following some HIRECs could render behavioral and
physiological traits associated with antipredator responses as
“useless”. Indeed, natural selection favors antipredator phenotypes
that efficiently reduces predation risk. But when the risk is low, these
costly phenotypes, including vigilance, high HPI/A activity, or flying
capacities, may become counterproductive. Consequently, constraints on
these phenotypes are released and the correlation between traits is lost
(Fig. 2).
Nevertheless, these effects observed in response to the reduction of
predation seem to come with additional constraints related to the
presence of human and their associated activities. Indeed, in response
to the presence of human, there might be selection for some specific
traits leading to new correlation between traits (Fig. 2). However, the
direction, intensity and speed of this selection are still unclear, and
we therefore face difficulties in predicting animals’ responses to human
presence.
Response to domestication can be used as a guide to predict the fate of
individuals in predator free areas and in interactions with human. Most
of our knowledge on the subject comes from foxes (Vulpes vulpes )
that have been domesticated for now more than 40 generations (Trut
1999), with mixed results. Selection for tameness led to a decrease in
fear-related traits (Trut 1999), cortisol production and associated gene
pathways (Trut et al. 2009) which means that animals are now more
bold and proactive (Fig. 1.3.1.3). However, it also decreased
aggressiveness (Trut 1999) and increased social cognitive abilities
(Hare et al. 2005) and neurogenesis (Huang et al. 2015),
which is consistent with them being more reactive (Rauw et al.2017) (Fig. 1.3.1.3). Notably, however, is that brain size reduction,
which often correlates with behavioral flexibility (Sol et al.2005, 2008), characterizes domestication in most species (excluding
foxes and mice) (Wilkins et al. 2014), and this, associated with
the development of routine-like behavior linked to a closed environment
(Rauw et al. 2017), would suggest that we should expect reduced
cognitive skills.
In the case of urbanization (Fig. 1.3.1.2), human contact also leads to
increased boldness (Shochat et al. 2006; Coleman et al.2008; Møller 2012; Thompson et al. 2018), and a reduced HPI/A
responses (Atwell et al. 2012), which should tend to create more
proactive individuals. Nevertheless, urbanization also comes with
increased cognitive abilities (Audet et al. 2015), and behavioral
plasticity (Carrete & Tella 2011; Sol et al. 2013; Thompsonet al. 2018), characteristics of reactive individuals. In the
context of urbanization, it is however important to notice the
difficulty to determine whether these characteristics emerged from
differential colonization according to an individual’s traits, or from
an evolutionary response that selected for specific traits. In other
words, did bold individuals invade towns (Fig. 1.3.1.2, dashed purple
arrow), or did shy individuals evolve towards boldness in urbanized
areas (Fig. 1.3.1.2, solid grey arrow) (Sol et al. 2013)?
In the context of tourism and ecotourism, similar results to those seen
with urbanization and domestication have been observed in animals that
are in frequent contact with humans. We have seen that boldness has
increased (Geffroy et al. 2015b; Arroyo et al. 2017), as
has neurogenesis (Geffroy et al. 2018). However, baseline and
post stress cortisol responses seem to strongly depend on the intensity
with which humans interact with animals, with severe disturbance
generally increasing cortisol production (Geffroy et al. 2017)
(Fig. 1.3.1.1).
Overall, wild animals exposed to HIREC that relaxes selection on
antipredator behavior and increases human contact would likely be bolder
but also less aggressive, more plastic in their response, with higher
cognitive abilities and lower HPI/A responses. We suggest a new term —
“preactive”— in that individuals are part proactive and part
reactive. The emergence of this new coping style would be the result of
uncoupling initatially associated traits (Fig. 2A), by a first step of
relaxed selection due to the creation of a human-shield (Fig. 2B) and a
second step where animals associated with humans selectively learn
(and/or have evolved) to deal with this new situation by displaying
overall decreased aggression, increased boldness and decreased HPI/A
reactivity while improving their capacities to be plastic in association
with higher neurogenesis (Fig. 2C).