Investigating wildlife tourism effects on African elephants, I predicted that elephants would perceive tourism as a stressor and, in response to high tourist pressure and presence of tourists observing them from vehicles, would alter their behaviour and space use and have increased glucocorticoid concentrations. Within the previous chapters, it has been discussed that high tourist pressure was related to increased concentrations of faecal glucocorticoid metabolites (see Chapter 3), that elephants were more likely to perform conspecific-directed aggression during high tourist pressure (see Chapter 4), and that elephant herds moved away from tourists observing them from game drive vehicles with increasing numbers of vehicles present (see Chapter 4).
However, high tourist pressure was not related to changes in spatial use, in form of home range size and distance travelled (see Chapter 5). I conclude that wildlife tourism is perceived as a stressor by free-ranging African elephants in Madikwe, South Africa.
In Chapter 1, I presented an overarching scheme of the potential interactions between the different components assessed in this study (Fig. 1.4). An unpredicted stressor leads to increases in physiological mediators, which brings these mediators into the range of reactive homeostasis (Romero et al., 2009). High tourist pressure was related to an increase in fGCM concentrations and increased conspecific-directed aggression and presence of game drive vehicles was related to elephant herds moving away from those vehicles. Changes in hormone concentrations affect effectors such as muscles and make energy available to respond to stressors, whilst they are regulated by the input of stimuli through the sensory system (see Chapter 1). The increase in fGCMs (see Chapter 3) could relate to an increased amount of energy being made available to perform aggressive behaviour and moving away from GD vehicles (see Chapter 4), or vice versa, the increase in aggression may have been related to the increase in fGCMs. Short-term, such
physiological and behavioural changes may have been adaptive coping mechanisms (see Fig. 1.4; Romero et al., 2009; Busch & Hayward, 2009; Sheriff et al., 2011; Nelson &
Kriegsfeld, 2017).
Although I reported an increase in GC concentrations during high tourist pressure (see Chapter 3), elephants did not perform more stress-related behaviour during high tourist pressure (see Chapter 4). Discrepancies between physiological and behavioural measures of the stress response are not uncommon (Ellenberg et al., 2006; Maréchal et al., 2011). For example, Barbary macaques did show behavioural stress responses related to high tourist numbers present and high rates of occurrence of neutral, feeding or aggressive interactions, but only high rates of aggressive interactions between tourists and macaques were associated with increased fGCMs (Maréchal et al., 2011). Similarly, high tourist pressure in Madikwe was related to increased fGCMs alongside increased occurrence of aggressive behaviours.
Elevated GC concentrations make animals more prone to aggression, but it is also possible that engaging in aggression is psychologically stressful, affecting GC
concentrations (Muller & Wrangham, 2004), and animals may become increasingly anxious with the threat of potential occurrence of aggression (Maréchal et al., 2011). The connection between aggressive behaviour and GC concentrations has been established elsewhere. Creel (2001) discussed that high levels of aggression are related to increased concentrations of GCs in a broad range of mammals and birds. However, in humans, rhesus macaques, Macaca mulatta, yellow-eyed penguins, and African elephants, aggression has been linked to lower cortisol levels (De Bellis et al., 1999; Dettling et al., 1999; Hart et al., 1995, 1996; Westergaard et al., 2003; Grand et al., 2012; Ellenberg et al., 2007). For example, captive chimpanzees that received more aggression had higher cortisol concentrations measured in hair, whilst individuals which initiated aggression had lower concentrations of hair cortisol (Yamanashi et al., 2016). The authors concluded that receiving aggression may be an important contributor to long-term stress (Yamanashi et al., 2016). Similarly, Scheun and colleagues (2015) found increased fGCM concentrations in female African lesser bushbabies, Galago moholi, living in urban environments, and suggested this may have been the result of increased conspecific-directed aggression.
Muller and Wrangham (2004) stated that it is unlikely that performing aggressive behaviours, even though it may present a metabolically significant demand on animals, is the driving factor of GC production. It appears that receiving aggression increases GCs, whilst being aggressive may present a type of coping mechanism which reduces GCs.
Following results reported in previous studies, it is possible that individuals who
performed more aggressive behaviour had reduced GC concentrations compared to those who did not perform aggressive behaviour or received aggression from conspecifics.
Although it was not possible with the data collected for the research presented in this thesis, a fine scale comparison between elephants who perform aggressive behaviours,
compared to those who receive it, and associated fGCM concentrations of those individuals would be interesting to investigate to assess whether this hypothesis holds and fGCM concentrations of individuals who are more aggressive are lower.
I suggest that increases in fGCM concentrations and increased conspecific-directed aggression in the Madikwe elephant population during high tourist pressure were a coping mechanism in response to a perceived stressor (tourism). The results reported in Chapter 3 and 4 are in line with previous studies which suggested increased perceived stress to be related to aggression towards other species such as rhinoceros, Ceratotherium simum, as well as conspecifics (Slotow & van Dyk, 2001; Bradshaw et al., 2005; Jachowski et al., 2012). Further, elevated fGCM concentrations have been linked to hyperaggression of elephants towards humans (Slotow et al., 2008), so-called refuge behaviour where elephants restrict their movement to specific areas of their habitat with lower anthropogenic disturbances such as tourism (Viljoen et al., 2008b; Jachowski et al., 2012, 2013b, c) and direct interactions with humans (Millspaugh et al., 2007). For any reserve depending on tourist satisfaction and income from tourism, aggressive elephants which cannot be approached for viewing purposes or actively attack human observers, pose a serious threat to human safety and likely lead to a negative reputation for
elephant viewing amongst tourists. Further, this would provide poorer welfare and likely poorer health for those elephants. Reserves should therefore monitor elephant behaviour and aim to reduce tourist impacts to a minimum.
In addition to increased fGCM concentrations and aggressive behaviour, elephants also became increasingly likely to move away from GDs with increasing numbers of vehicles present (see Chapter 4). This increase in movement likely presents a minor energetical cost if only performed for a short distance or occasionally, but, if it occurs at a high frequency, it may become significantly more costly to individuals as they incur a cost,
for example to their foraging time and also in terms of energy expenditure. Higher numbers of tourists require higher numbers of vehicles to accommodate them on game drives. As one vehicle can fit a maximum number of 10 tourists, lodges need to utilise more vehicles when they accommodate more tourists (K. Potgieter, C. Catton, P.
Hattingh, pers.comm.). This increases the chances and frequency of elephant herds encountering GDs and hence herds may be moving away from present GD vehicles more frequently during high tourist pressure. It is possible that the cost of performing
aggressive behaviour alongside increased movement away from vehicles is related to an increase in GCs to make energy available for such additional movement (see Chapter 1;
Fig. 1.4). Further, high tourist pressure was related to increases in three different
mediators (GCs, aggressive behaviour, movement). Nevertheless, this remains speculative and fine-scale measurements would be necessary to make a more detailed analysis of which of the coping mechanisms and reactions to the perceived stressor occur first and whether increases in all three above mentioned mediators do occur simultaneously and incur a high enough cost on, for example, foraging behaviour.
Chapter 5 reported on the fact that elephants did not appear to alter ranging behaviour in relation to high tourist pressure. This was unexpected, given that wildlife tourism was assumed to be a stressor to elephants based on the results presented in Chapters 3 and 4. However, the data stems from only three female elephants and, as discussed in Chapter 5, Madikwe may not be a large enough reserve to allow elephants to alter large-scale movement such as habitat size and distance travelled. Additionally, large areas of Madikwe contain dense habitat within close vicinity of the road (I. Szott,
pers.obs.) and elephants could have been a short distance from the road whilst being removed from the sight of tourists. This could have further reduced the need for large-scale alterations of spatial use for elephants. However, more data is required before either a conclusion or alternative explanation can be made. At this point, the observed
increase in GCs (see Chapter 3) did not appear to be related to increased amounts of energy related to changes in large-scale spatial movement of elephants in Madikwe (Fig.
1.4).
The coping mechanisms performed by elephants in response to wildlife tourism which have been reported in Chapters 3 and 4 may have been successful to cope with the perceived stressor (Romero et al., 2009). Therefore, large-scale alterations of spatial movement were not necessary for elephants to cope with the perceived stressor. As seen in the scheme in Fig. 1.4, I suggested that, if the stressor cannot be avoided by alterations in spatial behaviour, changes in behaviour may be necessary in order to cope, and this is what was reported in Chapter 4.
In response to a perceived stressor, physiological mediators increase (Romero et al., 2009). This itself is adaptive in the short-term and does not present an immediate concern for the individual’s welfare. However, high tourist pressure was observed for several months at a time and elephants may perceive stress long-term given the increase in GCs, aggressive behaviour, and movement away from the stressor. Even this may not be a welfare concern in itself. However, if individuals encountered additional stressors, such as extreme drought and increased competition over resources, they would be less well equipped to react and adapt to such additional stressors (see Fig. 1.1C; Romero et al., 2009). Further, when individuals perceive stress for a prolonged period of time, this can be chronic and lead to the associated negative implications discussed in Chapter 1, such as impaired immune function, loss in body condition or reproduction.
Overall, the results relating to high tourist pressure in Madikwe suggest some degree of negative impact of wildlife tourism on elephants, potentially chronic for several months each year, when tourist numbers are above a certain threshold. However, taking into consideration the lack of changes in large-scale spatial behaviour and average fGCM
concentrations comparable to reported values of other elephant populations, I suggest that the results presented in Chapters 3 to 5, at this current stage, do not present negative welfare concerns related to the effects of chronic stress. However, high tourist pressure was related to fGCM concentrations comparable to those of elephants with foot injuries (Chapter 3), as well as increases in aggressive behaviour (Chapter 4), both of which have been identified as stressors. Therefore, the results of the research presented here do warrant consideration and continued monitoring in terms of future management at Madikwe.