«Item type Thesis or dissertation Authors Davis, Nicolas Citation Davis, N., Schaffner, C. M., & Smith, T. E. (2005). Evidence that zoo visitors ...»
Firstly, the introduction of a new adult male spider monkey led to a variety of changes in the proximity dynamics for residents. The arrival of the new male was
*no samples were available from Poy as it was not possible to collect them from him associated initially with a significant increase in the proportion of time the female residents spent ‘in contact’ with other group members as compared to the preintroduction period with the original male. Over the following phases of the study this proportion gradually decreased, finally returning back to control levels in the last time period. An associated inverse pattern was also found for the proportion of time spent by the resident females in ‘no contact’ with a significant decrease from the control period to the period of the arrival of the new male. These proportions then increased over time with the final period again illustrating levels similar to the preintroduction period. There was also a trend for an increase ‘in proximity’, representing the number of residents within arms reach, following the introduction of the new male. This increase in contact is consistent with other studies that show that the presence of significant social partners can have beneficial effects during the exposure to a physical or psychological stressor (T. E. Smith, et al., 1998; see Chapter 5).
For the new male there was a lower proportion of time spent ‘in contact’ that he spent with other members of the group compared to the previous resident male, dropping to almost zero at the time when the new male was introduced. By the end of the study there was a slight increase, although this was still very small compared to the rate of contact that the resident male had with other members of the group.
There was also a corresponding change in time spent in no contact. Finally, there was a pattern of a reduction of time ‘in proximity’ over time. Contact and proximity towards the new male was almost exclusively by the sub adults and juveniles in the group, and this decrease may be explained by an initial interest in the new male waning. It is possible that these changes in proximity may have been influenced by the restrictions to the use of the enclosure, for example during the ‘introduction’ and ‘inside’ phase the group had only limited access to the outdoor enclosure. However, during the time of year when the study took place, the spider monkeys normally spend the majority of their time in the inside enclosure.
There were also significant changes in some self directed behaviours over the study period. There was a pattern of change for ‘self scratching’ behaviour in resident females, with an increase following the arrival of the new male as compared to the control, before a decrease back to control levels by the end of the study. The new male showed a gradual decrease in scratching rates over time. The new male also spent a considerably smaller proportion of time ‘auto grooming’ as compared to the previous male although this may be due to individual variation. Scratching and other self-directed behaviours have been used as an indicator of anxiety in other primate studies (Carder & Semple, 2008; Maestripieri, 2000; Maestripieri, et al., 1992), and its pattern in this study seems to demonstrate such a link.
For the resident females there were fluctuations in groom other over time.
There was a significantly high rate of grooming when they were restricted to the inside enclosure only, although there was no consistent pattern over time. This is not unexpected as grooming has been identified as an important tool in primate social relationships (Dunbar, 1988), in reducing tension and in mediating the adverse effects of conflict and aggression (Aureli, Preston, & de Waal, 1999; L. Barrett, et al., 2002). It was interesting that groom other was not significantly higher when the new male was in the back or first introduced to the females. However, given females were in close social contact with each other, this may have served the same reassuring function. In addition, the females may have been more focussed on monitoring the activity of the new male, which would have made grooming others an incompatible task. However, I did not score gaze direction or scanning in this study.
Furthermore, groom other may not have the same importance in regulating social relationships in spider monkeys as has been identified in other primate species (Schaffner & Aureli, 2005). The increase in grooming in females might have also reflected changes in the dynamics of female relationship regulation due to confinement in a smaller space (Caws & Aureli, 2003).
Regarding locomotion, there were no significant changes over time for either resident females or males. An increase in locomotion has been proposed as a potential indicator of stress in response to a variety of stressors (T. E. Smith, et al., 1998). For example, increases in locomotion have been found to be positively correlated with increases in urinary cortisol in marmosets during movement to a novel cage (T. E. Smith, et al., 1998). This study does not seem to illustrate such a link, but restrictions on movement due to being restricted to the indoor part of the enclosure may have had an impact. No changes were found over the study period for the proportion of time spent resting or feeding in either resident females or males.
Cortisol levels in the resident females were significantly affected by time but the expected increase following the arrival and the introduction of the new male was not apparent. Although post hoc tests did not reveal any significant changes across time there was actually a decrease in mean values of cortisol following the departure of the old male, and were actually at their lowest at the period of introduction, before rising again following full integration. The overall stress response was not as dramatic as seen in previous studies for other stressors and was comparable to events considered less severe, such as incidents of minor aggression, ovulation and temporary separation (Chapter 5) and this may be due to a number of reasons.
That cortisol levels fell following the departure of the previous male suggests that he may have been a source of stress for some of the resident females. This may not be surprising following the catalogue of aggressive incidents for which he was responsible (see Chapter 5). That the mean levels of cortisol did not increase greatly following the arrival of the new male suggests he was not seen as a threat, even though most of the adult females still had offspring in the group. That no aggressive behaviour was ever observed by him towards the other members of the group, and that throughout the study period only one aggressive incident occurred also supports this. This is in contrast to that recorded for introductions and group formations in other captive primates where aggression and injuries are frequent (Brent, et al., 1997;
M. R. Clarke, et al., 1996; Gust, Gordon, & Hambright, 1993; Westergaard, et al., 1999).
The aggressive event happened on the morning of the third day after the introduction with the group. The new male had approached a sub adult female when she was feeding and she responded with a small fear vocalisation. This small cry led to all of the adult females simultaneously launching a prolonged attack against the new male lasting for around 30 seconds. The fight resulted in minor cuts to two adult females (Mar and Chr) and to the separation of the male for a further 24 hours. Apart from the hours immediately following the fight the new male showed no obvious signs of anxiety throughout the study period and tended to keep away from other members of the group. The highest cortisol values were recorded in the new male immediately following his arrival, although the levels were not excessively high and later decreased. The low numbers of samples obtained from the new male over this study period was due to his reluctance to enter the tunnel for sample collection. This makes it difficult to know the extent of his physiological response to relocation.
Although there were no significant changes in cortisol in the resident females the significant changes in behaviour suggest that the introduction of the new male did evoke a stress response. The behavioural response is normally the first reaction by an animal with an attempt to avoid the stressor by simply removing itself from the threat (Sapolsky, 2000; see Chapter 1). This along with the social buffering effect of significant partners appeared to have reduced the need for an endocrinological response and demonstrates the importance of social partners when exposed to a stressor (T. E. Smith, et al., 1998). It would therefore have been expected that the new male without the benefit of an established social partner would have evoked an increased stress response. Unfortunately the lack of samples from the male in this study means that his endocrinological stress response could not be measured. Over the study period the male spent very little time in contact with the residents although there was a gradual increase in proximity. A follow up study would have been beneficial in establishing the overall time period for full acceptance with the resident group.
The likelihood of a successful introduction of an individual into a social group is dependent on a number of factors. Firstly, it is important that the species natural behavioural characteristics and social organisation are considered (Pfeifer, 1996). In this case the introduction of a male into a group of females is not what would be expected in the wild, with immigration normally carried out by the maturing females (Aureli & Schaffner, 2008; Fedigan & Baxter, 1984), although recent evidence from the field suggests some male immigration may occasionally occur when there are sufficient vacancies for breeding males in a given community of spider monkeys (Aureli & Schaffner personal communication). The fission fusion social organisation of spider monkeys may have also reduced the impact of the separation of the new male as they are more adapted to deal with such separations.
Individual characteristics and temperament may also be an important factor with certain individuals being more suited to successful introduction (Wemelsfelder, 2007). The new male appeared much less aggressive than the previous male, and this can be influenced by a variety of factors including age, sex, previous experience and previous housing. Based on the spider monkeys’ social organisation the introduction of another female into the group would not be expected to elicit a significant negative response in males, although resident females may aggressively target new residents initially (Asensio, et al., 2008; Slater, et al., 2009). If the current introduction had occurred while the previous male was still resident then integration into the group would have been much more difficult, with similar difficulties as reported in chimpanzees in captivity (Alford, et al., 1995; McDonald, 1994).
The relocation of animals between zoological parks is essential to ensure the genetic diversity of the populations of endangered animals is maximized. However, the consequences of such moves can be stressful for the relocated animals and the resident group members in which they are to be introduced (Kleiman, 1980). The monitoring of GC levels has been identified as a practical tool to identify the stress response following the relocation of animals and their subsequent introduction (Schaffner & Smith, 2005). A few previous studies have examined the stress response of relocation of animals between zoological parks (Goymann, Mostl, Van’t Hof, East, & Hofer, 1999; Laws, et al., 2007), but they are generally short term studies looking primarily at the effect of transportation rather than the effect of an introduction on the individuals. These current results show that this introduction of an adult male into an established breeding group of adult females and their offspring did result in an impact on the adult females HPA axis, associated with a stress response, although not in the manner predicted. There were also associated changes in some aspects of their behaviour. However, these changes were not comparable to previous stressful events such as aggressive incidents that had occurred at other times during the overall study (see Chapter 5), and so not enough to suggest that this particular introduction resulted in sustained levels of stress that would be deemed bad for their overall welfare (Moberg, 2000). In fact such controlled events may even be beneficial to the monkeys by providing a social stimulus and interest (Chamove & Moodie, 1990).
The technique of a gradual introduction although still eliciting an increase in GC levels for the resident females along with some associated behavioural changes seemed to follow previous studies in captive primates (Brent, et al., 1997; Reinhardt, et al., 1995) and reduce the overall impact of the introduction. By having the facility to separate individuals from a group but to remain in full visual and tactile contact helps facilitate what can be potentially stressful events such as introductions and should be recommended as a management technique for future introductions in spider monkey groups.