Dealing with aggression by marmoset finger monkeys

Strategies for avoiding aggression by marmoset finger monkeys

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† Training staff to understand, anticipate and respond appropriately to primate behaviour, encouraging positive staff–animal interactions

† Use of windows in the doors, or glass doors, so that animals can see human activity and know when humans are approaching

† Positioning verandas for small primates at the front of their enclosure to enable the animals to survey their environment and see humans arriving

† Use of widely spaced horizontal bars to construct enclosures (rather than tightly spaced, vertical ones), as this increases visibility and can facilitate human–animal interaction. It also allows animals to climb more easily

† Positioning water bottles and food hoppers at the front of the enclosure to encourage animals to come forward

† Holding a container (e.g. plastic ice cream tub) for marmosets to jump into to have their bodies tickled and for play with humans

† Minimizing excessive noise levels in the vicinity of the animals and talking to the animals in a calm voice

† Ensuring positive staff–primate interactions instead of only interacting with animals when an adverse event takes place (e.g. encourage animals to accept part of the daily ration or food treats, such as grapes, from the hand)

† Spending time each day (e.g. 15 min) sitting with the primates in their enclosure

† Playing games with the animals in their home enclosure (e.g. catch or find the food treat)

† When changing litter or spot-removing faeces, allowing the animals to remain in the enclosure with the staff

† Providing angled mirrors that the animals can adjust to allow a view of areas outside the enclosure 

Identifying the cause of aggression. 

The first step in effective management of aggression is to identify the reason for the behavior and the stimuli that trigger an aggressive response in a particular animal or group. Some useful questions to consider are listed below.

• Is the aggression within or between groups?
• Is there any particular timing of aggressive incidents throughout the day?
• Is it linked to any potential event that could increase the
• level of arousal in the animals such as feeding, moving or weighing animals?
• Is one particular animal always the aggressor or victim?
• Does it seem linked to a particular resource such as a perch or nest box?
• Is it linked to any particular member of staff?

It is important to record details of when the incidents occurred, who was present in the primate unit at the time, what activity was taking place (e.g. cleaning, feeding, weighing), the level of injury to the individual animals involved, and the behaviour of those individuals and other members of the social group before, during and after the incident. A video and sound remote monitoring system can be very helpful in this regard.

Reducing conflict. Ways to reduce the chances of conflict occurring are listed below.

† Identify animals likely to be compatible by careful obser- vation of their behaviour towards each other.

† Obtain primates in pre-existing groups or compatible pairs and avoid regrouping them on arrival at the scien- tific establishment.

† House individuals of different ages and/or body weights together since they are then less likely to compete with each other . For example, stability in groups of less than 10 young marmosets can be restored by introducing an older animal to the group, but manage this carefully in case the older animal is challenged.

† Design complex enclosures with escape areas, visual barriers and plenty of enrichment. 

• †  Increase enclosure size to permit more effective primate signalling of dominance, approach and withdrawal responses, avoidance of aggressive individuals and/or retreat to a safe distance 
  
  
• †  Maximize the stability of the group by reinforcing the natural social order within the group. Attend to the more confident individuals first when greeting animals, and allow these individuals to be the first of the group to go through doorways and receive treats or food. 

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• 0. Dealing with serious and/or persistent aggression. Where persistent aggressive behaviour cannot be prevented by increases in enclosure size and complexity, animals will need to be separated. Where serious aggression arises in an established group of animals, it may be possible to sep- arate them into compatible subgroups. It is advisable to remove animals to ‘neutral territory’ and put physical space between the subgroups, preferably moving them into separate units, rather than across the aisle of the same unit. This should avoid continuing displays of social conflict.
     
     Alternatively, an individual animal may need to be removed. However, removing one of two fighting individuals can be problematic. Removing the dominant aggressive animal may result in subsequent fighting to reinstate the dominance hierarchy in the enclosure. Removing the subordinate animal may result in the dominant aggressive animal intimidating another animal within the group. Both options have been tried with varying degrees of success, and more information needs to be gathered in order to determine the best approach. Individuals that have to be removed may find the social environment of another group more compatible; for example, a dominant animal may be less dominant in another group.