Operant training differences between male and female group-housed nonhuman primates (2009)

Egeler, J.

Abstract

Our study group consisted of 16 male (2.24-2.80 kg) and 16 female (1.96-2.91 kg) Chinese cynomolgus macaques (Macaca fascicularis), 2.5-3.5 years of age, that were housed in groups of 4. Our goal was to train the animals to come to the front of the cage, station, and stay at a target that was placed onto the front of the cage. Training sessions were conducted once a day, 3-5 days per wk, for approximately 10 min per group.Shortly into the training program, it became evident that the decision to house the monkeys in groups of four was having an effect on the training of the females. The females seemed to be much more cautious and reserved than the males. Although both sexes developed hierarchies within their groups, the difference was much more noticeable with the females. The gregarious nature of the males negated any effect dominance had on training; the drive for food seemed to outweigh any pressure the subordinate animal would receive from the dominant animal. The females' hierarchy, on the other hand, was so rigid that it prevented progress with the more subordinate animals. Approximately 8 wk into the training program, we moved the animals into slightly larger banks and separated males and females into their own rooms. The males adjusted quickly, and resumed their normal training schedules. The females, however, became more difficult to work with and even regressed in terms of the progress they had made prior to the move. There are several factors to consider when starting an operant conditioning program: the time needed to train animals, the necessity of training in groups (smaller groups are easier to train), and the animal's sex (males are easier to train). As we learned, some types of enrichment worked better for certain animals. You have to experiment with a variety of enrichment types to find out which kinds work best for your animals. Using a wide range of food items prevents the animals from losing interest in the training. It's also important to train in slowly, in small segments that maximize the time you can train without filling up the animals and losing their attention.Some animals responded better to the PVC elbow than to the pipe. If you have a difficult animal that won't touch the pipe, try skipping ahead to the elbow and see if that works.It is important to be patient when training monkeys. The work described above took place over a 6-mo period. Although many of our males were doing well by the 3-mo mark, training was a continual process. We had days where all of our work seemed to be heading nowhere, and other days where everything seemed to come together. Give your animals some time; they will surprise you!