Egeler, J. L. 2010. Operant training differences between male and female group-housed nonhuman primates. Tech Talk [The Newsletter for Laboratory Animal Science Technicians] 15(6), page numbers missing.

Operant training of animals is a widely accepted practice to train or condition animals to cooperate with technical procedures or perform certain tasks in a laboratory setting. This type of training has been proven to reduce stress on the animal and reduces potential injuries to the animal or its handlers. However, it has been suggested that female cynomolgus monkeys are more difficult to train than males. In conjunction with our goal of offering group housing that meets European standards for nonhuman primates at our facility, we implemented an operant training program to train animals to be removed from the new, larger-style caging. Our data support the theory that females are more difficult to train than males. This article outlines the necessary steps in developing and implementing a successful operant training program in untrained monkeys, and describes how we assessed program progress and adapted the program to meet various challenges. 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. Clicker training was used to connect a food reward with the desired behavior. We did this approximately twice a day during our normal cage side observations. Once animals showed no fear of the clicker (approximately 1 wk), we introduced the PVC pipe. Once or twice a day, we stuck a small length of 0.5-in. PVC pipe into the cage; when the animal touched the pipe, we pressed the clicker button and offered a reward. As animals became conditioned to touch the PVC pipe to receive a treat, we taught them to station. We attached PVC elbows to the front of the cage (one per animal). When animals came forward and touched the elbow, we pressed the clicker button and offered a reward. If animals wouldn't touch the elbow, we placed the food reward on the elbow and clicked when they came forward to retrieve it. To keep the training new and fresh, we varied the time of day training was conducted, and moved the targets to various spots of the cage to train the monkeys to follow the elbow instead of learning to stay at one particular place.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.To improve the success rate of our training program, we housed the females in pairs. We also provided positive human interaction to both males and females during handling by petting them, speaking to them in a soothing voice, then offering a treat before returning them to their home cage. Many of the females responded favorably to these changes. For some of our more difficult female pairs, separating the pair for the training session seemed to help. This separation allowed the submissive female to 'come out of her shell' and participate in the training without the disapproval of her dominant companion. For other females, improvement was achieved by trying different types of enrichment until we found one that they would respond to. Recommendations: 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 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!