This method can help to answer key questions in the emerging field of environment strategies for laboratory rodents, such as the stress reduction in routine husbandry procedures. The main advantage of this technique is that it can help to improve the routine process of cage-changing and in this way helps to improve the well-being of laboratory rats. Generally, individuals new to the method might struggle because the timing of the rewarding and the overall handling of the rats are critically important.
First, bring the home cage to the training area, which should be a quiet place with limited distractions. Ensure that all required materials, such as the reward, the clicker, the target stick, a timer, the metal tube, a clean cage, and any other specific training materials are on hand. Critically observe the rats for any sign of discomfort throughout the procedure.
Next, remove all items from the home cage. Only the trained rat and the observer rat and the bedding material should remain in the cage. Place a short tunnel in the home cage, preferably one made from a material that the rat is familiar with.
Wait until the rat sits in the tunnel and then offer the rat the reward. As soon as the rat shows interest, and is about to start nibbling on the reward, click, and then let the rat feed on the reward. To ensure that the pairing of the two reinforcers is successful, repeat clicking, and then rewarding for 15 seconds.
If the rat is not feeding under the circumstances of the training situation, the habituation phase must be extended or adjusted. If the rat did not participate, check for signs of a connection between the primary and the secondary reinforcer by administering the click without the reward. Signs of a connection include the rat sniffing for the reward, looking around for the reward, or lifting to its forelimbs to look for the reward.
If this occurs, move on with the next part, otherwise, repeat training day one. For the next phase of training, place a short tunnel of the same material as the tunnel to be used to link the two cages. Start the timer and immediately begin with the first 30 seconds of training.
The first time the rat shows interest in the tunnel, present the reward at the end of the tunnel. As soon as the rat enters the tunnel, click and then let the rat eat the reward. Take away the food reward and wait until the rat shows interest in the tunnel once more.
Click as soon as the rat enters the tunnel and present the reward at the end of the tunnel. After 30 seconds of training, remove the tunnel for a 15-second break. Repeat the 30 seconds of training with the subsequent 15-second break for four minutes.
If the rat shows the desired behavior more than four times a minute, stop clicking and just reward with the primary reinforcer. Start the timer and immediately begin with the first 30 seconds of training by placing the globe of the target stick near the rat. As soon as the rat shows interest in the globe, click and reward the rat.
Repeat this several times. Add a break every 15 seconds and then go on with the training. If the rat shows interest in the globe more than four times a minute, the next behavior to reinforce is touching the globe with the nose.
If the rat repeats that behavior for more than four times a minute, stop clicking and just reward with the primary reinforcer. Here, only the passing the tunnel towards the clean cage is reinforced. Build the connection between the home cage and a new clean cage by a tunnel by inserting a longer version of the tunnel already familiar to the rat.
On day one, perform no training and just let the rats inspect the tunnel. There is a good chance that they will pass through the tunnel on their own. On day two, give the rat two minutes to transfer through the tunnel on its own from the dirty to the clean side.
If the rat does not move through the tunnel, start the first 30-second training session by clicking and rewarding the rat as soon as it shows interest in the tunnel. Next, click and reward the rat's entrance into the tunnel and go on to click and reward if the rat goes deeper into the tunnel. Continue in a similar manner until the rat runs through the whole tunnel.
As soon as the rat starts peeking from the end of the tunnel into the clean cage, present the globe of the target stick, click, and reward for touching the globe. Lastly, guide the rat to leave the tunnel. Present the globe in front of the tunnel and click and reward the rat as soon as it steps into the new cage and touches the globe.
Put one hand under the belly or around the chest and support the hind legs of the rat to lift it out of the clean cage and place it back into the dirty cage. Then present the globe of the target stick in the center of the clean cage. Click and reward as the rat runs through the tunnel and touches the target stick.
If the rat repeats the behavior for more than four times a minute, stop clicking and just reward with the primary reinforcer. 10 female Lister Hooded rats were trained to change cage via a metal pipe by clicker training. The training was evaluated in three categories.
No participation, explorative behavior, and aimed behavior. All rats acquired the trained behavior after five days of training. After four weeks of observation, cage mates of trained rats were evaluated for voluntary cage-changing behavior.
Overall, 80%of the observational learning group changed cages via the metal pipe. After four weeks of training, all rats were restrained and vocalizations, defecation, and urination were recorded and summed to calculate a fear-related behavior score for each rat. The untrained group showed an increased fear-related behavior score, compared to that of the trained and observational learning groups.
While attempting this procedure, it's important to remember to observe the rats for any signs of discomfort and that all interactions must be in an animal-friendly way. Following this procedure, experiments in other scientific fields like behaviorism, neuroscience, or immunology can be performed with the benefit of happy, unstressed animals.
