Tue 20 May 2008
Since Penn State University in in the middle of Pennsylvania and has adequate amounts of farm land, there is also an on-campus creamery which contains various dairy products. I typically visit for the cheese, not the ice cream. During my last visit, I had the novel idea of trying to determine if rodents have a predisposition to cheese, as we have been taught by movies, cartoons and rat-trap vendors.
One of the groups at CNE that I design electronics for is looking at navigation and memory in Long-Evans rats. These rats look like little cows as they have both black (or dark brown) and white splotches covering the whole body. The rats typically run on a maze where they have to make appropriate path selection based on training and one of the rewards that they receive are pieces of a high-sugar kids cereal like Fruit Loops. At first, the rats are hesitant to eat them as they have no idea what the strange loops are and they see that they are different from their typical “Feed 5000″. After being given the fruit loops a few times, the rats become more accustomed to them and visibly prefer them to their normal feed. With this observation in hand, we set out to roughly see if rats ad an a priori preference for cheese.
We bought a fresh package of white cheddar cheese and broke off a few small pieces to offer to several rats that were not participating in any experiments. We only did one trial, however, we fed the cheese to several animals. The results were very similar to the fruit loops where the rats were hesitant at first to this novel object but eventually warmed up to it and also demonstrated visible preference over their normal feed. The important result was that none of the rats habitually went for the cheese after identifying it as though they had some kind of built-in fondness for cheese. Some took a few nibbles and then discarded it until a later time. From a practical standpoint, cheese may be a good reward snack for a rodent provided they have enough exposure to it to appreciate it, however, this poorly-controlled study leads me to believe that cheese would not attract rats like it does in cartoons (unless, of course, the rat had already been habitually eating the dairy product).
( Image is from the Spittoon. )
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May 21st, 2008 at 9:53 am
It’d be interesting to also try peanut butter.
Dave
May 21st, 2008 at 11:19 am
We might try it in the future. So far we have tried chocolate, nutella, ensure drink, and sugar water in addition to the above and have not noticed any “inherent” taste for the treats. That is, all of the rats enjoy the treats after a few tries, but none of the treats are well liked immediately.
May 22nd, 2008 at 10:53 am
The nice thing about peanut butter is that it has a “pleasing” aroma. I’m not sure how many of the other things have that much of an aroma.
Dave
P.S. Or, maybe you’ll discover that rats have peanut allergies?
May 23rd, 2008 at 10:00 am
Hi Dave,
We tried peanut butter today to test your hypothesis. We gave a little bit on the end of a wooden rod to a pair of rats that had tried both fruit loops and cheese before and also to a pair of rats that had never tried anything other than the standard rat feed. None of the animals were particularly excited about the peanut butter from the very start, however, they all acquired a preference for it more quickly than cheese or fruit loops. We had the lights on when we did this, so the rats’ vision was impaired, which leads me to believe that scent played an important role here. In the end, I think peanut butter might be a more pleasant reward, although it is messier than fruit loops. Maybe we will start keeping a jar in the lab. Thanks for the tip Dave!