This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
I’m rethinking my feeding enrichment protocols. My pouched rats, Cricetomys gambianus and C. ansorgei, are food generalists but in the lab we feed them commercially available rodent or rabbit chow. In the past I’ve included dog food as a part of their regular diet to get protein in the diet. Then I would offer fresh produce like citrus, carrots, celery, and bananas as treats.
Offering my subjects high value food treats is a carry over from my vole days. On cage cleaning day I would add a pinch of raw sunflower seeds to the cage. It seemed to be a good way to distract the voles from the stress of the big hand in the sky ripping their home away and transferring them into a strange foreign cage. The high fat seeds were a hit and in my mind chubby voles were happy voles and that was okay with me.
But now I’m working with a species that is not well-understood, so I need to be careful not to offer too many calories for my subjects. They aren’t as active as little voles and despite my investment in a wheel running apparatus, my pouched rats are not getting much aerobic exercise.
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Why does enrichment matter?
Overall, enrichment is valuable to keep animals healthy – physically and psychologically. In rats and mice, animals without enriching environments often demonstrate stereotypy and other negative behaviors including self harm.
Nutritional enrichment is beneficial because it not only offers animals important nutrients, but it can also be used to offer enriching experiences to ‘spruce up’ an animal’s bland living situation. After all, in nature animals aren’t living in 2x2x2 feet cages with a hopper of monotonous food with out the opportunity to encounter other animals including conspecifics and predators.
Enrichment is good and encouraged by animal oversight boards; but I had a real talk conversation with myself and realized that I was giving nutritional enrichment out of my own perceptions about food. I see food as a salve. In my personal life I have witnessed or routinely used food to make less pleasant situations better. Feeling sad? Here’s a cookie. Bored, wish you were somewhere else? Here, let’s snack on this popcorn. In my head, offering treats was a way to get my pouched rats to ‘settle into the routine’ of lab living — and it certainly can be. Offering a high value treat is a great way to get animals to go along with cage cleaning routines, be picked up and handled, and examined or even treated. But were these the reasons why I was doing it?
Right now, I have a major hurdle: getting my animals to spontaneously behave in my behavior experiments. I conduct research tests and one of the tests I’ve had the darnedest times executing is the T-maze. It’s an alternation-learning test where an animal discovers/learns that there is a treat on a certain side of the apparatus. After repeated consecutive exposures to the T-maze, subjects will find the treat on the same side of the maze – every time. Then finally, just as they get the hang of it, the experimenter switches sides.
Seems easy enough right? Well, in my attempts to execute this test I had so many woes. Most subjects didn’t care to enter the maze in the first place. Others weren’t very interested in the banana flavored sugar pellet treats.
I’ve talked to many researchers who employ this and similar tests and the conclusion is — sated rodents don’t perform. In many behavioral pharmacology and experimental psychology research labs animals are food restricted such that they are maintained at 85% of their body weight. Every time this suggestion has been made to me I hesitate and come up with list of reasons why this isn’t appropriate for my animals. “I conduct spontaneous behavior. External motivation isn’t required.”
Perhaps weight loss or hunger motivation isn’t all the way called for. (I’m such a sucker, but I admit that.) But I acknowledge that I need to at least make these guys “work for their treats”. What was once a buffet of seeds or produce is probably best saved for behavioral testing so that I can use the experiences to learn more about what they like, really like. This means I have to take the tasty seeds and random apple and orange slices offerings away. The next time they get snack it will associated with a behavioral experiment.
