In a shoebox-sized cage on their own floor in the Anderson Building at the Baylor College of Medicine, two little white mice with pink ears and skinny tails scurry over a bedding of corncob strips. They run from corner to corner, now and again standing on hind legs to press their paws against one of the cage’s clear plastic walls. Occasionally, they bump into each other and take a sniff. Mostly, they do their own thing.
On another floor of the same building, larger cages hold white rats that can’t seem to stay away from each other. They pounce, wrestle and roll. It’s impossible to avoid the comparison: They act like puppies.
“You can actually grab the rats and put them in your hand and treat them exactly how you would treat a puppy,” says Surabi Veeraragavan, a behavioral geneticist at Baylor in Houston, Texas. Regular handling, she says, helps rats get used to the scientists who study them. “You can put them on your shoulder, you can put them on your arms; they will go to sleep right away. You can pet them and play with them.”
Holding a rat can be like cradling a baby, adds Rodney Samaco, the molecular geneticist who leads the Baylor team. “They like to put their head in the crevice of your elbow,” he says. They practically purr. “You tickle their stomachs; they like that.”
“They love that!” says Veeraragavan.
The Baylor team also studies mice, which were there long before the rats and still outnumber them. But when Samaco and Veeraragavan talk about the lab’s mice, their words are less affectionate: The mice are less social, their behaviors simpler; they aren’t nearly as cute.
If you put a mouse on your arm, as you would a rat, it wouldn’t end well, says Samaco. “They would look very nervous,” he says. “Then, they would bite you.”See - it's not just me who finds them cute...