The Chemistry of Instinct: Here's What Makes Mice Freeze in Fear

By Eliza Strickland | May 18, 2010 1:05 pm

cat-mouseIt’s the essence of instinct: If you take a lab mouse who has never caught a glimpse of a cat and waft a little eau de feline towards it, the mouse will freeze in fear, and will then back away from the source of the odor. Now researchers have pinned down the chemical signals the mice are reacting to–and have shown in the process a fascinating new form of inter-species communication.

Mice have a specialized organ in their noses that picks up chemical signals, called the vomeronasal organ, which helps them detect pheromones emitted by other mice. These mice pheromones have a direct effect on behavior–most obviously in the realms of mating and fighting. In this new study, published in the journal Cell, neurobiologist Lisa Stowers decided to investigate whether the vomeronasal organ was capable of picking up signals from other species as well.

The reseachers took normal lab mice and mutant mice with inactive vomeronasal organs and presented them with cotton balls laced with predator smells, including cat saliva and rat urine. The normal mice backed into the corners of their cages as if trying to escape a predator’s attention, but the mutant mice showed no signs of concern. The mutants were so relaxed that they didn’t even react when a live but anesthetized rat was placed in their cages.

“In fact, one of our subjects curled up and went to sleep next to the rat,” Dr. Stowers said. “We think he was cold” [The New York Times].

The researchers then identified the precise chemicals that were triggering the fear reaction in mice by dripping one chemical compound at a time on to a cotton ball, and found that compounds called Mups, or major urinary proteins, were the active ingredient. Despite their name, Mups aren’t only present in urine, but also in saliva and other secretions.

Experts say this work is a major step forward for understanding the biology of fear.

“This paper moves the field forward by about a century, because it actually identifies the proteins that are responsible for eliciting fear in mice,” says Leslie Vosshall, a neurobiologist at the Rockefeller University in New York City. It also shows that “Mups can be used not only for chemical conversations of animals in the same species, but they can also send information across species” [ScienceNOW].

Related Content:
80beats: Sniffing Out Sickness: Mouse Noses Respond to the Urine of Diseased Mice
80beats: Mammals Have a Nose for Danger (Literally)
80beats: Do Humans Communicate Via Pheromones? The Jury Is Still Out
DISCOVER: The Brain: The First Yardstick for Measuring Smells
DISCOVER: Top 100 Stories of 2009, #75: Yes, You Really Can Smell Fear

Image: iStockphoto

  • Louie Gedo

    As someone who refuses to use glue traps and such and also as a big fan and admirer of mice because I feel they too, just as the cats and dogs we love, have a right to live their life, I wish someone would develop a liquid to be used in a small spritzer which contains the odors that mice fear so that people can deter mice from habituating an area (spritzing in areas inside or outside the home to deter mice from occupying certain areas) without having to resort to heinously cruel and diabolical devices such as glue traps. Think about owning the successful patent on a product that could hypothetically spare people from having to see, smell, and deal with dying or killed by poison mice in their home.

  • Scott

    Louie, good news and bad. You can already get this liquid, it’s called cat urine, and can be “harvested” directly from a small furry creature called a cat, many of which will be happy to apply the liquid directly to your walls and furniture for the nominal fee of providing “cat” food and entertainment.

  • http://discover Nancy

    Scott, I haven’t stopped laughing yet. However, I do think Louie was thinking more along the lines of some version of non-stinky eau d’ chat.
    It IS a great idea. I remember years ago some zoo was selling Tiger Scat to homeowners to scare away coyotes, same principle.

  • HC

    We have a cat. As far as I can tell, “when the cat is away, the mice are at play.” Aside from that, I know neighbor’s cats get into our yard and do their business. What they leave behind do not seem to deter the little squeaky critters.

  • AJC

    I wish I had more mutant mice round my house. Can’t tell you how many times I’ve chased a mouse around my living room after the cat has brought us a little pressie at bedtime!


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