The genetics are beautiful,” Dr. Bargmann added, “But it is only the beginning.

Now comes the hunt for the genes themselves, and perhaps even the biochemical pathways that show, step by step, how a DNA blueprint is transmitted to the scrabbling paws of a tiny mouse and translated into a hide-out from foxes, hawks and other predators.

The investigation of the genetics of behavior is a huge scientific enterprise, with great progress being made in a variety of species — roundworms, fruit flies, lab mice, sticklebacks. Dr. Hoekstra’s work is unusual in that it deals with a naturally occurring, complicated behavior in mammals that is important for survival. And it is significant that she has been able to separate that behavior into two modules controlled by separate and independent DNA regions — burrow length, and escape tunnels.

Dr. Bargmann said she was impressed at Dr. Hoekstra’s success in unpacking the behavior into modules, a result that adds to the likelihood of one day finding simple genetic controls underlying the mystifying diversity of natural behavior patterns. The extraordinary variety of animal body shapes, after all, has been found to grow out of a relatively few master control genes.

“I really believe that there are rules for behavior that go all the way back,” Dr. Bargmann said.

One component of Dr. Hoekstra’s success has been oddly low-tech: the kind of fast-hardening foam that can be purchased in a hardware store for home repair. It quickly produces an easily measured mold — behavior solidified.

Another important factor is as high-tech as tech gets. Decades ago the evolutionary biologist Richard Dawkins suggested that one could study the evolution and genetics of behavior just the way one studies the evolution of body shape: concentrate on what animals build — birds’s nests, beaver dams, termite mounds — and treat them like beak length or coat color. Writing before the development of enormously powerful technology for analyzing DNA, he regretted that his proposals were hypothetical.

They are hypothetical no longer.

From Volleyball to Research

Dr. Hoekstra spends a lot of time explaining that her first name has nothing to do with the Native American Hopi tribe. It comes from a Dutch term of endearment, meaning a little bundle, that her grandmother called her when she was a baby.