A rodent that can outlast a camel in the desert

  • Prairie dog

    Neal and Mary Jane Mishler
 

Note: in the print edition of this issue, this article appears as a sidebar to as essay, "'Nobody gives a damn about the prairie dog'."

It was a quote from naturalist J.R. Mead in 1859 that got University of Montana zoology professor Bert Pfeiffer curious about prairie dogs.

Mead wrote: "Not a drop (of water) could be found within several miles (of the prairie dog town) and none by digging above the rock, and not a particle of dew fell for weeks in the heat of summer. The scant grass was dry enough to burn an hour before sunrise; and I was forced to the conclusion that nature had constructed an animal capable of living for long periods of time without water."

But unlike Mead and other naturalists, Pfeiffer didn't just observe prairie dogs, he figured out how they survive. Now 81 and retired, Pfeiffer still gets excited when discussing an animal that he says can "outlast a camel in the desert."

Pfeiffer spent 15 years studying prairie dogs in the laboratory. In hibernation experiments on a dozen animals, Pfeiffer was able to induce torpor in about half of them. The sleeping animals' body temperatures dropped to about 7 degrees Celsius and they became paralyzed. They survived 60 days without food and water and only occasionally woke to urinate. The hibernating dogs lived off their fat deposits during this time - the normal hibernation process. The burning of fat supplied water.

What was unusual occurred in animals that remained awake. They retained normal body temperature, did not eat or drink for 60 days, and lost some weight, but still survived in good shape.

"I realized then we were studying a very unusual animal," Pfeiffer says. "These dogs had shifted to living off their fat too, even though they were active." Then Pfeiffer discovered he didn't even have to put them in a cold place to get them to switch to burning their fat.

"All we had to do was take them off food and water," he says. "These animals can survive for six weeks or more without food or water with weight losses approaching 50 percent during the summer."

In contrast, Pfeiffer says an active ground squirrel will die in no time without food and water; a human might last a few days.

The prairie dog can also retain its blood-sugar level when it isn't eating, and remain active. Sugar cannot be stored in fat. Humans can store only about 24 hours' worth of sugar in the liver and muscle for energy. Our bodies produce sugar without food by breaking down muscle. Amino acids in protein quickly convert to sugar. But the process produces excess nitrogen which is poisonous to our systems and which we cannot remove.

Starving prairie dogs also convert muscle protein to sugar, but are able to recycle the nitrogen to remake muscle. Pfeiffer, who hasn't figured out how the animal does that, hopes some medical physiologist will look into the matter.

"The prairie dog could be a marvelous model for studying hormonal control of obesity in humans," he says.

The prairie dog holds at least one other value for medicine, Pfeiffer says. "They make perfect lab animals. They are easy to catch and maintain. And they might breed like rats in captivity."

Note: the opinions expressed in this column are those of the writer and do not necessarily reflect those of High Country News, its board or staff. If you'd like to share an opinion piece of your own, please write Betsy Marston at betsym@hcn.org.