Inside a small clear tube, a naked mole-rat decides to change direction.
Contorting its wrinkled, hot dog-shaped body, the animal nearly somersaults over itself and pokes out its head on the other side. It shows off four big teeth, sniffs the air and turns around again.
Watch a naked mole-rat for a while, and you'll see this happen over and over and over. It's the nonstop movement and unusual characteristics - certainly not its beauty - that make mole-rats a hit with zoo visitors, especially children.
"They're so ugly, they're cute," said Knoxville Zoo keeper Cathleen Wise. "You can't help (look at them). There's always something to watch."
The Knoxville Zoo has joined a handful of zoos across the country with the strange creatures when it opened the "Naturally Naked Mole-Rats" exhibit on March 31.
Natives of Africa, naked mole-rats are the only eusocial mammals, meaning they live in a colony ruled by a queen, the only female who reproduces.
In the wild, they spend nearly all their time underground, but despite their name they are neither moles nor rats. Mole-rats are more closely related to chinchillas, guinea pigs and porcupines.
There are several species of mole-rats, but only naked mole-rats are, well, naked or nearly hairless. Some other types of mole-rats are not eusocial and live alone or in smaller groups.
Naked mole-rats are about 3 to 4 inches long and can look - to put it politely - downright homely in large up-close photographs that emphasize their little-to-no hair, wrinkly skin and walrus-like teeth.
Zoos are spreading the critters to other zoos when their colonies grow too large and need to be split.
Knoxville got one colony of 16 animals from the Brevard Zoo in Melbourne, Fla., late last year and then another of 39 animals in March from the Rio Grande Zoo in Albuquerque, N.M.
The queen of the first colony has already had a litter in which three babies survived. She's pregnant again now and expected to give birth in the next few weeks.
The critters have been a big hit in Albuquerque, said Rick Janser, the zoo's mammal curator.
"They go by and go, 'Ew! Gross! Ew!' and then they are there for 20 minutes watching them. There's the gross-out factor, but once they start watching them they're fascinated by how active they are," Janser said.
"It's not like the gorillas, but you usually have a large group of people watching them."
Besides Brevard, the other closest zoos to Knoxville with naked mole-rats include Louisville, Ky.; Cincinnati and the National Zoo in Washington D.C.
"They've always been very popular, especially with kids, because they're very active and unusual, always very busy," said Sarah Glass, Knoxville's curator of special exhibits and red pandas. "They're just odd."
The animals are displayed in a series of clear tubes and boxes.
"I love them. I just think they're fascinating," Glass said. "It's like watching mole-rat TV. Just watch them run around and do all the things they do."
Children and their parents may know more about naked mole-rats than other zoo visitors. Disney's cartoon show "Kim Possible" features Rufus the naked mole-rat who likes to eat nachos.
"The mole-rat raps too. It's kind of scary," Glass said.
Of course, real naked mole-rats are vegetarians, do not live alone and would not make good pets. And they squeak and chirp, but don't sing.
If you go:
: 3500 Knoxville Zoo Drive, Knoxville, Tenn., Exit 392 from Interstate 40; (865) 637-5331. Open weekdays, 9:30 a.m.-4:30 p.m., and weekends, 9:30 a.m.-6 p.m. After May 29, the zoo is open until 6 p.m. daily. Adults, $14.95; children 3-12, $10.95.