updated 2/5/2007 8:49:48 PM ET 2007-02-06T01:49:48

The Knoxville Zoo says it has become the first U.S. zoo to successfully breed Northern spider tortoises, a subspecies so rare they can no longer be exported from their native Madagascar off Africa's southeastern coast.

The first young tortoise hatched Dec. 23, and at 18 grams and an inch long is thriving. A second hatched Friday and five more eggs were in incubation.

They are the result of a courtship between a male acquired in 2004 and two females obtained in 1999 and 2005. There are only 12 adult males and 11 adult females in captivity in the United States at four zoos.

Nothing is fast about these spider tortoises, which are known for the web-like pattern on their shells. A female can take three to four hours to dig a hole, make a nest and lay an egg about half the size of a chicken egg. The eggs will spend 100 to 150 days in an incubator before they hatch.

Fully grown, the turtles will be 4 to 5 inches long and weigh about three-fourths of a pound.

Little is known about the numbers of Northern spider tortoises in their native environment — the spiny forests of Madagascar, which is home to a vast number of indigenous species.

But their forest habitat has declined 15 percent over the last three decades.

"Zoos are the last line against extinction," said Michael Ogle, lead keeper in the Knoxville Zoo's herpetology department.

The Knoxville Zoo also cares for the Northern spider tortoises' cousins _ the common spider tortoise and the even more rare Southern spider tortoise. The zoo has hatched 44 of the common variety since 2004 and has Southern spider tortoise eggs now incubating.

Copyright 2007 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments