"Tortoises don't just demonstrate behaviour," says U.S. Geological Survey biologist Kristin Berry, "they show personality."
"They are not the same inside their shells; they are individuals interacting in complex communities," she said. "And there may be behaviour occurring in ways we haven't yet learned to observe, or interpret. How does a tortoise exhibit joy, or play, or express frustration?"
In the Mojave Desert, tortoises display such a variety of personalities during courting season that it is hard to fully understand them.
On this arid stage, Berry has outfitted 28 tortoises with radio transmitters to learn all she can about "one of the few populations left in California that is remote, stable and relatively intact." She uses a hand-held antenna to pinpoint the locations of other tortoises.
With a wave of her hand, Berry said, "From that ridge all the way over to that one, a magnificent 10-pound alpha male tortoise we know as No. 43 reigns supreme."
"He's not good at mating — too eager. He just looks at a female and turns to mush," she said. "But he's a heck of a fighter and patrols a huge territory. We've seen him make long, arduous journeys across a wash and halfway up a mountain just to beat up a smaller male."
Tortoises spend most of their lives underground. But when mating season reaches its height — August through early October — they lumber forth in the mid-morning and late afternoon to forage for wildflowers, and display courting and dominance behaviors based on constant fighting.
In the afternoon, Berry caught up with a tortoise she officially knows as No. 29, and unofficially the "cad" and "fearless kingpin."
He probably hatched from an egg when Calvin Coolidge was president in the 1920s. As the big male was weighed and measured by an assistant — about 11 inches long and about 9 ½ pounds — she gazed into its eyes and said, "There is so much we still don't know about these creatures."
"At a time when disease is spreading among them and there are plans for translocation, we're only beginning to study their social lives," she said. "Determining how complex these creatures actually are can help us understand better how to save them."
The survival of the tortoises in the Mojave Desert depends upon whether scientists can discern what makes a tortoise tick.
The U.S. military plans to expand the area used for battlefield exercises to accommodate a new generation of weapons and tactics. Those plans include relocating about 1,500 of the reptiles, which are protected by state and federal law, to a new location where they won't be squashed by military equipment.
"Social behaviour is something we're seriously looking into in our translocation plans," said Mickey Quillman, natural and cultural resources manager at Fort Irwin.
"We'll be taking tortoises from the same general vicinity — big ones and little ones — and moving them together in one fell swoop," he said. "Kristin Berry's studies suggest there's a good chance those tortoises have intermingled in the past, and we don't want to break up that behaviour."