“The lizard brain is hungry, scared, angry, and horny.” — Seth Godin

Any attempt to infer what other species think is a mistake. Nevertheless, we can probably be safe to assume that survival is at both the forefront and backdrop of any individual’s thoughts, regardless of what species it is. Survival includes finding sustenance and safety (from both inclement weather and things that might do us/them harm). It is a common thread that ties us with all life. Finding food and safety are critical components of a where any species chooses to live, the place we might call its habitat, its home range, its territory, or for us, our community, and our home.

For a large vegetarian lizard like a chuckwalla, survival means finding a place where palatable plants grow — especially desert mallow and sweetbush — as well as fissures in rocks that are just the right size for them to just barely fit, while not being large enough for predators to reach in. Any vegetarian can thrive during wet years when the desert and the mountain slopes are carpeted in flowers. The occurrence of desert mallow or sweetbush, or a similarly palatable shrub, is critical because they are perennials with deep enough roots to find some moisture even in dry years, enough moisture to at least grow some leaves or a few flowers, sustenance to keep a chuckwalla alive even through droughts. The rock fissures provide escapes from predators but also are thermal sanctuaries keeping the lizards from getting too hot during the sizzling summer heat or freezing during the dead of winter. Knowing where the palatable plants grow and where those rock fissures occur are imprinted as a map within each chuckwalla’s brain. When danger is present, perhaps a red-tailed hawk soaring high above, the chuckwallas know exactly where the closest rock fissure sanctuary can be found, and they dive for cover. Any hesitation, any random search for a suitable crack in the rocks, will put the chuckwalla at risk of becoming sustenance for the red-tailed hawk and its nestlings.  

Sometimes, with the best intentions, people move tortoises, lizards, or snakes away from their home to someplace new. Sometimes it is because the habitat is being changed to build a solar collector array, a utility corridor, or for a housing development. Sometimes, after people move in, they are uncomfortable with sharing that habitat with a rattlesnake or Gila monster, poisonous species that represent perceived harm to their pets, children, and other loved ones. So, they move the tortoises, lizards, or snakes to someplace new, someplace that still appears to fulfill the reptile’s needs for survival. The technical term for such movements is translocation. The humans have their needs met, and they are satisfied in believing that the translocated individuals will live long and fulfilled lives elsewhere. Except they don’t.

Translocating animals has become a common management tool for reducing human-wildlife conflicts. But then some scientists began asking how effective those translocations were, so they equipped those tortoises, snakes, and Gila monsters with GPS transmitters so they could track their survival. Invariably the translocated individuals tried to return home. That neural map of their original homes is so imprinted in their brain, and is so important to their survival, for finding food, thermal sanctuaries, and protection from predators, that they have an overriding urge to return from whence they came. If they are moved a few miles away, they generally find their way home within less than a week. That ability to return home, across a terrain where they have never been before, is incredible.  Place a human a few miles from home, across an unfamiliar landscape and without a cell phone, compass, map, or the ability to ask for directions, and those humans will be truly lost, having no idea which way to head. Take that reptile further away, say ten or more miles, and they will still try their best to return home. Except the longer the distance, the longer they are exposed to risks of predation or from a one-sided encounter with vehicles while crossing the networks of roads we have created. They invariably perish in efforts to return home over those longer distances. Knowing this, scientists have found some success with translocating state and federally protected tortoises by constructing fences that keep the tortoises from moving back home. After weeks and months of trying to move through the fence, tortoises will eventually accept their new habitat. In most other instances, moving a rattlesnake or lizard and some how preventing their attempts to return home is not possible.

Still with the best of intentions, it is so difficult to watch bulldozers raze a species’ home and do nothing. Maybe five or six years ago we had an opportunity to translocate an isolated population of fringe-toed lizards on unprotected lands where a housing development was approved, and the bulldozers were ready to plow ahead. The USFWS expedited permitting so we could beat the bulldozers. Through a large volunteer effort, we captured 29 fringe-toed lizards and moved them about five miles away to a protected parcel which had once supported a healthy population of fringe-toed lizards, but the population had been extirpated by illegal off-road vehicle recreation. The vehicles were now fenced out, and this seemed to be a perfect way to re-establish a lizard population there and to protect the potentially unique genetic makeup that population possessed.  Each lizard was permanently marked so we could assess the success of this translocation effort. It all seemed straightforward and easy.

I returned to check on the translocated lizards that fall and each year thereafter to assess our success rate. That fall there was just one adult left on the protected dune, along with two juveniles, and a couple hatchlings. The one adult had been gravid when we moved her, and the hatchlings were likely from the clutch she would have laid soon after translocation. All the other 26 translocated lizards were gone and never seen again. I assume that the 26 missing lizards, using their imprinted homing maps all tried to return to their homes, except that they would have had to cross I-10 to get back “home”. Over the past five or six years since that translocation the remaining five or so lizards experienced annual attrition that exceeded their reproductive effort. By 2021-2022 no fringe-toed lizards remained. The high attrition was due to a combination of a small founder population, an on-going drought, and a pair of loggerhead shrikes that had moved in to prey on the abundant desert iguanas – and remaining fringe-toed lizards. Based on our experience, to be successful, only young hatchlings/very young juveniles who have not yet imprinted on a particular site, have any chance of successful translocation.

Lesson learned. Otherwise, for those pesky rattlesnakes that occasionally show up in folks’ yards lucky enough to live at the urban-wildland interfaces, it would be far better to learn to live together. The snakes are excellent at controlling rodents, some of which can carry diseases such as Hanta virus and bubonic plague. All it takes on our part is to watch where you walk and where you reach into dark places, both good lessons that are easy to follow.

Nullius in verba

Go outside, tip your hat to a chuckwalla (and a cactus), think like a mountain, and be safe