The desert tortoise (Gopherus agassizii) in the Mojave desert (north and west of the Colorado River) has been listed as a threatened species since 1990 under the Federal Endangered Species Act of 1973.
The US BLM, USFWS, Nevada Department of Wildlife and the Nature Conservancy conducted research, part of which was to create a plan to limit the interaction between humans and this species. One outcome was a group of standard specifications for construction methods within the Tortoises range, which include tortoise fence and the use of cattle guards as part of the fencing system.
In 2011 Big R worked with the BLM to make the first tortoise specific guard that used the current AASHOT HL-93 load rating. We were able to offer a more affordable crossing than a typical cattle guard, as tortoise guards only needed to be 3’ in the driving distance.
The risk level for a desert tortoise encountering a breach in the fence is greatest in the spring and fall, particularly around the time of precipitation including the period during which precipitation occurs and at least several days afterward. All desert tortoise fences and cattleguards should be inspected on a regular basis sufficient to maintain an effective barrier to tortoise movement.