(click on pick to see map at source)
More detailed maps on Wiki here)
“The most complete data is from the Beaver Dam Mountains. Woodbury and Hardy reported a tortoise population density of 150 per square mile in 1948. BLM reduced cattle grazing a few years later and eliminated cattle in 1970. Coombs reported a tortoise density of 39 per square mile in 1974. In these 26 years cattle use was reduced 100 percent and tortoise numbers were reduced 74 percent.
“These tortoises were doing so poorly a veterinarian, Dr. Jarchow, was consulted. He reported all six specimens were suffering from osteoporosis caused by a protein deficiency in their diet. Dr. Jarchow examined five specimens from the same mountains that shared their range with cattle. He reported these specimens were all healthy and well nourished.
“The historical record proves conclusively that tortoise thrive when cattle are on the range with them and without cattle grazing they are always malnourished and unhealthy and their numbers plummet.
But we have no idea what the population density of Desert Tortoises was before there was cattle grazing there. No one ever did a survey AFAIK. Was it 150 per sq mile as it was in 1948 or a higher or lower figure? Unless some early botanist did a well-studied survey we will probably never know. We do know that the BLM is intentionally killing several hundred of them that they failed to care for properly on their own reserve.