I was very disappointed in John McKinney's April 16 hiking column on the West Mojave Desert ("The Tortoise and the Hair-Raising Trail").
McKinney says that desert tortoises had adapted to changing environmental conditions until the arrival of grazing animals "that squashed them and collapsed their burrows, and off-road vehicles that did likewise, as well as residential and commercial development that obliterated their habitat." There is no question that these activities had a negative impact on the desert tortoise. However, one is left with the impression these are the major factors in the demise of the tortoise population.
There is no scientific proof that off-road vehicles have been a major contributor to the desert tortoise's difficulties. An area just outside of the preserve has been used for years by off-road vehicles and yet the tortoise survives. Why? First, because the area taken by a 12- to 18-inch-wide off-road trail is significantly less than the available surface area. And second, most tortoise burrows are at the base of bushes and scrubs that obviously don't grow in the designated off-road trails.
McKinney also refers to "diseases brought in by people who release captive tortoises in the natural area. As a result, the tortoises become afflicted with a difficult-to-cure upper respiratory condition that spreads rapidly through the population." Here, McKinney seems to downplay the significance of the respiratory disease problem. Recent scientific studies have indicated the two major factors in the decline of the desert tortoises have been the respiratory diseases that McKinney mentions and the aggressive attack by ravens on tortoises.