“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.
http://www.vinsuprynowicz.com/?p=80
I heard the Tortoises eat cow poop. I think there may be circumstantial evidence of this in the article...
Reminds me about the 1970's when the National Park Service contracted to remove the mountain lions (Pumas) from the Grand Canyon areas because they were picking on the deer. Guess what. About two years later the death rate of the deer skyrocketed because without the culling of the herds by the big cats, they were having all kinds of fun producing hundreds of babies. Suddenly the environment could not support the huge herds of deer and most starved to death.
The park rangers learned their lesson when the tourists started asking why there were so many skin and bones deer and dead ones everywhere.