Complex sentence: Many desert tortoises found on the site were relocated to other parts of the Mojave Desert; however, environmentalists raised concerns that relocated tortoises were more likely to die due to the stresses involved.
Split into simpler sentences: Many desert tortoises found on the site were relocated to other parts of the Mojave Desert. However, environmentalists have raised concerns that relocated tortoises are more likely to die due to the stresses involved.