<P> Ponderosa pine forests grow at elevations between 6,500 and 8,200 feet (2,000 and 2,500 m), on both North and South rims in the Transition life zone . The South Rim includes species such as gray fox, mule deer, bighorn sheep, rock squirrels, pinyon pine and Utah juniper . Additional species such as Gambel oak, New Mexico locust, mountain mahogany, elderberry, creeping mahonia, and fescue have been identified in these forests . The Utah tiger salamander and the Great Basin spadefoot toad are two amphibians that are common in the rim forests . Of the approximately 90 bird species that breed in the coniferous forests, 51 are summer residents and at least 15 of these are known to be neotropical migrants . </P> <P> Elevations of 8,200 to 9,000 feet (2,500 to 2,700 m) are in the Canadian Life Zone, which includes the North Rim and the Kaibab Plateau . Spruce - fir forests characterized by Engelmann spruce, blue spruce, Douglas fir, white fir, aspen, and mountain ash, along with several species of perennial grasses, groundsels, yarrow, cinquefoil, lupines, sedges, and asters, grow in this sub-alpine climate . Mountain lions, Kaibab squirrels, and northern goshawks are found here . </P> <P> Montane meadows and subalpine grassland communities of the Hudsonian life zone are rare and located only on the North Rim . Both are typified by many grass species . Some of these grasses include blue and black grama, big galleta, Indian ricegrass and three - awns . The wettest areas support sedges and forbs . </P> <P> Grand Canyon National Park is one of the world's premier natural attractions, attracting about five million visitors per year . Overall, 83% were from the United States: California (12.2%), Arizona (8.9%), Texas (4.8%), Florida (3.4%) and New York (3.2%) represented the top domestic visitors . Seventeen percent of visitors were from outside the United States; the most prominently represented nations were the United Kingdom (3.8%), Canada (3.5%), Japan (2.1%), Germany (1.9%) and The Netherlands (1.2%). The South Rim is open all year round weather permitting . The North Rim is generally open mid-May to mid-October . </P>

Which type of erosion most likely formed the grand canyon