rainfall, with of rain falling in January alone. Geology Located in the southern part of the Morondava Basin, the sedimentary Isalo Group is the main geological formation of the park, forming the Isalo Massif. The group is up to 6,000m thick, of Triassic to early Jurassic origin and made up of coarse-grained sandstone deposited by braided streams. The Isalo Massif has been eroded by wind and water, resulting in deep canyons, sandstone domes, flat-topped mountains and "runiform" mountains - steep sided outcrops that have been dissected into odd-shapes. These odd shapes are referred to as "runiforme", based on the French word for "carved". Tourism A local guide is required for visitors entering the park, and guides and porters can be hired in Ranohira. Treks in the park can last from several hours to a week or longer. The park includes several natural swimming pools which are popular among tourists, and are excellent sites to see the Benson's Rock Thrush. The main threat to this park comes from illegal wildfires set in the park. The wildfires limit the extent of forest and maximize grasslands used by cattle. Fauna Fourteen species of mammals are reported for Isalo NP, including several different species of lemur. Over 100 species of bird have been found here, including Benson's rock thrush (Monticola sharpei bensoni), the knob-billed duck (Sarkidiornis melanotos) and the Madagascar ibis (Lophotibis cristata). Twenty four amphibians and 47 reptiles have been documented in Isalo National Park, including a number of new “candidate” species. Species endemic to the Isalo area include four amphibians (Gephyromantis azzurrae, Mantella expectata, Mantidactylus noralottae, and the Malagasy rainbow frog (Scaphiophryne gottlebei) and one reptile species (Trachylepis nancycoutuae). Notable examples include the Madagascar ground boa (Acrantophis madagascariensis), Dumeril's boa (Acrantophis dumerili) and the white-lipped bright-eyed frog (Boophis albilabris). Flora Botanical inventory of the Isalo region began with collections by Perrier de la Bâthie in 1910. Only 10 of the over 400 species that have been documented in Isalo are non-native species. Most (over 70%) are vascular plants that are endemic to Madagascar. There are 13 species that have been found only in Isalo and another 35 are rare species, known from 2-5 sites. The following table lists the species known only from Isalo NP. Some entire families of plants are endemic to Madagascar. Examples of three of these families can be found in Isalo; Asteropeiaceae, Sarcolaenaceae and Sphaerosepalaceae. Not only is