The Thar or the Great Indian Desert, as it is generally known, is a fascinating area. It has taken its name from the word Tahl that in local dialect is the term for the sandy ridges of the dunes. The Thar Desert in spite of the inhospitable climate is not an endless stretch of sand, devoid of life and vegetarian. It is a living and dynamic eco-system. It is actually one of the most populous deserts of the world. In order to preserve its geo-morphological features, fauna and flora and to continuously study and understand their ecology under undisturbed desert conditions, an area of about 3,126 sq. kilometers.
Species of wild animals and plants that can adapt to these harsh climatic and environmental conditions flourish in the area. Amongst the mammals, chinkara (Gazella gazella), Indian fox, desert fox, jackal, desert cat, jungle cat and nilgai are common in the Desert National Park. The area provides suitable conditions for survival of a number of species of lizards, gerbils and snakes. The spiny tailed lizards with their prehistoric looks are quite common in many areas of the Park. Among the snakes the saw scaled viper, the large rat snake and sand boa are noteworthy. Most of these animals survive the scarcity of water by adopting special mechanism so that life can go on without water. They reduce their physical activity considerably and avoid exposure to hot winds by keeping in shade of shrubs or by burrowing down in the sand. Earth has an admirable insulator against heat and aridity, and an animal burrowing a few centimeters below the surface will comfortably survive the hottest day and coolest night. In the Desert National Park the foxes, cats, lizards and snakes all enter the burrows to avoid the hot and desiccating air outside. Most of the sunset animals are active in early morning or after the sun set, when the temperatures are much lower.

The chinkaras, which cannot enter a burrow, go under the shade of bushes. They can tolerate a rise in body temperature up to seven degrees above normal without serious injury to any vital organ. These animals can withstand considerable haemo-concentrations or blood thickening, which takes plated. Chinkaras for example can go without water for a number of days by feeding on green plants like Aak (Calotropics procera) and obtaining water from its leaves. Similarly, the gerbils, which serve as staple food for the desert fox and the desert cats, provide much of the water to these carnivores.

The plants in the desert also have to adopt various strategies to endure the intense heat, bitter cold and long dry spells. To reduce the water by evaporation the leaves of these plants are reduced in size, as is the case of khejri (Prosopis cinerara) with relatively few stomataon them. Some species like kair (Cappairs dedicua) and phog (Calligonum polkygonides) do away with the leaves altogether and develop stomata on the green stems which perform the work of photosynthesis. Sevan is one of the hardiest plants to grow in the Thar Desert. This perennial grass can stand long periods of drought.
The lesser bustard, locally called tilore is a winter visitor to the Desert. This bird is also extremely shy. Tilore has not been observed drinking water on the water hole so far. Foxes are generally shy of human beings but during the winter months they are visible throughout the day looking for the gerbils or just basking in the winter sun.

The Thar’s geological history; based on the study of fossils found in the area is interesting. The area has been in and out of sea at least four times during the last two hundred and eighty million years.

It appears that this area was under sea in the early Triassic period. The sea withdrew after twenty five million years and the sediments were uplifted animal fossils of that period are found in the rocks in many areas.

Again, after about twenty five million years this area came under the sea. The limestone and the sandstone of Jaisalmer with their fossils of ammonites were deposited during this period. During the lower Cretaceous period, between a hundred and thirty five million years and sixty three million years, the area became a land mass with forests. It is believed that the plant fossils of Paliwal village around Jaisalmer belong to this period. This was followed by yet another invasion of the sea when the rocks containing marine fossils were deposited. At the end of the Cretaceous period and in the beginning of Cenozoic, sixty three million years ago, the sea took over again and was inhabited by for aminifera or tiny unicellular, shelled organisms.
Accumulation of their dead bodies at the bottom of the sea and their slow decomposition is believed to be responsible for the formation of oil and natural gas in the Thar Desert. The sea finally withdrew from the area about thirty five million years ago.
Wood fossils found in Akal near Jaisalmer are the remains of the forests of cycades and ferns that flourished in the region during the early Jurassic period, that is about one hundred and eighty million years ago. At present about twenty five fossilized tree trunks are lying exposed on the grounds in the Akal wood fossil park. The largest is about seven meters long and one and half meter in girth. There are more wood fossils lying deep under the surface. Evidences of similar fossils are surfacing in other areas of Jaisalmer region. The whole area is now preserved as a natural wonder in the Desert.