Author : SubhronilRecently Indian ecologists and environmentalist were surprised when the forest department of India confirmed with photographic evidence the presence/report of an adult male, probably between 12-15 years old Royal Bengal Tiger (scientific name: Panthera tigris) from Lalgarh, Jhargram, West Bengal (Figure 1). Although leopards have occasionally been reported from this forest, citing of Royal Bengal Tiger is entirely surprising simply because the present cited location is about 200 kilometers from the nearest tiger reserve, Simlipal, Orissa (Figure 2). A recent census revealed that the Simlipal reserve has about 26 adult tigers, and the experts are assuming that one of them has come to this new territory, although the actual cause remain still elusive. The other possible source population, Sunderban, has been discarded because of these habitats are fragmented by dense human population and water bodies (i.e., the tiger would have had to cross several villages and towns, and water bodies to reach there, which is reasonably not possible). However, Singhbhum may also be the source, although the distance is more than 250 km. Now the question is, what caused this individual adult travelled from its core area to a new biogeographic region? Is it a random event or there is any specific cause behind it? Let’s check the common causes of species movement from its common habitat (i.e., where it lives). Figure 1. Real image of the Royal Bengal Tiger reported at Jhargram, as captured by trap cameras (photo courtesy: West Bengal Forest Department). In order to consider it as a case of migration, the animal will have to have seasonal or annual movement within its biogeographic areas. For example, migratory birds migrate from their actual habitat to a new area during a particular time of the year, and return back after certain time. Now the present tiger has been reported for the first time in last 100 years, so we cannot say this is a case of migration. It is therefore a case of dispersal. According to the tiger specialist Mr. Biswajit Roychowdhury, report of this type of long dispersal is unusual, but not rare. Old reports confirmed movement of tiger from Sariska Tiger Reserve to Bharatpur Bird Sanctuary, which is about 125 km apart. Interestingly that tiger, known as T-7, left its original home at Ramthambhore National Park and moved to Dholpur and Mathura in UP finally to move to Sariska. Similar report came when another individual travelled from Nagzira in Maharashtra to Umred Karhandla in Nagpur, travelling about 100 km. However, this type of movement is always rare, specially for the organisms which are territorial. Anyway, organisms generally disperse to a new location either because their actual habitat is disrupted/damaged (remember people are dispersed to new places after natural disaster), or the resources (food, space, mate) are becoming scanty at the actual habitat. In any way, this may indicate a case of disruption of their actual habitat. Figure 2. Probable dispersal route and probable source populations (photo courtesy: Anandabajar Patrika) This incident may suggest that the source population in Simlipal (so somewhere else) might have been disrupted by incessant forest fire, deforestation, human disturbance leading to habitat fragmentation, or poaching. Or may be the tiger ecology is being disrupted by other new ecological or environmental factors. We are wowed with the news, but now we should go back and check what’s caused this dispersal and should immediate take necessary measure to take care of this issue. Otherwise, we will be left with tiger reserves with no tigers at all!
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