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!
Author: Prof. Subhendu Bardhan
The article was initially published in a Bengali magazine called "Parbantar", and we have taken verbal permission from the author to republish it.
Disclaimer: The Pdf viewer may not be compatible in android devices. Suggested to visit it from laptop/ desktop.
To view from android device, Click here
Author:Prof. Subhendu Bardhan
The article was initially published in a Bengali magazine called "Parbantar" [details can be found on page 4], and we have taken verbal permission from the author to republish it.
Disclaimer: The Pdf viewer may not be compatible in android devices. Suggested to visit it from laptop/ desktop.
To view from android device, Click here Author : Subhronil Introduction: According to the “Red List” (Bible for the conservation biologists and ecologists), compiled by the International Union for Conservation of Nature and Natural Resources (IUCN), a huge part of our biotic world is suffering from severe biomass loss in terms of loss of habitable area and number of species. This loss is so severe that the entire ecosystem is under a critical crisis which needs to be studied and maintained to counteract the loss; this study involves categorization of organisms into several subgroups based on the severity of their loss. I will try to explain these categories in simple way. Nomenclature:
This categorization involves multilevel grouping of ‘evaluated’ organisms (organisms which have been studied for the aforesaid purpose) shown in the figure (figure redrawn from http://www.iucnredlist.org/about/introduction). The most severe of this group is called Extinct (EX; i.e., we have killed all the individuals of this species and no more living individual can be found anywhere in the world). A familiar example would be a Sabretooth or a Mammoth (remember the movie Ice Age?). A relatively less severe category is called Extinct in the Wild (EW), i.e, living individuals of those species can only be found in their non-natural habitat like zoo and other captivities. Some relatively luckier species are either Critically Endangered (CR; i.e., only few individuals are living sporadically in the wild and are near to become extinct in the wild [example: Javan Rhino]), Endangered (EN; i.e., only few individuals left and their number are decreasing rapidly [sea otters]), or Vulnerable (VU; i.e., not many individuals left alive in the wild and their habitat [where they live] are decreasing). Reasons: Reasons behind this criticality? Other studied groups are either least or not affected (NT and LC, simultaneously). Obviously, humans [the killers] belong to the LC category. An Anthropocentric view about those concerned species can be stated as: Least Concerned (LC): can be killed for fun/food/money in future Near Threatened (NT): need to kill more of it for food/fun/money Vulnerable (VU): very tasty and/or of high market value Endangered (EN): very very tasty and/or of high market value Critically Endangered (CR): will kill the last few members too Well, almost all of them are related to Humans! Under this series, in our following articles we will be talking about many of these unlucky guys and will try to show how they are doing these days and how human are silently or openly killing them with pride! Feel free to provide your views! Author : Subhronil Shells which we frequently encounter at the near-coastal areas are mainly the external skeletons of the two very abundant organisms – clams and snails. They are dead individuals of many different species, just like Homo sapiens, our own species. Logically, our skeletons resemble these shells, the only difference is that we have internal skeletons [i.e., our hard skeletons are hidden inside our skin] and those organisms have external skeletons. A more scientific description would suggest that snails and clams are basically the member of two Classes [it’s a biological nomenclatural hierarchy where one class include many orders, families, genus, and species] – namely Gastropoda and Bivalvia; both of these Classes are included in a relatively higher nomenclatural hierarchy called Phylum Mollusca [one Phylum will have many Classes (and one Class has many Orders, and so on!) into it]. Detailed anatomy reveals that these organisms may have liver, lung, kidney, stomach, penis, vagina, eye, and even heart! So, your selfish view towards the world may consider them ‘inferior’ and you may have self-proclaimed ‘right to kill’ license, but in fact these organisms are scientifically comparable with us – no more no less [unless you are irrational or a ‘believer’]. More fascinating part is, they do have beautiful legs too! Just look at this picture, it’s a perfect soccer foot (left image) [I am sure you like football!], and they use their foot for kicking! [obviously not to score a goal, but to flee or to hide within sediment (right image; photo from Stanley and Waller, 1978)]. So, next time when you collect a dead shell, remember they also had a life and a soul! P.S. if you really care, please come back to see our next post on their detailed body parts, activities, feeding issues, etc. |
|