Causes of Tiger (Panthera tigris) Population Decline, and Potential Consequences if the Decline Continues

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1 Causes of Tiger (Panthera tigris) Population Decline, and Potential Consequences if the Decline Continues ABSTRACT: The population decline of the Tiger (Panthera tigris) in the past decades has been a serious problem for conservationists. In the early 1900s, there were an estimated 100,000 tigers, but only around 3,200 remain today. This drastic drop in tiger population has triggered a concern for the future of the species, which has led to research developments and projects to help understand why the species is so threatened, and hopefully solve some of these problems. One research group in Nepal collected data from radio-collared tigers, and visual sightings to determine possible tiger habitat. They then surveyed these lands and monitored the effects of habitat quality on tiger populations, and determined that the condition of tiger habitat, including poaching threats, must be monitored or the species will not survive. The habitat integrity was also analyzed by a second research group, as well as the poaching threats and the current population status of different areas of land throughout South Asia. After observing these factors for a period of 10 years and gathering data, they discovered that large amounts of lands that would be suitable for tigers are not being protected. A final group collected data by capturing photos of tigers using camera traps. They used these photographs to estimate tiger populations, and theorize the reasons for the distribution of tigers. They concluded that more land should be reserved for tigers because tigers need more abundant prey to hunt. Although the methods used by each of the groups were different, the overall conclusion was that the current status of the tigers can be improved if they and their land are given more protection. [Abstract missing Methods, example geographic information system.] INTRODUCTION The tiger (Panthera tigris) is a large, carnivorous mammal, and is the largest in the cat (Felidae) family. There are six subspecies of tigers remaining and the size of the tigers varies depending on the subspecies which they belong to. The largest of which is the Siberian Tiger, which can weigh up to 600 pounds, and measure up to 13 feet in length, as shown in Figure 1. The Bengal Tiger, which is the most populous of tigers, weighs between 350 and 500 pounds. Most tigers have red-tan colored fur and dark stripes, with white fur on their undersides. However, their pigmentation varies depending on which subspecies they are classified with ( tiger 2012). Figure 1 Siberian Tiger (Source??) [You need a page number on each page.]

2 Tigers are found in various parts of South Asia. One of the most important characteristics of tigers is the way they have adapted to many different climate types. Some subspecies can live in places that reach temperatures as low as 40 F, while others have adapted to environments with temperatures as high as 104 F. Tigers can be found in dry or normal grasslands, rainforests, swamps, temperate forests, subtropical forests, and other climate types. The hunting habits of tigers vary depending on where they live, but they generally hunt by night and prefer large prey such as wild pigs and deer ( tiger 2012). Tiger Population Reduction Over the past century, the population of tigers in Asia has decreased significantly. In the past century, the world s population of tigers has dropped from an estimated 100,000 individuals to around 3,000 ( Tiger Population 2012). As their status of endangerment has been recognized on a global level, various research and legal groups have attempted to understand the reasons for tiger population reduction. They have discovered that the major reasons for the decline have been illegal poaching and habitat loss. While these are very different problems, they share common solutions, one of the most important of which is giving legal protection to tigers and their land. As mentioned above, one of the most eminent threats facing tiger populations is the loss of large amounts of habitat. In less than a century, Asia s largest predator, the tiger has been relegated to isolated populations residing in only a small fraction of the animal s historic range. This fraction is estimated to be as low as 7% (Dinerstein 2007). The loss of habitat has directly affected the population of tigers, as shown in Figure 2. As the percentage of remaining habitat has declined, the tiger population has fallen, and if forest land is not given more protection, recovery of the tiger may become impossible. Figure 2 (WWF 2010) METHODS AND MATERIALS Study of Tiger Distribution and Habitat Quality in Nepal James L. David Smith, from the Department of Fisheries and Wildlife, led a research group in Nepal and India to investigate the effects of habitat quality on tiger distribution. His research group used data 46 radio-collared tigers, as well as visual sightings to determine potential tiger lands. To narrow the amount of lands they would be surveying, they realized that tigers were not likely to be found in urban or agricultural areas, so they defined potential tiger habitat as all other lands (e.g., forest, grass, and shrub lands) below 1000 m in elevation. They then surveyed

3 all of the potential tiger habitats in Nepal and the correlating lands in India to confirm the presence of tigers in those areas. The survey sites they used were 3-15 km apart from each other. By using a geographic information system, they were able to calculate statistics telling the size of and distance between areas populated by tigers (Smith 1998). In order to understand the ways that populations are affected by habitat quality, they used a Landsat Thematic Mapper to classify areas of Nepal into different categories of forest cover and type. To better analyze the impacts on the type of habitats on the breeding tiger populations, they calculated the percentage of good to poor habitat quality in each unit of land. Their definition of poor-quality land was any land that less than 0.5 deer pellets per 10 square-meters. By grading habitat quality this way, they were able to understand if and how habitat quality was related to tiger populations (Smith 1998). The Tiger as Case Study for Large Mammal Conservation This research group used a hierarchical framework to ensure that each tiger habitat could be represented. They first divided tiger range into five bioregions, but included only three in their research for various reasons (such as awareness of very limited tiger populations.) The three they used in their research were: Indochina, Indian Subcontinent, and South-east Asia. They then added different habitat types (such as Tropical Dry Forests, the Mangroves, etc.) to their hierarchy to ensure that each one was distinguished in their research (Matthew 1998). The researchers then divided each bioregion into TCUs, (Tiger Conservation Units, which are blocks of habitat with the capabilities to support interacting populations of tigers) with about 5 km between each TCU. They delineated the TCUs on maps by using knowledge of the remaining forest cover and classifying them into groups based on their habitat type. They scored the TCU s using three criteria (1) habitat integrity, which indexes the size, degree of degradation, fragmentation, and connectivity of tiger habitat blocks (2) poaching pressure, which indexes the intensity of illegal hunting of tigers and their prey and the potential for its control ; and (3) population status, which indexes tiger abundance and recent population trends within each tiger habitat type (Matthew 1998). They assessed tiger populations in each TCU for a 10 year period, then assigned the following scores: an intact population is stable (10 points); a moderately depleted population is increasing (10 points), stable (8 points), declining (7), or its status is unknown (7); and a severely depleted population is increasing (7), stable (5), declining (1), or its status is unknown (3) (Matthew 1998). They analyzed the reasons for the population decline of tigers, (which they believed were poaching, habitat loss, and population status.) They used a 4:2:1 ratio between habitat loss, poaching pressure, and population status, in that order, based on the threat of each variable on tiger populations. They gave each variable a score, based on the rubric above, and then calculated a score that revealed the likelihood of the persistence of tiger life in those areas. Level I TCUs reflected high likelihood of supporting tigers in the future, with scores between 45 and 70 points, Level II TCUs reflected medium likelihood of supporting tigers in the future, with

4 scores between 32 and 44 points, and Level III TCUs reflected low likelihood of supporting tigers in the future, with scores less than 32 points (Matthew 1998). Assessing Tiger Population Dynamics This research group used camera traps, which were placed in location with presence of tiger signs, to capture tigers in photographs. By then end of their field research, they had a total 5725 photos of 74 different tigers throughout a 9-year time period. They were able to distinguish between tigers based on their fur and stripe patterns (Karanth 2006). Their study consisted of 10 primary periods, which covered a period of nine years, during which the tiger population was expected to fluctuate, and the primary periods were divided into secondary periods during which the population was assumed to remain close to constant. After examining about 30 models of the data, which they had created after obtaining data from the field studies, the researchers chose a transient model which included two types of survival rates: 1) the animals not previously caught in the primary period, and 2) the animals previously caught in the primary period. The researchers were then able to use various equations to calculate the number of new recruits in each period, the rate of increase, the average rate of change, and density-based estimates of population change. By calculating these different variables over a 9- year period, the researchers were better able to understand the fluctuations among the populations of tigers over time (Karanth 2006). RESULTS Study of Tiger Distribution and Habitat Quality in Nepal Based on natural barriers of tiger dispersal, the researchers divided tiger populations into four regions to better analyze their results. The regions are as follows: 1) Chitwan, 2) Bardia, 3) Sukla Phanta, and 4) Dudwa (Smith 1998). The Chitwan division, with an area of 2543 square-km, holds the largest tiger population, with about 196 tigers. Dispersal barriers within this region exist where there is heavy settlement or degraded habitat. The Bardia region holds the second highest tiger population, numbering approximately 143 tigers in total population, in an area that extends for 1840 square-km. Again, population dispersal barriers are prominent where human pressure has risen. In Sukla Phanta and Dudwa, smaller regions and populations of tigers, the rates of good to poor habitat range from 86% to 16% across the forest ranges classified by the researchers. They estimated that when the ratio of good to poor habitat drops below 50%, breeding amongst tigers will no longer occur, and when it drops below 30%, tigers will not be found in the area (Smith 1998). The Tiger as Case Study for Large Mammal Conservation The researchers found that in their research area (across the tiger range in Asia), there were 25 level I TCUs, 21 level II TCUs, and 97 level III TCUs. In the Indian subcontinent, there were a total of 59 TCUs, 11 of which were level I. Of these 59 areas, 20 did not currently contain any protection areas. In the Indochina Bioregion, they identified a total of 69 TCUs, 10 of which

5 were level I, and 8 were level II. 36 of the 69 TCU areas did not contain any strictly protected areas. The Southeast Asia Bioregion contained 31 TCUs, 4 of which were level I, and 6 of which were level II. Of these, 14 did not contain strictly protected areas (Matthew 1998). Assessing Tiger Population Dynamics The Population Dynamics were assessed by this group of researchers to see what was affecting the population changes of tigers. The abundance, recruitment, and population rate of increase were found for primary periods These periods were the most significant because they contained the largest samples. Recruitment estimates were imprecise, but ranged from Abundance estimates in a sampled area of 231 square-km ranged from The estimated rates of population change range from 0.76 to 1.35 (Karanth 2006). DISCUSSION The research done in Nepal showed direct correlations between habitat quality and tiger populations (Smith 1998). Setting aside land for tigers is essential, but it is not enough. The habitat quality of these lands must be monitored to ensure that they are able to support a living and breeding tiger population. Since the correlation between good habitat quality and high tiger populations is so direct, it is highly important that tiger habitat is not only legally protected, but also conserved. However, the first step must be to set aside priority land, and ensure that it is legally protected. The most important lands (level I or level II TCU) should be given immediate protection, because these are the lands which are most likely to support tiger life long term. Tigers need large amounts of land, because they are territorial animals, and they currently do not have enough strictly protected land. If all high level TCUs are given strict protection, tiger populations will benefit immensely (Matthew 1998). Also important to tiger populations is that the Population Dynamics continue to be monitored. The camera traps were effective, and there are other methods that can be used as well. Improved reserve management is essential to ensure that tiger populations remain viable (Karanth 2006). The populations must be monitored so that legal leaders and conservationists can know where their management needs are. CONCLUSION If the results from all of these research methods are incorporated in conservation methods, tiger populations could thrive. The habitat quality must be monitored and improved, because it is currently not able to support a growing population of tigers. Any other conservation efforts will be wasted if more reserves are not created, and if reserve management is not improved. Simply stated, Without wilderness, the wild tiger will not survive (Kasnoff 2012). Tigers will face extinction unless more legal protection is given to existing tiger reserves, and more tiger reserves are created.

6 [The below sources should be alphabetized.] LITERATURE CITED "tiger." Encyclopædia Britannica. Encyclopædia Britannica Online Academic Edition. Encyclopædia Britannica Inc., Web. 23 Nov < An Ecology-Based Method for Defining Priorities for Large Mammal Conservation: The Tigeras Case Study Matthew, Thomas, Wikramanayake, Eric D. et al. "Conservation Biology." Conservation Biology (1998): Web. 24 Nov Kasnoff, Craig. "Tigers in Crisis: The Problem." Tigers in Crisis. N.p.. Web. 25 Nov < Karanth, K. Ullas, James D. Nichols, N. Samba Kumar and James E. Hines Ecology, Vol. 87, No. 11 (Nov., 2006), pp Smith, James L. David, Sean C. Ahearn and Charles McDougal Conservation Biology, Vol. 12, No. 6 (Dec., 1998), pp Dinerstein, Eric, Colby Loucks, et al. "BioScience." BioScience (2007): n. page. Web. 23 Nov < WWF. Timeline WWF GlobalWeb. 24 Nov < ion/>. "Tiger Population." WWF Global. WWF, n.d. Web. 24 Nov 2012.