Characteristics of Population
Density, Distribution and Dispersion of The Bengal Tiger:
The Bengal tiger was classified as an endangered species by the International Union for Conservation of Nature (IUCN) in 2010. Bengal tigers are primarily found in India. The Bengal tiger also inhabits the regions of Bangladesh, Nepal, Bhutan, scarcely in Myanmar and in the eastern regions of Pakistan. The current population of the Bengal tiger has surpassed 2500 in the past couple of years, with the population projected to gradually increase in the immediate future due to various conservation efforts.
("Bengal Tiger," n.d.).
Density of Bengal Tigers: (Per 2008 Research and only in their inhabited habitats)
India:
Shivaliks-Gagnetic Flood Plain: 1 tiger / 17.1km².
Central India: 1 tiger/ 6.6km²
Eastern Ghats: 1 tiger/ 146.6km²
Western Ghats: 1 tiger/ 52.1km² (Status of Tigers, n.d.).
Bangladesh:
1 tiger/ 27.0 km² (H. Khan, 2012).
Nepal:
1 tiger/ 21.0km² ("121 Breeding," 2009).
Densities for regions of Bhutan, Myanmmar and eastern regions of Pakistan are currently unknown.
The Bengal tiger was classified as an endangered species by the International Union for Conservation of Nature (IUCN) in 2010. Bengal tigers are primarily found in India. The Bengal tiger also inhabits the regions of Bangladesh, Nepal, Bhutan, scarcely in Myanmar and in the eastern regions of Pakistan. The current population of the Bengal tiger has surpassed 2500 in the past couple of years, with the population projected to gradually increase in the immediate future due to various conservation efforts.
("Bengal Tiger," n.d.).
Density of Bengal Tigers: (Per 2008 Research and only in their inhabited habitats)
India:
Shivaliks-Gagnetic Flood Plain: 1 tiger / 17.1km².
Central India: 1 tiger/ 6.6km²
Eastern Ghats: 1 tiger/ 146.6km²
Western Ghats: 1 tiger/ 52.1km² (Status of Tigers, n.d.).
Bangladesh:
1 tiger/ 27.0 km² (H. Khan, 2012).
Nepal:
1 tiger/ 21.0km² ("121 Breeding," 2009).
Densities for regions of Bhutan, Myanmmar and eastern regions of Pakistan are currently unknown.
The Distribution of the Bengal Tiger:
The distribution of the Bengal tiger can be observed through camera traps, as well as sign surveys. As of 2011, the population of the Bengal tiger in India was estimated as 1706. Estimates have also been conducted in areas with a lower population of the Bengal tiger , such as 440 tigers present in Bangladesh, 155 tigers in Nepal, and 75 in Bhutan. ("Panthera Tigris," n.d.).The distribution pattern, or dispersion, of animals is the pattern in which a population is distributed in an area. The three types of distribution patterns of populations include uniform distribution, random distribution and clumped distribution (Carter-Edwards et al., 2011, p. 501-503). Tigers demonstrate random distribution. To begin with, Bengal tigers are territorial species, which defend their own territories. Bengal tigers mark their territory with urine, and typically only stay within their territory to hunt. (Brannan, 2014). Males will not share their territory with other males, but instead they may compete in a fight to determine which male will gain the territory. This occurs rarely. Males and females interact in order to create reproduction of new cubs, as well as to share the food obtained from a kill. ("Interactions and Behaviour," 2007). This demonstrates that the interactions between members of a population can be both positive and sometimes negative, which is known as neutral interactions. (Carter-Edwards et al., 2011, p. 503). It is also known that there are an abundance of resources in the area populated by the tigers, with many different types of species to prey on, distributed uniformly across the entirety of the tiger habitat. (Carter-Edwards et al., 2011, p. 503). As a result, it is determined that the distribution pattern of the Bengal tiger is uniform.
The distribution of the Bengal tiger can be observed through camera traps, as well as sign surveys. As of 2011, the population of the Bengal tiger in India was estimated as 1706. Estimates have also been conducted in areas with a lower population of the Bengal tiger , such as 440 tigers present in Bangladesh, 155 tigers in Nepal, and 75 in Bhutan. ("Panthera Tigris," n.d.).The distribution pattern, or dispersion, of animals is the pattern in which a population is distributed in an area. The three types of distribution patterns of populations include uniform distribution, random distribution and clumped distribution (Carter-Edwards et al., 2011, p. 501-503). Tigers demonstrate random distribution. To begin with, Bengal tigers are territorial species, which defend their own territories. Bengal tigers mark their territory with urine, and typically only stay within their territory to hunt. (Brannan, 2014). Males will not share their territory with other males, but instead they may compete in a fight to determine which male will gain the territory. This occurs rarely. Males and females interact in order to create reproduction of new cubs, as well as to share the food obtained from a kill. ("Interactions and Behaviour," 2007). This demonstrates that the interactions between members of a population can be both positive and sometimes negative, which is known as neutral interactions. (Carter-Edwards et al., 2011, p. 503). It is also known that there are an abundance of resources in the area populated by the tigers, with many different types of species to prey on, distributed uniformly across the entirety of the tiger habitat. (Carter-Edwards et al., 2011, p. 503). As a result, it is determined that the distribution pattern of the Bengal tiger is uniform.
Figure 1: This map represents the known habitats of the Bengal tiger.
Age Structure:
The Bengal tiger surpasses many milestones during their lifetimes. To begin with, the cubs endure a gestation period of 103 days in the mothers’ womb, creating a litter of two to five cubs on average. The cubs are typically feed with milk for about 6-8 weeks, followed by an introduction to meat. The cubs depend on their mother for up to one and a half years of birth. Once the cubs reach the age of 18 months, they have the ability to hint for food on their own. ("Indian Bengal," 2009). The most common period for mating occurs between the months of November and April, between a female, which reaches sexual maturity between 3-4 years of age, and a male tiger, which reaches maturity at the age of 4. ("Indian Bengal," 2009). The life span of a Bengal tiger is between 14 to 18 years of age, but Bengal Tigers have the ability to live up to 20 years in captivity. (Bradford, 2014) Tigers in captivity tend to have a longer lifespan to due to their enclosure, which provides a healthy diet, and eliminates the possibility of human hunting and poaching. Due to low number of offspring produced during reproduction, the female tiger has the ability to take care of the cubs so that they may be able to survive for their entire lifespan. Due to the demonstration of type I survivorship (Carter-Edwards et al., 2011, p. 504) studies have suggested that the highest percentage of tigers are in the grouping of 18 months and older, due to the high survivorship rate of the young cubs. ("India Has 2,226," 2015).
Genetic Diversity:
Genetic diversity refers to the number of different alleles of all the genes, and it incorporates the frequency in which these alleles appear. ("What Is Genetic," 2016). An allele is an alternative form of a gene, which determines distinct traits that can be passed on by the parents to their offspring. ("Allele - a Genetics," 2016). Genetic Diversity is important; because it contains a greater gene pool, which allows the population to have greater diversity, providing a greater likelihood of survival if there was a significant disturbance introduced to their habitat. ("The Importance," n.d.).
Bengal tigers contain three distinct mitochondrial nucleotide sites, and also contain 12 unique microsatellite alleles. ("Bengal Tiger," 2014). Recently, a study from Cardiff University has suggested that the endangerment of tigers is directly correlated to the lack of genetic diversity within the species. It was determined, through the comparison of DNA samples, that 93% of tiger DNA variations from past historical data are no longer present. In 2011, a study found that through the loss of many alleles, genetic diversity is posing a significant threat to the tiger population. Researchers concluded that the lack of genetic diversity is due to habitat loss, which diminishes the ability of tigers from dispersing and mixing across different habitats. This loss of genetic variation is detrimental for species survival when faced with drastic environmental change. Researchers continue to emphasize the importance of variation within the population of tigers in protected reserves and increase their connectivity with other members of their populations. (Gates, 2013).
A drastic environmental change will have a severe impact of the population due to the lack of genetic diversity, which will threaten the existence of this population.
The Bengal tiger surpasses many milestones during their lifetimes. To begin with, the cubs endure a gestation period of 103 days in the mothers’ womb, creating a litter of two to five cubs on average. The cubs are typically feed with milk for about 6-8 weeks, followed by an introduction to meat. The cubs depend on their mother for up to one and a half years of birth. Once the cubs reach the age of 18 months, they have the ability to hint for food on their own. ("Indian Bengal," 2009). The most common period for mating occurs between the months of November and April, between a female, which reaches sexual maturity between 3-4 years of age, and a male tiger, which reaches maturity at the age of 4. ("Indian Bengal," 2009). The life span of a Bengal tiger is between 14 to 18 years of age, but Bengal Tigers have the ability to live up to 20 years in captivity. (Bradford, 2014) Tigers in captivity tend to have a longer lifespan to due to their enclosure, which provides a healthy diet, and eliminates the possibility of human hunting and poaching. Due to low number of offspring produced during reproduction, the female tiger has the ability to take care of the cubs so that they may be able to survive for their entire lifespan. Due to the demonstration of type I survivorship (Carter-Edwards et al., 2011, p. 504) studies have suggested that the highest percentage of tigers are in the grouping of 18 months and older, due to the high survivorship rate of the young cubs. ("India Has 2,226," 2015).
Genetic Diversity:
Genetic diversity refers to the number of different alleles of all the genes, and it incorporates the frequency in which these alleles appear. ("What Is Genetic," 2016). An allele is an alternative form of a gene, which determines distinct traits that can be passed on by the parents to their offspring. ("Allele - a Genetics," 2016). Genetic Diversity is important; because it contains a greater gene pool, which allows the population to have greater diversity, providing a greater likelihood of survival if there was a significant disturbance introduced to their habitat. ("The Importance," n.d.).
Bengal tigers contain three distinct mitochondrial nucleotide sites, and also contain 12 unique microsatellite alleles. ("Bengal Tiger," 2014). Recently, a study from Cardiff University has suggested that the endangerment of tigers is directly correlated to the lack of genetic diversity within the species. It was determined, through the comparison of DNA samples, that 93% of tiger DNA variations from past historical data are no longer present. In 2011, a study found that through the loss of many alleles, genetic diversity is posing a significant threat to the tiger population. Researchers concluded that the lack of genetic diversity is due to habitat loss, which diminishes the ability of tigers from dispersing and mixing across different habitats. This loss of genetic variation is detrimental for species survival when faced with drastic environmental change. Researchers continue to emphasize the importance of variation within the population of tigers in protected reserves and increase their connectivity with other members of their populations. (Gates, 2013).
A drastic environmental change will have a severe impact of the population due to the lack of genetic diversity, which will threaten the existence of this population.
Fecundity: (Number of Cubs that the Female Produces Within Her Lifetime)
The fecundity is the average number of offspring that have been produced by the female member of a population over the female’s lifetime. (Carter-Edwards et al., 2011, p. 506). Female tigers tend to reproduce anywhere from 2-5 cubs, occasionally producing one offspring or even up to seven offspring. ("Tigers Birth," n.d.). Female tigers tend to give birth generally every two to two and a half years. ("Tigers Birth," n.d.). The female tiger can produce anywhere between 8-38 cubs in her lifetime, depending on litter size, how often a litter is created, as well as the female tigers’ lifespan and the age in which sexual maturity is reached.
Survivorship:
Survivorship is the percentage or the number of individuals in a given population that will survive to a given age. (Carter-Edwards et al., 2011, p. 506) The type of survivorship that is exhibit by tigers is Type I survivorship. This is due to the low number of offspring produced by the females during reproduction, which gives the ability of the female tiger to care for her offspring. ("Tigers Birth," n.d.). This parental care allows for the cubs to attain a high percentage of survival in order to reach the age in which they are able to sexually reproduce. Most mammals, such as Bengal tigers, experience a Type I survivorship pattern. Despite the fact that fewer offspring are produced, they experience a higher life survivorship rate. (Carter-Edwards et al., 2011, p. 507)
Survivorship is the percentage or the number of individuals in a given population that will survive to a given age. (Carter-Edwards et al., 2011, p. 506) The type of survivorship that is exhibit by tigers is Type I survivorship. This is due to the low number of offspring produced by the females during reproduction, which gives the ability of the female tiger to care for her offspring. ("Tigers Birth," n.d.). This parental care allows for the cubs to attain a high percentage of survival in order to reach the age in which they are able to sexually reproduce. Most mammals, such as Bengal tigers, experience a Type I survivorship pattern. Despite the fact that fewer offspring are produced, they experience a higher life survivorship rate. (Carter-Edwards et al., 2011, p. 507)
Figure 2: Three general patterns of survivorship are displayed as Type I, Type II and Type III.