- Human use of habitats impact prey species showed a study highlighting the difference in activity by the same species in two different protected areas – Kaziranga and Manas.
- Additionally, the study found that Manas offers the opportunity to assist in further growth of tiger and other large carnivore populations in coming years given that the prey population grows at a natural rate.
- Any recovery programme needs to address critical issues like non-lethal human disturbances on prey and habitats while the focus is on halting direct threats like poaching and retaliatory killing of tigers and co-predators.
Researchers in Assam studying the impact of human disturbance on prey species in two of the state’s wildlife habitats have found that some species, mostly active during the day hours in Kaziranga National park, are mostly active at night in Manas National Park. The variations in activity of species like barking deer, hog deer, wild pig, sambar and wild buffalo in these two protected areas, is likely because of the difference in human presence in both these parks.
The study published in Biological Conservation journal was carried out by researchers from Aaranyak and WWF-India to estimate the abundance of these species over three seasons during 2014-2017. The study highlighted the population density of the prey species and how human disturbances affect them.
In Kaziranga, human-use of the park is minimal, while in Manas, local communities access the park for natural resources. Manas experienced armed ethno-political conflict from the late 1980s until 2003 leading to over 40 percent of primary habitats within the Bodoland Territorial Autonomous District (BTAD) getting converted to settlements and agriculture.
Prey-rich environments with an assemblage of species differing in body-size are critical for the persistence and coexistence of large carnivore communities. Tigers and leopards consume prey animals that vary in body sizes and weight. The weight often varies in the range of 10-250 kg.
The study was limited to the Bansbari and Bhuyanpara ranges of Manas National Park, covering 398 square km in Assam in northeastern India, as these areas have remained largely conflict-free since 2003. It says disturbances caused by humans affect ungulate species, which are the primary prey of tigers, leopards and dholes in this region.
“People in wildlife habitat are a known source of disturbance. In Manas, people who collect natural resources in the park have not only impacted the presence of species in areas but also their behaviour if compared to species from a habitat that is mostly undisturbed (e.g. Kaziranga National Park). To understand this better, the study used 9,209 independent photographs of the seven prey species from Manas and Kaziranga taken by camera traps,” Dipankar Lahkar, tiger researcher in Aaranyak told Mongabay-India.
Prey species threatened by disturbances
The seven prey species under study are barking deer (Muntiacus muntjak), hog deer (Axis porcinus) wild pig (Sus scrofa), sambar (Rusa unicolor), swamp deer (Rucervus duvaucelii), gaur (Bos gaurus), wild buffalo (Bubalus arnee).
“All these species are threatened by habitat loss and hunting throughout their ranges that increase the challenges of recovering tiger population. Therefore, understanding the determinants of their occurrence and abundance is critical to initiate sustained efforts for recovery of both prey and large carnivore populations in any landscape” says Lahkar.
The results show that species like barking deer, hog deer, wild pig, sambar and wild buffalo that are mostly active during day hours in Kaziranga were found to be mostly active at night in Manas. “This is how species have responded to human disturbances within the park. This has serious implications on health and population growth of prey species that directly impacts the population of tigers and other large carnivores of Manas,” he said.
As a general understanding, wild animals face difficulties in breeding in an area that is disturbed as that impacts their natural hormonal balance.
The effects on prey species could include altering habitat selection, foraging and resting site selection, movement patterns, exposure to predation, individual fitness, survival, reproduction and ultimately distribution and population trends, said the study.
Six prey species occurred at a combined density of 51.84 individuals per sq.km in the grasslands whereas, four species occurred at a combined density of 14.88 in the woodlands. Across Manas, prey densities were estimated to be 42.66 individuals per sq.km.
“Manas is one of the crown jewels of the protected area network in India due to the vast biodiversity it supports. While most recent line transect studies either estimate total prey density or just encounter rates, this current study estimates species-specific densities which requires much higher effort and rigour in methods. The current study by scientists Dipankar Lahkar and colleagues is a shining example of how the use of robust monitoring techniques can help guide the recovery process of our National Parks and the species assemblage,” said Milind Pariwakam, a wildlife biologist with the Wildlife Conservation Trust (WCT), who was not associated with the study.
Dependence on park’s resources
The park’s natural resources also meet the livelihood requirement of local communities residing around park boundaries. The communities collect fuelwood, food (e.g. vegetables and fish), building materials (such as thatch) and graze their livestock.
A socio-economic study conducted by Aaranyak in 2015 estimated that 78 per cent of local communities are unable to fulfil their annual requirements from agriculture and thus access the park natural resources for their subsistence.
The study found that the prey population of Manas compared to several other well-protected forests across India and Nepal, is of less density. To be precise, it is 42.66 individuals/sq km in Manas versus 65.2 in Bardia, 60.13 in Chitwan and 60.00 in Shuklaphanta (all three are National Parks in Nepal), and 58.10 in Kaziranga.
“This means that the park has more opportunity to assist in further growth of tiger and other large carnivore populations in coming years given that the prey population grows at a natural rate,” Lahkar said.
Capacity to support more tigers in Manas
Given the population density of prey animals, this study predicts that Bansbari-Bhuyanpara ranges of Manas itself can support a potential tiger density of 8.77/100 sq. km, corresponding to a population of 35 tigers.
“This means tiger numbers in these two ranges can grow two-fold given that currently 15-20 tigers are known to live there (as per estimates of 2015,” according to Lahkar.
The study recommends that any such recovery programme needs to address critical issues like non- lethal human disturbances on prey and habitats while the focus is on halting direct threats like poaching and retaliatory killing of tigers and co-predators.
Manas National Park has recovered steadily since peace was restored in the landscape in 2003 through the efforts of different government agencies (Forest Department of Bodoland Territorial Council in particular) which received tremendous support from local communities and others.
“Manas has gone through a serious troubling phase since the late 80s and it has been a long-drawn effort of B.T.C. and other stakeholders since 2003. The depleted habitats and populations of animals are increasing steadily now. This study will definitely help us to manage the habitats further.” said Amal Chandra Sarmah, Field Director, Manas Tiger Reserve.
“Knowledge about population and distribution of a species is the key for its conservation planning and management” said M. Firoz Ahmed, Head, Tiger Research and Conservation Division, Aaranyak.
Banner image: Tiger in Manas. Photo courtesy Forest Department, Aaranyak and WWF.