Tigers at higher elevations outside their range: What does it mean for conservation?

Abstract

Nepal’s population of endangered Bengal tigers (Panthera tigris) is on the rise. In recent years, the presence of tigers has been documented at higher elevations. The objective of this study is to explore the possible reasons for the tigers’ presence at the higher elevations. It is critical that these high-altitude habitats for tigers be further explored and protected. The study points out the importance of the Mahabharat range and a longitudinal conservation gradient approach in Nepal. Apart from this, it is imperative to assess the density of tigers and tiger prey in the area. Even though high-altitude ecology may be suitable for tiger growth, the formulation of a high-altitude tiger conservation action plan with effective coordination between stakeholder organizations and concerned departments is of great importance. Tigers are an apex species of the terrestrial ecosystem and exist in a precarious state throughout their range. The tiger is a globally endangered species (Goodrich et al. 2015). In the past, the tiger once existed as nine subspecies, now reduced to only six subspecies that exist in the wild. The subspecies Bengal tiger (Panthera tigris) has the largest population and is restricted to South Asia, namely Bangladesh, Bhutan, India, and Nepal (Global Tiger Initiative 2010). In the past century, P. tigris numbers have plummeted from 100,000 to below 3,500. Presently, wild P. tigris’ habitat covers approximately 1.2 million km2 in 13 Tiger Range Countries (TRCs) (Global Tiger Initiative 2010). Faced with decreasing P. tigris populations, TRCs in 2010 proposed doubling P. tigris populations by 2022, from a global estimate of ~3,643 in the year 2010 to ~5,845 by the year 2022 under the Global Tiger Recovery Program (Global Tiger Initiative 2010). P. tigris are listed as endangered on the Red List of threatened species by the International Union for Conservation of Nature (IUCN) and under Appendix I by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In Nepal the National Parks and Wildlife Conservation Act, 1973, classified P. tigris as a protected species. India, along with Bhutan, Nepal, Russia and Indonesia, has successfully recovered wild P. tigris populations. In recent years, P. tigris have been recorded at higher elevations outside of their usual habitat (Figure 1). For example, presence of P. tigris was recorded from 3,602 m at Arunachal Pradesh and at 3,274 m in Uttarakhand in India, 4,038 m in Bhutan and 3,165 m from Nepal (Adhikarimayum & Gopi 2018; Bhattacharya & Habib 2016; Tempa et al. 2019). Similarly, the presence of P. tigris was documented at higher elevations in Nepal (i. e., 2,500 m) and in far-western Nepal bordering on Nanda Devi National Park in India, Uttarakhand. A camera trap also recorded P. tigris in Eastern Nepal at 3,165 m (Red Panda Network 2020) bordering on Singalila National Park in India, North Sikkim. P. tigris are not the only species that are being sighted at previously unheard-of altitudes. There have definitely been sightings of several species at higher altitudes. Scientists have also noted an upwards movement of the mountain-dwelling pika (Ochotona roylei and O. macrotis). Within a 46-year interval, the Pika habitat has moved up by 200 m (Koju 2018). Another study, conducted on the clouded leopard (Neofelis nebulosa) in 2020 in the Langtang area, found the elusive animal surviving at 3,498 m (Can et al. 2020). Previously the animal had been found only at 2,300 m. Another study revealed that the house crow (Corvus splendens) has been moving up by 136 m annually on average from 2,000 m to 4,200 m in Mustang district in Nepal (Acharya & Ghimirey 2013). This study concluded that climate change seems to be a possible reason behind this upward movement. And this kind of movement of wildlife has not just been witnessed in the mountains of Nepal. It has also been found with the red panda (Ailurus fulgens), Assam macaque (Macaca assamensis), flying squirrel (Pteromyini), Himalayan crestless porcupine (Hystrix brachyuran), Himalayan goral (Naemorhedus goral), Himalayan palm civet (Paguma larvata), Himalayan serow (Capricornis thar), leopard cat (Prionailurus bengalensis), leopard (Panthera pardus), marbled cat (Pardofelis marmorata), northern red muntjac (Muntiacus vaginalis), yellow-throated marten (Martes flavigula), red fox (Vulpes vulpes), wild boar (Sus scrofa), and the Himalayan black bear (Ursus thibetanus) (Red Panda Network 2020). In Nepal, P. tigris enjoy an exalted status because they are considered sacred and spiritually evolved. Nepalese people generally had a positive attitude toward P. tigris conservation and were willing to accept some losses of livestock, but not human casualties. (Bhattarai & Fischer 2014). Nepal has been a pioneer in P. tigris conservation since it established protected area systems. P. tigris are a priority species for tropical and subtropical ecosystem conservation in Nepal. Until the mid-20th century, P. tigris in Nepal were distributed along the contiguous lowland forests on the slopes of the Siwaliks, Bhabar and alluvial grasslands 44 Management & Pol icy Issues and riverine forests of Nepal (Smythies 1942; Gurung et al. 2006). P. tigris distribution is currently largely limited to five protected areas of the Terai Arc Landscape (TAL), including: Chitwan National Park, Parsa Wildlife Reserve, Bardia National Park, Banke National Park and Shuklaphanta Wildlife Reserve. Conservation activities in Nepal aim to connect several protected areas with habitat corridors to facilitate the movement and dispersal of wildlife primarily along the east-west corridor at lower elevations. TAL in Nepal is critical for doubling the P. tigris population. In Nepal, TAL covers 24,710.13 km2 across 18 districts and extends from the Bagmati River in the east to the Mahakali River along the western border with India. Apart from these protected areas, various national and community forests serve as P. tigris habitats that enable habitat interconnectivity and allow their dispersal. Previously the Bagmati River was considered the eastern boundary of P. tigris distribution in Nepal. In Nepal, P. tigris have been confined largely to the lowland habitat (below 1,000 m elevation) in the forests on the slopes of the Siwalik Range (1,000 to 1,500 m) (Miehe et al. 2016) up to the Bagmati River in the east. However, recent sightings of P. tigris across Nepal at higher elevations raise some critical questions that need to be addressed: a) Did these P. tigris’ seen at higher elevations just stray from their natural habitat? b) Does individual plasticity play a role in the occurrence of these P. tigris’ seen at higher elevations? c) Did a reduction in the prey population, scarcity of water, or elevated temperature force P. tigris to move higher? d) Do these higher elevations historically harbor P. tigris as folklore suggests? The Nepal Himalaya is divided into six biographic and bioclimatic zones in north–south direction: 1) Terai (the northern edge of the Indo-Gangetic plain), 2) Siwalik (Churia) range, 3) Mahabharat range, 4) Midlands, 5) Himalayas, and 6) Inner Himalayas and Tibetan marginal mountains (Figure 2). Each of these zones has distinct altitudinal variation, slope, and relief characteristics, as well as climatic characteristics (Figure 3). The Mahabharat range (also known as mid-hills), south of the Himalayan range and north of the Siwalik range, is a critical physiographic region in Nepal. The Mahabharat range rises higher than the Siwalik hills and reaches an altitude of 3,000 m (Hagen 1998). The Mahabharat is an east-west running mountain range. The Mahabharat has a subtropical climate at low elevations and temperate climates at higher elevations. It is well developed in eastern and central Nepal and underdeveloped in western Nepal. Since the mid-1990s, Nepal’s mid-hills have seen forest cover increase significantly as a result of community forestry. Moreover, mid-hill areas in Nepal have also witnessed a decline in human population due to out-migration and low birth rates. All these factors might have also resulted in P. tigris and other animals coming back in the mid-hills. Present frequent sightings of P. tigris in this range might not be just a fluke. All these sightings might suggest that this range is also an important hotspot for P. tigris and other wildlife populations that need to be protected. Or P. tigris might venture up into Figure 1 – Panthera tigris sightings at high altitudes in Hindu Kush Himalaya.