Doubling of Tigers in Royal Manas National Park

Report

BHUTAN

2017

Doubling Tigers in RMNP

POPULATION STATUS AND DENSITY OF TIGERS IN THE SOUTHERN BELT OF ROYAL MANAS NATIONAL PARK (2015-2016)

Report Preparation: Singye Wangmo, Senior Forestry Officer, RMNP Tenzin Wangchuk, Chief Forestry Officer, RMNP Dorji Wangchuk, Senior Range Officer, RMNP Report Edition: Dr. Phuntsho Thinley, Principal Research Officer, UWICER Dr. Abhishek Harihar, Tiger Biologist, Panthera Organization Sonam Wangdi, Deputy Chief Forestry Officer, NCD Phurba Lhendup, Director, Species Program, WWF Bhutan Program Tenzin Wangchuk, Chief Forestry Officer, RMNP Singye Wangmo, Senior Forestry Officer, RMNP Suggested Citation: RMNP, 2017. Population Status and Density of Tigers in the Southern Belt of Royal Manas National Park (2015-2016).

Technical Report.

Funded by: WWF Bhutan Program and Royal Government of Bhutan through Transboundary Manas Conservation Area (TraMCA) project.

Design and Layout:Sonam Chophel, Communication, WWF Bhutan Program Copyright: © 2017 Royal Manas National Park, Department of Forests and Park Services ISBN 978-99936-992-0-0 Cover Image: DoFPS/WWFBhutan

“Throughout the centuries, the Bhutanese have treasured their natural environment and have looked upon it as the source of all life. This traditional reverence for nature has delivered us into the twentieth century with our environment still richly intact. We wish to continue living in harmony with nature and to pass on this rich heritage to our future generations.”

His Majesty the King Jigme Singye Wangchuck

CONTENTS CHAPTER 1: BACKGROUND 14 CHAPTER 2: MATERIALS AND METHOD 19 CHAPTER 3: RESULTS 24 CHAPTER 4: CONSERVATION IMPLICATIONS AND 36 RECOMMENDATIONS ANNEXURES 43 REFERENCES 56 LIST OF TABLES AND FIGURES Table 1: Total number of tiger individuals, sampling area, sampling effort and capture events in RMNP 2015-2016 Table 2: Total number of tiger individuals in Manas and Umling Range in 2015 and 2016 Table 3: RMNP SPACECAP Estimate in 2015 Table 4: RMNP SPACECAP Estimate in 2016 Table 5: Estimated average habitat use of mammals in RMNP (2016) Table 6: Estimated beta coefficient for the top ranked models for five ungulate species (2016) Table 7: Estimated beta coefficient for the top ranked models for tiger (2016) Table 8: Best Models for predicting habitat use for each species in RMNP (2016) Figure 1: Map of Royal Manas National Park showing distribution of camera stations in 2015 and 2016 in a 2X2 km grid Figure 2: Map of the protected areas of Bhutan. Royal Manas National Park (RMNP) is shown in orange, located in the southern foothills of Bhutan.

Figure 3: Camera trap installation in the field

Figure 4: Different camera models used in the camera-trap survey 2015 and 2016

Figure 5 (a) and (b): Difference in stripe patterns between two tiger individuals in RMNP noted from photographic captures using camera trap images Figure 6 (c) and (d): Repeated photographic captures of same tiger individuals in RMNP Figure 7: Pictures of breeding female tigers and cubs photo captured in 2015 and 2016 Figure 8: Number of recapture rates of individual tigers in 2015 Figure 9: Number of recapture rates of individual tigers in 2016 Figure 10: Cumulative number of new individuals captured with an increasing sampling occasions in 2015 Figure 11: Cumulative number of new individuals captured with an increasing sampling occasions in 2016 Figure 12: Mean density of tigers with 95% CI in 2015 and 2016 Figure 13: Map showing estimated posterior density of tigers in RMNP (2015). Dark to light orange and cream shades indicate tiger densities in descending order.

Figure 14: Map showing estimated posterior density of tigers in RMNP (2016). Dark to light orange and cream shades indicate tiger densities in descending order.

Figure 15: Transboundary tiger detection polygons in TraMCA (2015-2016). Blue polygons indicate male tigers and pink polygons indicate female tigers Figure 16: Estimated probabilities of occurrence for Barking deer (Muntiacus muntjak), Gaur (Bos gaurus), Sambar (Rusa unicolor), Water buffalo (Bubalus bubalis), Tiger (Panthera tigris) and Wild Pig (Sus scrofa)(2016)

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ACKNOWLEDGEMENT

Acronyms

The annual tiger monitoring study in Royal Manas National Park was carried under the aegis of Transboundary Manas Conservation Area (TraMCA) project.

We would like to extend our sincere appreciation and gratitude to Lyonpo Yeshey Dorji, Honorable Minister, Ministry of Agriculture and Forests, Dasho Rinzin Dorji, Honorable Secretary of Ministry of Agriculture and Forests, Mr. Chencho Norbu, former Director General of Department of Forests and Park Services, and Mr. Phento Tshering, Director of Department of Forests and Park Services for their continued support for the long term monitoring of tigers in RMNP and various other conservation efforts in Bhutan.

AIC CMR CTFM GIS DoFPS GPS JSWNP JWS PWS MNP NCD NDVI RMNP RMT SCR SD SMART TraMCA TMT UWICER Research WWF

The survey wouldn’t have been possible, had it not been for the unparalleled commitment and exemplary teamwork shown by the group members in completing the fieldwork successfully.

We thank the foresters of RMNP for their passion, dedication and service to the nation in protecting our rich natural heritage.

We thank Dr. Abhishek Harihar, Tiger Biologist, Panthera Organization in guiding the core team members and further in reviewing the report. We also thank Dr. Phunstho Thinley, Principal Research Officer, UWICER and Dr. Qamal Quereshi, Wildlife Biologist of Wildlife Institute of India, Dehradun for thoroughly reviewing the report.

We owe a great depth of gratitude to WWF, Bhutan Program for the financial support and guidance rendered all these years towards conservation efforts in RMNP. Without their support, the tiger monitoring exercise wouldn’t have been possible at all. We also thank UWICER for providing some of the camera traps for the survey.

Akaike Information Criterion Capture Mark Recapture Camera Trap File Manager Geographic Information System Department of Forests and Park Services Global Positioning System Jigme Singye Wangchuck National Park Jomotshangkha Wildlife Sanctuary Phibsoo Wildlife Sanctuary Manas National Park Nature Conservation Division Normalized Difference Vegetation Index Royal Manas National Park Royal Manas Tiger Spatially Capture Recapture Standard Deviation Spatial Monitoring and Reporting Tool Transboundary Manas Conservation Area Transboundary Manas Tiger Ugyen Wangchuck Institute for Conservation and Environmental World Wildlife Program

We extend our appreciation to Field Director of Manas Tiger Reserve, Mr. Hiranya.K.Sarma and Tiger Biologists from Aaranyank, Guwahati for their support and cooperation in yearly joint monitoring of tigers between RMNP and Manas National Park, India. We thank them for being the closest alliance of our national park from India in supporting for the common cause of conserving tigers across TraMCA landscape.

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World Wildlife Fund Message from the Country Representative

FOREWORD FROM THE DIRECTOR, DoFPS The Royal Manas National Park (RMNP) is unequivocally one of the few protected areas in the country to harbor highest diversity of floral and faunal species of regional and global significance.

The results from the nation wide survey on tigers in 2015 affirmed RMNP as one of the important sites having highest densities of tigers in the country. Tigers undeniably form a compelling symbol of the national park´s rich biodiversity. They are a vital link in maintaining the health of the ecosystem.

While the protected area is increasingly eulogized for it’s rich biodiversity, the challenges to the ecological integrity of the landscape are pervasive. Wildlife poaching is emerging as one of the prominent threats to the burgeoning tiger population in RMNP. Providing protection to the critical tiger habitats backed by sound ecological knowledge on tiger population dynamics and their prey will be crucial for ensuring their persistence and of other wildlife species.

I am happy to learn that Royal Manas National Park is coming out with it´s second report on tiger population status. The long term scientific monitoring of tiger initiated in RMNP since 2010 is definitely one of the important milestones, the national park has achieved in an endeavor to conserve tigers and their habitats in RMNP and across TraMCA (Transboundary Manas Conservation Area). The state of art technology such as camera traps were used in addition to conducting extensive ground surveys over the years. The strong transboundary collaboration with Manas Tiger Reserve through yearly joint monitoring of tigers under the aegis of TraMCA is yet another important feat, RMNP has accomplished. This joint tiger monitor program is identified as one of the successful paradigms of a landscape level conservation of tigers across TraMCA region.

I applaud the sincerity and dedication put forth by the core team members and the field staff of RMNP to conduct such a mammoth task of conducting camera trap survey every year. This report shall not only help in broadening our knowledge on the ecology of tigers and other wildlife species but also serve as a guiding tool in setting informed conservation strategies. This science based monitoring and assessment would further strengthen our efforts to conserve tigers in the country.

Trashi Delek!

Tigers, one of the most charismatic species, are a vital link in maintaining the rich diversity of nature. WWF has long been associated with conserving this magnificent cat both in Bhutan and in other Tiger Range countries.

The survival of tigers in our forests is crucial for maintaining the integrity of ecosystem and healthy co-existence of every Bhutanese and nature. Therefore, it gives us immense joy in finding out that the population of tigers have doubled in Royal Manas National Park (RMNP) in just six years.

From a mere 10 Tigers in 2010, the population has risen to 22 in 2016, thus achieving the global mission of doubling the number of wild tigers by 2022 (the TX2 goal).

The beginning of Transboundary Manas Conservation Area (TraMCA) conservation program in 2010 has ensured robust scientific research and protection measures in the landscape, and in particular RMNP that serves as the heartbeat of TraMCA. We would like to thank the Royal Government of Bhutan for giving us the opportunity to assist in such an important endeavor.

We would also like to thank our WWF network and our donors for their continued support.

While we rejoice the doubling of tigers in RMNP, we must continue to design and implement effective evidence-based interventions. Poaching and illicit trading must be controlled by strengthening our regulatory and surveillance programs. In the face of increasing illegal wildlife trade, habitat loss and human-wildlife conflict, it is also imperative that tiger population continues to be scientifically assessed and their trends monitored.

Our numerous initiatives continue to indicate a healthy tiger population in Bhutan. Therefore, this doubling of tigers in RMNP gives us the confidence that the tiger can thrive if we accord the right protection including proper habitat conservation. We will continue to work with our partners on a holistic approach to ensure that this magnificent animal not only survives but also thrives and inspires the world to step up it’s efforts to save the vanishing species.

Dechen Dorji Country Representative WWF Bhutan

(Phento Tshering) Director Department of Forests and Park Services Ministry of Agriculture and Forests

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Tigers are the largest of the big cats in the world, weighing up to 660 pounds.

They can get up to 10 feet in length — with their tails alone measuring three feet.

Tigers are also incredible jumpers, able to pounce at least 10 meters (approximately 32 feet).

Tiger have a common signaling behavior such as urine spraying, scent deposition from anal glands, check rubbing, scraping the ground, clawing of trees and flattening vegetation by rolling. They use these signs in marking territory, communicating information on their individual identity, time of passage, social status and in determining sexual receptivity of conspecifics.

They have five different types of whiskers on their face and body that are used for picking up movement and vibrations to help the tiger navigate in darkness, detect danger, and hunt.

Tigers are mostly nocturnal and hunt their prey at night. Due to a retinal adaptation called the tapetum lucidum, which reflects light back into the retina, their night vision is about six times better than the vision of humans.

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Executive Summary Tigers have fascinated humans throughout history for their beauty and sheer magnificence and for it’s cultural and ecological significance. By the same token, ironically, the global tiger population has dwindled down to mere few thousands in the wild relegating them to only 7% of it’s natural range.

Shrinkage of tiger population due to impetuous poaching, fragmentation and loss of habitat and persecution of tigers arising from human tiger conflict has driven tigers in a quandary. In the face of all these challenges, it is crucial to identify the remaining defensible strongholds of tigers and that has the potential to help re-build meta-populations across conservation landscapes.

Home to an incredible diversity of wildlife, the Royal Manas National Park (RMNP) is unarguably one of the strongholds of tigers in Bhutan. It harbors one of the highest felid diversity of which tiger is a compelling symbol of park´s rich biodiversity and an excellent indicator of it’s health.

Realizing the importance of setting informed conservation goals guided by a reliable ecological knowledge on wildlife, a long term annual scientific monitoring of tigers was initiated in RMNP since 2010.The advancement in wildlife population estimation using new statistical models and state of the art technologies such as camera trapping method has made a major breakthrough in comprehending the population status of tigers in RMNP and across Transboundary Manas Conservation Area (TraMCA).

masl. The habitat use of tigers was high in the lower foothills as compared to higher elevation areas in the national park.

The study indicates that Royal Manas National Park could arguably hold one of the largest contiguous tiger populations in the country. The presence of healthy breeding tiger population linked together with tiger habitats of three other protected areas in Bhutan via Phibsoo Wildlife Sanctuary, Jigme Singye Wangchuck National Park and Jomotshangkha Wildlife Sanctuary and Manas National Park in India makes RMNP a potential ‘source site’ that has immense capacity to help build meta-populations across conservation landscapes.

While tiger population has increased significantly, poaching is still an immediate threat to tiger population in RMNP. Providing protection to the critical tiger habitats at both the site and landscape level through strong transboundary collaboration is crucial for long-term survival of tigers. In addition, it is strongly recommended to continue annual scientific monitoring of tigers and other wildlife in assessing the yearly population status and the dynamics of the tigers through robust analytical methods. An all-inclusive approach to monitoring wildlife population that includes assessment of predator and prey population as well as their habitat is a cornerstone in setting informed conservation strategies.

The report presents the population status and density of tiger population in the lower foothills of Royal Manas National Park in 2015 and 2016 using Bayesian based Spatially Mark–Recapture method in a closed-population framework. It also shows the habitat use and distribution of tigers and five important prey species modeled in relation to ecological covariates (average occupancy estimate of gaur, sambar, barking deer, water buffalo and wild pig, distance (m) to waterhole and saltlick, elevation (m), slope, Normalized Difference Vegetation Index (NDVI) in a single season occupancy-modeling framework.

The camera trap study spanning Manas and Umling Range covered an area of 332 km2 and 302 km2 in 2015 and 2016 respectively. The result shows a marked increase in the tiger population from an estimate of 12 individuals (7-17 individuals for 95% confidence interval) in 2015 to 22 individuals (13-30 individuals for 95% confidence interval) in 2016. The density of tigers has also increased from 1.7/100 km2 in 2015 to as high as 2.9/100 km2 in 2016. Given almost the same study area and sampling effort in two years, the significant growth in tiger number shows RMNP as one of the potential long-term defensible stronghold for tigers in Bhutan. The capture rate of cubs, juveniles and lactating female tigers were also reported higher in 2015 and 2016 substantiating a healthy breeding tiger population in RMNP. A total of 7 tiger individuals were found common in TraMCA landscape in 2015 and 2016 viz RMNP and Manas National Park in India.

The average occupancy varied from as low as 0.09 (SD±0.103) for Water Buffalo (Bubalus bubalis) to high average occupancy of 0.99 (SD±0.0006) for Gaur (Bos gaurus). Sambar (Rusa unicolor), Barking deer (Muntiacus muntjak) and Wild pig (Sus scrofa) had average occupancy of 0.59 (SD±0.17), 0.65 (SD±0.019) and 0.46 (SD±0.15) respectively. Tiger had an average occupancy of 0.53 (SD±0.14) within 616 km2 ranging from an elevation range of 90 masl to 1900 masl. The most wide spread species among the herbivores were Gaur, Barking deer, Sambar and Wild Pig. Conversely, the distribution of Water Buffalo was strictly confined to sporadic stretches of lower southern foothills of RMNP within the elevation range of 90-700

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heritage that favor tiger conservation.

The Royal Manas National Park (RMNP) is one of the strongholds of tigers in Bhutan. It is home to an incredibly diverse wildlife population, and tigers are the most compelling symbol of park´s rich biodiversity and an excellent indicator of it’s health. Providing protection to the critical tiger habitats and maintaining the ecological and genetic viability of tiger population in RMNP and across Transboundary Manas Conservation Area (TraMCA) is essential in realizing the global tiger conservation goal of doubling tiger population by 2022 (DoFPS, 2015 and Ahmed et al., 2016).

More importantly, linking science with on ground conservation through scientific monitoring of tigers is imperative in gauging the success of conservation interventions.

CHAPTER 1 Introduction

Realizing the need to establish proper scientific information on tiger ecology for effective conservation and in ensuring the viability of wild population of priority species, a long term scientific monitoring of tigers in Royal Manas National was initiated since 2010 under the aegis of TraMCA and Ugyen Wangchuck Institute for Conservation and Environmental Research (UWICER). The yearly joint scientific monitoring of tigers between RMNP and Indian Manas National Park (MNP), which also forms the core of TraMCA is a testimony to a successful transboundary conservation effort to safeguard tigers in the wild. Two joint transboundary tiger monitoring reports were released in 2011 and 2016.

Introduction Symbolizing beauty, power and resilience, the tiger (Panthera tigris) is one of the most ecologically adaptable, iconic and most revered species in the world. Notwithstanding the important role they play ecologically and culturally, ironically, wild tigers have become increasingly threatened throughout their range by poaching, depletion of natural prey and habitat degradation, thus relegating them to only 7% of it’s natural range (Carroll and Miquelle, 2006; Sanderson et al., 2006; Dinerstein et al., 2007).

Although the recent estimated global tiger population is now close to 3900 individuals, a major proportion of these remaining tiger populations are isolated in habitat fragments and most sub-populations are occurring at low abundance (Walston et al., 2010). Therefore, it is important to identify the certain strongholds of tiger populations that have the potential to sustain metapopulations across the tiger conservation landscapes (Karanth et al., 2009). Apart from India and the Russian Far East being two traditional strongholds for tigers, 14

Bhutan is arguably one of the major links connecting some of the important tiger conservation landscapes in the Eastern Himalayas. It forms an integral part of one of the global tiger conservation landscapes viz.

TCL 37 Northern Forest Complex-Namdapha-Royal Manas covering an area of 237,820 km2 and also forms an indispensable corridor for the Terai Arc Tiger Conservation Landscape (Sanderson et al., 2010).

The well-connected habitats coupled with rich species abundance across different altitudinal and climatic zones in Bhutan provide a safe haven for the big cats. The tiger is revered not only for their ecological significance as an apex predator in maintaining the ecosystem functionality but is also considered as a symbol of great social reverence in Bhutan. The deep spiritual and religious sentiments in Buddhism that revere all forms of nature, the farsightedness of our visionary monarchs who have always ensured that environmental conservation receives the highest priority, and the strong commitment from the government towards conservation have played a consequential role in maintaining and protecting our rich cultural and natural

While assessment of tiger population status is deemed important, understanding it´s population dynamics through critical demographic parameters such as survival, recruitment and movement are equally crucial in understanding the fate of the tiger population in the wild. In addition, appropriate monitoring strategies, which take into, account the scale and range of anthropogenic factors and natural temporal variations are imperative to make informed management decision (Gibb et al., 1998; Karanth et al., 2004; Barlow et al., 2009). Hence, a holistic approach to monitoring wildlife population that includes assessment of predator and prey population as well as their habitat are important to achieve effective tiger conservation besides strengthening site-based protection and enforcement in ensuring the wild population of priority species are stable or growing in RMNP and across TraMCA. The report presents the population status and density of tigers in the lower foothills of RMNP in 2015 and 2016 using the camera-trap-based mark–recapture model in a closed-population framework. We also assessed the habitat use and distribution of tigers and it’s five important prey species using ecological covariates in a single season occupancy-modeling framework (Mac Kenzie et al., 2006; Thinley et al., 2015).

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Study Objectives

The objectives of our study were to: 1. Estimate the tiger population abundance and density of 2015 and 2016 in an intensive study area in RMNP using photographic capture-recapture methods.

2. Understand the tiger population change from two years of camera trapping and assess the number of tiger individuals that are transboundary in nature.

3. Assess habitat use and distribution of tigers and important prey species using ecological covariates in a single season occupancy-modeling framewor

Study Site Royal Manas National Park The RMNP is the oldest National Park situated in the south central foothills of Bhutan (90°35’ E to 91°13’ E and 26° 46’ N to 27° 08’ N) (Figure 1). Spanning an area of 1057 km2, the national park falls within the political jurisdiction of three Dzongkhags i.e., Zhemgang, Sarpang and Pemagatshel. Connected by the biological corridors to Jigme Singye Wangchuk National Park in the northwest, Phibsoo Wildlife Sanctuary in the southwest, Phrumsengla National Park in the northern center, Jomotshangkha Wildlife Sanctuary in the southeast, the location of RMNP is notably outstanding and forms the cornerstone of protected area network in Bhutan.

Further the national park abuts with MNP in India to the south, forming a significant part of Transboundary Manas Conservation Area (TraMCA).

The elevation of RMNP ranges from 97 m asl at the southern foothills up to 2914 m asl in the north. The park has a moist subtropical to cool temperate climate with four distinct seasons.

Summer lasts from May to August with annual maximum temperature ranging from 20° C to 40° C. The rainfall ranges from 200 mm to 4400 mm annually. Autumn lasts between September and November experiencing changeable weather, which gradually takes on the shape of winter pattern. Characterized by cool weather and fog, winter is relatively drier with rare shower and average temperature ranges from 5° C to 20° C. The unique landscape of RMNP forms an important natural conservatory of the country representing outstanding habitat diversity ranging from tropical monsoon forests (<500 m) and subtropical forests (500 m-1000 m) to warm broadleaved forests (1000 m-2000 m) and cool broadleaved forests (2000 m-2714 m). RMNP is famed for harboring one of the greatest populace of wildlife diversity. The park has 558 species of flora, 65 species of mammals, 493 species of birds, 69 species of fishes and more than 180 species of butterfly species recorded till date (RMNP, DoFPS 2015). It is one of the few places in the world to harbor highest felid diversity of 8 species of which 5 species are listed in red list of IUCN. Renowned for it’s spectacular landscape suffused with one of the highest diversity of species in the country, it provides a safe refuge for charismatic species, which are endangered such as the Royal Bengal tiger (Panthera tigris), golden langur (Trachypithecus geei), clouded leopard (Neofelis nebulosa), Asian elephant (Elephus maximus), Asiatic water buffalo (Bubalus bubalis), Asiatic wild dog (Cuon alpinus) and Asiatic gaur (Bos gaurus). Carnivores other than tigers in RMNP are Common leopard (Panthera pardus), Clouded leopard (Neofelis nebulosa), Marbled cat (Pardofelis marmorata), Golden cat (Catopuma temmincki), Leopard cat (Prionailurus bengalensis), Jungle cat (Felis chaus) and Himalayan black bear (Ursus thibetanus) among others. Major prey species for carnivores are Gaur (Bos gaurus), Sambar (Rusa unicolor), Asiatic water buffalo (Bubalus bubalis), Barking deer (Muntiacus muntjak), Wild pig (Sus scrofa), Serow (Capricornis thar), Goral (Naemoherdus goral) and others.

Figure 1: Map of Royal Manas National Park showing distribution of camera stations in 2015 and 2015 in a 2X2 km grid

Based on the socio-economic survey conducted in 2014, there are a total of 1183 households within the administrative jurisdiction of the park of which 686 are located in multiple use zone and 497 in buffer zone covering all the five geogs. Of the total households, 670 are permanent residents and 513 are non-permanent residents (government offices and community centers).

The total population is 8936 of which 5331 people reside in multiple use zone and 3605 people inhabit buffer zone.

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CHAPTER 2

MATERIALS AND METHODS Camera trapping

Figure 2: Map of the protected areas of Bhutan. Royal Manas National Park (RMNP) is shown in orange, located in the southern foothills of Bhutan.

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Camera trap surveys using capture recapture framework to estimate population of large carnivores have proven to be amongst the most successful non-invasive population estimation method which make use of the natural markings of the species on their body parts, as in the case of the tiger (Panthera tigris) (Karanth and Nichols, 1998; Karanth et al., 2004; Karanth et al., 2006; Andheria et al., 2007; Sharma and Jhala, 2011; Kawanishi, 2002; Rayan and Mohamad, 2009), the leopard (Panthera pardus) (Mondal, 2006; Harihar et al., 2009), the jaguar (Panthera onca) (Silver et al., 2004), the cheetah (Acinonyx jubatus) (Marker et al., 2008), the clouded leopard(Neofelis nebulosa) (Borah et al., 2013) and the snow leopard (Panthera uncia) (Jackson et al., 2006).

A total of 94 and 88 camera stations were established in 2015 and 2016 respectively in the lower foothills of Royal Manas National Park. The total study area encompassed of 332 km2 and 302 km2 in 2015 and 2016 respectively, spanning Manas and Umling Range, which were divided into grid cells of 4 km2 (2km x2 km) to guide camera trap placement (Figure 1 and Figure 2). For maximizing the capture probability of large carnivores, we installed cameras based on presence of wild animal signs such as scats, scrapes, scent depositâ&#x20AC;&#x2122;s, tracks, along forest trails, waterholes and saltlicks, rivers and streams, ridge line and mergence of trails (Karanth, 1995;Karanth and Nichols, 1998; Gray and Prum, 2012). Two cameras were deployed in each station for obtaining pictures of both the sides of an individual (Figure 3).

Camera-traps were set at about 2 - 2.5 km apart from each other for ensuring that wild animals are exposed to at least 2-3 traps for maximizing the capture probability (Karanth and Nichols, 1998). Studies on large carnivores have shown that female tigers have as 19

small home range as 15 km2(Seidensticker et al., 1990; Karanth and Sunquist, 2000)and hence placing 2 to 3 camera stations within their home range allows other individuals to fall under the camera traps (Otis et al., 1978; Karanth and Nichols, 1998). All the cameras were kept operational for 24 hours a day for a minimum of 63 and 79 days in 2015 and 2016 respectively. Each day (24 h) was therefore defined as a sampling occasion (Otis et al., 1978).

Three different passive infrared camera models (Panthera-flash, Cuddeback Attack-Infrared (IR) -flash and Bushnell (IR) were used for the survey (Figure 4).

The cameras were mounted at a height of about 2060 cm on trees or poles depending on the slope and distance from the trail and were placed at about 2-3m from the trail to obtain clear photographs of both sides of an individual species. Because the cameras used in the survey functioned independently and were triggered by the body heat of the animal passing by, we set the cameras to high sensitivity and programmed them to capture 3 photos in rapid succession upon each trigger during the daytime and 1 photo in the nighttime in order to save the battery life (particularly of IR flash cameras such as Panthera and Cuddeback. The time delay was set at a minimum of 1 second for Panthera and Bushnell and 5 seconds for Cuddeback.

(a)

(c)

(b)

(d)

Figure 3: Camera trap installation in the field

VH4 1panthera

Cuddeback Flash

Cuddeback Flash

Bushnell Infrared

Figure 4: Different camera models used in the camera-trap survey 2015 and 2016

Figure 5 (a) and (b): Difference in stripe patterns between two tiger individuals in RMNP noted from photographic captures using camera trap images

Figure 6 (c) and (d): Repeated photographic captures of same tiger individuals in RMNP

Data Management and Identifying Tiger Individuals from Camera-Trap Photos The camera-trap images were archived into Camera Trap File Manager V3 3.16. Extensible Metadata Platform (XMP) stamping was done for all the photographs for appending additional data directly to the photograph so that even if the photograph was moved, the data remained attached enabling a high control over the data and for easier subsequent analysis. The identity and sex of each individual tiger was distinguished on the basis of their body size, stripe patterns, bellies of lactating tigers and the presence of testicles in male tigers. Tigers have unique stripe patterns, which help in identifying individual tigers from camera trap pictures (Karanth and Nichols, 1998; Karanth et al., 2002). Examples of such identification are given in Figure (5) and Figure (6).

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Data Analysis Population Abundance and Density Estimation The latest advancement in the development of spatial capture-recapture (SCR) model (Efford 2004, Borcher and Efford, 2008; Royal and Young, 2008) allows for a better estimation of species density which is basically an extension of the standard closed population models (Otis et al., 1978; Borchers et al., 2002; Lukacs and Burnham, 2005), by including a spatially explicit model for distribution of individuals in space. These models are parameterized in terms of a spatially indexed, individual random effect. The trap-specific detection probabilities are modeled as a function of distance between traps and individual activity centers. The assumptions of SCR models vary between models, depending on the approach used and the incorporation of covariates, but in general it is assumed that 1) the population is demographically closed 2) individuals have independent activity centers (although under- or over dispersion can be modeled with spatial covariates), 3) the locations of the activity centers are fixed during the survey period, 4) the probability of detection of an individual at a camera trap declines with increasing distance of it’s activity center from the trap (described by 1 of a choice of several functions (e.g., half-normal, exponential, hazard-rate), and 5) each capture is an independent event (Efford, 2004; Borchers and Efford, 2008;Royle et al., 2009a).

For this study, we used spatial capture-recapture data based on Bayesian analysis of the hierarchical model, facilitated by the use of data augmentation (Royle et al., 2007; Royle and Young, 2008) for estimating the population density of tigers using program SPACECAP (Gopalswamy et al., 2012) in program R (version 1.0.136 assessed 23/3/2017).

For defining the state space, we developed habitat mask using a buffer width of 15 km for both the study areas (2015 and 2016), containing trap array, which in turn contains fine grids of 3612 equally spaced points, each representing approximately 0.36 km2. The activity centers were assumed to be uniformly distributed over these points. The buffer helps include activity centers, which are outside the trapping grid allowing for a robust estimate of density.

One important assumption of capture-recapture studies is that captures are independent of one another. This is why we use 24 hours as the time unit to define a sampling occasion in our cameratrap study, as multiple visit’s to a camera station in one night are not likely to be independent events and will not contribute useful information. We used half-normal detection function using a Poisson distribution with the basic model (constant default models).

For the analysis of the data using SPACECAP, we augmented the capture history with 110 and 170 all zero encounter histories for 2015 and 2016 respectively, which was 10 times the number of individual tigers identified from the survey. The MCMC simulation was run for 60000 iterations with a burn in period of 5000 and a thinning rate of 5 for both the studies. We assessed model fit and validity by examining the Geweki Diagnostic, effective posterior sample size and Bayesian p Value and data augmentation. Posterior summaries are provided in Table (5).

Occupancy Modeling Framework

al., 2003; MacKenzie and Bailey, 2004) allows the use of data of repeated observations from each area using camera-trap images to deal with the false absences, situations where species could be present but not always detected by observers (detection probabilities <1, (MacKenzie et al., 2002;MacKenzie, 2006).

We used 88 camera-trap grids of 4 km2 from the 2016 study area for obtaining presence-absence data of tiger and other five important prey species viz., Sambar (Rusa unicolor), Gaur (Bos gaurus), Water buffalo (Bubalus bubalis), Barking deer (Muntiacus muntjak) and Wild pig (Sus scrofa). We fitted multiple models for all the 6 species using different ecological covariates in program PRESENCE (version 11.8) to model detection probabilities and estimate occupancy (MacKenzie et al., 2005a; Hines, 2006). As the occupancy and detection probabilities are influenced by site characteristics (Royal 2005), we took into account eleven habitat covariates for model development for each species. For all the five prey species, 6 covariates viz., Distance (m) to waterholes and saltlick, Elevation (m), Slope, Normalized Difference Vegetation Index (NDVI) and survey effort were used for covariate model development. For tiger, occupancy estimates (Ψ) of all five prey species including the 6 covariates used for prey model development were used for modeling. We used euclidean distance under Spatial Analyst Tool, Arc GI 10.2 for determining the distance to waterhole and saltlick. We used LANDSAT 5 imagery with 30 m spatial resolution for estimating NDVI for all the 88 camera stations. The NDVI is calculated on a per-pixel basis as the normalized difference between the red and near infrared bands from an image and is one of the commonly used indexes for determining the health of the vegetation.

The survey effort was based on the number of stations in each grid.

We defined each detection history into 4 days survey blocks for a maximum total of 19 repeat surveys per species. We used Logit-link function for modeling the detection probability and occupancy as a function of measured ecological covariates (MacKenzie et al., 2005). The probability of site i at which the species is detected as a function of U covariates associated with site i (xi1, xi2,…. XiU) can be estimated using logit-link where (βo) is the intercept and the U is the regression coefficient for each covariate to be estimated (MacKenzie et al., 2005) Logit (ψi) = βo + β1xi1 + β2xi2 + … + βuxiu

We used Akaike Information Criterion (AIC) for comparing the models which is based on the likelihood under parsimonious principle (tradeoff between bias and variance) and chose the model that minimizes AIC(Burnham and Anderson, 2002). Akaike´s weights (w) were used to compare the AIC from a suite of a priori models. We used model averaging based on the AIC model weight for multiple models supported by the data to estimate average predicted speciesspecific occupancy and effects of covariates on all the six species.

As the sample size was restricted to mostly lower foothills of Royal Manas National Park, we kept the predicted habitat use maps for all the species within 616 km2 from an elevation range of 90masl to 1900 masl. Further, in order to ensure spatial independence between the two camera station, the pattern of analysis of occupancy was limited to habitat use by the species in our study (Lazenby and Dickman, 2013).

To estimate tiger occupancy, we used the single season occupancy models developed by (MacKenzie et al., 2002; MacKenzie et al., 2005). In essence, the model estimates detection probability (p̂) and occupancy (Ψ) of a species using a maximum likelihood approach. Occupancy studies are designed to provide inferences about the presence of target organisms in geographical sample unit’s accounting for imperfect detection (Karanth et al., 2009). For addressing the issue of imperfect detection of species, the occupancy modeling framework (MacKenzie et al., 2002; MacKenzie et

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23

Results

CHAPTER 3

Tiger Individuals from Photographic Capture The total sampling effort of 4848 and 4811 trap nights yielded 51 and 49 independent captures of tigers in 2015 and 2016 respectively (Table 1). We identified a total of 11 individuals in 2015 and 17 individuals excluding the three cubs in 2016 (Table 1). Three breeding female tigers were identified in 2015. In 2016, 2 breeding female tigers along with 3 cubs were also captured on camera-traps (Figure 5). Only 2% and 8.5% detection of tigers in 2015 and 2016 didnâ&#x20AC;&#x2122;t lead to positive identification of individuals giving 98% and 92 % success rate at identifying individual animals in 2015 and 2016 respectively. From the two ranges, Manas Range recorded higher tiger individuals compared to Umling Range in both the years of camera trapping study (Table 2). This could be attributed to the larger study area in Manas relative to Umling resulting in higher detection of tiger individuals.

In general, we detected female tigers at relatively higher frequency than male tigers in both the years of study and the recapture rates of tigers ranged from 1 to 10 times of which female tigers were recaptured relatively higher than male tigers (Figure 8 and Figure 9).

The asymptote in the cumulative numbers of new individuals curve of 2015 and 2016 was realized at 30th and 40th sampling occasions respectively (Figure 10 and Figure 11).

Table 1: Total number of tiger individuals, sampling area, sampling effort and capture events in RMNP 2015 and 2016

Table 2: Total number of tiger individuals in Manas and Umling Range in 2015 and 2016

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Tiger Individuals RMT_002F in 2015

RMT_004F in 2015

TMT_039 TMT_038 TMT_037 TMT_036 TMT_026 TMT_025 TMT_024 TMT_018 TMT_012 TMT_002 TMT_001 0

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6 Recaptures

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Figure 8: Number of recapture rates of individual tigers in 2015

RMT_029F in 2015 and 2016 Tiger Individuals

RMT_016F in 2016

TMT_052 TMT_051 TMT_050 TMT_049 TMT_048 TMT_047 TMT_046 TMT_045 TMT_043 TMT_036 TMT_032 TMT_027 TMT_026 TMT_025 TMT_024 TMT_012 TMT_003 0

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4 Recaptures

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Figure 9: Number of recapture rates of individual tigers in 2016

Photograohs of tiger Cubsâ&#x20AC;&#x2122; captured in 2016

Figure 7: Pictures of breeding female tigers and cubs photo captured in 2015 and 2016.

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Cumulative number of new individuals

Estimates of tiger abundance and density in 2015 and 2016 Based on the Bayesian approach to SCR modeling, the tiger abundance in 2015 was estimated at 12 individuals (SD±3.18) with 95 percent credible interval of 7-17 individuals (Table 3). The 2016 estimate showed the abundance of tigers at 22 individuals (SD±54.47) with 95 percent credible interval of 13-30 individuals (Table 4).

12 10

We estimated the mean density of tigers at 1.7/100 km2 with 95 percent credible interval of 1.07-2.5 individuals per 100 km2 and 2.9/100 km2 with 95 percent credible interval between 1.76-4 individuals per 100 km2 in 2015 and 2016 respectively (Table 3 and Table 4; Figure 13).

The lower foothills of the national park virtually showed high tiger density. The highest activity centers of the tigers were reported from Gelongkhola, Specialthang, Bangkatar, Rebalingmin and Gayhati in Manas Range and Badamkhola, Rajakhola, Churikhola, Kanamakura, Jaikhar, Badamkhola in Umling Range.

8 6 4 2 0

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63

Sampling Occasion Figure 10: Cumulative number of new individuals captured with an increasing sampling occasions in 2015.

Cumulative number of new individuals

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As shown in the results (Figure 13 and Figure 14), there is a clear expansion of tiger hotspots in Manas Central and Umling Range. However the lower foothills of Manas East in 2016 showed contraction of tiger activity centers (Figure 14) For the 2015 tiger data, we estimated the mean spatial scale parameter of the detection function at 3997.18 m (SD±572m) and in 2016, the estimate was 3611.154 (SD±483m) .The expected encounter rate of an individual whose home range center is exactly at the trap location (lam 0) was estimated at 0.0071 in both the years of tiger population study. The probability that an individual in the augmented data set is a real member of the sampled population (psi) was 0.10 and 0.21 in 2015 and 2016 respectively (Table 3 and Table 4). The Bayesian p value based on individual encounter was 0.65 and 0.7 in 2015 and 2016 respectively. A value close to 1 and 0 implies that the model is inadequate (Royle et al., 2013). As the Bayesian values were close to 0.05, the model was adequate and the observed data set was in congruence with the realizations simulated under the model being fitted to the observed data ( Royle et al., 2013)

16 14 12 10 8 6 4 2 0

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79

Table 3: RMNP SPACECAP Estimate in 2015

Sampling Occasion

Figure 11: Cumulative number of new individuals captured with an increasing sampling occasions in 2016.

Table 4: RMNP SPACECAP Estimate in 2016

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Transboundary tigers in 2015 and 2016 A total of 7 tiger individuals were found common in TraMCA landscape in 2015 and 2016 viz., Royal Manas National Park and Manas National Park (MNP) in India (Figure 13). The detection polygons of seven adult tiger individualsâ&#x20AC;&#x2122; viz., four female tigers and three male tigers based on the location of photographic captures of two years ranged from 16 km2 to as large as 196 km2. The three male tigers had larger territory ranging from 76 km2 to 196 km2 and the territory of four female tigers ranged from 16 km2 to 58 km2. As evident from the result, all the transboundary tigers were found to use the southeastern section of Manas Range. This was because of the consistent annual monitoring of tigers in Bansbari and Bhuyanpara Range in eastern MNP. The mostly absent or intermittent tiger monitoring in southwest of MNP resulted in fewer records of transboundary tigers. The male tigers viz., TMT_018_M and TMT_003_M, which had the largest home ranges, overlapped with ranges of three female and four female tigers respectively.

Figure 12: Mean density of tigers with 95% CI in 2015 and 2016

Figure 13: Map showing estimated posterior density of tigers in RMNP (2015). Dark to light orange and cream shades indicate tiger densities in descending order.

Figure 15: Transboundary tiger detection polygons in TraMCA (2015-2016). Blue polygons indicate male tigers and pink polygons indicate female tigers.

Figure 14: Map showing estimated posterior density of tigers in RMNP (2016). Dark to light orange and cream shades indicate tiger densities in descending order.

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Top Ranked Models influencing Species Habitat Use and Detectability Distribution and habitat use by tigers and prey in Royal Manas National Park We averaged the occupancy estimates and developed predicted habitat use maps for tiger and five important ungulate species (Table 5). As the sample size was restricted to mostly lower foothills of Royal Manas National Park, we kept the predicted habitat use maps for all the species within 616 km2 from an elevation range of 90masl to 1900 masl. Further, in order to ensure spatial independence between the two camera station, the pattern of analysis of occupancy was limited to habitat use by the species in our study (Lazenby and Dickman, 2013).

The estimated average occupancy of all the six species was higher than the naïve occupancy especially for tiger. The individual species predicted average occupancy varied from as low as 0.09 (SD±0.103) for Water buffalo (Bubalus bubalis) to high average occupancy of 0.99 (SD ±0.0006) for Gaur (Bos gaurus). Sambar (Rusa unicolor), Barking deer (Muntiacus muntjak) and Wild pig (Sus scrofa) had average occupancy of 0.59 (SD±0.17), 0.65 (SD±0.019) and 0.46 (SD±0.15) respectively (Table 5). Tiger had an average occupancy of 0.53 (SD±0.14) in an area of 616 km2 of RMNP. The most wide spread species among the herbivores were Gaur, Barking deer, Sambar and Wild pig (Figure 14). Conversely, the distribution of Water buffalo was strictly confined in the sporadic stretches of lower foothills of RMNP within the elevation range of 90-600 masl. The habitat use of tigers was high in the lower foothills as compared to higher elevation areas in the national park (Figure 14).

A total of 21 top ranked models with 95 % confidence interval set were selected to determine the habitat use of tigers and 5 herbivore species in RMNP (Table 8). For Tiger, the additive effects of Normalized Difference Vegetation Index (NDVI), Elevation, average occupancy of Barking deer, Wild pig, Sambar, Gaur, and Water buffalo represented important predictor variables (i.e., models where AIC difference [ΔAIC] was <2; Table 8). The top model with the greatest support was Ψ(NDVI+ Barking deer + Wild pig + Sambar + Gaur + Water buffalo) p (Gaur) (Table 8). Based on this model, the habitat use of tigers correlated strongly with the presence of higher occupancy of prey species.

While, the β parameters for all the 5 herbivores were positive for tiger, the β parameters for Elevation and NDVI were negative (Table 6 and Table 7).

For Water buffalo, the top predictor variables included Slope, Elevation, NDVI and Distance to waterhole in the best-supported models. The β parameters for Slope, Elevation and Distance to waterhole and NDVI were negative (Table 6).

For Barking deer and Wild Pig, the top ranked models included NDVI, Elevation, Distance to saltlick, Distance to waterhole. For gaur, the additive effects of NDVI + Distance to saltlick + Distance to waterhole + Survey Effort (Table 8) represented important predictor variables. For Sambar, 4 bestfitted models comprised NDVI, Slope, Elevation, Distance to saltlick and Sampling Effort as the top covariates, which best described the distribution and habitat use of Sambars in RMNP. The β parameters for elevation of Gaur, Barking deer and Wild pig had negative impact on their distribution and habitat use (Table 6).

Table 5: Estimated average habitat use of mammals in RMNP (2016)

Table 6: Estimated beta coefficient for the top ranked models for five ungulate species (2016)

Table 7: Estimated beta coefficient for the top ranked models for tiger (2016)

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Table 8: Best Models for predicting habitat use for each species in RMNP (2016). ΔAIC is the absolute difference in AIC values relative to the model with the smallest AIC. AIC wgt is the AIC model weight. Npar is the number of estimated parameters in the model. Ndvi, Normalized Differential Vegetation Index; ele, Elevation; bd, Barking deer; wp, Wild Pig; sam, Sambar; wb, Water buffalo; sl, Distance to saltlick; wh, Distance to waterhole.

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Barking Deer (Muntiacus muntjak)

Waater Buffalo (Bubalus bubalis)

Gaur (Bos gaurus) Tiger (Panthera tigris)

Sambar (Rusa unicolor)

Wild Pig (Sus scrofa)

Figure 16: Estimated probabilities of occurrence for Barking deer (Muntiacus muntjak), Gaur (Bos gaurus), Sambar (Rusa unicolor), Water buffalo (Bubalus bubalis), Tiger (Panthera tigris) and Wild Pig (Sus scrofa) (2016).

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RMNP: a potential source site for tigers in Bhutan Our study based on two years of annual tiger monitoring in the lower foothills of Royal Manas National Park shows a marked increase in the tiger population from an estimate of 12 individuals (7-17 individuals for 95% confidence interval) in 2015 to 22 individuals (13-30 individuals for 95% confidence interval) in 2016. The density of tigers has also increased from 1.7/100 sq. km in 2015 to as high as 2.9/100 km2 in 2016.

CHAPTER 4

Conservation Implications and Recommendations

The drastic increase in tiger numbers in the lower foothills was mostly from addition of new juvenile/sub adult tigers in the RMNP landscape in 2016. It is highly possible that many of these juveniles could be litters of three lactating female tigers recorded in 2015. For instance, the three juveniles (RMT_034 M, RMT_035 F, RMT_048 F) in 2016 were photo captured in the same area where the lactating female tiger RMT_004 F was recorded in the previous year of tiger monitoring. Smith (1993) from a long-term study on the dispersal of tigers in Chitwan National Park found that the young juveniles/transients mostly settled near or partially within their mother´s territories.

The loss of some resident breeding tigers in RMNP in recent times could also be imputed to sudden increase in transient tigers trying to establish territories in vacant territories. The transients don’t have established territories and are on constant move leaving the natal areas in search of establishing territories (Smith 1993; Karanth and Stith, 1999). It will be important to monitor these individuals in order to further see if the transients have settled down in territories occupied by previous resident tigers. The other contributing factors could be because of the availability of varying size of large and medium prey base as evidenced from relatively high RAI estimated for ungulates (Ahmed et al., 2016, Tempa et al., 2011) and prime habitats being secured through protection in the landscape that resulted in the increase of tiger numbers.

Strong prey base is arguably the primary ecological determinant for tiger survival and studies have shown that the impact of prey depletion on population size is significantly higher than the impact of tiger poaching (Coss and Pelkey, 1999; Karanth et al., 2004; Miquelle et al., 2005, Karanth and Sunquist, 2000).

Given almost the same study area and sampling effort in two years, the marked increase in tiger number shows RMNP as one of the potential long-term defensible stronghold for tigers in Bhutan. The high photographic evidences of cubs, juveniles and lactating female tigers recorded in 2015 and 2016 substantiates a healthy breeding tiger population in RMNP (Figure 7).

Having a sizeable population of tigers in a contiguous pristine mosaic of grasslands and

forest habitats of RMNP that are strongly linked with tiger habitats of three other protected areas in Bhutan via Phibsoo Wildlife Sanctuary, Jigme Singye Wangchuck National Park and Jomotshangkha Wildlife Sanctuary and Manas National Park in India makes RMNP a potential ‘source site’ that has immense capacity to help build meta-populations across conservation landscapes. The photographic evidences of tigers prowling the subtropical jungle of TraMCA landscape to temperate forests in Jigme Singye Wangchuk National Park and alpine forests of Jigme Dorji Wangchuck National Park in Northern Bhutan is also a strong attestation of RMNP harboring source population of tigers critical for regional and global conservation of tigers in the wild.

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Need for Strengthening SMART patrol and wildlife law enforcement Notwithstanding that the tiger number is on a rise, poaching is still an immediate threat to tiger population in RMNP. In the last three years, two resident transboundary male tigers viz., TMT_018 M and TMT_ 003 M which had detection polygons as large as 141 km2 and 245 km2 respectively, were poached in the eastern section of Manas Range. As evident from our findings, the higher density of tiger shown along the eastern section of Manas Range in 2015 study had noticeably plummeted in the following year. Studies suggest poaching can deplete a source and cause extinctions within a short period of time (Ahearn et al., 2001; Kenney et al., 1995; Smith and McDougal, 1991) and loss of resident male due to poaching would suppress reproduction as a result of increased cub mortality thereby making the population more susceptible to threats (Barlow et al., 2009).

The use of SMART (Spatial Monitoring and Reporting Tool) in RMNP since 2013 has been instrumental in gauging, assessing and improving the effectiveness of wildlife law enforcement patrols and site based conservation management. Further for enhancing the efficiency of SMART implementation, the realtime SMART/SMART connect that provides real time connectivity in uploading information on location of poachers, patrols and key wildlife species into the system will be crucial in improving response time, functionality and coordination at the national as well as site level.

Need for annual monitoring of tigers in RMNP and across TraMCA Given the dynamics of transboundary landscape and higher risk of extinction of keystone species, a systematic and practical monitoring framework that aims to better assess the population status and the dynamics of the wildlife species through robust analytical methods will be important in gauging the success or failure of conservation interventions in the long run. The joint scientific monitoring of tigers between the RMNP and MNP, India, which was started since 2010, has been instrumental for the management in keeping track of tiger individuals and in understanding their population dynamics. In the absence of proper ecological knowledge of a species, conservation management decisions are undermined by crude estimates or educated guesses, which can be counterproductive for conservation (Blake and Hedges, 2004). Therefore, it is highly recommended to continue annual monitoring of tigers in RMNP and across TraMCA.

©simonrawels/WWFUK

The complacency of not having immediate, sustained and intensive protection to critical tiger habitats could have a long term bearing on the burgeoning tiger population in RMNP. Providing protection to the critical tiger habitats and maintaining the ecological and genetic viability of tiger population in RMNP and across Transboundary Manas Conservation Area (TraMCA) is of paramount importance in ensuring tigers persist for all times to come and in realizing the global tiger conservation goal of doubling tiger population by 2022. Besides, improving protected area management effectives and strengthening wildlife law enforcement are deemed crucial in maintaining the population viability of tigers and other associated wildlife species (Linkie et al., 2006; Dinerstein et al., 2007). As reported in our study; the high density and habitat use by tigers and other wildlife species in the lower foothills of the national park, the conservation investments must focus on prioritizing these critical habitats for intensive protection backed by strong monitoring approach (Walston et al., 2010).

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©simonrawels/WWFUK

Need for use of best science in wildlife studies The use of cutting edge wildlife scientific tools such as camera-traps has opened the horizon in understanding the ecology of tigers and other associated wildlife species in RMNP. The longterm research on tiger population status and it´s demographic parameters started since 2010 is based on capture-recapture analysis, which is firmly rooted in modeling approaches that explicitly deals with problem of imperfect detection. The use of capture–recapture sampling (Otis et al., 1978; Williams et al., 2002) and occupancy modeling (MacKenzie et al., 2002; MacKenzie et al., 2005) has emerged as a powerful tool for estimating animal abundance by overcoming the key problem of imperfect detection (Karanth et al., 2002; Jhala et al., 2010).

While conventional CR analyses were used for estimating the population status of tigers and other species initially, the recent development of spatially explicit capture–recapture (SECR) models (Efford, 2004; Borchers and Efford, 2008; Royle et al., 2009a) under a maximum likelihood-based estimation framework (Borchers and Efford, 2008) and under a Bayesian framework (Royle and Young, 2008; Royle et al., 2009a, b; Gardner et al., 2009; Efford et al., 2009) addresses many shortcomings of conventional CR analyses; one of which is the absence of spatial information of species capture location related to it´s home range and movement and the overestimation of tiger densities using the ad hoc approach of 1/2 MMDM as buffer (Gopalaswamy et al., 2012). Further, better understanding of factors influencing the population dynamics of tigers, their movement ecology and the carrying capacity of tigers in RMNP are imperative in understanding the in-depth ecology of tigers and to facilitate the design of informed conservation strategies.

Occupancy modeling framework: an important scientific tool in understanding the distribution and determinants of wildlife species The species distribution maps in our study using occupancy modeling framework in a single season (MacKenzie et al., 2002; MacKenzie et al., 2005) provides more insight on how tigers and other five important prey species viz., Gaur, Water buffalo, Sambar, Barking deer and Wild pig are spatially distributed in the national park. Range maps are widely used in streamlining conservation efforts by better understanding the environmental and social covariates and other determinants on species distribution (Guisan and Zimmermann, 2000; Karanth et al., 2009).

The predicted habitat use maps for this study was developed within 616 km2 from the southern boundary of the national park since the sample size was restricted mostly in the lower foothills due to logistic constraints.

We found all the five prey species especially Gaur, Sambar and Wild pig including NDVI and elevation were key determinants of tiger distribution in RMNP. The southern foothills of the national park, which abounds with alluvial plains and rivers, interspersed with intermittent stretches of grasslands and dense subtropical forests holds the highest density and habitat use by tigers and all the other five ungulate species. Tigers require reliable source of water, ample vegetative cover and grasslands over mountainous Gaur (Bos gaurus) areas (Schaller, 1967; Sunquist, 1981; Santiapillai and Ramono, 1985). Mountainous areas with severe seasonal fluctuations and low prey biomass are less optimal habitats and contain much lower tiger densities (Rabinowitz, 1993). Our results support previous studies (Seidensticker and Suyono, 1980; Sunquist, 1981, Karanth and Nichols, 2002) showing density of tigers positively correlated with larger ungulates (> 50 kg) such as gaur, sambar and water buffalo. In order to better comprehend the ecology of tigers and other sympatric carnivores in depth, we recommend study on the their dietary patterns through microscopic identification of prey hairs from predators scats using reference hair samples from known prey species (Sunquist, 1981;Mukherjee et al., 1994; Andheria et al., 2007).In-depth prey-base studies need to be conducted to ensure availability of prey to tigers.

Amongst the five ungulate species, gaur was the most widely spread species distributed throughout the forested tracts in the southern plains to cool broad leaved forests in the higher 39

altitude with average occupancy as high as 99%. Tiger and all the five ungulates were negatively associated with higher elevation. Our findings were in consistent with other studies where these ungulates were found to prefer low lying areas especially forest edges with a mosaic of open and closed forest cover than rugged hilly landscapes (Conry, 1989; Choudhury, 2002; Timmins et al., 2008).

Presence of waterholes and saltlicks were also important determinants for all the Leopard Cat (Felis bengalensis) ungulate species. The only limitation in the study is that the sampling size was restricted; the predicted habitat use for the six species was mapped within 616 km2 from an elevation range of 90m asl to 1900 m asl. Future studies may extend to the other parts of the park for yielding the overall species distribution/ occurrence pattern in relation with social and ecological characteristics of the park. Besides, different modeling approach like the two-species interactive multi-season occupancy models and multi-scale occupancy for mobile species could be studied further in order to understand the ecological dynamics of the mammals in RMNP.

Landscape connectivity for maintaining meta-population of tigers RMNP forms one the core of TraMCA landscape. Maintaining connectivity within these landscapes will be indispensable for ensuring population viability and resilience of tigers and also chances of doubling tiger population is possible in the larger landscape like TraMCA. Studies have shown that tiger population in larger landscapes can counterbalance losses from poaching and ensure population persistence (Linkie et al., 2006). Habitat linkages between the sources that permit exchange of individuals are important elements for long-term survival of tigers (Wikramanayaka et al., 2004; Dinerstein et al., 2007).

The three biological corridors connecting RMNP via Phibsoo Wildlife Sanctuary in the southwest, Jomotshangkha Wildlife in the southeast and Jigme Singye Wangchuck National Park and Phrumsengla National Park in North embody the essence of landscape level conservation.

The photographic record of an adult breeding female tiger with two cubs in Corridor number 3 viz. RMNP to Phibsoo Wildlife Sanctuary shows that the corridor are used by the tigers and other wildlife species. Connectivity is therefore, one of the links that not only helps in maintaining gene flow, allow movement of species, seasonal migration but also allows shift of a species ‘geographic range’ in response to climate change. Operationalization of these biological corridors will be essential in addressing the various threats impacting corridors, protect rich and varied ecosystem while ensuring people continue to benefit from nature. Reinforcing both site level protection and landscape level interventions should be given top priority in ensuring corridors are functional.

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Conclusion The tiger population in the southern foothills of RMNP showed a marked increase from an estimated 12 individuals (7-17 individuals for 95% confidence interval) in 2015 to 22 individuals (13-30 individuals for 95% confidence interval) in 2016.

Our findings indicate that Royal Manas National Park could potentially hold one of the largest contiguous tiger populations in the country and can act as a ‘source site’ to help build tiger meta-populations across conservation landscapes.

The future of tigers is promising given that the protected area is managed and protected effectively based on informed conservation interventions. What is even more promising of the future of tigers lies in the landscape-based tiger conservation strategies initiated through the TraMCA, which comprises RMNP and Manas National Park as the core tiger landscape embedded within the vital mosaic of conservation spaces in TraMCA region. Although, the joint scientific monitoring of tigers between the two national parks started since 2010 is a successful paradigm of a transboundary level conservation effort to safeguard tiger population across political boundaries; their conservation shall require more than just good science. Linking science to constructive, on ground conservation action will be crucial for the long-term survival of tigers in the wild. Besides, maintaining habitat connectivity, harmonizing conservation and economic needs of the people through innovative livelihood programs that helps in mitigating human wildlife conflicts and more importantly providing both stringent site level protection and landscape level interventions through strong transboundary collaboration will be crucial in tipping the scales in favor of the long term survival of wildlife in RMNP and across TraMCA.

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ANNEXURES

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Annexure 1: List of Survey Team Members for annual tiger monitoring in Royal Manas National Park Annexure 2: Tiger Individuals 2015

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Annexure 3: Tiger Individuals 2016

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Annexure 4: Camera trap datasheet 2015 and 2016

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