Ungulate densities and biomass in the tropical dry deciduous forests of Gir, Gujarat, India

The Ecological Separation of Deer and Domestic, Feral and Native Mammals in Tropical Northern Australia-A Review

We explored the ecological and historical factors that led to formation of the unique guild of native and introduced mammalian herbivores between 5 and 1000 kg in northern Australia. Following the disappearance of large native herbivores about 46 kya, and until the arrival of Europeans and their livestock, the only herbivorous mammals were mid-sized endemic marsupial macropods, which continued to utilise the same vegetation as their much larger former neighbours. Only one species of contemporary native herbivore has an adult bodyweight approaching 100 kg, and for the past 150-200 years, the total biomass of introduced domestic and wild vertebrate herbivores has massively exceeded that of native herbivorous species. We conclude that the current guild of native and introduced mammalian herbivores differentially utilises the landscape ecologically. However, climate- and anthropogenically related changes due to fire, drought, flooding, predation and introduced weeds are likely to have significant impacts on the trajectory of their relative ecological roles and populations. Given their differing ecological and dietary characteristics, against this backdrop, it is unclear what the potential impact of the dispersal of deer species could have in northern Australia. We hence focus on whether sufficient knowledge exists against which the potential impacts of the range expansion of three deer species can be adequately assessed and have found a dearth of supporting evidence to inform appropriate sustainable management. We identify suitable research required to fill the identified knowledge gaps.

The semi-arid ecosystem of Asiatic Lion Landscape in Saurashtra, Gujarat: Population density, biomass and conservation of nine wild prey species

The present study aimed to assess the population density, structure, and population change of nine wild prey species in the semi-arid landscape of Saurashtra, Gujarat, India. A total of eight sites, representing a gradient from highly protected woodlands and grasslands to unreserved grasslands, were selected for sampling. We employed the road transect methodology under a distance sampling framework to achieve our objectives. We evaluated the realized growth rate of the Gir ungulate population through linear regression analysis. Our findings revealed that deer species exhibited higher density and biomass in woodlands compared to grasslands and coastal forests. On the other hand, antelopes showed higher density and biomass in grasslands and coastal forests compared to woodlands. The density gradient of wild prey species was influenced by various factors, including habitat structure, social organization, grouping tendencies, and topography. Over the last four decades, the population of wild prey species in Gir showed minimal changes. Our study provides a comprehensive understanding of wild prey species' density and biomass patterns at the landscape level. The inclusion of findings from ecologically significant and unique areas, such as coastal forests, further enhances the importance of this study. The implications of this study extend beyond the conservation of wild prey species alone; they also contribute to the conservation of the large carnivore guild in the Saurashtra landscape.

Estimating deer density and abundance using spatial mark-resight models with camera trap data

Globally, many wild deer populations are actively studied or managed for conservation, hunting, or damage mitigation purposes. These studies require reliable estimates of population state parameters, such as density or abundance, with a level of precision that is fit for purpose. Such estimates can be difficult to attain for many populations that occur in situations that are poorly suited to common survey methods. We evaluated the utility of combining camera trap survey data, in which a small proportion of the sample is individually recognizable using natural markings, with spatial mark-resight (SMR) models to estimate deer density in a variety of situations. We surveyed 13 deer populations comprising four deer species (Cervus unicolor, C. timorensis, C. elaphus, Dama dama) at nine widely separated sites, and used Bayesian SMR models to estimate population densities and abundances. Twelve surveys provided sufficient data for analysis and seven produced density estimates with coefficients of variation (CVs) ≤ 0.25. Estimated densities ranged from 0.3 to 24.6 deer km-2. Camera trap surveys and SMR models provided a powerful and flexible approach for estimating deer densities in populations in which many detections were not individually identifiable, and they should provide useful density estimates under a wide range of conditions that are not amenable to more widely used methods. In the absence of specific local information on deer detectability and movement patterns, we recommend that at least 30 cameras be spaced at 500-1,000 m and set for 90 days. This approach could also be applied to large mammals other than deer.

Multi-scale habitat modelling and predicting change in the distribution of tiger and leopard using random forest algorithm

Tigers and leopards have experienced considerable declines in their population due to habitat loss and fragmentation across their historical ranges. Multi-scale habitat suitability models (HSM) can inform forest managers to aim their conservation efforts at increasing the suitable habitat for tigers by providing information regarding the scale-dependent habitat-species relationships. However the current gap of knowledge about ecological relationships driving species distribution reduces the applicability of traditional and classical statistical approaches such as generalized linear models (GLMs), or occupancy surveys to produce accurate predictive maps. This study investigates the multi-scale habitat relationships of tigers and leopards and the impacts of future climate change on their distribution using a machine-learning algorithm random forest (RF). The recent advancements in the machine-learning algorithms provide a powerful tool for building accurate predictive models of species distribution and their habitat relationships even when little ecological knowledge is available about the species. We collected species occurrence data using camera traps and indirect evidence of animal presences (scats) in the field over 2 years of rigorous sampling and used a machine-learning algorithm random forest (RF) to predict the habitat suitability maps of tiger and leopard under current and future climatic scenarios. We developed niche overlap models based on the recently developed statistical approaches to assess the patterns of niche similarity between tigers and leopards. Tiger and leopard utilized habitat resources at the broadest spatial scales (28,000 m). Our model predicted a 23% loss in the suitable habitat of tigers under the RCP 8.5 Scenario (2050). Our study of multi-scale habitat suitability modeling provides valuable information on the species habitat relationships in disturbed and human-dominated landscapes concerning two large felid species of conservation importance. These areas may act as refugee habitats for large carnivores in the future and thus should be the focus of conservation importance. This study may also provide a methodological framework for similar multi-scale and multi-species monitoring programs using robust and more accurate machine learning algorithms such as random forest.

Prey selection and food habits of the Tiger Panthera tigris (Mammalia: Carnivora: Felidae) in Kalakkad-Mundanthurai Tiger Reserve, southern Western Ghats, India

The Endangered Tiger Panthera tigris is the largest felid, distributed over 1.1 million km2 globally.  Conservation of Tigers largely depends on the preservation of its natural prey base and habitats.  Therefore, the availability of prey and its selection play a major role in the sustainable future of Tigers in the given landscape.  The current study assesses the prey selection patterns by Tigers in tropical evergreen forest of the Kalakkad-Mundanthurai Tiger Reserve (KMTR), southern Western Ghats, India.  Density of ungulates was assessed by distance sampling (line transect, N = 21) and diet composition of Tigers was evaluated by analysing their faecal samples (N = 66).  The study estimated very low ungulate density (26.87 ± 7.41 individuals km-2) with highest density of Gaur Bos gaurus (9.04 individuals km-2) followed by Wild Boar Sus scrofa (8.79 ± 2.73 individuals km-2), whereas, primate density was quite high (45.89 ± 12.48 individuals km-2), with Nilgiri Langur Semnopithecus johnii having the highest density (38.05 ± 10.22 individuals km-2).  About 74.62% of the biomass of Gaur constituted in the Tiger’s diet, consumed lesser than its availability, whereas Sambar constituted 16.73% of the Tiger diet consumed proportionally to its availability.  Chital Axis axis, Muntjac Muntiacus muntjak, and Indian Chevrotain Moschiola indica were not represented in the Tiger’s diet.  The current study is the first scientific information on prey selection of the Tiger in KMTR landscape, which will serve as a baseline for its conservation planning and management.

Spatially explicit density and its determinants for Asiatic lions in the Gir forests

Asiatic lions (Panthera leo persica) are an icon of conservation success, yet their status is inferred from total counts that cannot account for detection bias and double counts. With an effort of 4,797 km in 725 km² of western Gir Protected Area, India, we used polygon search based spatially explicit capture recapture framework to estimate lion density. Using vibrissae patterns and permanent body marks we identified 67 lions from 368 lion sightings. We conducted distance sampling on 35 transects with an effort of 101.5 km to estimate spatial prey density using generalized additive modeling (GAM). Subsequently, we modeled lion spatial density with prey, habitat characteristics, anthropogenic factors and distance to baiting sites. Lion density (>1-year-old lions) was estimated at 8.53 (SE 1.05) /100 km² with lionesses having smaller movement parameter (σ = 2.55 km; SE 0.12) compared to males (σ = 5.32 km; SE 0.33). Detection corrected sex ratio (female:male lions) was 1.14 (SE 0.02). Chital (Axis axis) was the most abundant ungulate with a density of 63.29 (SE 10.14) as determined by conventional distance sampling (CDS) and 58.17 (SE 22.17)/km² with density surface modeling (DSM), followed by sambar (Rusa unicolor) at 3.84 (SE 1.07) and 4.73 (SE 1.48)/km² estimated by CDS and DSM respectively. Spatial lion density was best explained by proximity to baiting sites and flat valley habitat but not as much by prey density. We demonstrate a scientifically robust approach to estimate lion abundance, that due to its spatial context, can be useful for management of habitat and human-lion interface. We recommend this method for lion population assessment across their range. High lion densities in western Gir were correlated with baiting. The management practice of attracting lions for tourism can perturb natural lion densities, disrupt behavior, lion social dynamics and have detrimental effects on local prey densities.

Leopard (Panthera pardus) density and diet in a forest corridor of Terai: implications for conservation and conflict management

Abstract ContextIncreasing forest fragmentation and degradation has forced wildlife to live in close proximity to humans, increasing the chances of human–wildlife conflict. Leopard (Panthera pardus) typifies the problem faced by large carnivores. It is a threatened species with a wide distribution, with a large part of their range outside protected areas, leaving them vulnerable to human–leopard conflict. Understanding their status and diet in such non-protected forests is necessary for their long-term conservation. AimsThe present study aimed to estimate leopard density and assess their diet in a non-protected forest. MethodsA camera-trapping survey was carried out in the Kamdi forest corridor outside of protected areas, covering 791.29km2 in the western part of Terai Arc Landscape (TAL) in Nepal. Leopard density was estimated based on the photographs obtained in camera traps, using Bayesian Explicit Capture–recapture (B-SECR) models. Scats of leopards were opportunistically collected (n=60) and their diet analysed through micro-histological characters of hair remains. The frequency of occurrence and relative biomass of different prey species consumed by leopard was calculated. Key resultsLeopard density was estimated to be 1.50 (±0.49 s.e.) 100km−2 in the survey area. Similarly, we identified 13 prey species in the leopard scats. Wild prey contributed the majority (67.8%) of leopard diet, including 23.2% of wild boar (Sus scrofa) and 18.3% of spotted deer (Axis axis). Nearly one-third of leopard diet consists of domestic livestock (cattle, goat, sheep) and dog. ConclusionsLeopard density was found to be relatively low in the forest corridor compared with protected areas. Nearly one-third of leopard diet from domestic livestock and dogs suggests that human–leopard conflict could be problematic in the survey area. ImplicationsIncreasing prey density in the forest corridor and improving livestock husbandry in the periphery will contribute to increase leopard density, reduce the human–leopard conflict and enhance the functionality of the corridor.

Spatial niche partitioning in sub-tropical solitary ungulates: four-horned antelope and barking deer in Nepal

Differential resource use allows a diversity of species to co-exist in a particular area by specializing in individual ecological niches. Four-horned antelope Tetracerus quadricornis is endemic to the Indian subcontinent and has a restricted distribution in Nepal and India; however, the barking deer Muntiacus vaginalis is relatively common throughout its wide distribution range. We wanted a better understanding of their habitats and how these two similarly sized solitary ungulates manage to coexist in lowland Nepal. We used fecal pellet belt transect surveys in the Babai valley, Bardia National Park to study the habitat associations of both species. We found empirical evidence that four-horned antelope prefer hill sal forest and deciduous hill forest at higher elevations, whereas barking deer preferred riverine and sal forest in lower elevations. We found a clear niche differentiation of four-horned antelope and barking deer that made the coexistence of these similarly sized solitary ungulates possible. Hence, resource partitioning is the key to coexistence of these solitary ungulates, and the fine-grained habitat mosaic of different forest types in the study landscape appears to be the underlying feature. Therefore, maintaining the habitat mosaic and preserving valuable hill sal and deciduous hill forests will facilitate the coexistence of herbivores in sub-tropical regions.

Predation ecology of large sympatric carnivores as influenced by available wild ungulate prey in a tropical deciduous forest of Central India

Predation ecology of large sympatric carnivores, tiger, leopard and dhole, as influenced by available wild ungulates, chital, sambar, nilgai, gaur and wild pig, were studied between January 2007 and June 2010 in a tropical deciduous forest of Central India. Both line transect and vehicle transect methods were used to estimate population structure and sex ratios of wild ungulates. The observed adult sex ratio (female:male) was found to be skewed towards females for all ungulates. A total of 123 tiger kills were recorded in the cold season and 162 in the hot season, 32 leopard kills were recorded during the cold season and 48 during the hot season and 32 dhole kills were recorded in the cold season and 55 in the hot season. The age–sex class distribution of each ungulate species in the kill data was compared with the corresponding population age–sex distribution recorded from line transects and vehicle transects. All three large carnivores preferred medium-sized prey species, e.g. chital. A significant difference was observed when comparing different health conditions of prey species predated by the three large carnivores. The observed difference in prey choice as per their body size is a strategy adopted by large carnivores to partition prey resources, thus increasing the potential to avoid intra-guild competition.

Can rare positive interactions become common when large carnivores consume livestock?

Livestock populations in protected areas are viewed negatively because of their interaction with native ungulates through direct competition for food resources. However, livestock and native prey can also interact indirectly through their shared predator. Indirect interactions between two prey species occur when one prey modifies either the functional or numerical responses of a shared predator. This interaction is often manifested as negative effects (apparent competition) on one or both prey species through increased predation risk. But indirect interactions can also yield positive effects on a focal prey if the shared predator modifies its functional response toward increased consumption of an abundant and higher-quality alternative prey. Such a phenomenon between two prey species is underappreciated and overlooked in nature. Positive indirect effects can be expected to occur in livestock-dominated wildlife reserves containing large carnivores. We searched for such positive effects in Acacia-Zizhypus forests of India's Gir sanctuary where livestock (Bubalus bubalis and Bos indicus) and a coexisting native prey (chital deer, Axis axis) are consumed by Asiatic lions (Panthera leo persica). Chital vigilance was higher in areas with low livestock density than in areas with high livestock density. This positive indirect effect occurred because lion predation rates on livestock were twice as great where livestock were abundant than where livestock density was low. Positive indirect interactions mediated by shared predators may be more common than generally thought with rather major consequences for ecological understanding and conservation. We encourage further studies to understand outcomes of indirect interactions on long-term predator-prey dynamics in livestock-dominated protected areas.

Estimating population densities and biomass of ungulates in the temperate ecosystem of Bhutan

In this study I estimate population densities and biomass of the major prey species of tiger Panthera tigris, leopard Panthera pardus and dhole Cuon alpinus in Bhutan’s temperate ecosystem and recommend measures for reducing crop damage whilst simultaneously protecting ungulate populations. Thirty-two transects totalling 849 km were walked to estimate densities and biomass of ungulates and primates in Bhutan’s Jigme Singye Wangchuck National Park during 2005–2006. Adequate detections (> 40 sightings) for analysis using Distance were obtained for wild pig Sus scrofa (n = 54), muntjac Munticus muntjac (n = 102) and sambar Cervus unicolor (n = 48). Because of similarity in morphology and habitat use, density of serow Capricornis sumatraensis was estimated using the detection probability for sambar. Detections for langur Trachypithecus geei and macaque Macca mulatta were combined (n = 39) to estimate primate density. Mean estimated densities were 3.68 wild pig, 2.17 muntjac, 1.19 sambar, 2.37 primates and 0.36 serow km-2. The three primary prey species of large predators, wild pig, sambar and muntjac, provided a biomass of 379 kg km-2, which could support up to 1.2 tigers per 100 km2. However, the presence of other sympatric carnivores competing for prey in the same area suggests that the actual number of tigers that could be supported is lower. Livestock (density, 6.0 km-2; biomass, 615 kg km-2) apparently supplement prey availability. Ungulate density in the study area is generally low compared to other areas in the Indian sub-continent, and this may be due to conflicts with farmers, excessive grazing of livestock in the forest and the rugged terrain.

Ungulate biomass across a rainfall gradient: a comparison of data from neotropical and palaeotropical forests and local analyses in Mexico

Using a data set from 36 studies, we evaluated variation in ungulate biomass across a rainfall gradient using polynomial models, aiming to: (1) compare neotropical and palaeotropical dry and wet forests as well as African savannas; and (2) evaluate the usefulness of polynomial models to predict ungulate biomass at neotropical sites using data from a dry forest (Chamela-Cuixmala Biosphere Reserve, CCBR) and a wet forest (Montes Azules Biosphere Reserve, MABR) in Mexico. Our results showed that an overestimation of expected ungulate biomass can be obtained for some tropical forests if data from African savannas are included in the model. This overestimation was particularly high for predicted ungulate biomass in neotropical dry forests. These ecosystems sustain different ungulate biomass values even when rainfall is similar. This was particularly true for some tropical dry forests and savannas. Rainfall predicted the expected ungulate biomass in neotropical ecosystems relative to that of palaeotropical ones under similar precipitation regimes, but did not correctly predict the observed ungulate biomass at local level if data outside the Neotropics are included in the model. This was more evident when we compared observed biomass against predicted biomass in the tropical dry forest of CCBR, while some polynomial models successfully predicted the observed biomass for the tropical wet forest of MABR. Factors such as Pleistocene extinctions and the absence of large, native grazers (i.e. Bovidae) that have kept ungulate richness and standing biomass relatively low in neotropical forests should be accounted for when comparing data sets from different regions.