Forestry & Forest Sciences · Forest Protection, Wildlife & Rangelands · also Wildlife Biology, Ornithology and Herpetology, Wildlife Ecology
The animals of forests and grasslands: mammals, birds, reptiles and amphibians, their habitats, behaviour and population ecology, and how populations are counted.
In the exams: ICAR AICE-JRF 59 Unit 10 (wildlife biology, ornithology, herpetology, census methods); IFoS Forestry Paper II Section B (forest protection and wildlife biology); ICAR AIEEA-PG Group 09 (wildlife); GATE EY; Wildlife Institute of India MSc entrance
Forests and grasslands are habitats as well as sources of timber, and foresters in India and many other countries are also wildlife managers. A range officer may spend as much time on elephant conflict, tiger monitoring and anti-poaching patrols as on plantations. Managing wildlife well requires knowing the animals: which species live where, what they need from their habitat, how they behave, how their populations grow and decline, and how to count them reliably.
This subject covers the biology and ecology of wildlife for foresters. It begins with definitions and values of wildlife and its distribution, then surveys the mammals, birds, reptiles and amphibians of forests and grasslands, with emphasis on India. It then covers habitat requirements, behaviour relevant to management, population dynamics, and the field methods used to estimate abundance and distribution: total counts, line transects, pellet and dung counts, camera traps, mark-recapture, radio telemetry and home-range estimation, and occupancy surveys for biodiversity monitoring. The companion subject wildlife-management-protected-areas covers habitat management, protected areas, human-wildlife conflict, enforcement, captive breeding, ecotourism, law and species recovery. Ecosystem concepts, food webs, diversity indices and plant-animal interactions are covered in forest-ecology, and the Wildlife (Protection) Act and international conventions in forest-policy-law-governance; this manual refers to them rather than repeating them. Animal health, capture drugs and wildlife disease are left to the Veterinary track.
The manual is written for students preparing for the ICAR AICE-JRF forestry paper (whose wildlife unit covers wildlife biology, ornithology, herpetology and census methods), the Indian Forest Service and state forest service examinations, the GATE Ecology and Evolution paper and the Wildlife Institute of India's MSc entrance, and for field staff and researchers. Population figures for species change with each survey and are given as approximate values from recent national estimates.
In its broadest sense, wildlife means all non-domesticated animals and plants living in the wild, although in common and management usage it often means wild vertebrates, especially mammals and birds. India's Wildlife (Protection) Act, 1972 defines 'wild animal' as any animal specified in its schedules and found wild in nature, and 'wildlife' as including any animal, aquatic or land vegetation which forms part of any habitat. Game animals are those hunted for sport or food; in India sport hunting has been banned since the Act came into force, so management focuses on conservation rather than harvest. The legal framework is covered in forest-policy-law-governance.
Wildlife has many values. Ecological values arise from the roles animals play in ecosystems: predators regulate prey, herbivores shape vegetation, frugivores disperse seeds, pollinators enable plant reproduction and scavengers recycle carcasses. The collapse of India's vultures in the 1990s and 2000s, for example, left carcasses uneaten and was linked to increases in feral dogs and possibly in rabies. Economic values include tourism, meat and other products where harvest is legal, and the contribution of wildlife to ecosystem services. Scientific and educational values, aesthetic and recreational values, cultural and religious values (many Indian communities protect sacred groves and revere animals such as peafowl, blackbuck and monkeys) and ethical or intrinsic values, the idea that species have a right to exist, all motivate conservation. Valuation of non-market benefits is discussed in forest-economics-valuation.
The distribution of animals reflects evolutionary history, climate, vegetation and human influence. Alfred Russel Wallace divided the world into six zoogeographic realms in 1876: Palaearctic, Nearctic, Neotropical, Ethiopian (Afrotropical), Oriental (Indo-Malayan) and Australian. India lies mainly in the Oriental realm but has Palaearctic elements in the Himalaya and Afrotropical elements in the arid west, which partly explains its high diversity. India is one of the megadiverse countries, with roughly 7 to 8 percent of recorded species on about 2.4 percent of the world's land, and includes parts of four global biodiversity hotspots: the Himalaya, Indo-Burma, the Western Ghats and Sri Lanka, and Sundaland (through the Nicobar Islands).
Rodgers and Panwar's classification, used for planning India's protected area network, divides the country into ten biogeographic zones: Trans-Himalaya, Himalaya, Desert, Semi-arid, Western Ghats, Deccan Peninsula, Gangetic Plain, North-east, Coasts, and Islands, further subdivided into biotic provinces. Each zone has characteristic fauna: the snow leopard, Tibetan wild ass and Tibetan antelope of the Trans-Himalaya; the great Indian bustard, blackbuck and chinkara of the desert and semi-arid zones; the lion-tailed macaque and Nilgiri tahr of the Western Ghats; the hoolock gibbon and many hornbills of the North-east; and the dugong and saltwater crocodile of the coasts and islands. Distribution maps are produced from survey records, museum specimens and, increasingly, species distribution models that relate occurrences to environmental variables.
India has over 400 species of mammals, including large carnivores, ungulates, primates, rodents, bats and marine mammals. Bats and rodents make up the largest share of species, while large mammals receive most management attention. Important orders include Carnivora (cats, dogs, bears, mustelids, civets, mongooses, hyenas), Artiodactyla (deer, antelopes, wild cattle, wild pigs, and in modern classifications whales), Perissodactyla (rhinoceroses and wild asses), Proboscidea (elephants), Primates, Rodentia, Chiroptera (bats), Pholidota (pangolins) and Lagomorpha (hares and pikas).
The tiger (Panthera tigris) is the flagship of Indian conservation. The All India Tiger Estimation of 2022 recorded a minimum of about 3,167 tigers from camera traps and estimated about 3,682, roughly three-quarters of the world's wild tigers. Tigers are solitary, territorial predators of large ungulates such as sambar, chital, gaur and wild pig. The Asiatic lion (Panthera leo persica) survives in the wild only in and around Gir in Gujarat, where its population has grown from under 200 in the 1960s to several hundred. The leopard (Panthera pardus) is widespread and adaptable, often living close to people. Other carnivores include the snow leopard of the high Himalaya, the clouded leopard of the North-east, the dhole or Asiatic wild dog (a pack hunter), the Indian wolf of semi-arid grasslands, the striped hyena, the sloth bear (which feeds largely on termites and fruit), the Himalayan black bear and many small cats, civets and mongooses.
Deer (family Cervidae) have antlers, bony structures shed and regrown each year, usually only in males; Indian species include sambar, chital (spotted deer), barking deer, hog deer, swamp deer or barasingha (whose hard-ground subspecies survives mainly in Kanha), the hangul or Kashmir stag in Dachigam, and the brow-antlered deer or sangai, confined to the floating meadows (phumdis) of Keibul Lamjao in Manipur. Antelopes and wild cattle (family Bovidae) have permanent horns of keratin over a bony core; Indian species include blackbuck, chinkara, nilgai, four-horned antelope, gaur, wild water buffalo and the mountain ungulates such as Nilgiri tahr, Himalayan tahr, bharal and ibex.
The Asian elephant (Elephas maximus) ranges through forests of the Himalayan foothills, the North-east, central India and the Western and Eastern Ghats; India holds the majority of the world's wild Asian elephants, with national counts of roughly 27,000 in 2017. The greater one-horned rhinoceros (Rhinoceros unicornis) lives in the floodplain grasslands of Assam, West Bengal and Nepal, with Kaziranga holding the largest population. Primates include rhesus and bonnet macaques, the lion-tailed macaque of the Western Ghats, langurs, the slow loris and the hoolock gibbon, India's only ape. Pangolins, among the most trafficked mammals in the world, eat ants and termites. Mammals of grasslands, such as blackbuck, wolf, hog deer and the pygmy hog, have often declined more than forest species because grasslands are less protected.
Ungulates show adaptations to diet: ruminants such as deer, antelope and cattle have a four-chambered stomach and chew the cud, which allows them to digest fibrous plants; non-ruminants such as elephants and rhinos are hindgut fermenters that process large amounts of lower-quality food. Grazers such as blackbuck and hog deer eat mainly grass, browsers such as barking deer eat leaves and shoots, and mixed feeders such as chital switch with season. Predators show adaptations for stalking, chasing or pack hunting. Body size influences home range, food needs and vulnerability to extinction: large-bodied species need large areas and reproduce slowly.
India has roughly 1,300 bird species, about an eighth of the world's total, including many endemics in the Western Ghats, the Andaman and Nicobar Islands and the Himalaya. Salim Ali, often called the 'birdman of India', laid the foundations of Indian ornithology. Birds are the best-studied wildlife group because they are conspicuous, diverse and easy to observe, and citizen science platforms now gather millions of records each year that feed national assessments of bird status.
Forest birds partition resources by foraging height, substrate and diet: some feed on the ground, some glean insects from leaves, woodpeckers excavate bark and wood, flycatchers sally for flying insects, and frugivores such as hornbills, barbets, pigeons and bulbuls feed on fruit and disperse seeds. Mixed-species foraging flocks, in which several species move through the forest together, are common in Indian forests and may reduce predation risk and improve foraging. Cavity-nesting birds such as woodpeckers, barbets, hornbills and owls depend on old and dead trees, so retaining snags and large trees in managed forests is important.
Hornbills have a striking breeding behaviour: the female seals herself into a tree cavity with mud and droppings, leaving a narrow slit through which the male feeds her and the chicks. This makes them dependent on large old trees with suitable cavities and on the male's survival. The great hornbill is the state bird of Arunachal Pradesh and Kerala, and community nest adoption programmes protect nesting trees in the North-east.
Birds show diverse breeding strategies. Altricial young, such as those of songbirds, hatch naked and helpless and need prolonged parental care; precocial young, such as those of ducks, pheasants and partridges, hatch with down and can walk soon after hatching. Brood parasites, such as many cuckoos, lay eggs in other birds' nests; the Asian koel, for example, parasitises crows. Mating systems range from monogamy, the commonest, to polygyny and lekking.
Many birds migrate. India lies on the Central Asian Flyway, along which millions of waterbirds and raptors move between breeding grounds in Siberia and Central Asia and wintering grounds in South Asia. The Amur falcon passes through Nagaland in large numbers on its migration between eastern Asia and southern Africa; community conservation stopped a large-scale hunt there after 2012.
Threats to birds include habitat loss, especially of grasslands and wetlands, collisions with power lines, poisoning and hunting. Populations of three Gyps vultures in India crashed by more than 95 percent from the 1990s, caused by the veterinary drug diclofenac in livestock carcasses; veterinary diclofenac was banned in 2006 and conservation breeding began. The great Indian bustard, a grassland bird of Rajasthan and Gujarat, is critically endangered with perhaps around 150 individuals, threatened particularly by collisions with power lines.
Reptiles are ectotherms (their body temperature depends on the environment) with scaly skin and eggs with shells, or in some species live birth. India has a rich reptile fauna of several hundred species of snakes, lizards, turtles, tortoises and crocodilians, with many endemics in the Western Ghats and North-east.
Of the many snake species, only a minority are venomous to humans. Four species, the 'big four', cause most snakebite deaths in India: the Indian cobra (Naja naja), the common krait (Bungarus caeruleus), Russell's viper (Daboia russelii) and the saw-scaled viper (Echis carinatus). Polyvalent antivenom is made against these four. India has a very high burden of snakebite deaths, concentrated among rural farm workers. The king cobra (Ophiophagus hannah), the world's longest venomous snake, feeds mainly on other snakes and builds a nest for its eggs. Pythons, rat snakes and many others are non-venomous and help control rodents.
India has three crocodilians: the gharial (Gavialis gangeticus), a fish-eating river specialist with a long narrow snout, now critically endangered and found mainly in the Chambal and a few other rivers; the mugger or marsh crocodile; and the saltwater crocodile in Bhitarkanika in Odisha, the Sundarbans and the Andaman and Nicobar Islands. In crocodilians and most turtles, the sex of offspring is set by incubation temperature (temperature-dependent sex determination), so changes in nesting conditions can skew sex ratios. Olive ridley sea turtles nest in mass arrivals called arribadas on the Odisha coast, notably at Gahirmatha and Rushikulya. Freshwater turtles and tortoises, such as the Indian star tortoise, are heavily traded illegally.
Amphibians, which include frogs and toads (Anura), salamanders and newts (Caudata) and legless caecilians (Gymnophiona), have permeable skin and most have an aquatic larval stage, making them sensitive to water quality, drying and pollution. India has several hundred amphibian species, many described in the last two decades, with the Western Ghats a centre of endemism. The purple frog (Nasikabatrachus sahyadrensis) of the Western Ghats spends most of its life underground and emerges briefly to breed in the monsoon. Caecilians live in soil and leaf litter.
Amphibians are among the most threatened vertebrate groups globally. Causes include habitat loss, pollution, climate change and disease, especially chytridiomycosis caused by the fungus Batrachochytrium dendrobatidis, which has caused declines and extinctions in the Americas and Australia. Amphibians are good indicators of stream and wetland health.
Reptiles and amphibians are surveyed by visual encounter surveys (systematic searches of defined areas or times), time-constrained searches, pitfall traps with drift fences, cover boards, acoustic surveys of calling frogs, and nest counts for turtles and crocodilians. Because many species are secretive, nocturnal or seasonal, surveys must be repeated across seasons and times of day, and detection probability should be accounted for, as discussed in the chapter on occupancy.
Habitat is the place where an animal lives and the resources and conditions it needs to survive and reproduce. Aldo Leopold, in Game Management (1933), identified the basic requirements, or 'welfare factors', as food, water and cover, arranged in space so that animals can use them. The amount and arrangement of these components determine how many animals an area can support.
Food requirements vary with species, body size, season and physiological state; lactating females and growing young need more energy and protein. Forage quality matters as much as quantity: young grass after burning or rain is more digestible and protein-rich than old dry grass. Water is critical in dry habitats and seasons, and the spacing of water sources limits where animals can feed in the dry season; ungulates such as nilgai and chinkara can obtain much of their water from food. Cover provides protection from predators (escape cover), weather (thermal cover) and disturbance, and sites for resting and breeding (nesting and denning cover). Space includes the area needed for home ranges and territories, and freedom from disturbance.
Leopold noted that many animals are most abundant where different habitat types meet, which he called the edge effect, and that interspersion, the intermixing of habitat types, increases the number of animals an area can support for species needing more than one type. Edges benefit generalist and edge species such as chital and many birds, but can harm forest-interior species through increased predation, nest parasitism and microclimate change. Modern management therefore aims for a mix of habitat types suited to target species, not edge for its own sake.
Habitat quality can be assessed by vegetation surveys of forage and cover, by animal indices such as density, body condition and reproduction, and by habitat suitability index (HSI) models, which score habitat variables on a scale from 0 to 1 and combine them into an index of suitability for a species. Resource selection functions, estimated from telemetry or survey data, compare used and available habitat to show which features animals prefer.
Carrying capacity is the number of animals a habitat can support over time without degrading it. For herbivores, a simple forage-based estimate divides the usable forage by the requirement per animal. For example, if 100 hectares produce 1,500 kg of dry forage per hectare, of which 50 percent can be used without damaging the vegetation, and each animal needs 2 kg of dry matter per day for a 180-day dry season, the area can support about 1,500 x 0.5 x 100 / (2 x 180) = 208 animals. Such estimates ignore nutrition quality, competition with livestock and other species, and spatial distribution, but are useful for planning. Carrying capacity in population models is discussed in the population dynamics chapter, and the ecological concepts of energy flow and productivity in forest-ecology.
Animals use space in characteristic ways. A home range is the area an animal uses for its normal activities; a territory is the part of it that the animal defends against others, usually of the same species and sex. Tigers and leopards are territorial, with males holding large territories that overlap those of several females; dhole and wolves live in packs that defend group territories. Social species such as elephants live in matriarchal family herds led by an older female, with adult males living alone or in loose bachelor groups. Dominance hierarchies regulate access to food and mates in many groups. Knowing these patterns helps managers interpret survey data, estimate the area needed for viable populations and predict where dispersing animals will go.
Mating systems influence population structure and management. Deer show a rut, a breeding season in which males compete through displays and fights; male elephants show musth, a period of heightened testosterone and aggression. Blackbuck in some areas breed in leks, where males gather on small display territories visited by females. Seasonal movements, from daily movements between feeding and resting areas to long-distance migrations of birds and some ungulates, determine which areas must be protected at which times.
Foraging behaviour is explained by optimal foraging theory, which predicts that animals choose food and feeding sites to maximise net energy gain, and by the marginal value theorem, which predicts when an animal should leave a food patch. Prey species balance feeding against predator avoidance: vigilance (scanning for predators) decreases per individual as group size increases, one benefit of living in groups. Alarm calls, such as those of langurs and chital that warn of tigers and leopards, are used by field biologists to locate predators.
Animals respond to people and disturbance in ways that matter for management. Flight initiation distance, the distance at which an animal flees from an approaching person or vehicle, indicates disturbance sensitivity and is used to set viewing distances in tourism. Habituation, the waning of a response to a repeated harmless stimulus, allows wildlife viewing but can lead animals to approach people for food and increase conflict. Learned crop-raiding, in which animals such as elephants learn to exploit crops, spreads through populations and makes deterrents less effective over time. Imprinting, described by Konrad Lorenz in geese, is important in captive rearing for reintroduction, where young must not imprint on humans. Applying behavioural knowledge to conservation problems, such as designing deterrents or release methods, is sometimes called conservation behaviour.
Population size changes through four processes: births (natality), deaths (mortality), immigration and emigration. Over a time step, N(t+1) = N(t) + B - D + I - E. For example, a population of 200 with 50 births, 30 deaths, 5 immigrants and 15 emigrants in a year becomes 200 + 50 - 30 + 5 - 15 = 210. The finite rate of increase lambda (λ) is N(t+1) / N(t); λ greater than 1 means growth. A population with λ = 1.2 grows from 100 to 144 in two years.
Natality depends on age at first breeding, litter or clutch size, breeding interval and the proportion of females breeding. Mortality depends on predation, disease, starvation, accidents and human causes. Life tables summarise age-specific survival and fecundity, and survivorship curves describe patterns of mortality: Type I curves, typical of large mammals such as elephants, show low mortality until old age; Type II curves show constant mortality at all ages, as in many birds; and Type III curves, typical of many fish, amphibians and invertebrates, show very high mortality among the young.
In unlimited conditions, populations grow exponentially: dN/dt = rN, so N(t) = N0 e^(rt), where r is the intrinsic rate of increase. A population of 100 with r = 0.1 per year reaches about 165 after five years, and its doubling time is ln 2 / r = 6.9 years. Real populations are limited by resources, and logistic growth describes slowing growth as numbers approach the carrying capacity K: dN/dt = rN (1 - N/K). With r = 0.4, K = 1,000 and N = 250, the population grows by 0.4 x 250 x 0.75 = 75 animals per year. Growth is fastest at N = K/2, where the maximum sustainable yield is rK/4, or 100 animals per year in this example.
MacArthur and Wilson distinguished r-selected species, with high reproductive rates, short lives and variable populations, from K-selected species, with low reproductive rates, long lives and populations near carrying capacity; large mammals such as elephants, rhinos and tigers are K-selected and recover slowly from declines. Density dependence, in which birth or survival rates change with density, regulates populations near K. Predator-prey dynamics can be described by the Lotka-Volterra equations, which predict linked oscillations of predator and prey numbers.
Small populations face extra risks: demographic stochasticity (chance variation in births and deaths), environmental stochasticity, catastrophes, loss of genetic diversity through drift and inbreeding, and Allee effects, in which individuals do worse at low density because, for example, they cannot find mates. The minimum viable population is the smallest population with a specified chance of persisting for a specified time; the classic 50/500 rule of thumb suggested an effective population size of at least 50 to avoid inbreeding depression in the short term and 500 to retain evolutionary potential, though later work suggests larger numbers. The effective population size is often much smaller than the census size: with unequal sex ratios, Ne = 4 Nm Nf / (Nm + Nf), so 10 breeding males and 40 breeding females give Ne = 32, not 50. Population viability analysis (PVA) uses simulation models to estimate extinction risk under different management options. Conservation genetics is covered further in conservation-biology-genetic-resources.
Wildlife population estimation ranges from total counts, which attempt to count every individual, to sample counts that estimate density from part of the area, to indices that track relative change without estimating absolute numbers. Total counts are feasible only for conspicuous animals in open habitats or concentrated groups, such as waterbirds on wetlands, ungulates from aircraft in open savanna, or animals at waterholes. Waterhole counts, once widely used in Indian protected areas, count animals coming to water over a 24-hour period in the dry season; they are simple but biased, because not all animals visit and some visit more than once, and are now regarded as indices at best. Indices, such as encounter rates of signs per kilometre, call counts or dung densities, are useful for tracking trends if detection is constant, which is often not the case. Pugmark-based tiger censuses, used in India until the mid-2000s, were abandoned because individual identification from footprints proved unreliable.
In a strip transect, observers count all animals within a fixed distance on either side of a line, and density is the count divided by the area of the strip. For example, 24 animals counted in a strip 2 km long and 50 m wide on each side (area 2 x 0.1 = 0.2 km2) give a density of 120 per km2. This assumes all animals in the strip are detected, which is rarely true at the edges.
Line transect distance sampling, developed by Buckland and colleagues, relaxes this assumption. Observers walk a line and record the perpendicular distance to each animal or group seen. A detection function is fitted to the distances to estimate how detectability declines with distance, and density is estimated as D = n f(0) / (2L), where n is the number of detections, L the total line length and f(0) the probability density of detection distances at zero distance. For example, 30 detections on 10 km of transect with f(0) = 20 per km give D = 30 x 20 / (2 x 10) = 30 animals per km2 (for groups, multiply by mean group size). Key assumptions are that animals on the line are always detected, that animals are detected at their initial location before moving, and that distances are measured accurately. In India, line transects are used to estimate prey densities in tiger reserves as part of the national tiger estimation.
Many herbivores are hard to see but leave countable signs. Pellet group counts estimate density by counting pellet groups in plots cleared at a known time, or of known age, and dividing by the defecation rate and the number of days of accumulation: density = pellet groups per unit area / (defecation rate x days). For example, 150 pellet groups per hectare accumulated over 50 days, for a species producing 15 groups per animal per day, give 150 / (15 x 50) = 0.2 animals per hectare, or 20 per km2. Elephant dung counts use the same logic but must also account for dung decay rates, which vary with season and habitat. Errors in defecation and decay rates translate directly into errors in density.
Camera traps, triggered by heat and motion, photograph passing animals day and night. They are used for inventories, activity patterns, occupancy, and, for individually identifiable species such as tigers and leopards with unique stripe or rosette patterns, for capture-recapture estimation of abundance and density. India's All India Tiger Estimation, conducted every four years since 2006, combines camera-trap capture-recapture in sampled areas with extensive sign surveys and habitat covariates across tiger range, an approach sometimes called double sampling. Spatially explicit capture-recapture (SECR) models, which use the locations of detections to estimate density directly, have become the standard method for camera-trap density estimation (see the next chapter).
Capture-mark-recapture methods estimate population size from the proportion of marked animals in later samples. In the simplest two-sample case, M animals are captured, marked and released; later a second sample of C animals is captured, of which R are marked. Assuming the proportion marked in the sample equals the proportion in the population, R/C = M/N, so the Lincoln-Petersen estimate is N = M C / R. For example, if 50 animals are marked, and a second sample of 40 contains 10 marked animals, N = 50 x 40 / 10 = 200. The simple estimator is biased upward in small samples; Chapman's modification, N = (M + 1)(C + 1) / (R + 1) - 1, reduces this bias and gives (51 x 41 / 11) - 1 = 189 for the same data.
The estimator assumes that the population is closed (no births, deaths, immigration or emigration between samples); that all animals have the same probability of capture in each sample; that marking does not affect catchability or survival; and that marks are not lost or overlooked. Violations bias the estimate: if marked animals become trap-shy, R falls and N is overestimated; if they become trap-happy, N is underestimated. Heterogeneity in capture probability among individuals, common in wild populations, typically causes underestimation. Study designs therefore keep sampling periods short to approximate closure and use models that allow for heterogeneity and behavioural responses.
With more than two sampling occasions, the Schnabel method extends the Lincoln-Petersen approach, and closed-population models, such as those implemented in the programs CAPTURE and MARK, compare models that allow for time variation, behavioural response and individual heterogeneity in capture probability (the Otis and colleagues models M0, Mt, Mb, Mh and combinations). For open populations, Jolly-Seber and Cormack-Jolly-Seber models estimate survival and recruitment as well as abundance over longer periods.
Camera traps have made capture-recapture practical for large carnivores with natural marks, such as tigers, leopards, snow leopards and clouded leopards: each photograph of an identified individual is a 'capture'. Because conventional estimates give abundance but not the area sampled, density was once estimated by adding a buffer around the camera grid, an approach sensitive to buffer width. Spatially explicit capture-recapture (SECR) models solve this by modelling each animal's activity centre and how detection declines with distance from it, giving density directly. Genetic capture-recapture uses DNA from scats or hair as marks, useful for species that are hard to photograph or trap.
Physical marks include ear tags, leg rings on birds, PIT tags (passive integrated transponders) injected under the skin, collars, and toe clipping or visible implant elastomer in amphibians, the last raising welfare concerns. Marks should be permanent for the study period, readable, harmless and approved under animal ethics and legal permits. Natural marks, such as stripe patterns, ear notches, tusk shape in elephants and scars, avoid capture altogether and are increasingly preferred.
Radio telemetry tracks animals fitted with transmitters. VHF (very high frequency) collars emit pulses that a researcher locates on the ground or from aircraft with a directional antenna, usually by triangulation from two or more bearings; this is cheap but labour-intensive and gives limited locations. GPS collars record locations at programmed intervals and store them or transmit them by mobile network or satellite; Argos satellite tags are used for long-distance migrants, including birds and sea turtles. Modern tags may also include accelerometers, which record activity and behaviour, temperature sensors and mortality sensors. Collars on elephants, tigers and leopards in India have revealed home ranges, dispersal routes, use of corridors and movements into farmland that inform conflict management.
Telemetry requires capture, immobilisation and handling, which carry welfare risks and require veterinary support and permits (capture drugs are covered in the Veterinary track). A widely used guideline is that a tag should not exceed a small percentage of body mass, often cited as about 3 percent for birds and up to about 5 percent for mammals; under a 5 percent guideline, a 40 kg animal could carry a collar of up to 2 kg. Collars must fit properly, include drop-off mechanisms where possible, and be monitored for effects on behaviour and survival.
Burt (1943) defined home range as the area traversed by an individual in its normal activities of food gathering, mating and caring for young. It is estimated from location data. The minimum convex polygon (MCP) joins the outermost locations to form the smallest convex polygon containing them; it is simple and comparable across studies but is sensitive to outliers and sample size and includes unused areas. Often 95 percent MCPs exclude the most extreme 5 percent of points. Kernel density estimation (KDE) builds a utilisation distribution, a probability surface of where the animal is likely to be, and defines the home range as the area containing, for example, 95 percent of use, with the 50 percent contour as the core area. The bandwidth or smoothing parameter strongly affects kernel estimates. Newer methods, such as Brownian bridge movement models and autocorrelated kernel density estimation, account for the time sequence and autocorrelation of GPS fixes.
Home-range size varies with body size, diet and habitat productivity: carnivores have larger ranges than herbivores of similar size, and ranges are larger where food is scarce. Tiger ranges in productive Indian reserves may be a few tens of square kilometres for females, while those in poorer habitats or of males are much larger. Overlap between ranges indicates social organisation.
Telemetry data are also used to study habitat selection, by comparing used locations with available locations in resource selection functions; movement paths and step selection; dispersal of young animals from their birth areas, which determines connectivity between populations; and responses to roads, fences and settlements. This information feeds into corridor design and conflict mitigation, discussed in wildlife-management-protected-areas.
Monitoring is the repeated measurement of the state of biodiversity to detect change, assess threats and evaluate management. Good monitoring programmes have clear objectives, measurable indicators, sampling designs that represent the area of interest, standardised methods, sufficient statistical power to detect changes of management interest, and a plan for using the results. Indicators may be species-level (abundance, distribution, demographic rates), community-level (species richness, diversity indices, covered in forest-ecology) or habitat-level (extent, condition, fragmentation).
Occupancy is the proportion of sites, such as grid cells or habitat patches, occupied by a species. It is often easier and cheaper to estimate than abundance, especially for rare or cryptic species and over large areas. The key problem is imperfect detection: a species may be present at a site but not detected during a survey, so the naive occupancy (the proportion of sites where the species was detected) underestimates true occupancy. Occupancy models developed by MacKenzie and colleagues (2002) use repeated surveys of each site to estimate the detection probability (p) and then the true occupancy (psi). With detection probability p per survey, the probability of detecting a species present at a site in K surveys is 1 - (1 - p)^K. For example, with p = 0.4 and three surveys, cumulative detection is 1 - 0.6^3 = 0.784; to reach 95 percent detection, about six surveys are needed, since ln 0.05 / ln 0.6 = 5.9.
Occupancy models assume that sites are closed to changes in occupancy during the survey period, that detections are independent, and that there are no false positives. Extensions model colonisation and extinction over seasons (dynamic occupancy), multiple species, and abundance-induced heterogeneity in detection. Occupancy surveys using sign or camera traps are widely used in India for tigers, leopards, elephants, dhole and other species across large landscapes.
Monitoring increasingly uses new tools: camera-trap networks, passive acoustic recorders for birds, bats and frogs, environmental DNA (eDNA) from water or soil to detect species, remote sensing for habitat change, and citizen science, such as bird-recording platforms that support national assessments of bird populations. At the global level, the IUCN Red List assesses extinction risk using criteria based on population size, decline and range, with categories Extinct (EX), Extinct in the Wild (EW), Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC), Data Deficient (DD) and Not Evaluated (NE). CR, EN and VU together are the threatened categories. The Living Planet Index tracks average trends in vertebrate populations. Monitoring results guide the management decisions covered in wildlife-management-protected-areas.
Learn Indian wildlife by zone and group, Leopold's habitat components, the differences between antlers and horns, survivorship curves, exponential and logistic growth, and the census and estimation formulas (strip, distance sampling, pellet counts, Lincoln-Petersen and Chapman, cumulative detection). Practise calculations and field identification, and join a transect or camera-trap survey if possible.
As a range officer, biologist or NGO field staff member you plan and run line transects, sign and occupancy surveys and camera-trap grids, maintain data, identify individuals from photographs, assist telemetry studies, and interpret results for management. Judgement is needed to keep methods standardised, to recognise biased indices such as waterhole counts, and to report uncertainty honestly.
At senior level you design state or landscape monitoring programmes, commission telemetry and population studies, interpret national estimates for policy, and decide on management actions for species and habitats. Decisions include the choice of methods and indicators, survey frequency, data sharing and how to communicate trends and uncertainty to decision-makers and the public.
Research questions include population dynamics and viability of large mammals, movement ecology and connectivity from telemetry, density estimation with spatial capture-recapture, occupancy dynamics across landscapes, behavioural responses to people, and the effects of land-use change on communities. Rigorous research combines careful field design, modern statistical models and long-term data.
Species numbers and population estimates change with each survey and taxonomic revision and are given as approximate values from recent national assessments. Tag-mass guidelines, defecation and dung-decay rates and detection functions vary by species and study; worked examples use illustrative values. Detailed statistical theory of distance sampling, capture-recapture and occupancy is outlined rather than derived. Wildlife law, protected areas and management are in wildlife-management-protected-areas and forest-policy-law-governance; ecosystem and community ecology in forest-ecology; conservation genetics in conservation-biology-genetic-resources; and animal capture drugs, health and disease in the Veterinary track.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions.
These notes are free to read here, with no account.
What the Laisha app adds:
Free for ten days, then a subscription. We would rather write that here than have you find it later.