Food Habit and Feeding Patterns of Great Indian One-Horned Rhinoceros ( Rhinoceros unicornis ) in Rajiv Gandhi Orang National Park , Assam , India

Food and feeding patterns of great Indian one-horned Rhinoceros (Rhinoceros unicornis) has been studied in Rajiv Gandhi Orang National Park. Altogether 75 species of grasses, 27 species of herbs-shrubs, 27 species of trees, and 9 species of aquatic plants species were identified as a food-plant species of Indian Rhino in the study area. Of the total 75 species of grasses, 48 species had a relative dominance of <1.0. The Saccharum spontaneum was ranked as the highest relative dominance food-plant among grasses (relative dominance value, 8.45%), while the Cyperus pilosus ranked the lowest (relative dominance value, 0.08%). Among 27 herbs-shrubs species, three had a relative dominance of <1.0. The Diplazium esculentum was ranked the highest relative dominance food plants among herbs-shrubs food plants (relative dominance value, 13.83%), while the Solanum viarum was ranked the lowest (relative dominance value, 0.66%). All tree species had a relative dominance of >1.0. The Dalbergia sissoo ranked the highest among all trees (relative dominance value, 7.94%), while the Anthocephalus cadamba ranked the lowest (value, 1.19%). Grasses constituted 86.66% of the total annual diet of Rhino, while the aquatic and woodland species constituted only 13.34% of the total annual diet. Altogether 71 plants species were identified as the Rhino food plants at Rajiv Gandhi Orang National Park. Of which, grasses constituted the highest (42 species), followed by woodland species (trees, herbs-shrubs), (20 species) and aquatic plants (9 species). The grass species Hemarthria compressa contributed a highest of 11.63%, while the aquatic plant Polygonum hydropiper was the least of 0.01% in total annual diet. Out of total 42 food-plant species, 20 grass species had no selectivity. The Hemarthria compressa was the top ranking grass species that has been selected as food by the Indian Rhino. Altogether, 36 food-plants (24 grasses, 9 woodland species, and 3 aquatic species) were identified as the staple food that constituted 83.64% of the total annual diet. Study showed that ten top ranking food plants constituted 56.44% and 20 top ranking food plants constituted 72.19% of the total annual diet. Thus, the grass species alone have enough to provide food for Indian Rhino in Rajiv Gandhi Orang National Park. Soil licking and crop depredation by the Indian Rhino were common in the fringe villages in study area.


Introduction
Food is the primary requirement of an animal to survive and maintain its good health.Hence, the animal must acquire food that contains enough nutrients to fulfill its physiological needs.Again, the distribution pattern of food resources over the habitat guides the distribution of male and female individuals.[1].Hence, the availability of food resource and its distribution pattern do not only affect the physiology of a species, but also the activity (or time budget) and the habitat utilization pattern of the wildlife species.
The study of species-specific food choice and the distribution pattern of food resources over the habitat are important prerequisites to improve the habitat quality and have a great value for in situ conservation of a species.It also helps to evaluate the habitat quality before initiating the species reintroduction programme.Hence, a number of keystone and flagship species [2,3] are subjected to study to layout a holistic approach for conservation and management action plan.During conservation and management process, the feeding ecology is one of the best tools to understand the food choice of a species, which further helps to understand the reasons of habitat selectivity and variation in time allocation in different activities.
A number of studies on feeding ecology of Indian Rhino were conducted by several authors in India and Nepal, such as [4][5][6][7][8][9][10][11][12][13].Apart from that, the studies on the chemical composition of food items [6,14], feeding behaviour of Rhino [4,5], analysis of Rhino dung, seed dispersal, germination of seed on Rhino dung [10,15], and so forth were carried out in India and Nepal conditions.Among those, most studies were conducted in Terai grassland and on natural and introduced Rhino population.Although few studies were carried out in the Brahmaputra floodplain area, most of them were qualitative in nature.Hence, the present study was aimed to quantify the data on feeding ecology of Rhino, to analyze the food and feeding habits, food preference, and food selectivity of Rhino in Rajiv Gandhi Orang National Park.
The present study aimed to find out the food and feeding habit and food selectivity of Indian Rhinos in order to lay out a comprehensive conservation strategy in the Brahmaputra floodplain habitats.The study emphasizes following objectives: (1) to investigate the food habitat of Indian Rhino in study area to find out the seasonal feeding pattern, (2) to identify the food plants species and its characteristics in different habitat of study area, (3) to identify the staple food of Indian Rhino, and (4) to find out the food selectivity and dietary spectrum of Indian Rhino in Rajiv Gandhi Orang National Park, based on gathered data.

Study Area.
The Rajiv Gandhi Orang National Park (coordinates: 92 • 15 -92 • 27 E and 26 • 29 -26 • 40 N) is situated in the north bank of the river Brahmaputra and within the administrative boundary of Darrang, Udalguri and Sonitpur districts of Assam, India (Figure 1).The study area is located about 130 km apart from the state capital city Guwahati and included under the jurisdiction of Mangaldoi Wildlife Division, Department of Environment and Forests, Government of Assam, India.The area of the park is 78.81 sq.km.The park harbours 64 Rhinos (2009 Census).
The eastern side of the study area is bounded by Borsola area and river Brahmaputra of Sonitpur district, southern side by the river Brahmaputra, western side by the tributary Dhansiri and Bagribari village area, and the northern side is bounded by Nalbari and Rangagora villages of Darrang district.
The study area comprises of alluvial floodplains of the river Brahmaputra.In fact, the complete study area is an alluvial terrace, and the entire Rajiv Gandhi Orang National Park could be divided into two halves, that is, lower Orang and upper Orang.The lower Orang portion is more recent origin, whereas the upper portion to its north is separated by high bank, traversing the park from east to west.The terrain is gently sloping from North to South.The altitude of the study area ranges between of 45-75 m MSL.
The entire protected area was a human habitat area till the last decade of the 19th century [16].Prior to declaration of Orang as a "Game Reserve" in 1915, different ethnic groups occupied the entire study area.Two large tributaries of the river Brahmaputra, namely, Dhansiri and Panchnoi are associated with numbers of streams and nullah that crisscrosses the park and became the source of water for the entire habitat.

Methods.
For the study of food and feeding ecology of Indian Rhino, the following methodologies were used for data collection.

Vegetation Sampling.
For vegetation sampling, a total of 80 quadrats (1 m × 1 m in size) for grasses, 20 quadrats (5 m × 5 m in size) for shrub and herbs, and 20 quadrats (10 m × 10 m in size) for trees were taken covering all the habitats in Rajiv Gandhi Orang National Park.Since the Rajiv Gandhi Orang National Park is primarily a grassland habitat dotted with scattered forests and shrub land, more quadrats were placed on grasslands, compared to other habitats.During sampling, the number of each individual plant species found on the quadrats was recorded to calculate the relative dominance [2,17].

Sampling for Food
Habits.Scan animal sampling and ad libitum sampling [18] methods were used to collect the data of food and feeding habit at Rajiv Gandhi Orang National Park.During study, the seasonal variation of time spent on feeding in different food plant species was recorded to identify the staple food, food selectivity, and dietary spectrum of Indian Rhino in Rajiv Gandhi Orang National Park from dawn to dusk.The staple food referred to here is the food items eaten by Indian Rhino throughout the year, irrespective of seasons.The food selectivity is the ratio of the percent of time spent and percent of dominance of each plant species.The ratio "R" indicated whether the consumed plant species had an effect on availability in the habitat or outcome of the food selection.If R > 1, then it suggests strong selection of feeding activity, and when R < 1, then it suggests that the feeding occurs due to availability of particular food items.Again, if R = 1, then it indicated that the particular plant species is consumed as per its distribution and dominance in the sampling quadrate.
The formulae of food selectivity could be represented as Selectivity = R = % of feeding records of A 1 , A 1 relative dominance, A 1 = Species 1. (1) The dietary spectrum was determined by quantifying the food dependency of Indian Rhino in study area.month was spent to visit each and every corner of the park.The field study was conducted using motor vehicles, bicycles, country boats, elephant back as well as on foot.During field visits, the sightings of Indian rhinos were recorded with their numbers, age-sex, GPS locations, and habitat types.The data were further analyzed to find out the daily range, home range, and habitat utilization pattern.The vegetation samplings were done covering all the habitats on seasonal basis.Again, the sightings of Rhino dung piles, and occurrences of any less frequent opportunistic behaviour (e.g., aggressive, reproductive, etc.) were also recorded in each and every visit.
The foraging tract was followed at the time of scan sampling, the grasses were identified if possible, and samples were collected to make herbarium sheet for identification of food plants.The plucked eaten food plants were confirmed by (a) direct observation of foraging rhino; (b) following the rhino food tracks; (c) by fresh Rhino dung analysis, that is, comparing undigested parts of food plants with herbarium sheet.

Relative Dominance and Frequency
3.1.1.Grasses.The study revealed the presence of 75 grass species under Poaceae and Cyperaceae family in Rajiv Gandhi Orang National Park during sampling.Of the total 75 grass species, 48 had a relative frequency <1, 13 had relative  1).The Saccharum spontaneum was the highest ranked relative dominance species, whose dominance value was 8.45%, while the Cyperus pilosus was the lowest ranked grass species with a dominance value of 0.08%.1).The species Diplazium esculentum was the highest ranked species among shrubs and herbs with a relative dominance value of 13.83%, while the Solanum viarum was the lowest ranked species with a relative dominance value of 0.66%.

Trees.
The study found altogether 27 tree species belonging to 8 families in Rajiv Gandhi Orang National Park with a relative frequency >1.0 (see Table 1).The Dalbergia sissoo was the highest ranked species with a relative dominance value of 7.94%, whereas the Anthocephalus cadamba ranked the lowest was species with a relative dominance value of 1.19%.

Food Items and Food Selection.
The study showed that, grass constituted the highest of 86.66% total annual food of Indian Rhino in Rajiv Gandhi Orang National Park, but the nongrass aquatic plants and tree species constituted only 13.34% of total annual diet, indicated the high selection of grasses by Indian Rhino in Rajiv Gandhi Orang National Park during foraging (Figure 2).The study also revealed that the Indian Rhino selected 89.13% grass species as food items during winter season and 83.50% during monsoon season (Figure 3).Of the total 42 grass species, 20 species had no selectivity but eaten during foraging time owing to availability in the grassland habitat of study area.

Food Items.
Study showed that altogether 71 plant species have used by Indian Rhino as food items throughout the year in study area, of which 42 species were grasses, 20 species trees, herbs, and shrubs, and 9 species were other aquatic plant.Again, among all the 71 food plant species, the Indian Rhino consumed a total of 63 plant species as food during premonsoon, 49 species during monsoon, 57 species   3).The Rhino consumed dissimilar categories of food items in various seasons of the year.The analysis of proportional use of food plant types by Indian Rhino showed that the plant types, namely, dry short grass (dsg), wet creeping short grass (wcsg), and wet tall grass (wtg) were consumed in maximum proportion during premonsoon compared to other types (Figure 4).Again, the proportional use of wet creeping short grass (wcsg), dry short grass (dsg), wet tall grass (wtg), and creeping aquatic beds (cab) were higher during monsoon season than other types of food-plant species (see Figure 5).Whereas, the wet creeping  short grasses (wcsg), wet tall grasses (wtg), dry short grasses (dsg), submerged (sm), and creeping aquatic beds (cab) types of food-plants were consumed in higher proportion during retreating monsoon season (Figure 6).During winter season, the Indian Rhino consumed higher proportion of wet creeping short grass (wcsg), wet tall grass (wtg), dry short grass (dsg), wet short grass (wsg), dry tall tree (dtt), and creeping aquatic beds (cab) types of food plants than other types of species (Figure 7).

Feeding Frequency.
The study revealed that the grass species Hemarthria compressa contributed the highest consumed (11.63%) food plant species of Rhino, while the marshyland plant species Polygonum hydropiper was the lowest consumed (0.01%) food-plant species, in their total annual diet.The annual feeding frequency of the ten top ranking plant species of Indian Rhino in their total annual diets were Hemarthria compressa, Hymenachne pseudointerrupta, Leersia hexandra, Arundo donax, Chrysopogon aciculatus, Phragmites karka, Brachiaria ramosa, Cynodon dactylon, Saccharum spontaneum, and Imperata cylindrica (Table 4).

Staple Food.
The analysis showed that altogether 36 plant species (Table 5) were selected by Indian Rhino as their regular food item.This 36 numbers constituted 83.64% of the total annual diet budget of Indian Rhino in Rajiv Gandhi Orang National Park.Among all the 36 plant species, 24 plant species were grasses that constituted 75.97% of the total selected annual food plant species; hence, it is referred to as staple food of Indian Rhino.But, among nongrass species, only 9 trees species and 3 aquatic plant were also Figure 4: Proportional use of food plants species by Indian Rhino in Rajiv Gandhi Orang National Park during premonsoon season (data was represented, Mean ± 2SE; wsg: wet short grass; wcsg: wet creeping short grass; dsg: dry short grass; dst: dry short tree; dtt: dry tall tree; dh: dry herbs; ds: dry shrubs; eab: emergent aquatic bed; cab: creping aquatic bed; ffab: free-floating aquatic bed; SM: submerged; sv: swampy vegetation).selected as annual food, which constituted only 7.67% of the total annual diet, that were also referred as staple food (Table 6).
3.1.9.Dietary Spectrum.The food selection pattern of the Indian Rhino showed a distinct dietary spectrum during present study.The study showed that up to 10 top ranking food plants species of Rhino constituted almost 56.44% of the total annual diet, but it was 72.19% up to 20 top ranking food plants species, whereas the rest 41 food plants constituted only 28% of the total annual diet of the Rhinos in Rajiv Gandhi Orang National Park (see Figure 8).Again, among the 20 top ranking food-plant species, 19 species were grasses, and only one species was aquatic plant species (Ipomea aquatica).This clearly indicated that the grass alone was the sufficient food items, of Rhino, necessary for survival in Rajiv Gandhi Orang National Park.

Cultivated Crop.
The study revealed that the Indian Rhinos in Rajiv Gandhi Orang National Park had often visited in fringe villages for depredation of cultivated crops.There were altogether 10 cultivated crops and 10 vegetables eaten by Rhino as their food.No quantitative analysis of the cultivated crops were made, that have consumed in dark hours of the day (Table 7).

Geophagy (or Soil Eating
).There were altogether seven soil eating (soil licking) sites of Indian Rhinos in Rajiv Gandhi Orang National Park during study period (Table 8).The Rhino frequently visited the soil eating sites during night hours.It was also reported by the forest personnel that the Rhino occasionally consumed soil near the forest camps.

Discussion
In present study, the consumption of 86.66% grass species followed by 6.68% aquatic plants and 6.66% woodland species (browse) by Indian Rhino indicates that, the grasses are the key food-plant species of Rhino in Rajiv Gandhi Orang National Park.This is also evident from the seasonal diet pattern, where 89.13% grasses were consumed during winter and 83.50% during premonsoon season.Laurie [4,5] also reported that Indian Rhino at Nepal also consumed 86.4% grasses, 5.2% aquatic plants, and 3.4% browse from February-May (spring season), while 88.7% grasses, 5.7%  Ipomea batatas (sweet potato) Lathyrus sativus (khesari dal) Carica papaya (papaya) aquatic plants and 5.6% browse from June-September (monsoon season) and 70.4% grasses, 8.0% aquatic plants and 21.6% browse from October-January (winter season).Those results supported the present findings of grass as the most preferred food items of Indian Rhino.Similar types of findings were also observed by Jnawali [19] in Bardia National Park and Chitwan National Park in Nepal.He suggested that a highest proportion of 92% grass species has used as the diet of Indian Rhino during monsoon in Bardia National Park and 86% in Chitwan National Park during hot season and lowest of 42-57% during winter season.Fjellstad and Steinheim [20] also suggested that the diet of Indian Rhino has consisted of 63% grass and 28% browse.This clearly indicates that, the Indian Rhino has mostly depended on grasses rather than browse or other aquatic plants.Hence, it could be opined that the Indian Rhino is more habitat specialized than any other large herbivore mammals.Fjellstad and Steinheim [20] also found in their study that Rhino depends on quality of food rather than quantity.They also found that Indian Rhino spent 85% total feeding time on three vegetation types, while there were six vegetation types for Asian elephant to reach the same habitat occupancy.Hence, the numbers of habitat types are limited for Indian Rhino.
Again, the number of food plant species of Indian Rhino varies from habitat to habitat, which was suggested by other studies.Laurie [4,5] has stated that Indian Rhino fed on 183 food-plants species under 57 families in Chitwan National Park.Ghosh [12] has stated that the Rhino consumed 82 plant species belonging to 34 families in Jaldapara Wildlife Sanctuary.So, it is varied in all occasions.The present study

Figure 1 :
Figure 1: Location map of Rajiv Gandhi Orang National Park.

Figure 3 :
Figure 3: Seasonal use of food plant species by Rhinoceros unicornis in Rajiv Gandhi Orang National Park.

Figure 8 :
Figure 8: Dietary spectrum of Indian Rhino in Rajiv Gandhi Orang National Park (based on actual collected data).
The study was carried out from April 2000 to March 2003 covering random sampling points of the whole study area of 78.81 sq.km. in Rajiv Gandhi Orang National Park (92 • 15 -92 • 27 E; 26 • 29 -26 • 40 N).A total of 10 days per

Table 2 :
Seasonal use of food-plant species by Indian Rhino in Rajiv Gandhi Orang National Park.

Table 4 :
Shows the ten top ranking annual food plants of Indian Rhino in Rajiv Gandhi Orang National Park.

Table 5 :
Staple food of Rhino in Rajiv Gandhi Orang National Park (a) grasses, (b) trees and (c) aquatic plants.

Table 6 :
Percent use of Staple food by Indian Rhino in Rajiv Gandhi Orang National Park (PM: premonsoon; M: monsoon; RM: retreating monsoon; W: winter).Figure6: Proportional use of food plants species by Indian Rhino in Rajiv Gandhi Orang National Park during retreating monsoon (data was represented, Mean ± 2SE; wsg: wet short grass; wcsg: wet creeping short grass; dsg: dry short grass; dst: dry short tree; dtt: dry tall tree; dh: dry herbs; ds: dry shrubs; eab: emergent aquatic bed; cab: creeping aquatic bed; ffab: free-floating aquatic bed; SM: submerged; sv: swampy vegetation).

Table 7 :
Cultivated crop and vegetable species eaten by Indian Rhino as food in association with natural food items (name written in parentheses are in local vernacular names).