Plant diversity of Point Calimere Wildlife Sanctuary and fodder species grazed by the Blackbuck Antilope cervicapra L.

IFS, wildlife warden (Retd.), Nagapattinam District for facilitating us to carry out the study. We would like to thank Mr. Leslie Lawrence, assistant professor, Department of Botany, Madras Christian College and Dr. Sheeba J. Irwin for their help during the study. We also extend our gratitude to all the field personnel of Point Calimere Bird and Wildlife Sanctuary for their involved help during the field studies. AKU would also like to thank the Director, Botanical Survey of India for providing lab facilities. Abstract: A rapid but intense survey was conducted using visual landmarks in the Point Calimere Wildlife Sanctuary to enumerate the flora and foraging habits of the Blackbuck Antelope cervicapra . The area was divided into various segments such as the sanctuary entrance, Maattu muni kovil, Savukku plot or Casuarina plantation, S-Bend road and the old light house for precise enumeration. A total of 111 plant species that include 50 herbs, 16 climbers/lianas, 30 shrubs and sub-shrubs, and 15 trees belonging to 39 plant families were recorded in this study. Visual observations showed that Blackbucks grazed on grasses such as the Mangrove Grass Aeluropus lagopoides (L.) Thwaites, Dog’s Tooth Grass Cynodon barberi Rang. & Tadul., Indian Durva Grass Cynodon dactylon (L.) Pers., Feather Finger Grass Chloris virgata Sw., and a sedge, the pointed fimbristylis Fimbristylis acuminata Vahl during the day time. They were also observed browsing on the leaves and pods of Algaroba Prosopis juliflora (Sw.) DC. in the evenings. Our observation on the presence of feral horses and stray cattle in the Point Calimere Wildlife Sanctuary shows that they compete for food and water with the Blackbuck. The spread of invasive alien plant species competes with and reduces the space for native species.


INTRODUCTION
Point Calimere Wildlife Sanctuary harbours a rich diversity of animals, among them is the Blackbuck which is the most exquisite animal in the sanctuary. The name Blackbuck is in reference to the dark-coloured coat of the adult male which varies from dark brown to black. The belly and hind side of the legs are white. The horns of the males are ridged and twisted. Blackbuck Antilope cervicapra L. is listed under Schedule I, Part I of the Indian Wildlife Protection Act, 1972. Habitats of the Blackbuck have been declared as protected areas in several parts of India, with the support of the local people. Punjab and Haryana have honoured the animal as their state animal (Hundal 2004) and the Bishnoi community of Rajasthan considers the blackbuck as a sacred animal. There are six protected areas in Tamil Nadu where Blackbucks occur in considerable numbers.  (Suresh 2015). The objectives of this study were (a) to survey the plant diversity and highlight the species of herbs, shrubs, and trees seen in PCWS and (b) to document the grasses and other plant species grazed by the Blackbucks.

Study area
PCWS is one of the largest tropical dry evergreen forests (TDEF) in India located between 10.2878°N & 79.8651°E with an expanse of 1,729 ha located in the Nagapattinam district of Tamil Nadu (Figure 1) (Ali 2005;Parthasarthy et al. 2015). TDEF are the areas of vegetation without a distinct differentiation between the small and canopy forming trees, having coriaceous leaves with an average height of less than 12 m, having a luxuriant growth of lianas and climbers along with an inconspicuous presence of grasses (Champion & Seth 1968;Parthasarthy et al. 2015). This vegetation receives both summer and winter monsoons due to depressions and cyclones in the Bay of Bengal (Meher-Homji 1974). It forms an interface between the coastal and the deciduous vegetation, having varied ecosystems with a visible change in the soil type from sandy, saline to alluvial.
Point Calimere was declared a wildlife sanctuary in 1967 for conserving the Blackbuck population that was dwindling due to intensive poaching and hunting (Baruah 2005). PCWS is bordered by Vedaraniyam salt pans in the north, Palk Strait in the south, Bay of Bengal in the east, and Kodiakadu in the west. It gets its name from the point at which both the Bay of Bengal and the Palk Strait meet. The human habitations around the forest are found mainly in two villages namely, Kodiakkarai and Kodiakadu. The sanctuary is an island which is connected to the mainland by the Vedaraniyam-Kodiakkarai road.

Data collection and analyses
The methods of assessment used were very simple and based on visual observations in the field, i.e., observing Blackbucks while they grazed, followed by visiting the grazing sites to identify the plant species (Altman 1974). Since, this was a rapid survey, methods such as quadrates and other indices were not planned for in the study. However, the sanctuary was divided into the following segments using visual landmarks for effective and efficient data collection: (a) sanctuary entrance, (b) Maattu muni kovil -a temple visited by local cowherds, (c) Savukku plot or Casuarina plantation, (d) S-Bend road, and (e) the old light house. Rapid survey was conducted within the sanctuary for almost a month and a total of about 120 hours were spent exclusively for observing foraging and resting habits of Blackbucks in the PCWS. During the study period, field binoculars were used to observe the grazing activities. The segments were explored to interpret the foraging pattern of Blackbucks and to make a list of plants available in the sanctuary, which was further used to understand the components of the vegetation. Most of the plant species were identified on the site and undesignated plant specimens especially the grasses were taken to the laboratory for identification. All the identified plant species were classified based on their J TT habitats. The botanical names of the plant species were updated using online databases such as POWO (2020), The Plant list (2013) and The International Plant Name Index (IPNI 2018). Specimens were also photographed and kept for reference.

RESULTS
A total of 111 plant species that included 50 herbs (12 grasses, five sedges and four creepers), 16 climbers/ lianas, 30 shrubs & subshrubs, and 15 trees belonging to 39 plant families were recorded in this study ( Figure  2). Of the plant families recorded Fabaceae, Poaceae, Amaranthaceae, Lamiaceae, Cyperaceae, Rubiaceae, Convolvulaceae, and Asteraceae were the most speciesrich families having four or more species each ( Figure 3). The term 'mound' used here is to distinguish elevated patches of land from the rest of the study area. Many plant species (except mangroves) were not rigidly habitat specific and were observed occurring in different habitats. A checklist of plants with their local Tamil names and habitats within the sanctuary was also prepared (cf. Appendix I).
Visual observations from a distance followed by instantaneous site visits in the field showed that the Blackbucks preferred to graze on selected grasses such as Aeluropus lagopoides (L.) Thwaites, Cynodon barberi Rang. & Tadul., C. dactylon (L.) Pers., Chloris virgata Sw.,

DISCUSSION
Conservation of the whole habitat of blackbucks in the sanctuary initially resulted in multiplication of their numbers but that was impeded due to the increase in the number of feral horses and stray cattle over the years. Entry of feral horses and stray cattle into the sanctuary poses two main problems: (a) competition for food and water and (b) spread of invasive alien plant species. Pods of Prosopis juliflora (Sw.) DC., one of the most aggressive invasive alien species is preferred by these cattle and the seeds were dispersed through their faeces into the sanctuary area, leading to the spread and increase in its population. By trampling the vegetation, altering the soil texture and overgrazing, these animals have a penetrating effect on the ecosystem. Feral horses build up to high numbers during good years, and many starve during drought (Wilson et al. 1992). Quality and nutritional value of plants available for grazing influences the diet and habitat relationship in large herbivores (Ahrestani et al. 2012). The distribution pattern of plant species and their dominance in an area plays an important role in their preference by these herbivores (Chamaille-Jammes & Bond 2010). Blackbucks, cattle from nearby villages, and feral horses, all compete for the same forage stock and there are not many differences between their foraging habits.
To control the competition faced by Blackbucks in PCWS by feral horses and stray cattle a few steps may be implemented.
1. Native fodder species can be introduced into the sanctuary on an experimental basis to provide more fodder to herbivores and to enhance local biodiversity (Dayanandan 1994). A few fodder species including grasses and leguminous trees have been listed for this purpose. (Table 1). 2. Stray cattle from the nearby villages can be stopped by fencing at strategic places where they are most probable to enter inside, and awareness programs can be conducted to educate the nearby villagers about the ecological and cultural significance of Blackbucks and the ill-effects of stray cattle grazing in the sanctuary premises. The population of feral horses can be controlled by methods such as relocation and sterilization (Khan et al. 2019).

CONCLUSION
This study has employed a very simple direct observational methodology for collection of data sets from PCWS. In spite of the seasonal limitations experienced, it provides a base for possible furthering of full-fledged ecological, floristic, and conservation studies in the area. Field surveys in different seasons need to be undertaken for a holistic understanding of the ecology of Blackbuck in Point Calimere with emphasis on the fodder species, especially the grasses. This study is expected to help prepare policies for plantation of fodder species in the sanctuary, and help in conservation of Blackbuck population with their long-term survival. The suggested mitigation measures are expected to help in controlling the spread of invasive alien plant species too, thereby, enriching the local flora.

Grasses to be introduced in sandy areas
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