Living by the Sea: Range and Habitats of Asiatic Lions

Educational field

The Saurashtra region in western India, in the south-western part of the state of Gujarat, typically represents the semi-arid state of Gujarat-Rajputana 4B23, covering 11 of the 33 districts of the province. The region consists of a rocky plateau (height 300–600 m) surrounded by coastal plains with an undulating central plain broken by hills and cut by various rivers flowing in all directions.24. With India’s longest coastline (~1600 km), Gujarat has rich coastal biodiversity.25,26. Saurashtra coast in Gujarat is surrounded by open sea between two gulfs (68° 58′–71° 30′ N and 22° 15′–20° 50′ E) and divided into two segments viz.. Southwest coast from Dwarka to Diu (~ 300 km stretch) and Southeast coast from Diu to Bhavnagar (~ 250 km stretch)26.

The Asiatic Lion Landscape covers an area of ​​~ 30,000 km2 (permanent lion distribution range: ~ 16,000 km2; visiting record range: ~ 14,000 km2) different habitat types within Saurashtra. The landscape includes five protected areas (Gir National Park, Gir Wildlife Sanctuary, Paniya Wildlife Sanctuary, Mitiyala Wildlife Sanctuary and Girnar Wildlife Sanctuary) and other forest classes (protected forests, reserved forests and unclassified forests).

Coastal habitats extend across the districts of Bhavnagar, Amreli, Gir-Somnath and Junagadh (Figure 1). Within these districts (Figure 1), Mangrol, Malia, Patan-Veraval, Sutrapada, Kodinar and Una tehsils (sub-divisions/taluka) constitute the south-west coast (hereafter west coast habitat), Jafabad, Rajula,. form the southeast coast and the Mahuva and Talaja Bhavnagar coast and represent distinct lion range units (Fig. 1). The total area covered by the study is 2843 km2 on the east coast and 1413 km2 on the west coast (Fig. 1).

Saurashtra region is given three distinct chapters viz. dry and hot summer (March-June), monsoon (July-October) and mostly dry winter (November-February). The average annual precipitation is ~ 600 mm, most of which occurs during the southwest monsoon.27. The average maximum and minimum temperatures are 34 °C and 19 °C respectively28. There are 110 km2 stretching of forests along the coast. The rest of the land is multi-use, consisting of private, industrial, pasture and waste land with various ownerships. Natural vegetation consists primarily of Prosopis juliflora and Casuarina equistetifolia. As vegetation in coastal and dune areas Ipomea pescaprae, Sporobol trios, Fimrystylis sp., Crotalaria sp.and Euphorbia nivuleria29. Along the coast mudflats are confined to Talaja, Mahuva, Pipavav port, Jafrabad creek and Porbandar areas. Avicennia marina29. Fishing, agriculture, horticulture, animal husbandry and some large and small scale industries are the leading economies along the coastline.

Coastal segments are characterized by a diversity of vegetation, sandy beaches, small cliffs, undulating platforms, open and submerged hills, small estuaries, beaches and a transition from the open sea to a bay environment with tidal mud.26,29 and also supports a diverse set of biodiversity25. This biodiversity is further enriched by several perennial/ephemeral rivers originating from Gir PA (Shetrunji, Machundari, Raval, Ardak, Bhuvatirth, Shinghoda, Hiran, Saraswati etc.).12. These rivers merge with the sea at different parts of the coast to form outstanding coastal ecosystems.25. Riverways serve as important corridors for wildlife movement9, 12, 30. Through these corridors, lions began to settle in these coastal habitats30,31.

Methods

All research activities involved in this study on Asiatic lions were undertaken after obtaining appropriate approval from the Ministry of Environment, Forests and Climate Change (MoEF&CC), Government of India (Letter No: F. No. 1-50/2018 WL). ) and Chief Conservator of Forests (Wildlife) and Chief Wildlife Warden, Gujarat, Gandhinagar (Letter No: WLP 26B 781-83/2019-20). Procedures and protocols were followed as per the Standard Operating Procedures for handling wild animals of the Gujarat Forest Department, Government of Gujarat. Qualified and experienced veterinarians and their team performed all procedures involving radiotherapy. In addition, the study is reported in accordance with Animal Studies: Reporting of In Vivo Experiments (ARRIVE) guidelines.

In 2019, a long-term lion monitoring project was launched by the Gujarat Forest Department to understand the movement patterns and ecology of lions in the Asian Lion Landscape. Considering the heterogeneity and extent of coastal areas, ten individuals were carefully selected for satellite radio-collaring and monitored from 2019 to 2021 based on their frequent movements in different coastal habitats.

Lions, regardless of age or sex, were fitted with Vertex Plus GPS Collars (Vectronics Aerospace GmbH, Berlin, Germany) weighing less than three percent of the individual’s body weight. Lions were immobilized using a combination of Ketamine hydrochloride (2.2 mg per kg body weight; Ketamine, Biowet, Pulawy) and Xylazine hydrochloride (1.1 mg per kg body weight; Xylaxil, Brilliant Bio Pharma Pvt. Ltd., Telangana).32 administered intramuscularly using a gas-powered Telinject™ GUT 50 (Telinject Inc., Dudenhofen, Germany) dart delivery system. A curtain was placed to protect the eyes and reduce visual stimuli33,34. Each tranquilized individual was sexed, aged and weighed as per standard operating procedure (SOP) of Gujarat Forest Department, Government of Gujarat and recorded the data in capture data sheet. Radiocollars are placed by ensuring free movement of the person, taking into account the neck circumference, so as not to interfere with the daily activities of the person. After placement of the radiocollar, we administered a specific antidote for Xylazine, namely, Yohimbine hydrochloride (0.1–0.15 mg per kg body weight; Yohimbe, Equimed, USA) intravenously, resulting in complete recovery of the immobilized subjects.32 Within 5-10 minutes. Individuals were intensively monitored for 72 hours and then regularly monitored throughout the functional life of the radiocollars. The entire radiopaque exercise was carried out by trained and experienced veterinary staff and their teams of wildlife health professionals and field staff.

Each collar had a unique VHF and UHF frequency. The radio collars were equipped with a programmable GPS chart and were configured to record hourly position fixes and provided data via the quadruple low-orbit Iridium satellite data service (Iridium Communications Inc., Virginia, USA) constellation. – time intervals after activation. Data logs include position corrections in degrees decimal format (latitude/longitude), speed (km/h), altitude (meters above mean sea level), UTC timestamp (dd-mm-yyyy h:m:s), direction (degrees) . ) and temperature (Celsius). Radio-collars are equipped with death sensors and a programmable download activation system. Gir Hi-Tech Monitoring Unit, Sasan-Gir, Gujarat, monitored and coordinated these activities. Location data were downloaded from each radio collar using GPS Plus X software (Vectronics Aerospace GmbH, Berlin, Germany) at the Gir Hi-Tech Monitoring Unit (a technology-based landscape scientific monitoring initiative established at Sasan in 2019). Gir, Gujarat).

Data analysis

In this study, we estimated the home range of coastal lions using the Fixed Kernel method. To summarize total home range and core area, we expressed them as 90% and 50% Fixed Core (FK), respectively.35,36,37. In addition, the home range of lions classified as ‘capture lions’ and protected area lions is summarized for comparison (Table 1).

MaxEnt (version 3.4.1) standalone software38 applied to fine-scale lion distribution modeling39,40. Logistic output format is set for MaxEnt output. 30% random lion occurrence points were used as test data to evaluate the performance of the model. The area under the receiver operating characteristic curve (AUC) was used to assess the discriminatory ability of the model based on sensitivity (correct discrimination of true positive loci) and specificity (correct discrimination of true non-negative loci) values.41. A Jackknife regularized training gain for species was used to understand the effect of each variable in model building. The logic output of MaxEnt is presented in tabular format as “percent contribution” and “significance of change” (0 to 100%). Spatial entries were made in a GIS platform using ArcMap (version 10.8.1, ESRI, Redlands, USA).42. Input data for MaxEnt were classified as (i) lion occurrence data, (ii) model variables were developed as described below:

  1. i.

    Occurrence data

    At the first level, inconsistent location fixes (records with missing coordinates, timestamps, and elevation) and outliers were filtered out. Next, hourly GPS location fixes of each lion derived from remotely sensed radio-telemetry data were randomized to remove spatial and temporal biases. Data were reduced by correcting the location every three hours43,44. The data were further classified by season, viz. summer, monsoon and winter. This consolidated data was then subjected to one kilometer spatial thinning using SDMtoolbox (version 2.0).45,46.

  2. ii.

    Model variables

The variables used for distribution modeling broadly covered different categories of land use, including both natural habitats and anthropogenic factors such as roads and human settlements. All variables are rasterized at a spatial resolution of 10 m.

Land Use Land Cover (LULC) data of Saurashtra are available from Bhaskaracharya National Institute of Space Applications and Geo-Informatics (BISAG-N), Gandhinagar, Gujarat. The data was then further classified into 18 sub-classes – Forest, Sandy Areas, Salt Affected, Shrub, Open Bush, Dense Bush (Desolated Lands), Flooded, River/Stream/Drain, Lakes and Ponds, Mining/Industrial Areas, Water storage /Tanks, Mangrove/Wetland, Cropland, Agricultural Plantation (horticulture and agroforestry), Main city, Mixed settlement, Suburban, Village (Fig. 2).

Roads and highways were also analyzed as separate variables in the model. Roads were classified as rural roads, major district roads, and state and national highways and individually digitized to further estimate Euclidean distance (Table 2). Euclidean distance from human settlement (Urban-urban, suburban, rural and mixed settlements) was analyzed and treated as a separate input variable for the model.

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