# Locomotory behaviour during basking and spoor formation in the gharial (Gavialis gangeticus) > How does a gharial leave their mark on a riverbank? Watching wild and young captive gharial in India’s Mahanadi river, two researchers broke basking into six phases, from surfacing near the bank to sliding back into the water, and showed how a slow belly walk and a swinging tail leave a compact, inverted U-shaped spoor. They explain why the clearest tail scute marks form as the gharial moves off, and how the sliding mark helps surveyors find basking sites. Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/1977-singh-bustard-locomotory-behaviour-during-basking/ ## Citation and access - **Authors:** L. A. K. Singh and H. R. Bustard - **Year published:** 1977 - **Journal or source:** British Journal of Herpetology - **Full citation:** Singh, L. A. K. and Bustard, H. R. 1977. Locomotory behaviour during basking and spoor formation in the gharial (Gavialis gangeticus). British Journal of Herpetology 5(9): 673–676. - **Access status:** Hosted (freely available elsewhere) - **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/1977_Singh_and_Bustard_locomotory-behaviour-during-basking-and-spoor-formation-in-the-gharial.pdf ## Tags - **Species:** Reptiles > Gharial - **Region:** Asia > India - **Tracking:** Gaits; Tracking; Tracks; Tracks and signs identification - **Behaviour and ecology:** Behaviour; Movement - **Methods and technology:** Direct observation - **Data type:** New field data - **Observer qualification:** Not reported - **Discipline:** Behaviour and ecology; Wildlife tracking - **Year published:** 1977 ## Detailed keywords - **Species:** Studied: gharial (Gavialis gangeticus), wild adults and juveniles and young captive gharial up to 10 months old. In the study area but not studied: mugger (Crocodylus palustris). Also mentioned: Crocodylus porosus (named only by scientific name, as one of the three Indian crocodilians and as the subject of Zug’s 1974 gait study) and Nile crocodile (Crocodylus niloticus, in the title of Cott’s 1961 study cited). - **Location and habitat:** Satkoshia Gorge of the River Mahanadi, Orissa, India: a deep river (10 m deep in the dry season) with sandy basking sites on the banks, from steep slopes to almost flat ground. The authors worked at the Gharial Research and Conservation Unit, Tikerpada, Orissa, where young captive gharial were also observed. - **Topics:** basking behaviour; six phases of basking (preparatory, emergence, pre-basking, basking, post-basking, re-entry); terrestrial gaits of crocodilians (high walk, belly run, gallop, and the slow belly walk used in basking); spoor formation; tail scute spoor (the inverted U-shaped spoor left by the part of the tail with a single row of ventral scutes); tail drag and sliding marks; paw and foot impressions (pugs); direction of emergence and slope of the basking site; forces acting on the tail (propulsive, lifting and lateral); detecting basking sites in surveys; using spoor to estimate body size (mentioned as unpublished work); seasonal basking (daily in winter, rare in summer); differences between gharial and mugger in basking. - **Statistics or models:** None - **Data type:** New field data: observations of wild gharial in the Satkoshia Gorge and of young captive gharial studied up to 10 months of age. No dates of observation are given; the paper was received on 1 July 1976. Local count in the gorge at the time: two juvenile and three adult muggers, one juvenile and four adult gharial (two males and two females). ## Synopsis ### 1. What they did Crocodilians are known to have three ways of moving on land: the high walk, the belly run and the gallop. The authors, working at a gharial research and conservation unit in Orissa, India, describe a fourth, slower movement that gharial use when they come out to bask, and explain how it leaves a distinctive spoor. They watched wild gharial basking on the sandy banks of the Satkoshia Gorge on the River Mahanadi, and young captive gharial up to 10 months old. They divided basking into six phases and described the body and tail movements in each, the tracks and signs each phase leaves, and the forces acting on the tail that shape the spoor. ### 2. What they found Gaits - In the wild, the authors had not seen gharial use the high walk, belly run or gallop, because a basking gharial is never far from water. One gharial 5.5 m long simply wheeled round and went into the water when their boat was about 45 m away. - Young captive gharial used all three gaits: the high walk when something seemed suspicious, and the belly run and gallop when suddenly frightened. - Both wild and captive gharial use a slow, leisurely belly walk when basking. This belly walk is what makes the spoor. Who basks, and when - In the gorge, muggers were seldom seen out of the water, probably because the deep water kept them warm. Gharial, especially the juvenile and the males, basked a few hours after sunrise and sometimes at other times of day. - Basking took place daily in winter but rarely in summer. The six phases of basking, and what each leaves behind - Preparatory phase. A wild gharial surfaces near the basking site three or more times, 10 to 30 minutes apart, then suddenly moves onto the bank. Young captive gharial skip this phase. - Emergence phase. The gharial climbs the sand slope with their forelimbs and lies with half the body or the tail still in the water, at a right angle or an acute angle to the water’s edge. The steeper the bank, the more likely a right angle; on almost flat ground, right and acute angles are equally likely. The gharial stays longer in this position when the sun falls on their side, and only briefly when the sun is in line with the body. - Pre-basking phase. The whole body comes out along the same line, pushed by the fore and hind limbs. The paws and feet make deep impressions, depending on the ground. No good scute spoor forms, because the body and tail move straight, without sideways movement. - Basking phase. The gharial turns to the side and slides the body and tail sideways until the body lies at right angles to the line of emergence. The tail is dragged over the sand and leaves spoor from the part of the tail with a single row of ventral scutes. These marks are not clear, because a lifting wave along the tail keeps it from touching the ground completely. - Post-basking phase. The gharial moves forward and sideways. Three forces act on the tail together: a forward pull from the limbs, a lifting wave from the base of the tail that dies away towards the tip, and a sideways force from the tail muscles. Together they drag the tail along a curved path, producing the clearest scute spoor. The front part of the tail seldom touches the ground and leaves no scute marks, even if it moves sideways. - Re-entry phase. Usually short, sometimes with brief pauses. The gharial normally enters the water in a single sliding movement. The steeper the bank, the less the limbs are used, so good pugs (foot and paw prints) are less likely at this stage, and no tail scute spoor is left. The sliding mark itself, though, helps surveyors find basking sites. Together these movements leave a compact, inverted U-shaped spoor. ### 3. What they concluded - Besides the three known land gaits, gharial use a slow belly walk when basking, and this belly walk is responsible for spoor formation. - The clearest tail scute spoor forms in the post-basking phase, when the forward, lifting and sideways forces act on the tail together; little or no scute spoor forms when the gharial moves in a straight line or slides back into the water. - The sliding spoor at re-entry is important to surveyors in detecting basking sites. - The authors use this spoor to estimate body size (described as unpublished work). ### 4. How tracking was or was not used The paper is about how tracks and signs are made. The authors linked each phase of basking to the marks it leaves on the sand: deep paw and foot impressions while climbing out, the tail scute spoor while turning and moving off, the overall inverted U-shaped pattern, and the sliding mark into the water. They note that they use the spoor to estimate body size and that the sliding spoor helps surveyors find basking sites. No trailing is reported. ### 5. Tracker or observer certification Not reported. The observations were made by the authors. L. A. K. Singh held a research scholarship from the Orissa Forest Department, and H. R. Bustard was supported by a United Nations Development Programme and Food and Agriculture Organization (UNDP/FAO) project on crocodile breeding. Nothing is said about tracking experience or skill. ### 6. Other technologies, skills or innovations - Diagrams that explain the shape of the tail spoor through three forces acting on the tail: a forward pull from the limbs, a lifting wave along the tail, and a sideways force from the tail muscles. - Comparison of wild and young captive gharial. ### 8. Implications for tracking (Original Wisdom's observations) _These are Original Wisdom's observations, not the authors'._ - The paper is an early example of reading a track by understanding how it was made: each phase of a gharial’s basking leaves a different mark, so the sequence of paw prints, tail scute marks and sliding marks on a sandbank can show how the animal came out, turned, lay and left. - The marks that tell you most are not always made at the same moment: deep foot impressions come from climbing out, while the clearest tail spoor comes from moving off after basking. ## Cite this summary Lawrence, K. 2026. Summary of: Locomotory behaviour during basking and spoor formation in the gharial (Gavialis gangeticus) (Singh and Bustard, 1977). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/1977-singh-bustard-locomotory-behaviour-during-basking/