Aquatic behavior in the pitviper, Trimeresurus malabaricus

Bhaisare and Pelling (2015)report on diving behavior in Trimeresurus malabaricus, a species otherwise considered a terrestrial-arboreal snake. The authors based their report on two observations made on free-ranging Malabar Pit Vipers diving voluntarily. Observations were made in the tropical moist evergreen forest of Agumbe, which is located in the central Western Ghats of Karnataka State in India. This region receives heavy annual rainfall (7,500 to 10,000 mm) during the monsoon season (June to September). On 10 April 2011 at 11 am while following a King cobra during a telemetry project, which was moving along a shallow, slow-flowing stream, an adult T. malabaricus (total length approximately 35 – 40cm) was seen on the same bank. After the cobra had passed the T. malabaricus proceeded to move into the stream. Swimming at a slow pace, the snake was observed to halt in the middle of the stream (approximate depth 35–45cm). The stoppage was followed by a short backward jolt of the leading half of the body, causing the snake to completely submerge 8–10 cm below the surface. After the backward jolt, the snake remained underwater for 5-6 seconds, of which approximately 3-4 seconds it was completely motionless. Resurfacing involved a slight forward progression during which only the head broke the surface for approximately 1-2 seconds, before repeating the backward jolt action. The snake repeated this action three more times, remaining submerged for 5-6 seconds each time. After surfacing for the fourth time, the snake swam a further 3 m downstream to a submerged horizontal branch. It then wrapped its tail around the branch and coiled its body in a typical ambush position, fully submerged approximately 5cm under the surface, with its head facing upwards. Underwater tongue flicks with the occasional slow sideward movement
of the head were observed. The snake remained in this position without any attempt of surfacing to breath for approximately 20 minutes and then surfaced in a slow and controlled manner with tongue flicking, leaving the body still submerged and coiled. The snake was not visibly gasping or heavily breathing on surfacing. At this point, the observation ceased due to the necessity of following the studied O. hannah.

A Malabar Pit Viper coiled on a banch under water.
In a second observation on 22 July 2015 at 10:20 pm, another adult T. malabaricus (total length approximately 35 – 40cm) was observed in an open concrete tank (80 cm wide, 250 cm long and 45 cm deep) at Agumbe Rainforest Research Station (13°31’3.76”N, 75° 5’21.39”E). This tank is a regular breeding site for Malabar gliding frogs (Rhacophorus malabaricus) during the monsoon season, which are common prey for T. malabaricus. The snake was initially observed floating, partially submerged, at the surface of the 30 cm deep water. The snake remained motionless with its head under the surface pointing downwards and floating in unusual sideward position due to an inflated body (Fig. 2). After approximately 1 minute the snake surfaced and swam a little distance. Once stopped, the snake retracted its body, with its head, once again, in a submerged downward position and kept floating.

The snake repeated this action of partial submergence for four more times, remaining apnoeic for approximately 1 minute during each submergence event within 15 minutes of observation before it ceased due to heavy rain. Aubret (2004) has shown that snakes may develop apnoea relative to the usage of aquatic habitat. His study, along with our observations, raise questions about the diving and apnoea capabilities of all non-aquatic snake species. Furthermore, Heatwole (1977) suggests that all reptiles already possess advantageous fundamental physiology to allow survival in an aquatic environment if required.

Citation
Bhaisare D, Pelling E. 2015. Trimeresurus malabaricus (Malabar pit viper): Diving behaviour and underwater apnoea duration. Herpetological Bulletin 134:33-4.

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