drowning it or thrashing it around. Pieces of prey are subsequently torn off by forceful, thrashing head and body motions, the feet anchoring the crocodile in place. Thewissen believed Ambulocetus used a similar feeding tactic, though Ambulocetus was probably capable of chewing, unlike crocodiles. Ambulocetus may have attacked large mammals which approached the water's edge, and semi-aquatic mammals including early (possibly herbivorous) sirenians (now manatees and the dugong) and the probably amphibious anthracobunids. These two seem to have been rather common on the coasts of the Indian subcontinent, which could mean they were regular prey items. Since Ambulocetus was found in marine deposits (where animals would not come to drink), it is possible it hunted in river deltas which were recorded in the Kuldana Formation. Ambulocetus probably went after fish and reptiles when given the opportunity, though it may not have had the agility to commonly catch them. Locomotion Thewissen hypothesised that Ambulocetus was a drag-powered swimmer, and used its huge feet as its primary propulsion mechanism, much like modern river otters including the giant otter, and species in the genera Lontra and Lutra. Based on the length of the known tail vertebrae, Ambulocetus may have had an inflexible tail, which would have made the tail an inefficient primary propulsion mechanism due to poorer lever arm (modern cetaceans have relatively short tail vertebrae). Ambulocetus therefore likely did not have a tail fluke. Nonetheless, drag powered swimmers still have powerful tails for producing lift, and the tails of river otters are 125% the size of the thoracolumbar series. So, using river otters as a model, Ambulocetus was a pelvic paddler—swimming with alternating beats of the hindlimbs (without engaging the forelimbs)—and also undulated (moved up and down) its tail while swimming. Like the sea otter, pelvic paddling may have been done at the surface to move at slow or moderate speeds. At higher speeds fully submerged, undulation of the spine would have become more prominent, though the feet still would have acted as the primary propulsion mechanism. Based on the pelvis and robust forelimbs, Thewissen believed Ambulocetus was capable of venturing onto land, and was more efficient at doing this than remingtonocetids and protocetids (it is unclear if the latter two were capable of bearing weight on the limbs). Ambulocetus possibly used a sprawling gait on land, similar to modern sea lions. In 2016, Japanese biologists Konami Ando and Shin‐ichi Fujiwara performed