Grass Snake

The grass snake is a slender, nonvenomous snake, commonly olive, grey or brown with dark side markings. Many individuals show a pale yellow, cream or white collar edged with black behind the head, though the collar can be reduced in some populations. The round pupil, narrow head and long tail contrast with the stockier body, triangular head and vertical pupil typical of vipers. (Wikipedia, grass snake account)

Grass snakes are strongly associated with ponds, marshes, streams and damp grassland, where they swim and hunt mainly frogs and toads, also taking fish and small mammals. They are active by day and often flee into water. Females lay eggs in warm decomposing vegetation or similar sites, and groups may share winter refuges. The source opened for this entry did not give a reliable Mongolian locality or local phenology, so the ecology is presented only at species level. (Wikipedia, grass snake account)