a water moccasin

• 2190, 533, -32
• 2020, 994, -32 (seen once)
• 915, 740, -33 (seen once)
• -134, 1298, -26 (seen once) (1 of 2 spawns here)
• -333, -546, -30 (seen once)
• -374, -544, -30 (seen once)
• -634, -250, -32 (seen once)
• -903, -514, -15 (seen once) (1 of 2 spawns here)
• -1853, -420, -32 (seen once)
• 2254, 1402, -31 (seen once)
• 1878, 89, -19 (seen once)
• 2259, -128, -26 (seen once)
• 1584, 87, -25 (seen once) (1 of 2 spawns here)
• 2194, -278, -32 (seen once)
• 1586, -622, -25 (seen once)
• 150, 902, -20 (seen once)
• -204, 191, -30 (seen once)
• -400, 967, -32 (seen once)
• -443, 636, -32 (seen once)
• -1868, 541, -31 (seen once)
• 1535, 1131, -48 (seen once)
• 1181, 746, -32 (seen once)
• 2126, -447, -39 (seen once) (1 of 2 spawns here)
• 646, -80, -32 (seen once) (1 of 2 spawns here)
• 117, 818, -30 (seen once)
• 798, -630, 5 (seen once) (1 of 3 spawns here)
• -476, 1324, -32 (seen once)
• -90, -470, -32 (seen once) (1 of 3 spawns here)
• -479, 233, -29 (seen once)
• -193, -596, -28 (seen once) (1 of 2 spawns here)

As /loc gives them: Y, X, Z, the most used first; nearby spawns share a spot, and one seen in a single visit may be where the mob had been pulled to.