a giant briar snake

• 0, 0, -2018 (seen once) (3 of 42 spawns here)
• -1424, -149, 14
• -1389, -639, -45 (seen once) (1 of 7 spawns here)
• -1219, -391, -52 (seen once) (1 of 3 spawns here)
• -1218, -358, -50 (seen once)
• -2074, -462, -50 (seen once)
• -517, -408, -44 (seen once) (1 of 2 spawns here)
• -1846, 247, -62 (seen once) (1 of 3 spawns here)
• -1858, -508, -52 (seen once)
• -2022, -439, -49 (seen once) (1 of 6 spawns here)
• -1571, 852, -32 (seen once)
• -1697, -34, -50 (seen once)
• -1289, -706, -43 (seen once) (1 of 2 spawns here)
• -1542, -142, -38 (seen once)
• -827, -67, -22 (seen once)
• -1310, -950, -38 (seen once)
• -1099, -645, -60 (seen once)
• -1340, 339, -36 (seen once) (1 of 3 spawns here)
• -1374, 348, -27 (seen once)
• -1695, 932, -17 (seen once)
• -951, -445, -80 (seen once) (1 of 2 spawns here)
• -1392, -208, 32 (seen once) (1 of 5 spawns here)
• -1548, -116, -39 (seen once) (1 of 2 spawns here)
• -1253, -125, -35 (seen once) (1 of 3 spawns here)
• -1865, -150, -80 (seen once)
• -1227, -418, -52 (seen once)
• -1743, 62, -36 (seen once) (1 of 2 spawns here)
• -544, -601, -33 (seen once) (1 of 2 spawns here)
• -1333, 397, -37 (seen once)
• -1660, -660, -27 (seen once) (1 of 5 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.