a giant thistle snake

• -1215, 102, -39 (2 of 4 spawns here)
• -1017, -890, -69 (2 of 11 spawns here)
• -918, -591, -63 (seen once) (1 of 2 spawns here)
• -1902, -667, -35 (seen once)
• -1445, -92, -18 (seen once) (1 of 2 spawns here)
• -798, -177, -21 (seen once)
• -1730, 142, -25 (seen once) (1 of 2 spawns here)
• -2135, -730, -94 (seen once) (1 of 3 spawns here)
• -1779, 130, -54 (seen once) (1 of 2 spawns here)
• -2099, -9, -45 (seen once) (1 of 2 spawns here)
• -1421, 197, -35 (seen once)
• -832, 35, -15 (seen once) (1 of 3 spawns here)
• -1429, -640, -42 (seen once) (1 of 5 spawns here)
• -1170, -348, -57 (seen once) (1 of 2 spawns here)
• -2064, 30, -47 (seen once) (1 of 2 spawns here)
• -1682, 713, -67 (seen once)
• -1261, -539, -51 (seen once)
• -1445, 1024, -40 (seen once)
• -890, -188, -43 (seen once)
• -2265, -249, -46 (seen once)
• -1917, -671, -42 (seen once) (1 of 2 spawns here)
• -1253, 503, -37 (seen once) (1 of 2 spawns here)
• -1466, 781, -42 (seen once)
• -1461, -244, 4 (seen once) (1 of 2 spawns here)
• -722, -578, -44 (seen once)
• -1466, 100, -38 (seen once) (1 of 2 spawns here)
• -1807, 861, 44 (seen once) (1 of 2 spawns here)
• -970, -746, -59 (seen once)
• -902, -242, -48 (seen once)
• -1827, 632, -55 (seen once)

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.