I can't say I've ever seen this particular behavior before. This is not the first…
I was surprised this meandering mare even noticed this passing tarantula. She briefly lipped the spider, and passed over it, probably narrowly avoiding a painful bite. Once cast aside, sheer luck spared the tarantula a smashing from her stepping hooves. After this hoof, then another, the spider negotiates a few other passing mares, is spared again and again, and goes about it’s charmed tarantula life.