Thermotaxis refers to sperm migration towards:
Thermotaxis enables sperm to detect subtle temperature gradients along female tract and migrate toward warmer regions. Ovulation raises ampullary temperature by approximately two degrees compared to cooler isthmic reservoir where sperm are stored. Sperm express thermosensitive channels including TRP family members and rhodopsin that translate thermal cues into intracellular calcium pulses altering flagellar bending. Directed movement toward warmth guides sperm over centimeters toward recently ovulated oocyte, bridging gap between long-range rheotaxis and short-range chemotaxis during narrow reproductive window for effective fertilization and conception success.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Thermotaxis and sperm migration toward warmer oviductal gradients.