Diamond spoke with Mary Brophy Marcus. Only dolphins and pygmy chimps. Both wild and captive dolphins have been observed having sex at all times of the female cycle, not just during ovulation. This suggests that it's just for fun.
Pygmy chimps have sex slightly before, during, and after their ovulation.
You write that human sexual behavior is quite different from that of most other animals. The females of most species flaunt their fertility. Numerous monkey species turn bright red, pink, or blue around the vagina. Outwardly, you can't tell when women are ovulating. Muscles tell a woman what she's getting.