I don't know if this would apply to leos but from my mammal experiences, you keep a lot of female dogs together and eventually they will all go into heat around the same time, birth at the same time if bred, etc. I notice the same thing with my rabbits 'cept they don't go into heat but they all seem to want bred at the same time, and birth the same times. Same thing when I use to go to summer camp. All the girls in my cabin would start to have their cycles the same time. My hubby said it best yesterday "put a bunch of gals together and they'll start doing everything the same, bleed, bitch, birth, you name it".