Every six months on average.
Dogs come into heat every 6 months.
At around 6 months of age.
Every 6 months.
Dogs usually go into heat twice a year, although some individual dogs will go into heat more or less often. Typically, a female will remain in heat for about three weeks, although she will only bleed for the week to a week and a half.
No, spaying eliminates heats and is permanent. A spayed dog will never go on heat again.
Usually once every six months.
Dogs get the heat twice a year.
That is not exactly what happens. See, unlike humans, dogs don't have crushes or anything like that. The female dog goes into heat, and the male dogs smell it and know they are supposed to mate with the girl dog. The boy dog then mates with the girl dog, and usually it is successful and they have puppies.
No. Dogs don't have periods either. Does ("girl" bunnies) go into heat much differently than dogs do; they don't bleed out the vagina before they are really receptive to mating.
heat in sheep
Yes, because sheep can over-heat or get heat exhaustion in the spring and summer if their thick wool coats are not shaved off. Shearing sheep does not hurt the sheep in any way: the benefits actually vastly out weight the costs of sheering sheep.
Should be the same as every other dog. Twice a year.