My parents have two dogs - one male & one female. Currently the female one is "in heat" meaning she's fertile and ready to go. This has been the fourth time she has been in heat and seeing our two dogs interact has lead to many conclusions.
Firstly sexual intercourse is natural but possessing the knowledge of how to perform sexual intercourse correctly is not. Thanks to the pheromones in the vaginal secretions of my female dog Nala, my male dog Simba is rather 'stimulated' to put it mildly. Every single moment of the day is basically Simba trying to shag Nala doggy-style. Unfortunately he is not very good at doing so. For those who don't know of how this is done, the male dog grabs the female dog at the neck with his mouth, clambers on top of the female dog whilst both are standing and then the male dog inserts his penis into the female dog's vagina leading to sexual intercourse. Unfortunately for Simba that last step doesn't happen and he usually is shagging thin air.
I often hear this happening with people, that young people don't know how to have sexual intercourse. I often wondered how this can be true since I thought sexual intercourse is 'natural' and everybody would assume how to do it. Clearly looking at my dogs and hearing these stories this is not. Probably I assume everybody has watched porn like me and they would know where to insert the cock (I presume they don't insert it up the arse). Probably it is the lack of foreplay, leading to very bad sex - who knows?
Secondly it seems oral sex is quite natural. Simba tends to like at the vaginal area of Nala, probably due to the pheromones in the pussy juices. I don't know if Nala is turned on by this but it seems part of the natural processes.
Thirdly I'm rather glad this doesn't happen to humans. If we had that kind of smelling power as dogs have, rape would be a rather frequent event.