This mother mule deer in Arizona, doting and attentive just a week before, warns her young buck away. Why?

It turns out she is pregnant with a new fawn, and that she’s taught the year-old buck all she can about survival. Her hormones have kicked in, and her brain is wired for the survival of the new fawn growing inside. After the new fawn is up and walking about, she will accept the young buck, again, but will still display her dominance.

Nature can, indeed, be tough to watch – especially as this buck is smaller than usual due to severe drought conditions the year prior.