In the last two months, the BLM rounded up all of the wild horses. Of about 160 horses, 109 were returned to the desert valley. All of the mature females were branded with the BLM brand and treated with a birth control. Although the pregnant mares were also treated with the birth control drug, it did not affect their current pregnancies. Many have since given birth since being released.

From what I understand, the infertility drug will wear off in about four years.

As I was filming this sequence a week ago, it made me a little sad that we may not experience it again for quite a few years.