A male follows this female. As you will note from the photo, he is already sexually aroused and the female has her tail partly raised.
This tail scratching behaviour is common among kangaroos wishing to mate, and the female often responds favourably to it. It has been described as a kind of "kangaroo foreplay".
The classic mating photo. The male leans back slightly on his tail and holds the female in place with his powerful forearms. The female leans forward on her arms to afford better access to her cloaca.
Here is a somewhat less chivalrous male who was rather rough with his beau, frequently scratching at her head. It's worth pointing out I never saw him actually achieve penetration, although the female did put up with this behaviour for longer than I would have.
The male's prehensile penis helps him to get past the large tail.
The exact moment of release. This is a photo from an earlier coupling I observed; the pair who provided the new improved photos were engaged for so long that I missed out on photographing the actual event. The female was clearly getting more and more impatient and in the end gave an angry grunt and broke free.
The disappointed male was left to his own devices while the female hopped a short distance away. If you look closely, you will see blood coming from the female's cloaca, which explains why she was getting so impatient. Although it did appear to cause her some pain, this is not indicative of an injury; bleeding is a fairly common event for female kangaroos after copulation.
The female licked her pouch and cloaca vigorously.
She ended up smearing some of the blood on her fur.