Kylie Jenner and Kendall Jenner take part in the Dolphin Trainer For A Day at the Mirage hotel. Credit: Albert Michael/

Kendall and Kylie Jenner make friends wherever they go.

The newest addition to their entourage? A couple of dolphins, whom they swam with during a trip to Siegfried and Roy's Secret Garden and Dolphin Habitat at the Mirage hotel in Las Vegas earlier this month.

Kendall, 16, and Kylie, 14, worked on their dolphin-training skills -- helping one learn some dance moves, giving one a peck on the nose, and hitching a ride on the fin of another.

While the Jenner girls hung out in Vegas, their older sister Kim Kardashian has been busy jetting around the globe with love Kanye West. Though they've only been together since March, their romance continues to heat up -- most recently, the pair have been talking about taking a major step together.

"They're seriously talking marriage," a source tells Us Weekly of the reality star and her rapper beau. "And yes, she would accept [his proposal]."