Also known as road trains, or land trains.
Dr. Carter is a well known (at least in academic circles) as an Indiana Jones-esque scholar of the occult and professor of pre-human culture, a Mars born swashbuckler in her youth, now a tenured and crafty acquisitionist.
A slight rustle of the wind... and it stands before you. A Unicorn, whiter and more beautiful than you ever imagined it. It has deep wonderful eyes, and you can't help but admire this creature. It came to have a look at you, and now it freely goes. You have not the heart to stop it, and it silently vanishes between the trees.
Note: unless specially needed, this encounter should never happen again.