This is a close up of a vine that is called a "monkey ladder." I took this picture while walking on the trail back from the cave entrance in Barra Honda National Park, which has been the subject of my photos during the past week.
My photos of the caves began with the metal, human ladder used to access the cave. I think nature's "monkey ladder" is a more artful design.
Below is a second photo that shows a more distant view of this same vine to give the perspective of how it leads from the ground up to the higher tree branches.
It is easy to see why it is called a monkey ladder. As is common in Costa Rica, during our hike we could hear the low, gutteral calls of howler monkeys.
I am sorry that I do not know the scientific name for the monkey ladder. I could not find it in my reference books.