They are tiny. Most are only about 2 cm (1 inch) in length, and large ones get to about twice that size.
Poison dart frogs display remarkable parenting behavior for animals other than mammals and birds. Their courtship ritual includes the male calling a mate, then she follows him to a suitable site for laying eggs, usually a moist leafy area. After some foreplay rubbing and touching, the eggs are laid and fertilized. This rather typical frog behavior is followed by something very unusual.
Either the male or female stays with the eggs to guard them until they hatch into tadpoles. The parent will then pick up the tadpoles and carry them on his or her back up a tree and deposit the tadpoles in the little pools of rain water that gathers in the the central areas of bromeliad plants. Even more amazing, the female frog will return to the tiny puddles of rain water and deposit unfertilized eggs for the tadpoles to eat.
How many amphibians or reptiles care for their young with such devotion? Even the fathers are involved. One difference between the fathers and mothers is that when they carry the baby tadpoles up the trees to the bromeliad sisterns, make frogs will carry up to 6 tadpoles at a time, but mothers will carry only 1 or 2 at a time. I guess the males must have better upper body strength from all those years carrying the trash out of the kitchen on trash collection day.
I previously mentioned how Tortuguero gets so much rainfall each year. The rain and humidity are obviously necessary to maintain the supply of water in the little pools in the plants to nurture the tadpoles.
Please excuse the quality of the photos. The forest canopy is thick, so I took the photos in low light and zoomed in, which narrowed the depth of field. The top photo is cropped to enlarge the frog. The second photo shows the full frame. I did not want to get closer and disturb the frog.
I will show another poison dart frog in a few days.