This is common for frogs. Males attach themselves to the backs of females when the female's eggs are mature. The male fertilizes the eggs as they emerge from the female. He will not leave until all of the eggs have been laid, usually 30 - 50 pale eggs. This process may last for a day or longer.
Reproduction takes place on the underside of leaves.
The female must hold on with her suction cup toes. As each clutch emerges from the female she must enter the water and fill her bladder with water. If she does not, the next clutch of eggs to emerge will dry up and die. When the females enter the water, it's sort of like entering a war zone for the male, who is still attached to her back. If other males see the couple, they may try to fight the male off of the female and take his place.