Foothill Yellow-legged Frog - Mating Habits

Mating Habits

The mating “ceremonies” begin in spring where adult frogs congregate on sandy and/or rocky bars to mate. It was previously believed that they did so from March to May, but recent experiments have determined that time to be closer to April to late June. High stream velocities, however, may dislodge R. boylii egg masses from oviposition substrates. Thus, R. boylii avoids rapid waters to protect the egg masses from being swept away. This technique is why the species has a wide window for breeding season. If the conditions are not perfect to their standards, they will refuse to mate and will wait until the water velocities go back down to ideal.

For the Foothill Yellow-Legged Frog, the oviposition, or the depositing of eggs, is somewhat sporadic because delays such as rains could cause problems like unwanted removal of eggs. The males also perform mating calls mostly underwater, and those above the water are faint and hard to hear over fifty meters. After the frogs have successfully mated, the egg masses are ovipositioned about half a meter down in the river and with flow velocities ranging from 0.1 to 0.6 m3/second. These egg masses can be anywhere from 100 to 1000 eggs in one batch. They are contained in a bluish gel that disappears once the eggs take on water, and the dark ovum, center of egg, is covered by three jelly envelopes that are about 5.4 mm in diameter. Eggs hatch in about five to over thirty days depending on the temperature that the mass is at and the surrounding water. The tadpoles continue to stay associated with the egg mass for several days, and continue to need higher temperatures to grow quickly. By the time the tadpoles reach about forty millimeters, roughly 1 and a half inches, they are adults and their reproductive organs are mostly functional. The frogs are usually fully developed by the summer after their first metamorphosis, though some begin breeding after six months.