BREEDING BIOLOGY 
OF THE MEXICAN LEAF-FROG
page 2 of 3
by T. A. Wiewandt
reprinted with permission of the author from Fauna magazine, March/April, 1971

Three hours before sunrise the female crawled to the water's edge and settled down in the mud with her posterior end in the water for almost an hour. She then climbed a small tree nearby where four males had spent the night calling. The four jumped on her but failed to catch a hold as she and her partner approached, and she reacted immediately by rapidly walking away. Still carrying her partner, the female leaf-frog later returned to the same site twice, her visits eliciting similar behavior from the males there. She had apparently selected that location to deposit her eggs. Near dawn, as the pair approached the chosen site on the branch of the tree for the third time, the males resumed their jostling for favorable positions on the female. Each male objected by "purring" continuously if clasped by a fellow male, but all quieted immediately when the female began laying her eggs.

female leaf-frog depositing a 
second egg clutch and 
manipulating the leaves
to secure her eggs
egg mass of the leaf-frog 
four days after deposited 
in a papache tree 
(Randia echinocarpa)
While hanging from the slender branch by her massive forearms, she released a clear, shimmering, gelatinous stream containing regularly spaced, pale green, spherical eggs. Each egg was ejected in assembly line fashion with successive contractions of her cloaca and all four males contributed sperm to the emergent egg mass. The sticky mass adhered to the twigs and leaves, which she periodically manipulated with her dangling hind legs to secure the eggs to them. The eggs and tiers of fushing jelly formed a pendant, ovoid mass of approximately six by three and one-half centimeters measured along the axes. I saw no sign that the males used their hind legs to help guide the emergent egg mass onto the leaves, although such behavior was recently observed in a Mexican leaf-frog population in Nayarit by Dr. W. F. Pyburn of the University of Texas.

Twenty-five minutes after she had begun laying, the female descended the tree headfirst while carrying a different male with her. She had left about two hundred eggs. The pair moved to the pond, where the female again settled down in the mud with only her posterior end submerged in the water. Later she made two more visits to her spawning site in the tree, both times depositing additional eggs which were fertilized by males as she laid them. Altogether, in the course of three and one-half hours, the leaf-frog deposited a total of about five hundred eggs. She interrupted that activity by two visits to the pond where she submerged her posterior end.

The female's behavior at the pond is significant. As I suspected, and Dr. Pyburn demonstrated experimentally, the female Mexican leaf-frog must take up additional water through the cloaca for successful oviposition. While in amplexus, or the mating embrace, the female fills her bladder with water which in turn is released as she deposits the eggs. An empty bladder stimulates her to cease

laying and return to the pond for more water. The water supplied from the frog's bladder is a necessary component of the gelatinous matrix of the egg mass. Captive females deprived of free water laid eggs that failed to swell and develop properly.

Shortly after sunrise as the air began to warm from a pleasant nighttime low of 73' to temperatures near 80'F, the males, unless actively engaged in breeding, retired to their diurnal retreats.

Most found shelter in rodent burrows, mainly those of spiny pocket mice (Liomys pictus) that were plentiful along the banks of the pond. While at rest in the moist, cool burrow a male frog does not tolerate intrusion by his fellows. When another male enters, the occupant promptly evicts him by squawking, jumping on and attempting to clasp him, or even by chasing him for a few inches outside the burrow.
 It appears that male Mexican leaf-frogs congregate at ponds and defend their daytime retreats only during the breeding season and disperse thereafter. Toward the end of the season in August, I found a male I had previously marked calling about twenty feet away from the pond, and another was in an open cornfield some 125 feet distant. Mexican leaf-frogs have been seen in early spring sitting or creeping about, perhaps in search of food; but throughout hot, dry periods they are surely forced to seek more humid conditions underground, beneath the litter of fallen leaves or under logs.

While studying leaf-frogs in July and August, I located twenty spawning sites, all at the same pond, and observed nine females. Six of the females were in amplexus and I witnessed four of them depositing eggs. They all behaved very much as the first pair had. They began breeding in early July and continued with remarkable uniformity throughout the summer until August 19th when the last gravid female arrived at the pond. Such prolonged breeding activity is characteristic of many species adapted to tropical conditions.

To Leaf-frog page 3