The Amphibians and Reptiles of Sinaloa, Mexico - Smithsonian ...

AMPHIBIANS AND REPTILES OF STNALOA, MEXICO 87
the temperature slightly cooler than the previous night. There was
no indication of rain that afternoon, although it may have rained
that morning. We began collecting frogs of several species from
choruses congregated at roadside ponds. The second pond visited
contained several hundred Diaglena. Males were calling from about
35 centimeters above the edge of the water or on rocks in the water.
No males were observed calling from the water. There appeared
to be established calling sites around the pond, Most of the calling
males were spaced about 50 centimeters apart on the bank. Several
amplexing pairs were noted swimming in the water; amplexus is
axillary. Some of the pairs were put in gallon jars and remained in
amplexus for several days. We encountered many more Diaglena
hopping toward the pond as we returned to the road. When the
lights of the field vehicle were turned on, amphibians were seen
everywhere on the road. The high density of frogs extended for
nearly 5 miles. Diaglena were very abundant; an estimate of a
thousand individuals is considered conservative. The road was dry
at the time. Although no males were calling from the road, twelve
pairs in amplexus were collected as they hopped along the pavement.
The ditches on each side of the road were full of water 50
to 100 centimeters deep. Breeding in the same ditches with Diaglena
were several other amphibians, including: Scaphiopus couchii, Bufo
kelloggi, Bufo mazatlanensis, Hypopachus oxyrrhinus, Gastwphryne
olivacea, Phyllomedusa dacnicolor, Pternohyla fodiens, and Similisca
baudinii. The following night we returned to the area only to find
the breeding ponds deserted. Except for the eggs and tadpoles
there was no sign of the previous night's activity.
On July 8, 1963, the first author collected 17 specimens (KU
75273-89) in rain pools in association with Scaphiopus couchii,
Pternohyla fodiens, Smilisca baudinii, Phyllomedusa dacnicolor,
and Hyla smithi. Some males were calling and one pair was found
in amplexus. No specimens have been collected later than August 20.
Peters (1955:1) reviewed the current knowledge of frogs of the
genus Diaglena and pointed out that breeding activity of D. reticulata
in Michoacan apparently is correlated with the first heavy
rain of the year. Duellman (1960:59) mentioned choruses of D.
reticulata immediately following torrential rains. The enormous
breeding population of this supposedly rare hylid that was encountered
near La Cruz suggests that the paucity of specimens is
due to poor tuning on the part of collectors. While the exact
ecologic stimulus for breeding remains unknown, we suspect that a