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

64 UNIVERSITY OF KANSAS PUBLS., MUS, NAT. HIST.
habitats created by irrigation projects associated with the tremendous
agricultural development in the Los Mochis and Guasave
areas. This is especially true of the frogs Leptodactylus occidentalis,
Rana catesbeiana, and R. pipiens, and the snakes Leptodeira punctata,
Natrix v. valida, and Thamnophis cyrtopsis collans.
Most of the amphibians are nocturnal and generally are found
close to permanent water. Many of the lizards, however, including
several species whose ranges he primarily in northern desert regions,
are diurnal and terrestrial. Characteristic species exhibiting this
distributional pattern are Dipsosaurus dorsalis, Urosaurus ornatus,
Phrynosoma solare, Sceloporus magister and Cnemidophorus tigris.
Nocturnal lizards with similar distributions to the north are Pkyllodactylus
homolepidurus and Heloderma suspectum.
With the exception of the three species associated with irrigation
ditches and the two large diurnal racers, Masticophis ftagellum and
M. striolatus, snakes are not particularly abundant in the thorn
woodland zone.
Tropical Semiarid Forest.—Semiarid forest is the most extensive
plant formation in Sinaloa, covering nearly one-half of the state.
The number of amphibian and reptilian species is correspondingly
large. Of the 96 species and subspecies recorded from this zone,
43 are considered abundant.
The amphibians that were listed as abundant in the thorn woodland,
as well as the following species, are abundant in the semiarid
forest: Bufo marmoreus, Hyla smithi, Phyllomedusa dacnicolor,
Pternohyla fodiens, Smilisca baudinii, and Gastrophryne olivacea.
Hylid frogs constitute the major additions.
Among the lizards, the increase in relative density of Anolis nebulosus,
Ctenosaura pectinata, Iguana iguana, Sceloporus nelsoni,
Urosaurus bicarinatus, and probably Eumeces callicephalus is correlated
with the increase in vegetation density and number of
suitable habitats therein.
Several species of snakes are more abundant in the semiarid
forest than in the thorn woodland. Included are Boa constrictor,
Drymarchon corais, Elaphe triaspis, Imantodes gemmistratus, Lampropeltis
triangulum, Leptophis diplotropis, and Oxybelis aeneus.
The appearance or increase of these species probably reflects change
from a dry to a more moist environment. Several of these species
are primarily arboreal and appear in response to the greater complexity
and density of the semiarid forest vegetation.