Geography Reference
In-Depth Information
the pinyon mouse and desert woodrat, give way to more typical grassland in-
habitants, such as the California meadow mouse, harvest mouse, and Pacii c
kangaroo rat.
Where outright changes in species occurrence do not result, the barriers
to movement inherent in a city, such as freeways, reservoirs, and channeled
rivers, often af ect the genetic composition of mammals that remain. Coyotes
and bobcats live on either side of the Ventura Highway that cuts through Los
Angeles. Though many animals cross the freeway, few from the east side of
the road successfully breed on the west side, and vice versa. Dispersers have
dii culty breaking into the breeding population because when animals cross
the road, they immediately encounter a dense wall of breeding territory own-
ers; territories seem especially to pack up against either side of the highway.
The result is that the road disrupts gene l ow among the coyotes and bob-
cats of Los Angeles, and slight genetic distinctions between east and west
are apparent.
Amphibians and reptiles, or what we science geeks call “herps” (from “herpe-
tology,” which is the study of amphibians and reptiles), fare even worse than
native mammals in urban settings. Around the world, the diversity of these
animals plummets in the city. Losses of native herps are not balanced by gains
in nonnative, urban adapters. There are few examples of apparently benign
introductions of anoles, geckos, and lizards in cities and luckily just as few
devastating examples of nonnative snakes invading sparsely inhabited ecosys-
tems, such as the limestone forests of Guam or the Everglades of Florida. Most
of the missing herps of subirdia are snakes and salamanders; some lizards,
turtles, and frogs are usually retained. A few tolerant ones—northern brown
snakes, bullfrogs, and red-eared sliders in the eastern United States; oblong
