Species Distributions and Management Status
For this gap analysis, we limited the predicted distributions
of terrestrial vertebrates to habitats within each species’ range
that were rated as 4 or 5, i.e., most of the land-cover/habitat
polygon was classified as moderate to high suitability. The full
table of the proportions of each species’ distribution by management
status level is contained in Appendix 6-1. The table also lists
the total predicted distribution of each species and the percent
of the total land area of the state occupied by this suitable habitat.
For instance, 30.3% of the state (123,727 km²) was predicted to
have suitable habitat for the Black-headed grosbeak (Pheucticus
melanocephalus, WHR code B475—see Figure 3-1). Over 9% of this
habitat is currently in status 1 or 2 managed areas, 31% is in status
3, and almost 60% is in status 4, which is primarily private land.
Only three species have no protection whatsoever. These unrepresented
species are the Inca dove, Bronzed cowbird, and Woodhouse’s toad,
all of which prefer urban or agricultural habitats near the Colorado
River and thus do not require permanently protected reserves for
Several species have very low levels of representation (<5 %)
in managed areas. These species fall into four general groupings:
1) adapted to human-dominated habitats (similar to the unrepresented
species mentioned in the previous paragraph), 2) very limited ranges,
3) marginal to the state, and 4) diminishing or degraded habitats.
Species adapted to human-dominated habitats are generally not vulnerable
to extinction. Most of the poorly-represented birds are in the first
category (Black phoebe, Western kingbird, American crow, Red-winged
blackbird, Hooded oriole, and American goldfinch). Black- and Yellow-billed
magpies commonly feed in agricultural habitats but also depend on
riparian or oak woodland habitat for breeding and cover.
The very narrowly endemic species are best evaluated in a "fine-filter"
approach to complement the "coarse-filter" gap analysis.
The subspecies of Townsend’s pocket gopher found in California is
restricted to the Honey Lake area in Lassen County (Zeiner et al.
1990). The White-footed vole is restricted to a small section of
the north coast of the state. The state- and federally-listed Fresno
(or San Joaquin) kangaroo rat is similarly restricted to remnant
patches of alkali desert scrub in the San Joaquin Valley. Among
the amphibians, these least well-represented taxa tend (Tiger salamander,
Redbelly newt, Siskiyou Mountains salamander, Shasta salamander,
and Spotted frog) to be those that have very small ranges that happen
to be outside of existing managed areas. The Spotted frog may, in
fact, never have occurred in California but may be misidentified
specimens. The Grasshopper sparrow has a wider range than these
other species, but its abundance is erratic from year-to-year.
Species that are widespread outside California should be re-assessed
in ecoregional gap analyses or over their entire range. Marginal
breeding species in California include the Gila woodpecker, Cordilleran
flycatcher, and Cedar waxwing. Northern pocket gopher and pronghorn
are restricted in California to the Great Basin but are widespread
outside the state. The only poorly-represented reptile is the Short-horned
lizard. This species is the most widely distributed lizard in North
America but in California only occurs in the Modoc Plateau region
at the margin of its range (Zeiner et al. 1990).
Those that occur in habitats that are diminishing or are degraded
from neighboring land uses, such as on the south coast or the Great
Central Valley, are generally the most vulnerable group of species
when they have low levels of representation. Swainson’s hawk and
Black-chinned hummingbird were predicted in the Central Valley and
other degraded habitats. The California kangaroo rat is the most
widespread of the mammals in this group, but its range is limited
to grassland in northern California. The range of the Western spadefoot
is relatively large but its grassland habitat has been severely
Table 6-1 summarizes the status information from Appendix 6-1 to
show the number of species in each taxonomic group with <10,
10-20, 20-50, and >50 % of the predicted suitable habitat in
status 1 and 2 managed areas. Of all native vertebrates, the largest
group has 10-20 % in managed areas, with about equal numbers with
<10 and 20-50 %. Very few species have > 50 % protection and
these tend to be species with very small ranges, such as the Alpine
chipmuck (Tamias amoenus), which was predicted over only
444 km², or <0.1% of California’s land area, in the rocky habitats
above 2800 m in the High Sierra.