SANTA CRUZ GOPHER SNAKE
Pituophis melanoleucus pumilus
Description: A medium-sized (70-110 cm), yellow or cream-colored snake with black, brown, or reddish dorsal blotches, and smaller secondary dorsal blotches (Klauber 1946). Undersurfaces are nacreous white or cream often becoming somewhat yellow on the throat and ventral surfaces of the neck and tail with three rows of dark spots along the sides of the body. The iris is dark brown (pers. observ.).
Taxonomic Remarks: Pituophis melonoleucus pumilus is a dwarf subspecies of gopher snake that can be distinguished from other subspecies of P. melanoleucus in California based on the presence of > 29 dorsal scales rows at the mid-body. It is thought to be most closely related to one of the two adjacent mainland forms, P. m. annectens and P. m catenifer (Klauber 1946). Although it is considered a valid taxon (Sweet and Parker 1990), verification of the validity of this taxon on other than morphological grounds has not been addressed (see Collins, ms). Genetic variation within P. m. pumilus has not been examined and should be studied to evaluate its distinctiveness. The scientific name of this taxon is often incorrectly spelled as "P. m. pumilis" in the literature (e.g., see Stebbins 1985 and Collins, ms).
Distribution: This California endemic has only been recorded on Santa Cruz and Santa Rosa (Orr 1968) islands off the coast of southern California (Wilcox 1980; Figure 46). The statement by Stebbins (1985) of this taxon occurring on San Miguel Island is based on an unverified sight record (P. Collins, pers. comm.). The known elevational range extends from near sea level to 640 m (on Santa Cruz Island).
Life History: Allowing for its smaller body size and the depauperate island fauna where it occurs (see Wenner and Johnson 1980), this island-dwelling gopher snake has a life
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history
that is anticipated to be similar to gopher snakes found on the adjacent
mainland (e.g., see Fitch 1949). In spring, juveniles and adults emerge from
rodent burrows or rock fissures, where they hibernate during the colder months
of fall and winter (P. Collins, pers. comm.). Adults probably reproduce in May
with females depositing clutches from late June through July and hatchlings
emerging in September and October (Van Denburgh 1898, Stebbins 1985; P. Collins,
pers. comm.); the reproductive ecology of this taxon is currently being studied
(R. Fisher, pers. comm.). Santa Cruz gopher snakes are probably surface active
during the day whenever temperatures are high enough to elicit movement (see
Rilthling 1915). Because the island fauna is depauperate, the prey base
available to gopher snakes is limited. Potential prey are limited to southern
alligator lizards (Elgaria multicarinata), westem fence lizards, side-blotched
lizards, deer mice (Peromyscus maniculatus), western harvest mice (Reithrodontomys
megalotis), and a variety of land birds (Diamond and Jones 1980, Wenner and
Johnson 1980, Laughrin 1982). Of these, adult Santa Cruz gopher snakes probably
consume mice, adult lizards, and the eggs or nestlings of the birds that are
small enough to eat, whereas juvenile gopher snakes probably take juvenile
lizards, mouse pups, and possibly insects (e.g., Jerusalem crickets,
Stenopelmatus sp.; Laughrin 1982). Island foxes (Urocyon littoralis: Laughrin
1977) occasionally eat Pituophis m. pumilus as do feral pigs (Sus scrofa),
red-tailed hawks, and common ravens (Laughrin 1982; P. Collins, pers. comm.). A
captive-bom snake lived for 16.5 years in captivity (P. Collins, pers. comm.).
Data are lacking on the growth or movement ecology of this taxon.Habitat: Pituophis m. pumilus, like its mainland congeners, is a habitat generalist. It can be found in all vegetation associations on the two islands, but it is most common in open areas such as grasslands, dry streambeds, and oak and chaparral woodlands (Laughrin 1982). No data are available on either overwintering or oviposition sites.
Status: Special Concern; introduced ungulates, which destroy and modify the vegetative cover, and feral pigs, which eat snakes, continue to threaten the Santa Cruz gopher snake on both islands on which the latter occurs. Gopher snakes are rare on Santa Rosa Island, yet are still relatively common on Santa Cruz Island for reasons not well-understood (Laughrin 1982; Collins, ms.; P. Collins and R. Fisher, pers. comm.).
Management Recommendations: Exclusion fencing needs to continue as long as feral livestock threatened the native fauna (and flora) on any of the Channel Islands. Particular effort should be made to remove wild pigs from islands on which this taxon occurs because of the greater degree of destruction wild pigs can inflict on snake populations and habitat. Even after threat from the feral fauna has been alleviated, Santa Cruz gopher snake populations need study to gain a better understanding the natural history of these island populations. Emphasis should also be placed on reevaluating its taxonomic status via genetic and morphometric techniques. Much basic data, including that on distribution, habitat affinities, abundance, reproductive biology, food habits, and factors affecting mortality are needed to improve management guidelines for this taxon.