57
the La Mota Mountain region ofTrans-Pecos Texas.
TEXAS JOURNAL OF SCIENCE 5W:
^03-415.Thegeomorphology, topography, vegetation and climateofthe area are described in detail. 8 vegetational-topographical associations are described, and the lizardspecies found in each are listed. Cnemido- phorus inornatus is found only in the ocotillo-catclaw association of mesa tops. _C. tesselatus is the most widespread species, occurring in 7 associations. The confusion over the type-locality of this species is detailed, and is herein restricted to "Pueblo, Pueblo County, Colo- rado: collectedon the morningof 19July 1820 near the mouthofCastle Rock Creek (probably =Fountain Creek)." C.tigrismarmoratus wascol- lected from ^-association. It was more numerous than C. tesselatus in
twoofthem andlessnumerousinthe other two; about equalnumbersof the two species were collected in the i4- associations. Biogeographical relationships are discussed.
15*.
—
. 1957a. Observations on the natural history of ^ species of whiptail lizard, Cnemidophorus (Sauria, Teiidae), in Trans-Pecos Texas.58
out the area; interspecific competition is implicated. Plains habitats are preferred by gularis, inornatus and tigris whereas roughland habi- tats are preferred by exsanguis and tesselatus. Competition betweena species in its preferred habitat and one "invading" it (i.e. not in the invader's preferred habitat) almost always occurred between a sexual and a parthenogenetic species. Intraspecific aggression occurred, par- ticularily in inornatus, but not on a predictable basis. Interspecific aggression did not occur, although lizards did meet and notice one an- other. Territoriality was not evident. It was found that a meeting between two lizardsisnot a
common
occurrenceevenwherelizards are numerous. Species and geographic differencesexisted inpreyconsump-tion; in general, Isoptera
>
Orthoptera > Coleoptera>
Lepidoptera>Hemiptera. Termites are byfarthemostimportant food item and
may
be regarded as the staple food for all species; indeed, the genus is adap- ted morphologically for this. Competition for the staple food sourceis the only obvious explanation for the ecological separation of the species, because size differences and alternate food differences do not allow them to coexist. Differences in foraging activities reflect tem- perment; inornatus is not easily excited whereas tigris is very nervous and wary, the other species falling between these extremes. Lizards are active only when soil temperatures range between 30-50°C.
No
interspecific differences in reproduction were observed; multiple clutches are indicated.
No
competition exists with other lizard genera, they are essentially ecologically invisible. It is possible that individual Cnemidophorus species that are in competitive asso- ciations mutually inhibit their own potential increase more than that of the other species and thus can continue to coexist. If, as pre- sumed in this study, no species has an advantage or if reciprocating ones exist, itmay
be predicted that all 5 species will continue to exist in the Chihuahuan Biotic Province, but weight of numbers or chance will eventually remove all but oneof them from any given as- sociation within the province.156.
—
. 1958.A
list of arthropodsfound in the stomachs of whip- tail lizards from four stations.TEXAS
3.SCIENCE
lO(^): ^^3-'f'f6.A
list as precise taxonomically as possible of the food items eaten by ll'fl lizards (exsanguis, gularis, inornatus, tesselatus and tigris) is presented. Taxa are indexed relative to lizard predator and specific locality.No
millipedes or lubber grasshoppers (Taeniopoda eques) andonly 1 meloid beetle were eaten, indicating unpalatibility.157.
—
. 1959. Drift-fence trapping of lizards on the Black Gap Wildlife Management Areaof southwest Texas. TX. 3. SCI. 11:150-157.Themethod of trapping and weather conditions in the mesquite- huisache association are described. Cnemidophorus inornatus,_C. tigri:
andfour otherspecies weretrapped.
No
inornatuswererecaptured. 3159
tigris were marked and 23 recaptureda total of 8^^times. One individ- ualrecaptured17times hada
home
range of.53 acresbased on theout- er polygon method. It wasnotedthat tigrismakes alowclickingsound when handled.158.
—
. 1960. Supplementarynotes on the herpetofaunaofthe Stock- ton Plateau.TEXAS JOURNAL OF SCIENCE
12(3/if): 228-231.Cnemidophorus gularisand_C.inornatus, which occurinthe cedar- savannah association on mesa tops, were virtually wiped out by a 10- year drought while_C. tesselatus went from virtually absent to quite abundant.
159.
—
. 1961a. Observations of the activities of small animals (ReptiliaandMammalia)on aquadrat in southwest Texas.AMERICAN MIDLAND NATURALIST
65(1): 127-138.Drift-fence trappingwasdonefor 5weeksbeginninginJune 1 mi.
E. of Alpine, Brewster County. Thevegetation of the quadrat, located in the short-grass—mesquite association at ^600 feet, is described.
Weather during the study period is described. ^7 female and 32 male Cnemidophorus sacki (= exsanguis + gularis) were marked and released.
51 lizards were recaptured at least once for a total of 156 recaptures.
Theaverage
home
rangewas .34(.25-.43)acres; lizardswere apparently not territorial.A
modified Lincoln Index gave a density estimate of 20-25 resident lizards per acre.One
lizard was eaten by the snake Hypsiglena torquata. Foraging behavior is described; lizards were ob- served to feed upon scorpions, grasshoppers, termites, candleflies, le- pidopteran larvae, and ant lions. Lizards emit an audible squeakwhen picked up.160.
—
. 1961b. Competitive relations in lizard populations. _inVERTEBRATE
SPECIATION, Blair, W. F., editor. University of Texas Press, Austin, pp. 460-489.Four species of Cnemidophorus in Trans-Pecos Texas (inornatus, sacki (= exsanguis + gularis), tesselatus and tigris) appear to present an exampleof competitionintheabsence ofan advantage. They occur sympatrically within this region, although all 4 species are seldom found at any onelocality, and rarely do more than 2 species occur in equal concentrations. Furthermore, no twospecies appeartooccupy the same ecological associations in the same areas, although all 4 species do appear to occupy the sameecological niche. Thediets of all4 spe- cies are similar and have the samestaple food items. There is some active intraspecific but no active interspecific competition. Foraging abilities appeartobe equal or complementary, and activity periods and
60
reproductivepotentials appeartobe the same. Thegeographicand eco- logical distributions of whiptails in southwest Texas imply that, al- though all ^ species are capable of living in most of the ecological associations ofthe ChihuahuanDesert, no twoof thespecies can simul- taneously do so successfully.
161. —. 1965. Changes in competing populations of whiptail lizards (Cnemidophorus) insouthwestern Texas.
AMER.
MIDL. NAT.73(1):75-80.Population studies of _C. inornatus, _C. septemvittatus, and _C.
tigris done at the Black Gap Wildlife Management Area in 1952 were repeated in 1962. The area had recoveredfrom asevere drought during that time span. Cnemidophorus tigris increased in density in the eco- logical association it dominatedin 1952 as well as in the associations dominated by the other twospecies. Population estimates were 17.85 /acre and 7^.3/acre for 1952 and 1962, respectively. The two other species were quite rare in 1962. Changesindiet are documented; lepi- dopteran larvae had increased and termites decreased in importance.
The evidence suggests a tigris "bloom" and superior short-term compe- ting abilityoverthe other twospecies based on sheer numbers. _C._in-
ornatus and_C. septemvittatusare relegatedto morexeric, lessproduc- tive habitats.
162.