Sceloporus Graciosus Research Articles

Orientation and homing behavior as a measure of affinity for the home range in two species of Iguanid lizards

AbstractThe relationship between home range affinity and homing ability was studied in Phrynosoma douglassi and Sceloporus graciosus in southeastern Idaho. Movement patterns for P. douglassi were typical of an animal moving from one site of activity to other sites, whereas S. graciosus movements were typical of an animal using a single site of activity. Only S. graciosus was able to orient towards the home range when displaced, indicating an affinity for this site. Adult S. graciosus oriented and homed more consistently than did juveniles. P. douglassi did not orient homeward when displaced and returned less frequently than did S. graciosus. Recapture locations along with data regarding homeward orientation and homing indicate that P. douglassi has a lesser affinity than does S. graciosus for the home range. Some gravid females of both species left the home range to deposit eggs or young and later returned. Use of areas outside the home range for egg-laying and birthing and movements out of the home range resulting from chases by predators may represent natural means of displacement that select for homing behavior. Because most lizards experience only short displacements during their life histories, long distance homing reported for snakes, turtles, and salamanders is absent.

Perch Height Selection by Juvenile Sceloporus Lizards: Interspecific Differences and Relationship to Habitat Use

Perch height selection was studied in juvenile western fence lizards (Sceloporus occidentalis) and sagebrush lizards (Sceloporus graciosus) in the field and in the laboratory. In nature juvenile S. occidentalis were more arboreal than were juvenile S. graciosus. In laboratory experiments with lab-reared 3-4 wk old lizards, S. occidentalis perched off the ground more frequently. Differences between these two species in habitat preference are inferred to be at least partly innate, and emerge at an early age. Within each species, juveniles from different field populations differed in habitat use in the wild: lizards were more terrestrial at higher elevations. However, lab-reared juveniles from different populations of each species did not differ in laboratory tests of perch selection. In S. occidentalis there was evidence of individual variation in perch selection in the laboratory, but no among-family variation was detected.

Larval nematodes (Ascarops sp.) in stomach granulomas of the sagebrush lizard, Sceloporus graciosus.

Wild populations of the sagebrush lizard (Sceloporus graciosus) are reported as paratenic hosts for third stage larvae of Ascarops sp. Larvae were found in stomach submucosal granulomas which averaged 350 microns in diameter and consisted of histiocytes and layers of fibrocytes. Prevalence of infection was 16% (27 of 170 infected); mean intensity was 3 (1 to 8 nematodes/host). Prevalence was significantly higher in male than female lizards.

Physaloptera retusa (Nematoda, Physalopteridae) in naturally infected sagebrush lizards, Sceloporus graciosus (Iguanidae).

Of 292 adult sagebrush lizards (Sceloporus graciosus) examined for the stomach nematode, Physaloptera retusa, 81 (28%) were infected. Attached nematodes caused erosive inflammatory foci in the stomach mucosa. Early lesions were U-shaped. Degenerating gastric glands occurred in the adjacent mucosa. Healed lesions were fibrous connective tissue scars; regenerating gastric glands occurred at the periphery. There were no externally visible signs of infection.

Venom Ontogeny in the Pacific Rattlesnakes Crotalus viridis helleri and C. v. oreganus

Ontogenetic variation in venom composition was examined in the Pacific rattlesnakes Crotalus viridis helleri and C. v. oreganus. Venoms were analyzed for protease, phospholipase A2, L-amino acid oxidase, exonuclease and elastinolytic activities, and toxicity toward a native prey (Sceloporus graciosus). Protease activity increased significantly with size; L-amino acid oxidase and exonuclease activities also tended to increase. Phospholipase A2 activity decreased significantly with size, as did venom toxicity. These factors produce a highly toxic venom with low protease activity in juvenile snakes, which facilitates efficient handling of lizards and young rodents. Analysis of gut contents of museum specimens showed that lizards constitute a major fraction of prey taken by juvenile rattlesnakes. Lizards continue to be taken with high frequency until snakes reach approx. 500 mm in total length; above this size, mammals are taken exclusively. As snakes increase in size, they feed on larger mammalian prey, and a functionally different venom is produced. Venom from adult Pacific rattlesnakes is less toxic but has high protease activity, aiding in the digestion of prey in a thermally variable environment.

COMPARISON OF POPULATION STRUCTURE IN CHROMOSOMALLY POLYTYPIC AND MONOTYPIC SPECIES OF SCELOPORUS (SAURIA: IGUANIDAE) IN RELATION TO CHROMOSOMALLY-MEDIATED SPECIATION.

Sceloporus grammicus has been used as an example of stasipatric speciation, and some models of chromosomal speciation have assumed that the fission rearrangements which distinguish the chromosome races within this complex are negatively heterotic in the heterozygous state. Consequently, such rearrangements are assumed to be fixed by drift in small, inbred populations. Allelic variation at 19 presumptive gene loci was examined in 13 samples of a chromosomally conservative congener, Sceloporus graciosus, and was compared to an equivalent data set for the chromosomally polytypic S. grammicus. Several estimates of population variability and structure were calculated, and results were inconsistent with models of extreme population subdivision and/or frequent bottlenecks and extinction-colonization events in S. grammicus. For example, mean level of heterozygosity and mean number of alleles per locus were significantly higher in S. grammicus than in S. graciosus, while the average genetic distance (D) was significantly higher in S. graciosus. These results are considered in light of expected "Wrightian" population genetic parameters, and we conclude that S. grammicus does not seem to have the population structure necessary for the fixation of strongly negatively heterotic rearrangements.

Two aberrant karyotypes in the sagebrush lizard (Sceloporus graciosus): Triploidy and a "supernumerary" oddity

Two aberrant karyotypes in the sagebrush lizard (Sceloporus graciosus): Triploidy and a "supernumerary" oddity

Thermal ecology and activity patterns of the short-horned lizard (Phrynosoma douglassi) and the sagebrush lizard (Sceloporus graciosus) in southeastern Idaho

A mark-recapture study of the short-horned lizard (Phyrnosoma douglassi) and the sagebrush lizard (Sceloporus graciosus) was performed from 1976 to 1977 in southeastern Idaho. Both species had mean cloacal temperatures of approximately 33 C. However, P. douglassi had more variable cloacal temperatures, particularly during morning and evening periods. This was caused by differences in sleeping sites chosen by the two species. Adults of both species were active from mid-April through late August, with peak activity in June. Juvenile P. douglassi displayed a seasonal activity pattern similar to that of adults. Juvenile S. graciosus were most active later in the year (August), when adults were disappearing. In both species, young-of-the-year appeared in early to mid-August. Adult and juvenile P. douglassi were active during all daylight hours and displayed no activity peaks, whereas young-of-the-year displayed a bimodal activity pattern. Adult and juvenile S. graciosus were active over all daylight hours but had peak activity between 1200 and 1500 h. Ants (Pogonomyrmex) were the lizard's principle prey. However, only young-of-the-year P. douglassi had activity patterns that paralleled that of ants on their mounds. 22 references, 4 figures.

Rapid Development of the Clonal State in Successive Gynogenetic Generations of Carp (Cyprinus carpio)

DERICKSON, W. K. 1974. Lipid deposition and utilization in the sagebrush lizard, Sceloporus graciosus: its significance for reproduction and maintenance. Comp. Biochem. Physiol. 49A:267-272. . 1976. Lipid storage and utilization in reptiles. Amer. Zool. 16:711-723. DUNHAM, A. E. 1978. Food availability as a proximate factor influencing individual growth rates in the iguanid lizard, Sceloporus merriami. Ecology 59: 770-778.

Energy expenditure in free-ranging sagebrush lizards (Sceloporus graciosus)

Metabolic rates of free-ranging Sceloporus graciosus (Sauria: Iguanidae) were measured during the summer using doubly labeled H2O. Adults of either sex and juveniles did not differ in field metabolic rates (0.26 mL CO2∙g−1∙h−1or 160 J∙g−1∙day−1). Field metabolic rates were 2.4 times the resting metabolic rate, and activity respiration was 3.1 times the resting metabolic rate at lizard activity temperatures. Activity accounted for 59% of the energy consumption due to respiration. Calculated rates of feeding indicated a 415 J∙day−1 deficit in metabolizable energy intake, and this was reflected in rate of loss of body mass throughout the study. Daily energy harvested by 200 lizards (31 kJ∙day−1), which approximates densities (per hectare) on the study area, would supply only 40% of the daily energy requirements of one insectivorous bird with similar body mass and activity level of a Phainopepla (79 kJ∙day−1).

Ash-Throated Flycatcher Takes Sagebrush Lizard

Ash-Throated Flycatcher Takes Sagebrush Lizard

Geographic Differences of Growth Rate of Sceloporus Lizards (Sauria: Iguanidae)

Laboratory produced hatchlings of Sceloporus graciosus graciosus, S. undulatus consobrinus, S. u. garmani and S. u. undulatus that were raised under identical social, thermal-gradient and feeding environments grew at significantly distinct, population-specific rates. Growth rates expressed in the laboratory closely approximated those measured in the field for some populations, but were higher in the laboratory for others. Juvenile growth rate differences measured in the field seem due in part to genetic differences and in part to differences in the quality of the natural growing environment. T HE field studies of Tinkle (1967), Tinkle and Ballinger (1972) and others have pointed out that geographic variation of lifehistory parameters exists in lizards. At least two important questions, germane to the study of any trait differences, remain. First, what kinds of genotypic-environmental interactions result in these differences? Second, if there is some degree of genetic determination of these differences, how have environmental pressures selected for the evolution of differences?

Ecology and Physiological Aspects of Reproductive Strategies in Two Lizards

Two lizard species, the northern prairie lizard (Sceloporus undulatus garmani) from Reno County, Kansas and the northern sagebrush lizard (Sceloporus graciosus graciosus) from Washington County, Utah, were used to test four hypotheses and one assumption related to the theory of r— and K—selection. The northern prairie lizard is short—lived, matures early, and has a high reproductive effort (r—strategist) while the northern sagebrush lizard is long—lived, has delayed maturity, and a low reproductive effort (K—strategist). One of the assumptions of the r— and K—selection theory is that competition for food is more intense for K—strategists than for r—strategists. Given this assumption, greater food availability for the prairie lizard was hypothesized to result (1) a higher level of body lipids, (2) a higher rate of lipid utilization, (3) a lower percentage of ingested energy available for metabolism, and (4) and expenditure of less energy per offspring than in the sagebrush lizard. Total lipid levels in the two species collected before and after hibernation indicated that prairie lizards had significantly higher lipid levels than sagebrush lizards during both collection periods. A comparison of the amount of body lipids lost and the amount of egg lipids gained during vitellogensis of the first clutch suggested that more lipids are being utilized for egg production in prairie lizards than in sagebrush lizards. Sagebrush lizards apparently are better adapted physiologically to lower food levels since they had lower rates of lipid utilization during starvation studies and they extracted more energy usable for metabolism from ingested food than prairie lizards. Although both species expended about the same amount of energy on a given clutch of eggs, prairie lizards produced more offspring per clutch and therefore expended less energy per offspring. Prairie lizards produced as many as three clutches per season as compared to two clutches per season for sagebrush lizards, and changes in length—lean weight relationships for the two species over a given season suggested that the additional clutch of eggs produced by prairie lizards may be contributing to the higher mortality observed in this species. Indirect evidence, based on precipitation levels and insect biomass at the two study sites and mouthgapes of the two species, supported the assumption that more food was available to the prairie lizards than the sagebrush lizard. Higher precipitation levels (indicating greater insect biomass) occurred at the prairie lizard collection site and this species had a smaller mouthgape index, indicating greater specification in utilization of prey sites.

Habitat and Prey Selection of Sceloporus Occidentalis and Sceloporus Graciosus

Sympatric populations of the western fence lizard, Sceloporus occidentalis and the sagebrush lizard, Sceloporus graciosus were compared with respect to morphological measurements, and habitat and resource utilization. An allopatric population of S. occidentalis was studied to determine whether any differences among sympatric populations result from species—specific differences or from a shift in characteristics of S. occidentalis because of the presence of a congener. The presence of sympatric S. graciosus does not alter the size of prey selected by S. occidentalis. Sceloporus graciosus selects a significantly smaller mean length of prey (4.6 mm) than S. occidentalis (5.4 mm). Two factors theoretically contribute to the variation in size of prey taken by a population: each individual shows variation in length of prey, and morphological variation in size of adult lizards results in differences among individuals in average length of prey. The first factor explains the variation in size of prey taken by these populations, because there is no correlation between mean prey length and adult body length for either species. Although there is a significant difference between the two species in mean size of prey taken, extensive overlap in prey utilization is revealed directly by the high overlap values between species (66%) and indirectly from the low value of niche separation to niche width ratio. The significantly larger mean prey size of adults to immatures reduces the intraspecific competition between age classes. Adult S. graciosus, with a smaller mean prey length than S. occidentalis, overlaps the most with immatures, particularly S. occidentalis immatures. The significantly larger head size of sympatric compared with allopatric S. occidentalis is not explained by character displacement in trophic apparatus to decrease overlap between species in prey utilization because the same size prey is selected in both areas and by both sexes. The larger head size of S. occidentalis males in sympatry may increase species identification between species in push—up displays. Sympatric S. occidentalis and S. graciosus segregate themselves significantly between habitats, and within a habitat between structural microhabitats. This minimal spatial overlap between sympatric species allows their coexistence despite extensive overlap in prey utilization.

Lizard Reproductive Effort: Caloric Estimates and Comments on Its Evolution

The energy content of eggs of 10 lizard species was determined and used as a measure of reproductive effort (ratio of clutch calories to body calories). Values for eggs ranged from 5.87 to 7.20 cal/mg ash—free dry weight (°=6.37). Species differences in calories going into reproduction during a breeding season, however, were primarily due to differences in clutch size and clutch frequency between species. Correlation analysis between three measures of reproductive effort, including the preceding, and a suite of demographic variables revealed only one significant correlation (negative) between clutch calories to body calories ratio and mean annual adult survivorship. The energy allocated to eggs in comparison to total annual energy expenditure was estimated for three of the species investigated. Sceloporus graciosus had the highest reproductive effort, with proportional values for first and older breeders about the same. The proportion of total energy expended on reproduction was slightly lower for UTA stansburiana, with first and older breeders exhibiting the same effort. Sceloporus jarrovi had the lowest reproductive effort, but showed an increasing effort with increasing age. These data suggest that the demographic environment may not be the primary selective pressure determining reproductive effort, and that reproductive effort may not be positively correlated with age in all species.

Fat and Breeding Cycles in a Montane Population of Sceloporus graciosus

Sceloporus graciosus, at 1600m on the western slope of the California Sierra Nevada, is active from mid-April (males) or early May (females) until late August (females) or late September (males). Young and immature lizards are active from mid-April to early October. Fat accumulates at the end of the breeding season to maximal levels prior to hibernation. During dormancy, males use about half the autumnal fat, at a rate of 0.04 KCal/gm body weight/month. During dormancy, females use 0.01 KCal/gm body weight/ month. In the spring in females fat is used for egg production, and fat bodies shrink as eggs develop. Liver lipids of females are maximal during ovogenesis. Breeding females comprise two size groups: about 2/3 females are estimated 2-3 years old (49-58 mm SLV) and 1/3 are estimated 4 or more years old 59-4 mm SVL). The smaller group has a mean clutch size of 4.80 ane d the larger has a mean clutch size of 5.41 ? .23. Most of the larger females breed at the ae ea beginning of the breeding season (in late May) and younger females may breed from the same time until July. A few large females may lay a second clutch, but a single clutch is the rule. Incubation takes at least 6 or 7 weeks but a late summer decline in soil temperatures seems to prolong development. It is suggested that, under certain conditions, a few young may not emerge until spring.

Lipid deposition and utilization in the sagebrush lizard, Sceloporus graciosus: Its significance for reproduction and maintenance

1. 1. Seasonal cycling of lipids in fat bodies, carcass, tail and eggs was observed in female Sceloporus graciosus. 2. 2. Lipids from fat bodies are mobilized for metabolism during hibernation, while remaining fat body lipids and other depot lipids are used, in part, for egg production. 3. 3. Experimental comparisons of rates of lipid utilization and deposition indicated that fat bodies were mobilized the most rapidly and the tail the least rapidly.

A Population Analysis of the Sagebrush Lizard, Sceloporus graciosus in Southern Utah

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Age-dependent allozymic variation in a natural population of lizards.

An analysis of allozymic variation at 17 loci in a population of the sagebrush lizard (Sceloporus graciosus) in southern Utah yielded an estimate of genic heterozygosity of 0.028. Seven of the loci were variable, but only one, Est-1, was strongly polymorphic. The observation that the frequency of the common genotype (MM) at the Est-1 locus declined monotonically in successive age classes from 0.74 in hatchlings to 0.58 in adults 4 years old or older suggests that allele frequencies at this locus are not independent of selective influences.

On the Climatic Determination of Scale Size in a Lizard

Soule', Michael (Department of Biology, University of California, SanDiego, La Jolla, California, 92037) and Kerfoot, W. Charles (Museum of Zoology, University of Michigan, Ann Arbor, Michigan, 48104). On the climatic determination of scale size in a lizard. Syst. Zool. 21:97-105.-The relation between climate and scale size was studied in the two northern groups of Sceloporus graciosus. In the western section, an area of intense summer drought, 84 percent of the geographic variation in the number of mid-dorsal scales was explained in a multiple regression model by August rainfall and annual pan evaporation. Desiccation is probably the relevant selective factor. In the eastern section where the summer drought is variably ameliorated by the summer Sonoran monsoon rains, especially in the south, winter maximum temperatures and August rainfall, in that order of importance, account for 83 percent of the geographic variation. It is hypothesized that scale size, by partially determining cutaneous surface area, is an important component of both thermoregulatory and water balance systems in this animal. [Scale size; lizards; Sceloporus; multiple regression.]