Sceloporus Jarrovi Research Articles

Luteal development, placentation, and plasma progesterone concentration in the viviparous lizard Sceloporus jarrovi.

Abstract Corpus luteum development, placentation, and embryonic development were observed in pregnant viviparous lizards ( Sceloporus jarrovi ). Plasma progesterone concentration was also determined monthly during pregnancy using radioimmunoassay. S. jarrovi exhibits gonadal growth, ovulation, and fertilization in the autumn. Embryonic development occurs throughout the winter at a reduced rate. Four simultaneous events occur during the fourth month of pregnancy (March): (1) a significant decrease in the diameter of the corpora lutea, (2) the onset of rapid embryonic growth, (3) the formation of the chorioallantoic placenta, and (4) a marked increase in plasma progesterone concentration. These observations suggest that the corpora lutea are not the only source of progesterone during pregnancy in S. jarrovi , as they have degenerated when the major peak in progesterone concentration is observed. The most likely candidates for progesterone biosynthesis and secretion during pregnancy are the chorioallantoic placenta or the corpora atretica of this species.

Field Observations on the Use of the Tongue-Jacobson's Organ System in Two Iguanid Lizards, Sceloporus jarrovi and Anolis trinitatis

Field Observations on the Use of the Tongue-Jacobson's Organ System in Two Iguanid Lizards, Sceloporus jarrovi and Anolis trinitatis

Intraspecific Variation in demography and Life History of the Lizard, Sceloporus Jarrovi, Along an Altitudinal Gradient in Southeastern Arizona

Mark—recapture studies were conducted on a low (1675 m) and high (2542 m) altitude population of Sceloporus jarrovi in southeastern Arizona, USA from 1973 through 1976. Average age—specific mortality rates differed between altitudes only in the 0—1 yr age class. The increased mortality of neonates are low altitude was correlated with an increased number of potential predators and a significantly greater frequency of natural tail—breaks. Tail—break frequency did not differ between sites for older age classes. Survivorship and age at maturity were greater at high altitude. Low—altitude females mature in their first reproductive season. Transfer of neonates between altitudes indicate that high—altitude females do not mature in their first season even if raised at low altitude. Age at maturity appears to be adaptively adjusted by the demographic environment. Fertility schedules indicate that °40% of the replacement of low—altitude populations results from reproduction by 1st yr animals. There was a greater variation in replacement rate and population size at low than at high altitude.

Stimulation of parturition in a viviparous lizard ( Sceloporus jarrovi) by arginine vasotocin

Pregnant, adult female Sceloporus jarrovi were randomly partitioned into three groups. The control subjects received a single intraperitoneal injection (0.1 ml) of 0.75% physiological saline ( N = 4), whereas the experimental animals received 0.02 μg AVT/0.1 ml saline ( N = 5) or 2.0 μg AVT/0.1 ml saline ( N = 5). Several dependent measures of parturition were obtained, including (1) initial contraction latency, measured as the duration from injection to first effective contraction, (2) parturition latency, or the time lapse between injection and first birth, and (3) interbirth duration, representing the period of time between individual births. Neither oviductal contractions nor parturition were observed in saline-treated females, whereas both concentrations of AVT induced parturition in all experimental subjects. No significant differences were indicated between the two AVT groups for initial contraction latency and parturition latency. Mean duration between individual births for the 2.0 and 0.02 μg AVT groups did not differ and were found to be similar to those reported for natural births.

Food Resource Utilization during Periods of Low and High Food Availability in Sceloporus jarrovi (Sauria: Iguanidae)

Food Resource Utilization during Periods of Low and High Food Availability in Sceloporus jarrovi (Sauria: Iguanidae)

Supercooling in the Iguanid Lizard Sceloporus jarrovi

Throughout the year Sceloporus jarrovi is capable of significant supercooling of the deep-body temperature below the freezing point of its tissues. For S. jarrovi there was no seasonal acclimatization of the supercooling limit (SL). In fact, during the more severe winter of this study the ability to supercool decreased significantly from the levels measured during the summer and second, more moderate winter. There was a significant and positive linear regression of SL on freezing point (FP), and this relationship has a higher elevation than that reported for reptiles as a whole. There appears to be an optimum constant acclimation temperature for maximum supercooling (i.e., about 25 C). Below this level the ability to supercool decreases. Although constant low-temperature exposure decreased supercooling ability, there was no such effect following daily cycled-temperature exposure (-2 C to 30 C). There was a significant lowering by dehydration of the SL and FP at constant temperatures from 15 to 25 C. At 25 C a 5% water loss resulted in significant reduction in the SL and FP. Further dehydration beyond 5% did not lower either parameter. For animals measured directly from the field there is a significant relationship between both the SL and the FP and the body water content. The predicted effect on the SL may be overridden by exposure to constant low temperature. An animal of higher water content held at 30 C, for example, may actually have a lower SL than an animal of lower water content but kept at 15 C. It appears quite likely that supercooling is important for survival during the winter of populations of S. jarrovi at high elevations. At an air temperature of about -10 C, hibernaculum temperatures could be as low as -5 C, which approaches very closely the field SL for the populations studied.

Energetics, Temperature and Water Relations in Winter Aggregated Sceloporus Jarrovi (Sauria: Iguanidae)

Metabolic rates and water fluxes in winter—aggregated Yarrow's spiny lizards (Sceloporus jarrovi) were measured in the field using doubly—labeled water. Resting metabolic rates were estimated from measurements of microhabitat and lizard body temperatures. During the month (November) following aggregation at the hibernaculum and the month (April) before dispersal, lizards were relatively active and their metabolic rates averaged 0.071 ml CO2°g—1°h—1, °40% of their warm season rates. From December through March, lizards basked but were relatively inactive with metabolic rates averaging 0.031 ml CO2°g—1°h—1, °15% of warm season rates. Water influx rates averaged 10.3 ml°kg—1°day—1 during the 120—day inactive period. Water loss was slightly higher than gain and lizards lost weight slowly while hibernating, having ended the 6—mo aggregation period with a 22% decline in body mass. Total energy expenditures during the aggregation period averaged °7.53 kJ, <2 of which could have been supplied by stored body fat. This, together with other direct and indirect evidence, suggests that lizards fed during the cold season. As a result of basking and displaying some activity, S. jarrovi spent >3 times as much energy during the aggregation period as would a lizard remaining inactive in a crevice at 10°C for the entire 6 mo. Possible benefits of winter basking are discussed.

Seasonal Changes in the Territorial Behavior of the Iguanid Lizard Sceloporus jarrovi

Territorial behavior of Sceloporus jarrovi was observed in Arizona during 3 years. Male aggression, activity and home range size increased and overlap between home ranges decreased as the fall breeding season approached. Most animals defended the entire home range. Males shifted their positions to maximize overlap with females in the fall. Females were less aggressive, occupied smaller areas and shifted positions less.

Iguanid Substrate Licking: A Response to Novel Situations in Sceloporus jarrovi

Many lizards extrude the tongue and touch the substrate under natural conditions. Reasons for this have never been examined. Eight Sceloporus jarrovi, Yarrow's spiny lizard, were exposed to three novel situations: a rock placed in the home cage; a previously unoccupied, unfamiliar cage; and an unfamiliar cage where another lizard had been kept. The rates of substrate licking under these conditions were compared to the rates of substrate licking in the home cage. Significantly more licking occurred when lizards were exposed to the novel situations than when in their undisturbed, home cages. It is proposed that Sceloporus jarrovi explores new situations mediated by its Jacobson's organ through substrate licking.

The Function of Shudder Displays in the Lizard Sceloporus jarrovi

Rapid head-nod displays, called shuddering, have previously been considered a courtship display used only by males in iguanid lizards. Field observations of Sceloporus jarrovi indicate both sexes shudder during the non-breeding season although the display retains its courting function in breeding males. A new hypothesis is proposed, that the display represents a high level of excitement and a potential for attack. Intruder retreat or imitation of a female will prevent the attack. The selective regime which favored the change in display function can only be conjectured from existing comparative data.

Resource Partitioning by an Iguanid Lizard: Temporal and Microhabitat Aspects

Sceloporus jarrovi exhibits intraspecific differences in temporal and microhabitat resource usage. During the summer months of 1974 and 1975, most adult activity occurred in the early morning while most juvenile activity occurred near noon. Lizards were active an average of only 2.5 days/wk. Because the animals were active on different days and at various times of the day, defended territories sometimes overlapped spatially. Territoriality of S. jarrovi is closely tied to the maintenance of an adequate food supply a temporal distribution of territories may increase feeding efficiency. Perch site differences were also noted.

Size Selection of Prey by the Lizard, Sceloporus jarrovi

Size Selection of Prey by the Lizard, Sceloporus jarrovi

The Influence of Food Abundance on Territory Size in the Iguanid Lizard Sceloporus jarrovi

This study was designed to determine how food abundance affects territory size for the insectivorous lizard Sceloporus jarrovi. Observations and experiments were performed in the field in southeastern Arizona during 1971 and 1972 summers. Territories were defined as defended areas, and the convex polygon method was used to determine territorial boundaries. Preliminary studies showed that all adult and most juvenile lizards defended territories against lizards of the same species, size, and sex. Sex and body size influenced territory size. Within size classes, territories of ♂ ♂ averaged more than twice territory size of ♀ ♀. Lizards in the larger size class had territories more than twice those of smaller animals. Natural food abundance, determined with adhesive—coated Masonite® boards, was inversely correlated with territory size. Summer territories compressed significantly when food was added even through natural food supplies seemed adequate. Terrtories returned to initial sizes with the removal of additional food. Experiments involving the locations of concentrated food sources within the territory provided some evidence for the hypothesis that ease of food obtainment may be an important factor in determining summer territorial size and location.

Altitudinal Acclimation and Seasonal Variation in Hemoglobin of the Iguanid Lizard Sceloporus jarrovi

Altitudinal Acclimation and Seasonal Variation in Hemoglobin of the Iguanid Lizard Sceloporus jarrovi

Reproductive Effort and Winter Activity in the Viviparous Montane Lizard Sceloporus jarrovi

GORMAN, G. C. 1968. The relationships of Anolis of the roquet species group (Sauria; IS, D. E. 1958. The role f density in agessive behavior of house mice. Anim. Behav. Iguanidae)-III. Comparative study of display behavior. Brevoria, Mus. Comp. Zool. No. 284:1-31. GREENBERG, B., AND G. K. NOBLE. 1944. Social behavior of the American chameleon, (Anolis carolinensis). Physiol. Zool. 17:392-439. JENSSEN, T. A. 1970. The ethoecology of Anolis nebulosus (Sauria, Iguanidae). J. Herpetol. 4: 1-38. MILSTEAD, W. W. 1970. Late summer behavior of the lizards Sceloporus merriami and Urosaurus ornatus in the field. Herpetologica 26: 341-357. RAND, A. S. 1967. The ecology and social organization in the iguanid lizard Anolis lineotopus. Proc. U. S. Nat. Mus. 122:1-79. SCHOENER, T. W., AND G. C. GORMAN. 1968. Some niche differences in three Lesser Antillean lizards of the genus Anolis. Ecology 49: 819-830. STAMPS, J. A., AND G. W. BARLOW. In Press. Variation and stereotypy in the displays of Anolis aeneus (Sauria, Iguanidae). Behaviour.

Comparative Demography of Two Viviparous Iguanid Lizards (Sceloporus Jarrovi and Sceloporus Poinsetti)

Population studies of Sceloporus jarrovi using mark—recapture procedures were conducted on two study plots near Portal, Chiricahua Mountains, Cochise Co., Arizona during the summer months of 1969 and 1970. Similar studies of Sceloporus poinsetti were conducted on a study plot near Mertzon, Irion Co., Texas during the summer months of 1968, 1969, and 1970. Series of these lizards were taken from areas near the study plots and autopsied to determine their reproductive condition. The reproductive cycle of both species involved mating in the fall, with parturition occurring the following June. A single litter was produced each year. S. poinsetti attained maturity during the second mating season after birth, at about 16—17 months, although approximately 60% of the S. jarrovi females matured in their first mating season at about 5 months. Female S. jarrovi which matured as yearlings produced an average of four young in their 1st year, whereas older females produced an average of 10.5 young (7—15). The increase in litter size with snout—vent length was one embryo per 3 mm of body length. S. poinsetti females produced an average of 10.4 young (6—23) with an increase of one embryo per 3 mm of body length. Body sizes of young at birth were 29—35 mm in S. poinsetti and 25—32 mm in S. jarrovi. Newborn of both species were larger than hatchlings of similar sized oviparous species of Sceloporus. Newborn of S. poinsetti from large litters were significantly smaller than newborn from small litters. Populations of both S. jarrovi and S. poinsetti had 50:50 sex ratios. In June, the ratio of yearlings to older animals was approximately 50:50 in S. poinsetti and 60:40 in S. jarrovi. Of the eggs ovulated, 4.5% died before parturition in both species. Percent annual mortalities of S. poinsetti and S. jarrovi were respectively 86% and 81% (newborn), 54% and 56% (yearlings), and 57% and 63% (adults). The life history strategy of S. poinsetti appears to be relatively K—selected. S. jarrovi is more r—selected than S. poinsetti but more K—selected than most oviparous species.

The effects of altitude on oxygen-binding parameters of the blood of the iguanid lizards, Sceloporus jarrovi and Sceloporus occidentals

1. 1. Red blood cell counts and hemoglobin content were determined for blood samples from Sceloporus jarrovi collected at altitudes of 5100, 6000 and 8600 ft. 2. 2. Oxygen capacity was determined for blood samples from Sceloporus occidentalis collected at altitudes of 500, 4000, 6000 and 7000 ft. 3. 3. Oxygen-binding parameters of blood from both species showed significant differences for populations from 6000 ft and above as compared with lower altitude populations. These differences are attributed to the more restricted annual heat budget of the higher altitude lizards.

Seasonal Weight and Cytological Changes in the Fat Bodies and Liver of the Iguanid Lizard Sceloporus jarrovi Cope

vival. Fat bodies reach maximum sizes in autumn at the start of vitellogenesis and minimal sizes in late spring. Females have larger fat bodies than males prior to vitellogenesis. Extreme depletion of fat bodies in early spring indicates they are used as an energy source for winter survival. The liver undergoes an autumn hypertrophy in females but not in males. Electron micrographs from autumn females revealed an abundance of cytoplasmic lipid droplets which are presumably utilized during vitellogenesis. These droplets are essentially gone by spring. Livers in females

The Herpetofauna of Queretaro, Mexico, with Remarks on Taxonomic Problems

For the past three years, a herpetofaunal study of an ecological transect through the eastern front range of the Sierra Madre Oriental has been conducted in the Mexican states of San Luis Potosi and Queritaro. The transect passes through tropical deciduous, semi-cloud, pine-oak, dry oak and desert scrub forests within the first 65 kilometers, transversing elevations from 90 to 2,550 m. Brief descriptions of the various major vegetational areas are included. Sixty-five new herpetofaunal records are listed for the state of Queretaro. A discussion of systematic problems includes the species Pseudoeurycea cephalica, Sceloporus jarrovi, Eumeces lynze, E. tetragrammus, Lepidophyma flavimaculatum, L. gaigeae, and L. smithi. A vast amount of information on the distribution and systematics of Mexican reptiles and amphibians has accumulated over the past 20 years, or since the last publication of the Smith and Taylor (1945, 1948, 1950) checklists on the herpetofauna of Mexico. During this surge of interest, large amounts of data were accumulated on various aspects of the biology of families, genera and species, including specific studies on their distribution within political boundaries of Mexico. Smith and Taylor (1945, 1948, 1950) included state lists in each of their publications, and some major contributors to specific state and regional studies were Alvarez del Toro (1960); Bogert and Oliver (1945); Davis and Dixon (1959, 1961, 1965); Davis and Smith (1953a, 1953b, 1953c); Duellman (1958, 1960a, 1961, 1965a, 1965b); Hardy and McDiarmid (1969); Martin (1958); Schmidt (1922); and Taylor (1949, 1952, 1953). In general, there are several hundred assorted notes and short papers on range extensions, systematics, ecology and morphology of Mexican amphibians and reptiles. Specific locality records of amphibians and reptiles for Queretaro are given by Altig (1964); Chrapliwy (1964); Dixon and Ketchersid (1969); Duellman (1960b, 1970); Klauber (1952); Lynch (1970); Martin del Campo (1936); Rabb (1965); Smith (1942); Smith and Brandon (1968); Smith and Taylor (1945, 1948, 1950); Webb (1968); and Zweifel (1956).

Effect of Temperature on Heart and Ventilatory Rates of Sceloporus jarrovi

Effects of temperature on heart and ventilatory rates of Sceloporus jarrovi were studied. Heart rates over the 30 C range (10-40 C) were exponential, with temperature coefficients ranging from 1.8 to 2.9. Ventilatory rates did not show the same exponential response, indicating that ventilatory rates may be independent of temperature. Ventilatory periods were interspersed with periods of apnea lasting up to 58 minutes at lower temperatures. Unlike more thermophilic lizards, S. jarrovi did not pant or hyperventilate at higher temperatures. INTRODUCTION. Metabolic response of lizards to increasing and decreasing temperature is reflected in heart and ventilatory rates. In general the heart rate exhibits an exponential increase with rising temperatures (Dawson and Templeton, 1966). The slope of the curve describing this increase differs with each species (Templeton, 1964) and prior thermal history (Murrish, 1965). Although ventilatory rates increase with rising temperatures, the rate increase is not necessarily exponential. Responses of different species of lizards to varying temperatures are important as they affect periods of activity. In the case of those lizards indigenous to high altitude, the ability to remain active at lower en- vironmental temperatures would seem to be advantageous. Among those lizards inhabiting higher elevations are members of the torquatus group. One species of this group Sceloporus jarrovi inhabits elevations of 4800 to 10713 ft. (Nickerson and Mays, 1967) in southeastern Arizona. At the higher elevations S. jarrovi is found to be active at ambient temperatures as low as 14WC (personal data). Finding lizards at such low temperatures prompted me to initiate a study of the effects of temperature on heart and ventilatory rates. METHODS AND MATERIALS. Specimens of S. jarrovi were collected in the Graham (Pinalefio) Mountains of southeastern Arizona during the month of June