Gambelia Research Articles

Mitochondrial phylogeography of the endangered blunt-nosed leopard lizard,Gambelia sila

To assess the genetic diversity and phylogeography of the blunt-nosed leopard lizard (Gambelia sila), we sequenced 1,285 base pairs (bp) of the mitochondrial cytochrome oxidase-b (cyt-b, 682 bp) and cytochrome oxidase III (CO3, 603 bp) genes from 33 individuals representing eight natural populations in central California. Phylogenetic analysis indicated that 17 observed haplotypes are partitioned into two major clades, which correspond geographically to where the lizards were collected. We also conducted a focused analysis of individuals collected from the canyons leading into the Cuyama Valley in Ventura and Santa Barbara counties, a geographic area with lizards possibly representing a remnant hybrid (with G. wislizenii) population. All lizards from the Cuyama Valley and adjacent canyons exhibited the mitochondrial haplotype of G. sila and were embedded within one clade. Our morphological analysis placed some leopard lizards collected from Cuyama Valley with true G. sila, whereas some individuals aggregated with G. wislizenii. This finding suggests that the quantitative morphological characteristics often used to distinguish between the two species are fairly labile and may be influenced by prevailing environmental conditions.

Respiratory Biology during Gravidity inCrotaphytus collarisandGambelia wislizenii

During gravidity lizards experience a striking decrease in lung volume as a result of lung compression by eggs growing within the body cavity. In order to understand the effect of this decrease in lung volume on the respiratory biology of gravid egg-laying lizards, we measured changes in total lung volume, resting and postexercise expired volume, minute volume, respiratory frequency, and carbon dioxide production rate during reproduction in the Collared Lizard, Crotaphytus collaris, and the Leopard Lizard, Gambelia wislizenii. We found that compression of the lungs by shelled eggs resulted in an average 48% (range: 26–70%) decrease in total lung volume compared to the same postlaying C. collaris females, and an average 38% (range: 29–46%) decrease in G. wislizenii. CO2 production rates were altered significantly during reproduction in female C. collaris and were 58% higher in females carrying late-stage follicles, compared to after laying. Despite the remarkable reduction in lung volume in both of these species and the increase in CO2 production rates in C. collaris, no ventilation parameters changed over the course of reproduction. The highly distensible body cavities of C. collaris and G. wislizenii appear to be able to accommodate both growing eggs and adequate lung volumes for normal respiratory function during gravidity.

Effects of grazing and invasive grasses on desert vertebrates in California

AbstractMuch of California's San Joaquin Valley is a desert and, like portions of other North American deserts, is experiencing an ecological shift from being dominated by ephemeral native forbs, with widely spaced shrubs, to fire‐prone non‐native annual grasses. Small terrestrial vertebrates, many of which are adapted to open desert habitats, are declining. One hypothesis is that the invasive plants contribute to the decline by altering vegetative structure. Although cattle may have originally been a factor in the establishment of these non‐native plants, their grazing may benefit the terrestrial vertebrates by maintaining an open structure, especially during average or wet winters when the exotic grasses grow especially dense. We experimentally tested the effect of cattle grazing on invasive plants and a community of small vertebrates at a site in the southwestern San Joaquin Desert. We established and monitored 4 treatment (grazed) and 4 control (ungrazed) plots from 1997 to 2006, and assessed the abundances of blunt‐nosed leopard lizards (Gambelia sila), giant kangaroo rats (Dipodomys ingens), short‐nosed kangaroo rats (Dipodomys nitratoides nitratoides), and San Joaquin antelope squirrels (Ammospermophilus nelsoni), all of which are listed as threatened or endangered by state or federal agencies. We also recorded abundances of the non‐protected western whiptail lizards (Aspidoscelis tigris), side‐blotched lizards (Uta stansburiana), San Joaquin pocket mice (Perognathus inornatus inornatus), and Heermann's kangaroo rats (Dipdomys heermanni). Based on repeated measures analysis of variance (ANOVA) and a 0.05 alpha level, only Heermann's kangaroo rats showed a treatment effect; they were more abundant on the control plots. However, this effect could be accounted for by the natural re‐establishment of saltbush (Atriplexspp.) on part of the study site. Saltbush return also favored western whiptail lizards and San Joaquin antelope squirrels. A regression analysis indicated that populations of blunt‐nosed leopard lizard and giant kangaroo rat increased significantly faster in grazed plots than the ungrazed controls, and abundances of 6 of 8 species were negatively correlated with increased residual dry matter. With relaxed alpha values to decrease Type II error, populations of blunt‐nosed leopard lizards (500% greater), San Joaquin antelope squirrels (85% greater), and short‐nosed kangaroo rats (73% greater) increased significantly on grazed plots over the course of the study compared to ungrazed plots. We did not find grazing to negatively affect abundance of any species we studied. When herbaceous cover is low during years of below average rainfall in deserts and other arid areas, grazing may not be necessary to maintain populations of small vertebrates. However, if cattle grazing is closely monitored in space and time to minimize adverse effects on the habitat, it could be an effective tool to control dense stands of non‐native grasses and benefit native wildlife. © 2011 The Wildlife Society.

FOOD HABITS OF THE BLUNT-NOSED LEOPARD LIZARD (GAMBELIA SILA)

We quantified the food habits of the endangered blunt-nosed leopard lizard (Gambelia sila), an endemic species of the San Joaquin Valley, California. Based on analyses of stomach contents and prey remains in scats, we determined that this species is an opportunistic predator that eats large numbers of orthopterans, coleopterans, and hymenopterans, with dipterans, hemipterans, and lizards taken in lesser numbers. These data are similar to the qualitative or unpublished data of previous studies, and also are similar to the food habits of the congeneric Gambelia wislizenii.

ONTOGENETIC AND SEASONAL CHANGES IN COLORATION OF THE BLUNT-NOSED LEOPARD LIZARD (GAMBELIA SILA)

Abstract Among crotaphytids, the blunt-nosed leopard lizard (Gambelia sila) is one of only 2 species known in which adults do not have permanent dichromatic patterns, but both males and females display bright breeding colors. Males in most populations develop a salmon color over most of their head and body, whereas females develop rusty red blotches laterally along the head and trunk. Also unusual is the yellow color exhibited by juveniles. Between 1992 and 1994, we captured adult and juvenile G. sila on the Elkhorn Plain, San Luis Obispo County, California, and scored individuals for their coloration. Juvenile G. sila developed a yellow color on the undersides of their hind limbs and tail that was apparent when they were about 55 mm snout-vent length (SVL) and was prominent until about 85 to 90 mm SVL. Both males and females developed breeding colors between 85 and 95 mm SVL. Breeding colors of adults developed soon after they emerged each year in April or early May, and most adults retained breeding col...

Some Nematode and Acanthocephalan Parasites of the Longnose Leopard Lizard, Gambelia wislizenii (Lacertilia: Crotaphytidae), from Arizona, California, and Texas, with a Summary of the Helminths Reported from this Host

Eight adult longnose leopard lizards, Gambelia wislizenii, previously deposited in the Angelo State Natural History Collection (ASNHC) and collected between 1964 and 1969, were examined for helminth parasites. These lizards came from locales in Cochise County, Arizona (n = 1), San Bernardino County, California (n = 2), Mesa County, Colorado (n = 1), and Winkler County, Texas (n = 4). Five of the 8 ASNHC lizards (62.5%) were infected with 1 of 3 species of nematodes or an acanthocephalan, including 1 (12.5%) with larval Porrocaecum sp., 2 (25%) with Cyrtosomum penneri, 1 (12.5%) with Skrjabinoptera phrynosoma, and 1 (12.5%) with oligacanthorynchid acanthocephalan cystacanths. New helminth records for this host are documented for Porrocaecum sp. and the oligacanthorhynchid acanthocephalan cystacanth.

Early Pliocene Crotaphytus and Gambelia (Squamata: Crotaphytidae) from the Panaca Formation of Southeastern Nevada

Two localities in the Panaca Formation, Meadow Valley, Lincoln County, Nevada, have produced squamate remains that date to 4.9–4.7 Ma. Included are fossil maxillae of Crotaphytus sp. (Collared Lizards) and a dentary of Gambelia sp. (Leopard Lizards). To identify these fossils, diagnostic dental characters were used to distinguish the two genera. The toothrow of Crotaphytus exhibits wide, robust teeth and consists of mostly tricuspid teeth that show little or no recurvature. Gambelia dentition differs in having highly recurved, parallel-sided teeth throughout the toothrow, which contains more unicuspid than tricuspid teeth. Published records of valid Crotaphytus date to the middle Pliocene (3.7–3.1 Ma) and Gambelia date to the early to middle Pliocene (4.18–3.58 Ma). The Panaca Formation fossils described herein mark the oldest known record of both taxa.

Abundance of the Long-nosed Leopard Lizard (Gambelia wislizeni) is Influenced by Shrub Diversity and Cover in Southeast Oregon

Abstract The abundance and distribution of animal species appears to be limited by availability of suitable habitat, and often a critical component to these suitable habitats is the presence of one or more particular plant species, and/or plant species diversity. Abundance of the Long-nosed Leopard Lizard (Gambelia wislizenii) is inversely related to percent cover by all shrubs combined, in addition to percent cover by sagebrush, throughout the Alvord Desert in southeast Oregon. In many locales throughout the Great Basin desert sagebrush (Artemisia tridentata) is the dominant shrub, and its abundance is inversely related to shrub species diversity. However, in the Alvord basin, where there are abundant dry lake beds and salt-flats, G. wislizenii lizard abundance is relatively high, percent cover by shrubs varies and shrub species diversity can be high. In these areas Greasewood (Sarcobatus vermiculatus) is the dominant shrub, while sagebrush is non-abundant. Gambelia wislizenii population density patterns...

Feeding behavior modulation in the leopard lizard ( Gambelia wislizenii): Effects of noxious versus innocuous prey

Feeding, a fundamentally rhythmic behavior in many animals, is expected to exhibit modulation with respect to prey type. Using high-speed videography (200 frames s −1) and kinematic analysis, we investigated prey-processing behavior in the long-nosed leopard lizard ( Gambelia wislizenii). The effects of two prey types were examined, innocuous immature crickets ( Acheta domesticus) and noxious stinging hymenopterans (honeybees [ Apis mellifer] and yellow jackets [ Vespula sp.]). Stinging hymenopterans are processed more extensively, with higher gape-cycling frequencies, and for a greater duration than are crickets. Generalized tetrapod feeding models were used as a framework to test the hypothesis that gape profile characteristics are modulated in response to prey noxiousness. Cricket processing generally fits the models, but hymenopteran processing departs from typical model parameters. In particular, the SO phase is absent to barely detectable during hymenopteran processing. This likely represents an effect of extrinsic neural input on a centrally directed rhythmic motor pattern, possibly to avoid being stung. Differences in the capture behavior of crickets versus hymenopterans indicate that G. wislizenii assesses prey noxiousness before physical contact with prey and modifies its capture behavior accordingly. These results add to the growing body of evidence that sensory information can play a critical role in shaping stereotyped rhythmic behaviors in non-mammalian tetrapods.

Population Ecology of Blunt-Nosed Leopard Lizards in High Elevation Foothill Habitat

We captured 1078 Blunt-Nosed Leopard Lizards (Gambelia sila) 2396 times between 1989 and 1994 on the Elkhorn Plain, San Luis Obispo County, California. Based on size at first capture, we caught 119 adult (� 90 mm snout-vent length (SVL)) and 430 hatchling/juvenile (<90 mm SVL) males, and 139 adult and 390 hatchling/juvenile females. Sex ratio of males to females was 1.04 (549 males/529 females). Adult G. sila generally became active in April, and activity remained relatively high into July. Hatchlings were first noted in either July or August and generally could be found until early November, except in 1990 when no hatchlings were found at any time. Mean number of adults and hatchlings found active each day differed significantly across years, but as many as 32 adults and 42 hatchlings were seen on a plot during a census. Estimates of population abundance on a plot also varied yearly from 20-164 adults and 0-273 hatchling/juveniles and seemed to be affected either by too little or too much rain. Differences in daily activity varied and were moderately well explained by environmental factors. We estimated survivorship of lizards and found 29.0% of hatchlings from 1992 survived to 1993, and 14.6% of hatchlings from 1993 survived to 1994. The oldest G. sila found was a female estimated to be 4 years, 10 months when last caught, although most adults were not seen after 2 yr. Growth of individuals varied by year: highest growth rates were for lizards that hatched in 1991 and 1992, and lowest growth occurred in lizards that hatched in 1989. We found adult leopard lizards with eggs in all years but 1990. Females generally were gravid by late April or early May, and some females were found with eggs in early July. Female size at first reproduction was about 90 mm SVL, clutch size ranged from 1-6 eggs, and overall mean clutch size regardless of year or clutch order was 3.4 eggs. Many females produced multiple clutches in a year, and we found up to four clutches by a single female.

Sexual Dimorphism as It Relates to Natural History of Leopard Lizards (Crotaphytidae: Gambelia)

Sexual dimorphism is a phenomenon that occurs in a variety of animal taxa, and its occurrence can reflect and/or influence crucial aspects of the natural history of organisms. We examined the external morphology of three lizard species, Gambelia sila, G. wislizenii, and G. copei. Gambelia sila shows the prevalent sexually dimorphic condition among iguanian lizards of males attaining a larger head relative to body size (snout-vent length) and larger overall body size than females, whereas in G. wislizenii and G. copei, females attain a larger body size than males. We performed a detailed morphometric examination of these three taxa to (1) characterize interspecific differences in sexual dimorphism among these three closely related lizards, (2) test the hypothesis that sexual dimorphism in cranial shape exists in G. wislizenii and G. copei, and (3) examine intersexual body size and cranial shape variation among G. wislizenii populations inhabiting major North American geophysical regions. Morphometric analyses support the results of previous studies. Cranial shape dimorphism is present in some G. wislizenii populations, particularly those of the Great Basin, and in G. copei. Interregional comparisons reveal that G. wislizenii populations vary both in the degree of intersexual body and head size differences as well as in cranial shape dimorphism. Among regional groups, body and head size and cranial shape dimorphism exhibit an inverse relationship. These patterns of morphological variation are correlated with aspects of the ecology, behavior, and phylogenetic history of these taxa.

Phylogeography of a Wide-Ranging Desert Lizard, Gambelia wislizenii (Crotaphytidae)

Intraspecific phylogeography of the long-nosed leopard lizard (Gambelia wislizenii) was examined using 419 base pairs of sequence of the mitochondrially encoded COIII gene from 23 individuals sampled from populations representing five regional deserts in western North America. Intraspecific population structure was evaluated under two biogeographic models: (1) gene flow among populations during late Pleistocene to Recent times, possibly in conjunction with range expansions from Pleistocene refugia; or (2) subdivision among southwestern desert regions that occurred in conjunction with late Pliocene/early Pleistocene geological events or as a result of isolation in separate Pleistocene refugia. Phylogenetic analysis indicated subdivision of 18 mitochondrial DNA haplotypes into two major clades separated by approximately 6.1% sequence divergence: Western (Mojave + Great Basin + Colorado Plateau deserts) and Eastern (Chihuahuan desert). A third, more divergent, lineage with unknown geographic distribution was represented by a single haplotype from southwestern Arizona. The Western clade contained two northern Great Basin subclusters (eastern Great Basin and western Great Basin), representing populations separated from one another by approximately 5.4% sequence divergence. These phylogeographic breaks are consistent with the second model of late Pliocene/early Pleistocene vicariance. These data are also consistent with assessments of the biogeographic histories of several other arid-dwelling vertebrates.

Microhabitat Use and Home Range Characteristics of Blunt-Nosed Leopard Lizards

We used radiotelemetry to determine habitat use and home range characteristics of 16 blunt- nosed leopard lizards (Gambelia sila) at two sites on the Naval Petroleum Reserves in California. Space use parameters of eight lizards occupying an area of relatively dense vegetation in 1982 and eight lizards inhabiting a sparsely vegetated site in 1984 were compared. Home range size, core area size, and amount of overlap of ranges did not differ significantly between sites. The difference in average home range size between males (4.24 ha) and females (2.02 ha) was borderline significant (P = 0.054). Female home ranges and core areas were overlapped extensively by male ranges (x = 79.8% and 50.3%, respectively). There was no evidence of intrasexual overlap of core areas. Male home ranges overlapped the ranges of up to four other males but female ranges did not overlap one another. At the more densely vegetated site, leopard lizards used washes significantly more than grassland, floodplain, and road habitats and they used grassland significantly less than other habitats. At the sparsely vegetated site, grassland was used more than wash habitat and hills were used less than all other habitats. Our data indicate that leopard lizard activity is concentrated in washes and other open areas when herbaceous cover is dense, but they are capable of utilizing the more extensive grassland habitat if vegetation is sufficiently sparse. Creating open space within the grassland habitat may have important management implications for this species in some areas.

Food-Item Use by Coyotes at the Naval Petroleum Reserves in California

Coyote (Canis latrans) food habits have been extensively documented (Bekoff, 1977). Use of food items by coyotes varies with location and time in response to spatial and temporal variation in food availability. Thus, siteand time-specific investigations are necessary to accurately describe local coyote foraging patterns. Relatively few investigations of coyote food habits have been conducted in California (e.g., Ferrel et al., 1953), and none were specific to the San Joaquin Valley. Additionally, coyotes in the southern San Joaquin Valley are sympatric with the endangered San Joaquin kit fox (Vulpes macrotis mutica = V. velox macrotis, cf. Dragoo et al., 1990) and potentially compete with foxes for food resources. Also, several other federally listed and candidate species occur in the southern San Joaquin Valley and may be preyed upon by coyotes. These species include the endangered giant kangaroo rat (Dipodomys ingens) and the blunt-nosed leopard lizard (Gambelia silus), and candidate species shortnosed kangaroo rat (Dipodomys nitratoides) and San Joaquin antelope squirrel (Ammospermophilus nelsoni). We investigated food-item use by coyotes at the Naval Petroleum Reserves in California (NPRC) to (1) determine annual and seasonal item use, and in particular to evaluate the dietary importance of leporids which are important prey for kit foxes (O'Farrell et al., 1987; J. H. Scrivner et al., in litt.), (2) assess the effect of annual leporid abundance on coyote food habits, and (3) determine whether coyotes prey on giant kangaroo rats, blunt-nosed leopard lizards, shortnosed kangaroo rats, and San Joaquin antelope squirrels. NPRC is an area of active petroleum production located 42 km SW of Bakersfield in western

Effect of Drought on Blunt-Nosed Leopard Lizards (Gambelia sila)

Effect of Drought on Blunt-Nosed Leopard Lizards (Gambelia sila)

Search tactics of desert lizards: how polarized are they?

The patterns of foraging movements of the teiid species Cnemidophorus tigris (western whiptail) and four iguanid species, Gambelia wislizeni (leopard lizard), Uta stansburiana (side-blotched lizard), Phrynosoma platyrhinos (desert horned lizard), and Callisaurus draconoides (zebra-tailed lizard), were investigated between 1978 and 1981. Rates and frequencies of movement while foraging, based on more than 44 000 minutes of observation of over 500 different lizards, were analysed with respect to temporal variation on yearly, seasonal and daily time scales and compared to expectations froma dichotomous view of foraging modes. The notion of polarized foragiing tactics among lizards was partially supported. Among the iguanid species, only Gambelia exhibited rates of foraging movements that were not always significantly less than those of the active forager, Cnemidophorus. Nevertheless, the analyses also revealed temporal variation in the search tactics of iguanid species. Gambelia exhibited a seasonal decline in foraging movements during three out of four years. Phrynosoma, Callisaurus and Uta all exhibited seasonal declines in their foraging movements in some years, but not in others. The foraging movements of all iguanid species increased during the early-season of 1978, corresponding to a marked increase in late winter/early spring rainfall that year. Uta showed diurnal shifts in foraging movements during most years. Such diurnal variation was also apparent in Callisaurus in some years. Despite consistent differences between Cnemidophorus and most iguanid species, the presence of temporal variability in foraging movements of iguanid lizards indicates a capacity for shifts in tactics in these species. Thus, this variability more realistically reflects a continuum of foraging tactics than it does dichotomous strategies.

Observations on the Ecology and Reproduction of the Leopard Lizard, Gambelia wislizenii (Iguanidae), in Southeastern Arizona

Observations on the Ecology and Reproduction of the Leopard Lizard, Gambelia wislizenii (Iguanidae), in Southeastern Arizona

Aggressiveness and vocalization in the leopard lizard ( Gambelia wislizennii): The influence of temperature

In both the laboratory and the field, body temperature alters the defensive responses of leopard lizards ( Gambelia wislizenii) toward predators. At high body temperatures lizards flee rapidly from predators. At lower body temperatures, which greatly retard running ability, lizards switch to a stationary defence consisting of aggressive postures, vocalizations and attacks. This temperature-dependent switch from flight to aggressive defence may be selectively favoured in species capable of inflicting damage on a predator. Increased ‘shyness’ at low body temperature may function as an alternative response in species lacking the ability to inflict damage upon a predator.

The Social Behavior of two Species of Closely Related Leopard Lizards, Gambelia silus and Gambelia wislizenii

Abstract and SummaryThe displays and social behavior of two closely related species of leopard lizards, Gambelia silus and Gambelia wislizenii, are described. The main difference between the social behavior of the two species is the presence of home range defense in G. silus and the lack of it in G. wislizenii. G. silus is typical of iguanids in its use of displays and defense of a home range by males. However, G. wislizenii is unusual because both sexes display infrequently, the displays do not appear to be associated with interactions between conspecifics, and neither sex defends a home range. Male G. silus are most likely defending an area where they can find a female on a day to day basis. The larger male home ranges included more females than the smallest home ranges. Food, burrows, basking, and shelter sites did not appear to be the primary defended resource. The absence of home range defense in G. wislizenii is related to its diet of vertebrate prey, mode of foraging and poor visibility in the habitat. The costs of destroying its camouflage in terms of capture of prey and predator avoidance appear to be greater than the benefits of defending a territory.

A Population Model of the Lizard Uta stansburiana in Southern Nevada

Population densities, reproduction, and survival of the lizard Uta stansburiana were measured at the Nevada Test Site in southern Nevada, USA, between 1964 and 1974. These data were used to develop a model of the population dynamics of this species. Results of irrigation experiments in 0.4—ha enclosures near Mercury, Nevada, were used to formulate multiple—regression equations predicting frequency and size of clutches laid by two age—classes of females in terms of winter rainfall, March air temperatures, and Uta population density. Densities of Uta in these enclosures were manipulated, and age—specific survival modeled in terms of spring densities of Uta. Experiments in which an important predator on Uta (the leopard lizard, Crotaphytus wislizeni) was removed from enclosures were used to estimate the influence of the predator on basic survival rates of hatchling and older Uta. The model was generally developed from data acquired in the small enclosures, but predictions were compared with actual observations of changes in Uta populations in Rock Valley (19 km west of Mercury, Nevada) between 1966 and 1972. Agreement between model predictions and actual numbers was fair. The model predicted a decrease in density from 1966 to 1967, but numbers of Uta actually increased conspicuously at this time. This was the only major discrepancy between predictions and observations. The observed mean spring density (d) between 1967 and 1972 was 41.4 Uta/ha (Sd = 20.8), while the model predicted a mean density of 37.8 Uta/ha (SD = 13.6). Observed and predicted mean proportions of yearlings in spring populations were identical (0.78). The basic version of the model estimated different survival rates for two age—groups of adult Uta. A simpler version of the model, using a common survival rate for both age—groups, gave predictions essentially identical with those of the basic model. Other tests of the basic model showed it to be most sensitive to changes in winter rainfall and predation pressure, much less so to air temperatures. Fifteen— and 30—yr synthetic sequences of predator densities were used to examine model stability over longer periods of time. When predator densities were drawn randomly from distributions with a mean of 2 individuals/ha, model populations exhibited lower mean numbers and amplitudes than actually observed during 9 yr in Rock Valley. The basic model included three density—dependent parameters: clutch frequency, clutch size, and adult survival. The model was modified so that (1) egg production was density independent, while adult survival was not; (2) adult survival was density independent, but egg production was not; and (3) there was no density dependence in the model. Thirty—year tests showed that cases 1 and 2 did not differ markedly from the basic model, although the removal of one density—dependent constraint resulted in slightly higher mean densities. In case 3, the model lacked stability and predicted numbers increased to unrealistic levels within 5 yr. We conclude that processes relating to egg production were modeled more effectively than those influencing survival, and that improvement of the model will depend on more detailed studies of the impact of predation on age—specific survival rates of Uta.