Spatial Use and Survivorship of Translocated Wild-Caught Texas Horned Lizards

The Texas horned lizard (Phrynosoma cornutum), a state threatened species in Texas, USA, appears to be declining throughout much of its distribution. Because of popular interest in restoring lizard populations, we conducted a 3-year radio-telemetric study to evaluate the feasibility of reintroducing Texas horned lizards into previously occupied areas with suitable habitat characteristics. We translocated lizards from natural populations in western Texas to the McGillivray and Leona McKie Muse Wildlife Management Area (MWMA) in the Cross Timbers and Prairies of north-central Texas, an ecoregion that has experienced apparent local extirpations of horned lizards. We translocated lizards after partly restoring a 32.5-ha portion of the MWMA from ashe juniper (Juniperus ashei)-honey mesquite (Prosopis glandulosa) woodland to mid-grass prairie. After a 10-day acclimation period and soft release, we tracked 57 horned lizards from March 2014 to October 2016 to evaluate daily movements, spatial use, sources of mortality, reproduction, and changes in body condition. Daily movement averages (1.16–174.18 m) and area used by individuals (<0.01–6.81 ha) were similar to those recorded for natural populations, with peaks in movement occurring in May and June. Annual survivorship for individuals (1.1–47.2%) was also similar to that reported from natural populations; however, survivorship declined across the 3 active seasons. Although mortality of translocated lizards was high, body condition remained relatively stable across active seasons, and reproduction occurred each year, indicating that translocation could be a viable option for restoring horned lizard populations to previously occupied parts of their range. © 2019 The Wildlife Society.     

Roller Chopping Effectively Reduces Shrub Cover and Density in Pine Flatwoods

Changes to fire regimes have resulted in excessive shrub growth and declines in the species rich herbaceous ground layer of pyric savanna and grassland systems worldwide, including the pine flatwoods of the Southern Coastal Plain of the United States. Prescribed burning and roller chopping during growing (April–October) and dormant (November–March) seasons are management practices promoted to reduce shrub invasion and increase herbaceous plant growth in flatwoods. However, relatively little is known about the seasonal effects these activities have on shrubs and herbaceous vegetation. We assessed the effects of prescribed burning and roller chopping on herbaceous and shrub characteristics in pine flatwoods and explored how grazing may mediate these treatments. We used a paired design, with comparison made between sampling locations randomly located within treated (e.g. burned) and adjacent untreated areas. Growing season burning was more effective at reducing shrub cover and height than dormant season burning. However, shrub re‐growth occurred the second year post‐burn. Roller chopping and roller chopping/burning combinations led to decreases in shrub cover and height for 2 years post‐treatment. Decreases in shrub density were seen on sites subject to growing season roller chopping and grazing. Decreases in herbaceous vegetation were observed following all treatments, possibly the result of grazing. If reductions in shrub density are required, growing season roller chopping in combination with grazing may be the only effective treatment. However, initial deferment from grazing following burning and roller chopping treatments may be necessary to permit re‐establishment and growth of forbs and graminoids.     

Survivorship and Spatial Patterns of an Urban Population of Texas Horned Lizards

Habitat fragmentation has negative consequences on threatened and endangered species by creating isolated populations. The Texas horned lizard (Phrynosoma cornutum) is experiencing population declines and localized extirpations throughout its range and has been classified as a species of greatest conservation need in Oklahoma, USA. Younger age classes have been poorly studied but may be vital to the stability of remaining populations. To address gaps in knowledge concerning subadult (hatchling and juvenile) morphometrics, survivorship, and home range sizes, we studied 2 cohorts of subadults, for 2 years each, covering their hatching and juvenile years (2016–2019). We used a combination of radio-telemetry and novel harmonic radar methodology to study a closed population of Texas horned lizards in 15 ha of native grassland at Tinker Air Force Base, Oklahoma. Population abundance for adults and juveniles was estimated as 56.5 ± 5.5 lizards and density as 7.96 lizards/ha. Our lowest estimates of survival indicated an average survival probability for the hatchling life stage of 0.285 (95% CI = 0.15–0.44), which is lower than for adults on the site. Average home range size increased from hatchling to adult life stages. Our results will have an immediate effect on the planning and assessment of ongoing headstart and management programs for Texas horned lizards. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

Effects of Prescribed Fire on Shinnery Oak ( Quercus havardii) Plant Communities in Western Oklahoma

Changes in structural and compositional attributes of shinnery oak (Quercus havardii Rydb.) plant communities have occurred in the twentieth century. These changes may in part relate to altered fire regimes. Our objective was to document effects of prescribed fire in fall (October), winter (February), and spring (April) on plant composition. Three study sites were located in western Oklahoma; each contained 12, 60 × 30‐m plots that were designated, within site, to be seasonally burned, annually burned, or left unburned. Growing season canopy cover for herbaceous and woody species was estimated in 1997–1998 (post‐treatment). At one year post‐fire, burning in any season reduced shrub cover, and spring burns reduced cover most. Winter and annual fires increased cover of rhizomatous tallgrasses, whereas burning in any season decreased little bluestem cover. Perennial forbs increased with fall and winter fire. Shrub stem density increased with fire in any season. Communities returned rapidly to pre‐burn composition with increasing time since fire. Fire effects on herbaceous vegetation appear to be manifested through increases in bare ground and reduction of overstory shrub dominance. Prescribed fire can be used as a tool in restoration efforts to increase or maintain within and between community plant diversity. Our data suggest that some plant species may require or benefit from fire in specific seasons. Additional research is needed to determine the long‐term effects of repeated fire over time.     

Effects of prescribed burning on avian nest survival in the southern Great Plains

Shrubs, such as mesquite (Prosopis spp.) and cholla (Opuntia spp.), now dominate fire-suppressed grasslands in southwestern North America. Responses of birds to prescribed burning of the shortgrass prairie in this region are poorly understood. We examined daily survival rates of mourning dove (Zenaida macroura) and lark sparrow (Chondestes grammacus) nests in an experimental landscape (4,811 ha) of spatially replicated, inter-annual fire frequencies (burning every 2 yr, 4 yr, or 10 yr) near Amarillo, Texas. Herbaceous habitat structure was most developed in infrequently burned plots, but shrub densities were less variable among the burn treatments. We modeled daily nest survival (DSR) against burn frequency, shrub density at nest sites, and nest stage (incubation or nestling). Daily survival of mourning dove nests was not well-related to any measured covariate, but lark sparrow DSR was negatively related to the duration of inter-annual burn frequency. In semiarid grasslands heavily inundated with shrubs, prescribed burning may positively influence the nest success of some bird species. © 2011 The Wildlife Society.     

Natural oak forest vs. ancient pine plantations: lizard microhabitat use may explain the effects of ancient reforestations on distribution and conservation of Iberian lizards

Natural vegetation in Europe appears nowadays deeply modified by human activities. In the Guadarrama Mountains (Central Spain), ancient reforestations with Scots pines, Pinus sylvestris, replaced original deciduous pyrenean oak, Quercus pyrenaica, forests (since the Roman period). However, the effect of reforestations on fauna remains little known, especially in reptiles. We described patterns of microhabitat selection in several species of Lacertid lizards, and analyzed whether the modification of the original vegetation affected distribution and population densities of lizards. The species of lacertid lizards found in oak forests (Psammodromus algirus, Lacerta lepida and Podarcis hispanica) were different to those of in pine plantations (Podarcis muralis and Podarcis hispanica). Lizards did not use habitat at random and this could explain differences in species found in both forests, which differed in some microhabitat structure characteristics. Most lizards selected microhabitats with rocky outcrops, with low cover of trees, and close to refuges. These microhabitat preferences also explained abundance of lizards in transects. From the perspective of conservation and management of lizards, pine plantations seem not to contribute too much to the diversity of lizard species because species typical from oak forests were lost. This study has implications for pine reforestation management, because allowing the recolonization by understory␣oaks, and leaving some open areas, without trees but with dense shrubs and rocks inside reforestations would contributed to maintain lizard populations.     

Susceptibility of burned black spruce (Picea mariana) forests to non-native plant invasions in interior Alaska

As climate rapidly warms at high-latitudes, the boreal forest faces the simultaneous threats of increasing invasive plant abundances and increasing area burned by wildfire. Highly flammable and widespread black spruce (Picea mariana) forest represents a boreal habitat that may be increasingly susceptible to non-native plant invasion. This study assess the role of burn severity, site moisture and time elapsed since burning in determining the invisibility of black spruce forests. We conducted field surveys for presence of non-native plants at 99 burned black spruce forest sites burned in 2004 in three regions of interior Alaska that spanned a gradient of burn severities and site moisture levels, and a chronosequence of sites in a single region that had burned in 1987, 1994, and 1999. We also conducted a greenhouse experiment where we grew invasive plants in vegetation and soil cores taken from a subset of these sites. In both our field survey and the greenhouse experiment, regional differences in soils and vegetation between burn complexes outweighed local burn severity or site moisture in determining the invasibility of burned black spruce sites. In the greenhouse experiments using cores from the 2004 burns, we found that the invasive focal species grew better in cores with soil and vegetation properties characteristic of low severity burns. Invasive plant growth in the greenhouse was greater in cores from the chronosequence burns with higher soil water holding capacity or lower native vascular biomass. We concluded that there are differences in susceptibility to non-native plant invasions between different regions of boreal Alaska based on native species regeneration. Re-establishment of native ground cover vegetation, including rapidly colonizing bryophytes, appear to offer burned areas a level of resistance to invasive plant establishment.     

Burning the Seasonal Mosaic: Preventative Burning Strategies in the Wooded Savanna of Southern Mali

Data are presented indicating a seasonal mosaic pattern of burning in the savanna of southern Mali. A seasonal mosaic is a landscape that is annually re-created by people, and which contains patches of unburned, early burned, and recently burned vegetation. A survey of over 100 farmers and in-depth interviews demonstrates that rural inhabitants of southern Mali begin an annual burning regime early in the dry season in order to fragment the landscape, with the goal of preventing later fires that can damage natural resources. The process of gradually burning off the driest vegetation creates a seasonal mosaic of habitat patches that increases the potential of the landscape for a variety of dry season land uses, including hunting, gathering of savanna products, and grazing. An analysis of a series of Landsat images shows that the practice of mosaic burning is widespread in the wooded savanna, in which burning usually begins early and large fires are rare. On the basis of recent developments in ecological theory and empirical evidence from similar burning regimes in parts of Australia, it is suggested that seasonal mosaic burning in Mali not only prevents damaging late-season fires but increases biodiversity. It is concluded that discourse on African savanna burning overemphasizes the ecologically detrimental aspects of fire, while neglecting the beneficial ones resulting in misguided policies that pose a threat to human livelihoods and savanna ecosystems.     

Response of Reptiles and Amphibians to Repeated Fuel Reduction Treatments

Abstract: Recent use of prescribed fire and fire surrogates to reduce fuel hazards has spurred interest in their effects on wildlife. Studies of fire in the southern Appalachian Mountains (USA) have documented few effects on reptiles and amphibians. However, these studies were conducted after only one fire and for only a short time (1–3 yr) after the fire. From mid-May to mid-August 2006 and 2007, we used drift fences with pitfall and funnel traps to capture reptiles and amphibians in a control and 3 replicated fuel-reduction treatments: 1) twice-burned (2003 and 2006), 2) mechanical understory cut (2002), and 3) mechanical understory cut (2002) followed by 2 burns (2003 and 2006). We captured fewer salamanders in mechanical + twice-burned treatment areas than in twice-burned and control treatment areas, but we captured more lizards in mechanical + twice-burned treatment areas than in other treatment areas. Higher lizard captures in mechanical + twice-burned treatment areas likely was related to increased ground temperatures and greater thermoregulatory opportunities. Higher and more variable ground temperatures and faster drying of remaining litter and duff may have led to fewer salamander captures in mechanical + twice-burned treatment areas. Our longer term results, after 2 prescribed burns, differ from shorter term results. After one prescribed burn at the same site, eastern fence lizard (Sceloporus undulatus) captures were greater in mechanical + burn treatment areas but salamander captures did not differ among treatment areas. Our results indicate that multiple (≥2) fuel-reduction treatments that decrease canopy cover may benefit lizards but negatively affect salamanders.     

Fire Management Effects on Long-Term Gopher Tortoise Population Dynamics

Long-term datasets are required to understand the response of long-lived organisms (e.g., gopher tortoises [Gopherus polyphemus]) to management actions, such as prescribed burns. Our objective was to estimate the effects of prescribed burning on gopher tortoise population dynamics over decadal time frames at Fort Stewart Army Reserve, southeastern Georgia, USA. We captured and marked adult tortoises from 1994–2020. In addition, since the early 1990s, managers at Fort Stewart collected spatial records of prescribed burns; thus, we could compare demography of the population to prescribed burning. We used a Bayesian hierarchical model (open population Jolly-Seber model) to estimate population parameters (emigration and survival, immigration and recruitment, and adult abundance) and their relationships with years since burn. We observed opposing responses to years since burn at 2 sites: abundance and the probability of staying (survival plus not emigrating) increased within 1 site when it had been more recently burned (F zones), but abundance and probability of staying in a second site increased when it had been longer since the site was burned (E zones). Some of these effects were weak but indicative of different responses to burning between the sites. Although the sites experienced similar burning regimes, they differed substantially in other habitat features: the F zones had almost twice the tree cover and lower soil sand composition, indicating that tortoise population responses to burning depend on habitat context. We inferred that the primary mechanism for demographic responses to years since burn was likely emigrating adults, which indicates the need for more detailed movement data. Our results demonstrate that gopher tortoise population responses to prescribed burning are complex, context dependent, and primarily influenced by tortoise movements. Therefore, prescribed burn plans may best accommodate spatially dynamic tortoise populations when they create spatial heterogeneity in burn ages within the range of typical tortoise movements. © 2021 The Wildlife Society.     

Horned lizards (Phrynosoma) incapacitate dangerous ant prey with mucus

Horned lizards (Iguanidae, Phrynosomatinae, Phrynosoma) are morphologically specialized reptiles characterized by squat, tank-like bodies, short limbs, blunt snouts, spines and cranial horns, among other traits. They are unusual among lizards in the degree to which they specialize on a diet of ants, but exceptional in the number of pugnacious, highly venomous, stinging ants they consume, especially harvester ants (genus Pogonomyrmex). Like other iguanian lizards, they capture insect prey on the tongue, but unlike other lizards, they neither bite nor chew dangerous prey before swallowing. Instead, they employ a unique kinematic pattern in which prey capture, transport and swallowing are combined into a single feeding stage, apparently leaving the mouth, pharynx, esophagus and stomach vulnerable to bites and stings. Nevertheless, horned lizards consume dozens of harvester ants without harm. We show that their derived feeding kinematics are associated with unique, mucus-secreting pharyngeal papillae that apparently serve to immobilize and incapacitate dangerous ants as they are swallowed by compacting them and binding them in mucus strands. Radially branched esophageal folds provide additional mucus-secreting surfaces the ants pass through as they are swallowed. Ants extracted from fresh-killed horned lizard stomachs are curled ventrally into balls and bound in mucus. We conclude that the pharyngeal papillae, in association with a unique form of hyolingual prey transport and swallowing, are horned lizard adaptations related to a diet of dangerous prey. Harvester ant defensive weapons, along with horned lizard adaptations against such weapons, suggest a long-term, predator-prey, co-evolutionary arms race between Phrynosoma and Pogonomyrmex. J. Exp. Zool. 309A:447-459, 2008. (c) 2008 Wiley-Liss, Inc.     

Influence of late season fire on early successional vegetation of an Oklahoma prairie

Abstract. The study of vegetation dynamics in tallgrass prairie in response to fire has focused on dormant season fire in late successional prairies. Our objective was to determine if late season fire of varying frequency results in divergent successional patterns in an early successional tallgrass prairie disturbed by grazing and cultivation. Specifically, we evaluated the influence of late‐summer fires of varying frequency on community composition and species richness. We collected vegetation and environmental data on two sites burned in the late growing‐season at varying frequencies. These communities differed in composition depending primarily on edaphic factors, time since the last burn, and year‐to‐year variation. We interpret the time effect as related to changes in species composition accompanying plant succession that followed disturbance either from cropping and heavy grazing on the loamy site or heavy grazing on the shallow site. Other unidentified factors also have a role in vegetation dynamics on this prairie. Community composition and species richness were not consistently responsive to frequency of growing‐season fires.     

Effects of fire on landscape heterogeneity in Yellowstone National Park,Wyoming

Abstract. A map of burn severity resulting from the 1988 fires that occurred in Yellowstone National Park (YNP) was derived from Landsat Thematic Mapper (TM) imagery and used to assess the isolation of burned areas, the heterogeneity that resulted from fires burning under moderate and severe burning conditions, and the relationship between heterogeneity and fire size. The majority of severely burned areas were within close proximity (50 to 200 m) to unburned or lightly burned areas, suggesting that few burned sites are very far from potential sources of propagules for plant reestablishment. Fires that occurred under moderate burning conditions early during the 1988 fire season resulted in a lower proportion of crown fire than fires that occurred under severe burning conditions later in the season. Increased dominance and contagion of burn severity classes and a decrease in the edge: area ratio for later fires indicated a slightly more aggregated burn pattern compared to early fires. The proportion of burned area in different burn severity classes varied as a function of daily fire size. When daily area burned was relatively low, the proportion of burned area in each burn severity class varied widely. When daily burned area exceeded 1250 ha, the burned area contained about 50 % crown fire, 30 % severe surface burn, and 20 % light surface burn. Understanding the effect of fire on landscape heterogeneity is important because the kinds, amounts, and spatial distribution of burned and unburned areas may influence the reestablishment of plant species on burned sites.     

Northern bobwhite breeding season habitat selection in fire-maintained pine woodland

Despite the acknowledged importance of prescribed fire in creating northern bobwhite (Colinus virginianus) breeding cover, little research has investigated bobwhite breeding season habitat selection relative to time since fire. In 2016 and 2017, we monitored radio-tagged bobwhite on a 17,000-ha portion of a military installation managed with frequent (every ~3 years) prescribed fires, applied during the growing and dormant seasons. We monitored bobwhite to determine which vegetation characteristics associated with prescribed burning were important to bobwhite breeding season habitat selection at the microsite (i.e., telemetry location compared to nearby random location) and the macrosite scale (i.e., the burn-unit containing the location compared to study area availability). During 2 breeding seasons, we collected 2,315 bobwhite locations and compared percent cover of vegetation, days since burn, basal area, and distance to key landscape features (e.g., stream, wildlife opening) at a subset of microsite locations (301 locations during 2016 and 890 locations during 2017) to paired random locations. At the microsite scale, bobwhite selected lower basal area of hardwoods, greater woody understory cover, greater other (not wiregrass [Aristida stricta]) grass cover, and greater forb cover than at random points. At the macrosite scale, bobwhite selected units with <4.6 m²/ha basal area (combined hardwoods and pines) in 2016 and units with <9.2 m²/ha basal area in 2017. At the macrosite scale, bobwhite selected for areas burned in the dormant season of the same year, avoided areas burned in the growing season of the same year, and used other times since last burn categories proportionate to their availability. The selection for a low basal area at both scales indicates prescribed fire effects would be limited by shading from dense overstory, and the shrubs, grasses, and forbs that provide essential cover for bobwhite during the breeding season will not develop. In lower productivity soil regions similar to our study area, we advise that thinning operations set target basal areas below 10 m²/ha to create and maintain breeding season habitat for northern bobwhite. © 2019 The Wildlife Society     

Restoring riparian meadows currently dominated by Artemisia using alternative state concepts ‐ the establishment component

Abstract. We evaluated the potential for restoring riparian grass and sedge meadows currently dominated by Artemisia tridentata var. tridentata with an experiment in which we burned sites with low, intermediate, and high water tables, i.e., dry, intermediate, and wet sites. To define the alternative states and thresholds for these ecosystems, we examined burning and water table effects on both abiotic variables and establishment of grasses adapted to relatively high (Poa se‐cunda ssp. juncifolia), intermediate (Leymus triticoides), or low (L. cinereus) water tables. Wet sites had lower soil temperatures and higher soil water contents than dry sites. Burning increased soil temperatures on all sites. Undershrub microsites on control plots had the lowest temperatures, while former undershrub microsites on burn plots had the highest temperatures. Surface soil water was low on burn plots early in the growing season due to desiccation, but higher at deeper depths after active plant growth began. Emergence was generally greater on wet sites, but survival was microsite‐ and species‐specific. Undershrub microsites on control plots facilitated emergence and first‐year survival, but seedlings that survived initially harsh conditions on burn plots had similar numbers alive at the end. In general, favorable environments and establishment of species adapted to mesic conditions indicate that wet sites represent an alternative state of the naturally occurring dry meadow ecosystem type, and can be restored to grass and sedge meadows. Harsh environments and lack of establishment of species adapted to mesic conditions indicate that dry sites have crossed a threshold and may represent a new ecosystem type. Understory vegetation and seed banks on dry sites have been depleted, and restoration will require burning and reseeding with species adapted to more xeric conditions.     

Experimental trial of Australian arid zone reptiles as early warning indicators of overgrazing by cattle

The value of reptiles as bioindicators of the initial effects of heavy cattle grazing in a South Australian chenopod shrubland was assessed in an experimental trial. Reptiles were sampled in three different subhabitats within two replicate treatment paddocks and a control region. A total of 30 sites was sampled in two sessions before grazing and four sessions after the commencement of intensive pulses of grazing. Capture rates of most common reptile species, fecundity of abundant gecko species and reptile species composition within different subhabitats were largely resilient to the initial effects of overgrazing. However, agamids in general, and particularly Ctenophorus nuchalis, increased at grazed sites relative to controls following grazing. Most changes observed in the reptile assemblages were predictable based upon species response to alteration in vegetation cover. Because vegetation cover can be rapidly and efficiently monitored, the use of reptiles as early warning indicators of unsustainable pastoralism in the study region was not supported.     

Winter Burning and the Reduction of Cornus sericea in Sedge Meadows in Southern Wisconsin

To control shrubs, which are increasing in dominance in wetlands worldwide, winter burning may be an important tool, especially from the perspective of minimizing urban hazards. The goal of this project was to determine if winter burning was successful in reducing the dominance (mean percentage cover and maximum height) of Cornus sericea in sedge meadows in southern Wisconsin, where shrubs proliferated after cattle were excluded. Experimental burn and control plots were set up within sedge meadows, including an ungrazed “reference” site that had been little, if ever, grazed and a “historically grazed” site, a recovery site that had not been grazed by cattle since 1973. None of the dominant species including C. sericea was significantly affected by burning for either mean percentage cover or maximum height (analysis of variance: no burning × species interaction). Both mean percentage cover and maximum height were only weakly related to burning (28.1 and 14.3% of the variability contributed to the cumulative percentage of the coefficient of determination, respectively) at both sites based on non‐metric multidimensional scaling analysis. Although species richness increased in burned plots in 1999 and 2000, no differences were apparent between pre‐burned and unburned plots in 1997 and unburned plots in 1999 and 2000 (analysis of variance: year × burning interaction). After burning in the ungrazed site, herbaceous species appeared that had not been detected for decades, including Chelone glabra and Lathyrus palustris. Exotic species were present in both the ungrazed reference and recovery site. Although winter burning treatments did not reduce the dominance of woody shrub species in the site recovering from cattle grazing, burning was useful in stimulating the maintenance of species richness in the ungrazed sedge meadow.     

Geographical Variation in Body Size and Sexual Size Dimorphism in an Australian Lizard,Boulenger's Skink (Morethia boulengeri)

Ecogeographical rules help explain spatial and temporal patterns in intraspecific body size. However, many of these rules, when applied to ectothermic organisms such as reptiles, are controversial and require further investigation. To explore factors that influence body size in reptiles, we performed a heuristic study to examine body size variation in an Australian lizard, Boulenger''s Skink Morethia boulengeri from agricultural landscapes in southern New South Wales, south-eastern Australia. We collected tissue and morphological data on 337 adult lizards across a broad elevation and climate gradient. We used a model-selection procedure to determine if environmental or ecological variables best explained body size variation. We explored the relationship between morphology and phylogenetic structure before modeling candidate variables from four broad domains: (1) geography (latitude, longitude and elevation), (2) climate (temperature and rainfall), (3) habitat (vegetation type, number of logs and ground cover attributes), and (4) management (land use and grazing history). Broad phylogenetic structure was evident, but on a scale larger than our study area. Lizards were sexually dimorphic, whereby females had longer snout-vent length than males, providing support for the fecundity selection hypothesis. Body size variation in M. boulengeri was correlated with temperature and rainfall, a pattern consistent with larger individuals occupying cooler and more productive parts of the landscape. Climate change forecasts, which predict warmer temperature and increased aridity, may result in reduced lizard biomass and decoupling of trophic interactions with potential implications for community organization and ecosystem function.     

Demographic correlates of variable egg survival for a tropical lizard

Summary Anolis limifrons is a small iguanid lizard that is found in lowland rainforest in Central America. Important life attributes include early maturity (3–4 mo), multiple clutches of a single egg per breeding season, and low survival. Population turnover is essentially annual as less than 5% adults live more than one year. My objectives were to resolve the following specific questions: 1) Where are eggs laid? 2) Does survival differ among different types of oviposition site? 3) How is the survival of eggs related to the density and age distribution of lizards at different areas? Most eggs are laid beneath litter on the ground. Eggs laid aboveground are placed in accumulations of soil and litter in stumps, crevices in buttressed trees and vines, holes in trees, and on the tops of logs. Eggs were found in aboveground sites in proportion to the abundance of those sites. The major cause of mortality was predation by Solenopsis ants. Judging by the ratio of eggs known to have hatched to those that were predated, survival did not differ among the various types of oviposition site. Study areas with high egg survival in the middle of the wet season had relatively more young (<4–6 mo old) lizards at the end of the wet season than areas with low egg survival. The strong correlation between the relative number of young individuals and egg survival is a consequence of the seasonal cycle of growth and reproduction. Most eggs are laid in the wet season (May–December). Hatchlings complete growth during the dry season (January–April) and become reproductive adults in their second wet season. However, because hatchlings can grow to reproductive size in approximately 3 months, individuals that hatch early in the wet season may themselves produce offspring that will be <4–6 mo old in the late wet season. The relative survival of juveniles (eggs) and adults is an important datum for many theories of life history evolution. For A. limifrons, survival of eggs was two to three times more variable than survival of lizards on both temporal and spatial scales. Comparative data for reptiles are not available to put this information into an evolutionary prespective.     

The distribution, density and biomass of terrestrial reptiles in Dominica, West Indies

Fourteen species of reptiles have been recorded from the island of Dominica, Lesser Antilles. As part of a larger study of the ecology of Dominica's forests, the distribution, density and biomass of three widespread lizard species ( Anolis oculatus, Ameiva fuscata and Mabuya mabouya ) were estimated in all major vegetation types. No consistent differences between seasons occurred for any of the three species, and at no site was a definite breeding season detected. Densities, estimated mainly by plot counts, were highest in coastal woodlands where mean densities reached 2148 Anolis per hectare, 379 Ameiva per hectare, and 751 Mabuya per hectare. Densities in rain forest sites were often very low. Combined biomass for the three species also reached a maximum in coastal woodlands of 44.7 kg/ha. This value is amongst the highest recorded for terrestrial reptile assemblages, and suggests that Dominica's coastal woodlands are unusually favourable habitats for reptiles.
Previous studies of Caribbean lizards have suggested that either competition or predation from birds may influence lizard densities. The present study, however, found no such relationships, and it was concluded that lizard density was independent of bird density.