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Patterns of habitat use in animals can vary over time and space in predictable ways. For ectotherms, behavioral cycles are tightly linked to varying temperatures in the environment such that microhabitat availability can constrain individual performance, fitness, and life history. A long history of research on diurnal microhabitat use in lizards exists; however, comparatively little is known about nocturnal microhabitat use that might also constrain individual lizard performance, fitness, and life history. In this study, we compared diurnal and nocturnal microhabitat sites of the reticulate collared lizard (Crotaphytus reticulatus), a threatened species in Texas, to available microhabitat sites. We found significant differences between diurnal and nocturnal microhabitat characteristics, and both of these were significantly different from random microhabitat sites available. We observed that C. reticulatus used diurnal and nocturnal microhabitats with a gravel substrate and scattered boulders that were covered by a short overstory of woody and succulent plants rather than more heavily vegetated sites with dense grasses and forbs. We also observed that diurnal microhabitats were moderately open, shallow gravel slopes compared with nocturnal microhabitats that contained dense thickets of woody and succulent plants. The open, gravelly characteristics of diurnal microhabitats with occasional vegetative structure were more consistent with microhabitat descriptions of other Crotaphytids, which as a group are visual predators. However, the daily shift to dense, thorny plant cover at night appears unique to C. reticulatus among Crotaphytids in general. This study suggests that private land stewardship across the C. reticulatus distribution in Texas has benefitted the species by maintaining habitat used by the lizard, and it suggests that future conservation actions for the species will be most successful with continued engagement with private landowners.
White-nose syndrome (WNS) represents an emerging infectious disease in bats caused by the fungal pathogen Pseudogymnoascus destructans (Pd). The fatal disease has devastated populations of several species of bats in North America, so there is interest in delimiting its current range to aid containment and other management efforts. Early detection of the fungus aids in risk assessment of the disease and managing its presence in areas with hibernating bats. Infection by Pd in bats has been neither surveyed nor reported in Louisiana, despite the fact that WNS has been recorded approximately 150 km across the border of two neighboring states, Arkansas and Mississippi. Between December 2015 and January 2016, we surveyed 190 culverts distributed across the northern portion of Louisiana. In total, we encountered 801 individual bats (355 Perimyotis subflavus, 299 Myotis, 54 Eptesicus fuscus, 47 Tadarida brasiliensis, and 46 Corynorhinus rafinesquii). We used ultraviolet illumination to inspect each individual for presence of WNS symptoms, and no visible symptoms were detected. We also swabbed the skin of 244 bats and 316 habitat walls, and swabs were returned to the laboratory and analyzed using quantitative polymerase chain reaction and Pd-specific primers for presence of the pathogen. No genetic detections occurred in any bat or habitat wall samples. Based on negative detection, we hypothesize that the fungus has not yet been introduced into the state of Louisiana or the environmental conditions of culverts found in Louisiana are not conducive to persistence of the fungus; however, ours is the first survey to assess the status of Pd in the state. Monitoring should continue to confirm that no evidence of the fungal pathogen exists anywhere in the state and to enable rapid response if detection occurs.
Predation of dunes sagebrush lizards (Sceloporus arenicolus) by loggerhead shrikes (Lanius ludovicianus) is not well-understood. The goal of this project was to determine if the frequency of dunes sagebrush lizards as prey by loggerhead shrikes was greater in areas that were fragmented by oil and gas development compared with unfragmented habitat. We deployed motion-activated game cameras at shrike nests to determine what prey was being fed at the nests, we quantified the amount of time shrikes spent hunting from power lines or other anthropogenic perches, and we collected shrike pellets to look for the presence of dunes sagebrush lizard scales. Camera data results indicate that lizards make up approximately 10% of the prey items that loggerhead shrikes take to the nest. The difference in overall lizard captures between fragmented and unfragmented habitat was not statistically significant. Power-line survey results indicate that loggerhead shrikes hunt from anthropogenic perches approximately 50% of the time. The analysis of camera-trap images allowed us to identify two individual dunes sagebrush lizards, each from a nest in fragmented habitat, and the pellet analysis documented one instance in unfragmented habitat. An opportunistic finding in a shrike food larder in unfragmented habitat documented six additional dunes sagebrush lizards that were impaled on barbed wire. These results indicate that loggerhead shrikes do sometimes predate dunes sagebrush lizards, although samples sizes were too small to determine predation rates between the habitat types.
In 1975, wildlife managers reintroduced desert bighorn sheep (Ovis canadensis mexicana) to Tiburón Island, Mexico, where endemic mule deer (Odocoileus hemionus sheldoni) occur. We predicted that these species would use both mountain and plains habitats, but would have different diets, minimizing negative interspecific effects. By censusing pellet groups, we found that both ungulates occurred in both habitats, but bighorn sheep were more abundant in mountains and mule deer were more abundant in plains. Microhistological analyses determined that diets of both species consisted of the same 39 plant species, of which 13 plant species each composed ≥4% of the diet and together composed 70–80% of the total diet. Plants in low abundance represented 26–32% of diets in the mountains and 45–56% of diets in the plains. Overall diet overlap was 68% and overlap did not differ between mountains or plains, but did differ among seasons. Overlap in habitat agreed with predictions, but diet overlap was contrary to our predictions. Our results differ from studies on the mainland, which found overlap in habitat use, but not in diet. Overlap in resource use coupled with the rapid increase in abundance of bighorn sheep since their reintroduction to Tiburón may have an impact on mule deer. Additional research is needed to determine whether abundance of mule deer has changed in response to the reintroduction of bighorn sheep.
We used occupancy modeling to investigate habitat use by White Sands pupfish (Cyprinodon tularosa) in a 53.4-ha ciénega supported by discharge from Malpais Spring. The ciénega has been subject to considerable alteration by humans over the last ca. 200 years, resulting in dynamic conditions of emergent wetland vegetation structure and composition and spatial variation in surface water characteristics. Site occupancy models were developed to describe variation in probabilities of detection and habitat use. Detection of White Sands pupfish was negatively influenced by total emergent wetland plant cover, and less so by survey-specific measurements of water temperature and cloud cover. Site occupancy, which we interpreted as habitat use because we did not assume site closure, was consistently influenced by additive effects of water depth and cover by beaked spike-rush (Eleocharis rostellata) in top-ranked models. In the top-ranked model, with other covariates set at their mean value, habitat use probability reached a plateau at 1 at a water depth of ≥30 cm, and habitat use probability fell below about 0.6 when beaked spike-rush cover was ≥0.7. The top-ranked models indicated that habitat use was also influenced to a lesser extent by chairmaker's bulrush (Schoenoplectus americanus) cover and floating algal mats. The negative effect of chairmaker's bulrush cover on habitat use probability was moderated by water depth. Application of depth and spike-rush cover criteria taken from the top-ranked model produced an estimate of 1.58 ha of high-use probability habitat in the ciénega. The results have implications for monitoring the pupfish population and its habitat, and for development of reference conditions for management of the Malpais Spring ciénega.
We collected and analyzed a 6-year remote game camera data set from the Mojave National Preserve for determining factors influencing occupancy and detection rates for mountain lions (Puma concolor) in the Mojave Desert. We detected mountain lions in 37 of 186 sampling periods at 36 sites monitored by remote game cameras. Detection rates decreased rapidly with increasing distance to shrub cover, and there was no relationship between season and detection rates. Occupancy was found to be constant across sampling periods. Our results suggest mountain lions are present in the Mojave National Preserve year-round. Our analyses can serve to further the understanding of mountain lion spatial ecology and community-level interactions in the Mojave Desert ecosystem. Lastly, our analyses represent the first occupancy and detection estimates for mountain lions in the Mojave Desert and can serve as a baseline for tracking populations over time.
We surveyed a summer population of Tadarida brasiliensis mexicana in south-central Colorado to gain an initial characterization of the resident mycobiome (i.e., fungal biota) present on their body surfaces. We cultured fungal spores from bats captured in early and late summer and then conducted DNA barcoding analysis for taxonomic identification. Phylum Ascomycota dominated the ectomycotal (i.e., fungi present on body surfaces) community, with the most common genera including Aspergillus, Penicillium, Cladosporium, and Eurotium. Phylum Basidiomycota constituted a smaller proportion of fungal isolates and was composed primarily of Cryptococcus, Peniophora, Cystofilobasidium, and Sistotrema. We found seasonal differences in fungal community composition, with diversity and evenness increasing from June to August. There were notable differences in fungal communities present on adult vs. juvenile bats, with juveniles having a greater number of unique genera, greater fungal diversity, and lower species evenness compared with adults. We isolated a number of fungal species that are capable of growing at low temperatures, indicating that T. b. mexicana harbors viable psychrophilic fungi.
Snakes are a known predator of quail; however, the influence of snake predation on quail populations is unknown. We used a long-term data set collected by eight radiotelemetry studies in Texas, encompassing 23 years (1994–2017) and 5,369 quail, to quantify snake predation on quail. We documented that northern bobwhite (Colinus virginianus) and scaled quail (Callipepla squamata) mortalities were caused by three species: western diamondback rattlesnakes (Crotalus atrox), prairie rattlesnakes (Crotalus viridis viridis), and Texas rat snakes (Pantherophis obsoletus). This study is the first to document predation of quail (Odontiphoridae) by the latter two species. We found 30 mortalities (0.6%) attributable to western diamondback rattlesnakes. We found 1 mortality (0.03%) attributable to a prairie rattlesnake and 2 mortalities (0.06%) attributable to Texas rat snakes of the 3,206 quail exposed to predation by those two species. We concluded that snakes are not major predators of adult quail, but that they will prey opportunistically upon them.
San Joaquin kit foxes (Vulpes macrotis mutica) are typically socially monogamous. During the 2012 breeding season in Bakersfield, California, where food is abundant, population density is high, and dispersal potential is low, we documented two cases of social polygyny. Both groups had two litters; we documented allonursing in one group. In both groups the two mothers were not closely related and the “helper” was not closely related to the other adults. All four reproducing females had at least one pup sired by an extragroup male. One female had three inbred pups that resulted from matings with first-degree relatives. The unique conditions associated with the urban environment may alter kit fox social ecology.
Predation can significantly affect prey populations, which could be significant for recovering species threatened with extinction. As part of a study on home ranges of the endangered blunt-nosed leopard lizard (Gambelia sila), I found lizards killed, or presumed killed, by predators. Predators that I could identify killing G. sila were the northern Pacific rattlesnake (Crotalus oreganus oreganus) and birds. The overall annual rate of predation during the active season of these lizards was 0.181, or 0.233 if lizards presumed killed are included. Based on published literature by others and other events of predation that I have published, birds and snakes seem to be the major predators of G. sila.
Razorback sucker (Xyrauchen texanus) and flannelmouth sucker (Catostomus latipinnis) live in sympatry in the Colorado River basin. Although morphological intermediates have been described since 1889, hybrids were seemingly rare. Rarity of hybrids was likely attributed to razorback suckers' ability to find conspecific mates throughout the basin. Dams have segmented the Colorado River, altering habitat and isolating native fish populations. As a result, razorback suckers became endangered. Razorback suckers are uncommon in the Colorado River and hybridization could increase because of limited conspecific mates. To understand the impacts of hybridization on recovery of the razorback sucker, information on hybrid viability is needed. We compared hatch success and larval survival of artificially spawned razorback sucker, flannelmouth sucker, and their hybrids. We were able to successfully spawn and rear all combinations, implying that there are limited pre- and postzygotic isolation mechanisms, and hybrids are likely to survive in the wild.
Introduced (or exotic) species are any taxa living outside their native range. The ecological impact of these species is highly variable although many have altered, at the ecosystem level, biological communities and their native fauna. Millipeds (Diplopoda) are known to have arrived into many nonnative sites via potted plants and compost from greenhouses. Here, we provide a summary of the introduced millipeds of Arkansas, Louisiana, Oklahoma, and Texas.