Species distributions may be determined by a variety of biotic and abiotic factors. The model ciliate Tetrahymena thermophila exhibits an unusual distribution limited to the eastern United States. In this study, we assess the roles of species interactions and habitat requirements in driving this restricted distribution by studying laboratory populations of T. thermophila and Tetrahymena gruchyi. We find that priority effects and habitat requirements are likely to be important factors driving the distribution of Tetrahymena species.

Woodhouse's scrub-jay (Aphelocoma woodhouseii texana) is a relatively understudied subspecies inhabiting juniper scrub and woodland in central Texas. We estimated density and examined habitat associations at the eastern edge of their breeding range. Scrub-jays were strongly associated with intermediate proportions of juniper land cover at a 100-m scale and showed lower density in areas of greater mixed oak-juniper woodland and greater urban land cover at a 1-km scale.

Increasing urbanization over the last century has resulted in a greater abundance of invasive species. Invasive feral pigeons (Columba livia) damage critical urban infrastructure and pose risks to human health. Universities, including Texas Tech University (TTU), located in Lubbock, Texas, have difficulty decreasing adverse effects caused by pigeons. Assessing reliable estimates of population demographics is an important first step to understanding and managing damaging pigeon populations. Our goal was to estimate pigeon abundances at TTU and understand the underlying mechanisms that facilitated pigeon persistence on campus. We surveyed 23 independent locations from March to April 2017 to estimate pigeon abundance across the entire campus. Separately, we also examined pigeon densities on two campus buildings from March to December 2017 to assess and quantify variation in pigeon detection probabilities and abundance both during the diurnal period and among calendar seasons. Our estimates suggested campus abundance was comparable to other urban areas (1,584.4 pigeons/km², SE = 43.58, 95% CI = ±1,969). Our results indicated hot spots (i.e., high pigeon abundances) existed on campus; for example, we estimated ∼2,819 pigeons (SE = 76, 95% CI = ±138) on a single building on campus during our surveys. Enumeration of pigeon abundance on two campus buildings (mean = 326, SE = 16, 95% CI = ±11) indicated abundance was greatest in the fall and during the morning hours, and peak abundance occurred shortly after 0700 h and declined during the day. Our results suggested pigeons were abundant on campus due to structure and composition of buildings that facilitated nesting and loafing spots that likely maximized efficiency and effectiveness of thermal regulation as well as direct access to water during the study period. In general, pigeons clustered on two buildings on campus and our findings suggested success of population-control measures may be maximized if they are implemented around these buildings.

Rio Grande sucker (Pantosteus plebeius) is continuously distributed in parts of its range, but occurs in geographically isolated populations at the periphery. We used 10 microsatellites and DNA sequence data from the mitochondrial cytochrome b gene to characterize genetic diversity and reconstruct evolutionary relationships of five peripheral populations in the southwestern United States. An isolated population in Rio Bonito (Pecos River drainage) is most closely related to a central Rio Grande population in Alamosa Creek, and part of the monophyletic Rio Grande lineage. Another disjunct population, Bluewater Creek in the western Rio Grande drainage, has a Mimbres lineage mtDNA haplotype that likely originated via interbasin transfer. Both peripheral populations are important for conservation of the species as a whole. Three other isolated populations are closely related to mainstem “core” populations in the Mimbres and Gila rivers that colonized these intermittently connected tributaries. One peripheral population in Allie Canyon, Mimbres River, has persisted longer in isolation than Rocky Canyon or Trout Creek in the Gila system. In general, a process of range expansion during relatively cool and wet periods, followed by retreat to wetted refugia during warm and dry periods, leads to genetic differentiation of peripheral populations of Rio Grande sucker at local and across-basin scales.

Tourist activity in natural areas may impact species' behavior and ecology as well as predator-prey dynamics. Although previous research has demonstrated effects of human disturbance on wildlife communities, only a limited number of studies have focused on small mammals and coyote predator-prey systems. To generate an overview of human impacts on these wildlife communities, we analyzed camera trap data from a human-disturbed site at Lake Tahoe, California. To compare species' activity patterns in relation to distances from human-disturbed areas, we used single-species occupancy models, estimations of species' temporal activity overlaps, and the time between detections of different species at camera sites. We found that in general black bears (Ursus americanus) avoided areas of high human disturbance, whereas coyotes (Canis latrans), rodents, and lagomorphs favored them. However, rodents and lagomorphs also avoided areas with high coyote detections, indicating that rodents and lagomorphs mostly used human-disturbed areas that were not highly frequented by coyotes. Additionally, all aforementioned species avoided humans temporally and this avoidance increased in closer proximity to human-disturbed areas. These findings indicate that while some species frequented human-disturbed areas more than others, all species studied exhibited greater temporal avoidance of humans when closer to areas of higher human activity. Our results also indicate that rodents' and lagomorphs' activity patterns overlapped more with coyotes' activity patterns closer to human-disturbed areas and rodents and lagomorphs avoided coyotes less in these areas. The greater overlap of the species' activity patterns suggests that there is likely more interaction between coyotes and their prey closer to areas of high human activity. The changes in the behavior and ecology of wildlife communities closer to human-disturbed areas reported here emphasize how proximity to human-disturbed areas may influence both predator and prey demographics.

In 2012, we conducted a mammal survey in the cloud forest of the Otonga Forest Preserve on the western slope of the Andes in Cotopaxi Province, Ecuador. We used Sherman traps, Tomahawk traps, pitfall traps, and mist nets to collect mammal specimens at 2,070 m in elevation. We collected 148 specimens representing 19 species from the survey area. The species collected include Caenolestes convelatus, Marmosops caucae, Sturnira bidens, Sturnira erythromos, Sturnira ludovici, Anoura caudifer, Anoura peruana, Platyrrhinus dorsalis, Platyrrhinus nigellus, Myotis oxyotus, Mazama rufina, Melanomys caliginosus, Neusticomys monticolus, Thomasomys baeops, Thomasomys silvestris, Nephelomys moerex, Dasyprocta fuliginosa, and Bassaricyon neblina. We documented Notosciurus granatensis with photography.

Springs are essential sources of water for humans and wildlife in the Sonoran Desert and, despite their isolation, they often support diverse aquatic communities. However, flows in these systems are declining due to groundwater pumping and increasing temperatures and aridity. In the western Sonoran Desert, two spring-fed systems represent the vast majority of perennial surface water along the U.S.-Mexico border: Quitobaquito, an upland hillslope spring, and a nearby spring-fed reach of the Rio Sonoyta. In this study, we quantified how aquatic invertebrate species richness and community composition varied by habitat type and season at these two sites. We found that habitat was a significant driver of composition for both sites, but seasonal variation was only influential for species richness in the Rio Sonoyta. Continued declines in flow will likely lead to significant losses of aquatic invertebrate biodiversity at both sites.

Systematic larval fish surveys increase the probability of detecting rare species and provide ecological insights for more common species that can be difficult to infer from surveys of older life-stages. To characterize the reproductive success of the extant fish assemblage in the western Grand Canyon portion of the Colorado River, we conducted systematic larval fish surveys in 2014 and 2015. The effort identified endangered razorback sucker (Xyrauchen texanus) as initiating spawning in February with a continuation through July. We collected recently hatched protolarval fish throughout the study area including the most upstream sample sites, suggesting fish spawned throughout and upstream of the study area. Our collection of a protolarval endangered humpback chub (Gila cypha) supports the hypothesis that the population increased in range within the Grand Canyon from its dramatic 2001 contraction into the Little Colorado River and suggests localized spawning. Back-calculating hatching dates indicated humpback chub began hatching in late April and continued through mid-May. Native fishes numerically dominated larval fish collections (97.6 and 99.3% for 2014 and 2015, respectively) and recruitment to the early juvenile life-stage was documented for all fish species captured except razorback sucker. Abundance, measured as catch per unit effort and frequency of occurrence, was different between years for each native species captured (n = 5). Interannual differences in abiotic factors (discharge, diel fluctuations in discharge, and water temperature) were significantly different for most months between years. A redundancy analysis, evaluating the relationship between abiotic environmental factors and catch rates, suggested both discharge and water temperature were associated with speckled dace (Rhinichthys osculus), bluehead sucker (Catostomus discobolus), and flannelmouth sucker (Catostomus latipinnis), with a positive correlation to water temperature and a negative correlation to discharge. We were unable to identify associations between abiotic factors and the endangered fishes, which may have been due to the lack of variability in those species' catch rates. Improving our understanding of the relationship between reproductive success and abiotic factors would enhance management of the system to benefit native fishes.

The unique biogeography of the Madrean Archipelago facilitates the cohabitation of species that otherwise rarely overlap in their spatial distributions. As part of a long-term study at Cuenca Los Ojos, Sonora, we deployed 25 cameras along washes within the property from October 2018 to April 2019, adding to the camera-trap information collected at the site since 2016. Ocelot (Leopardus pardalis) was recorded once in 2018, twice in 2016 and 2020, but not during the 2018–2019 study period. Black bear (Ursus americanus) was recorded regularly throughout the season with several images including cubs. One picture and several signs of beaver (Castor canadensis) were discovered in 2018 and 2019. Lastly, the first record of jaguar (Panthera onca) in Cuenca Los Ojos was recorded in February and March 2019 at four different sites. All species are considered endangered in Mexico and species of conservation concern in the United States and were recorded within 5 km south of the USA–Mexico border wall. Our addition of the new ocelot sighting in this region marks the only known location with records of all four species overlapping in space and time despite historical distribution ranges of black bears, jaguars, and beavers overlapping. Given the current border wall construction and highway development, which both affect the natural connectivity of the region, it will be necessary to incorporate the presence of the four species in all future mitigation efforts.

Previous work shows that individuals of the keystone cactus Carnegiea gigantea found in slower-growth, more arid populations live longer than those in wetter areas. This study follows by adding data for youth for these populations. The median age and the cut-off ages for the youngest deciles confirm that populations in wetter areas with faster growth have the most compressed life cycles, exhibited at all life stages. Populations are more youthful in wetter, faster-growth environments.

We observed a common raven (Corvus corax) flying to an electrical transmission line tower with a Wilson's warbler (Cardellina pusilla) in its beak. Upon inspection of the ground under the tower, additional warbler carcasses were discovered. Questions arise with regard to predation versus scavenging, and it is often difficult to determine. However, knowing what species are considered prey by predators is a first step. Our observations were opportunistic and our report documents the collection of Townsend's (Setophaga townsendi) and Wilson's warblers by a common raven in the Mojave Desert.