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Astrophytum asterias (star cactus) is an obligate outcrosser that does not reproduce vegetatively, so all reproduction is the result of inter-plant transfer of pollen by insects. By measuring seed set resulting from single pollinator visits, we evaluated effectiveness (mean seed set per visit) and importance of pollinator (effectiveness times frequency of visitation) of insects visiting flowers of A. asterias. Results indicate that the most common visitor, Macrotera lobata, is a relatively ineffective pollinator, while the less common Diadasia rinconis is the most effective and important pollinator. Two behavioral variables (duration of visit, whether or not visitors landed on the stigma) were assessed as possible predictors of fruit set. While duration of visit was not predictive of fruit set, there was a positive correlation between fruit set and the proportion of visits a visitor landed on the stigma when entering the flower.
Mechanical thinning is an important silviculture technique for timber production and reducing woody fuels in coniferous forest, but little is known about its effect on wildlife in mixed-coniferous forests in the American Southwest. During 2005–2006 we examined diversity, abundance and survival of terrestrial mammals in thinned and non-thinned mixed-coniferous forest in the Sacramento Mountains, Lincoln National Forest, in southern New Mexico. The three thinning treatments included two non-commercial thins with different slash treatments (i.e., lop-pile, lop-scatter) and a commercial harvest using selective logging. There were two non-thinned treatments that differed in age of stand (i.e., 20–30 years and 60–100 years post harvest). In general, thinned treatments had higher richness and abundance of mammals in comparison with the older non-thinned stand, but did not differ in richness and abundance from the younger non-thinned stand. Abundance of the North American deermouse (Peromyscus maniculatus) and red squirrel (Tamiasciurus hudsonicus) did not differ among treatments. However, survival of P. maniculatus varied more in the non-thinned stands. Abundances of the gray-footed chipmunk (Tamias canipes) and long-tailed vole (Microtus longicaudus) were significantly lower in the older non-thinned stand than in all thinned treatments. Most large mammals were documented in thinned treatments. These results suggest that thinning older stands of mixed-coniferous forest that are overly dense compared with historical conditions benefit the mammal community through increases in diversity and abundance. In comparing the three mechanical-thinning treatments evaluated, none provided a clear cost or advantage to mammals. However, additional controlled experiments are needed to further corroborate these results.
The Great Plains ratsnake (Elaphe guttata emoryi) is a poorly known species of the central and southern United States. We captured 24 Great Plains ratsnakes over 3 years at Fort Hood, Texas, and used radiotelemetry to determine habitat use and seasonal activity patterns of five adult male snakes. Great Plains ratsnakes showed an affinity for human-made structures with the majority of locations in rock structures used to control erosion. When compared to random sites, snake-selected sites were in areas of increased structure with more trees and ground cover and closer to habitat edges. Despite Great Plains ratsnakes having been documented preying on nests of arboreal birds, tracked snakes were found almost exclusively at or below ground level. Snakes were active year round and did not exhibit distinct hibernation times or sites. Snakes exhibited a bimodal pattern of activity with peaks in late spring and autumn, most likely due to temperature constraints.
Researchers using drift-fence sampling with associated pitfall traps have analyzed a number of problems associated with this technique. One unquantified problem is the effect foraging vertebrate predators might have on animals captured in pitfall traps. We used Deer Cam® cameras and track-monitoring stations to estimate amount and variety of vertebrate predators attending pitfall arrays in Bastrop and Guadalupe counties, Texas. We recorded 316 photographs of 19 species of vertebrates over 327 camera days among 16 drift-fence arrays. During 1,838 trap nights, we documented 679 individual track sets at track-monitoring stations established on 50 individual pitfall traps and 8 control plots. Ten potential vertebrate predators were documented visiting pitfall arrays with the raccoon (Procyon lotor) being the most frequently recorded species. Statistical analyses indicate that presence of predators at track-monitoring stations or pitfall traps did not influence detectability or capture success of small vertebrates. However, these results could be confounded by the low effect size and reduced power due to low number of animals captured in pitfall traps during the study. Consistent and frequent visits by predators to pitfall traps indicate that risks exist for confined animals and the potential consequences increase for rare or endangered taxa, which potentially could be exposed to higher levels of predation when confined to pitfall traps.
The ecology of Lilaeopsis schaffneriana ssp. recurva Apiaceae (Huachuca water umbel), an endangered wetland plant, is poorly understood. In spring 2001, L. schaffneriana ssp. recurva was discovered in two areas in a dense cattail-bulrush marsh at Bingham Cienega Preserve, Pima Co., Arizona, which is located in the floodplain of the middle portion of the San Pedro River, ca. 60 km north of, and 295 m lower in elevation than, all known sites of the subspecies at the time. In autumn 2001, monitoring plots were established within the population at Bingham Cienega Preserve to document phenology and the role of interspecific competition. In one-half of monitoring plots, potentially competitive vegetation was clipped at the ground surface during autumn 2001–autumn 2002. Clipped plots censused in autumn 2001 and spring 2002 had more leaves and produced flowers, whereas no flower was present in control plots. By autumn 2002, however, persistent drought may have caused a decrease in number of leaves of L. schaffneriana ssp. recurva in both control and clipped plots. By late October 2002, all aboveground evidence of plants disappeared and leaves did not reemerge, presumably due to low soil-moisture levels related to severe drought. During the study, we discovered a herbarium specimen that documented L. schaffneriana ssp. recurva ca. 55 km downstream of the study population. More recently, we discovered a new population within the Babocomari River, a major tributary to the upper San Pedro River. These newly documented occurrences verify that L. schaffneriana extends beyond the known area occupied when the plant was listed as endangered, and is not limited to the upper portion of the San Pedro Drainage.
I compared population trends of 32 species of shrubland and woodland birds generated from 10 years (1995–2004) of point counts on Fort Hood Military Reservation, Texas, with trend data for the same species and time period generated by the Breeding Bird Survey for the entire Edwards Plateau region of Texas. Regardless of scale, most (>90%) species exhibited acceptable population trajectories (i.e., stable or increasing trends). Trend directions were the same at local and regional scales for the majority (62.5%) of species despite differences in land use and management at local and regional scales. Most trend differences were attributable to stable populations on Fort Hood while populations increased on the Edwards Plateau, or vice versa. Stable or increasing population trends for most of the species I examined likely are related to continued or increased availability of woody habitat. Only two species, ladder-backed woodpecker (Picoides scalaris) and field sparrow (Spizella pusilla), exhibited declines at the regional level, possibly due to afforestation or development, which may be cause for concern. Because the population status of many of the species that use woody habitats on the Edwards Plateau appear to be acceptable, greater research and management emphasis should be placed on grassland birds, a group that has experienced substantial declines on the Edwards Plateau and nationally.
The use of dogs (Canis lupus familiaris) trained to locate wildlife under natural conditions may increase the risk of attracting potential predators or alter behavior of target species. These potentially negative effects become even more problematic when dealing with threatened or endangered species, such as the Mojave Desert tortoise (Gopherus agassizii). We addressed three concerns regarding use of dogs trained to locate desert tortoises in the wild. First, we looked at the potential for dogs to attract native and non-native predators to sites at a greater rate than with human visitation alone by comparing presence of predator sign before and after visitation by dogs and by humans. We found no significant difference in predator sign based upon type of surveyor. Second, we looked at the difference in risk of predation to desert tortoises that were located in the wild by humans versus humans with wildlife-detector dogs. Over a 5-week period, during which tortoises were extensively monitored and a subsequent period of 1 year during which tortoises were monitored monthly, there was no predation on, nor sign of predator-inflicted trauma to tortoises initially encountered either by humans or wildlife-detector dogs. Third, we looked at movement patterns of tortoises after encounter by either humans or wildlife-detector dogs. Movement of desert tortoises was not significantly different after being found by a human versus being found by a wildlife-detector dog. Based upon these initial results we conclude that use of trained wildlife-detector dogs to survey for desert tortoises in the wild does not appear to increase attraction of predators, increase risk of predation, or alter movement patterns of desert tortoises more than surveys conducted by humans alone.
Data on effects of fire on herpetofauna generally are lacking. With increased use of prescribed fire to manage rangelands in South Texas for wildlife and livestock, a better understanding of effects of fire on the herpetofauna is needed. We investigated effects of combinations of winter and summer prescribed fire on rangeland sites on the Chaparral Wildlife Management Area in southern Texas. Dormant-season fires had little effect on diversity and abundance of the herpetofauna. Inclusion of growing-season fire into the burning regime tended to increase diversity and abundance of grassland species, such as the six-lined racerunner (Cnemidophorus sexlineatus). Although our experimental design limits interpretation of results to the study site, our data suggest that prescribed fire may be used to manage rangelands in South Texas without negative affects on the herpetofauna. A varied burning regime is recommended to increase herpetofaunal diversity.
The endangered bonytail Gila elegans, a large-bodied, main-stem cyprinid endemic to the Colorado River Basin of the American Southwest, was once widespread and abundant in warm-water-stream reaches. Negative effects of altered flow and temperature regimes downstream of dams, other habitat changes, and establishment of nonnative fishes have reduced populations of native fish throughout the basin, and wild bonytails may be extirpated. Hatchery reared bonytails are stocked in formerly occupied habitat to rebuild depleted populations, but their ecology is poorly understood. In 2002–2007, sampling in the middle Green River from upstream and downstream of stocking locations in Dinosaur National Monument documented survival of bonytails for ≤4 months, but apparently none survived longer. Many fish at large ≤4 months had Lernea or fungal infections, weighed an average of 20% less than fish when released, and had relatively low rates of growth. Post-stocking rates of dispersal downstream (ca. 1 river km/day) were considerable, and potentially, biologically significant. Bonytails occupied pools, eddies, runs, backwaters, and riffles, and co-occurred in eddies with the roundtail chub Gila robusta and humpback chub Gila cypha in Whirlpool Canyon. We also documented two instances of predation by smallmouth bass Micropterus dolomieu on bonytails ≤225 mm in total length. Reduced predation by large-bodied, nonnative, piscivores and increased resistance to disease and other stressors that reduce body condition may increase survival of stocked bonytails in this portion of the Green River. Alternative stocking strategies, including use of alluvial and floodplain areas, and effects of size on survival, are being evaluated.
We studied germinable seed banks in soil associated with grasslands, relatively young (<40 years) Juniperus ashei (Ashe juniper), and long-established Quercus virginiana var. fusiformis (plateau live oak) patches of woody plants in a central-Texas savanna to ascertain the degree to which Ashe juniper alters the seed bank of sites previously inhabited by grassland vegetation, and to assess how seed banks differ beneath two common types of patches associated with woody plants in this savanna ecosystem. Across all habitats and over an annual growth cycle, 3,364 seedlings representing 116 species emerged from these seed banks. Annual forbs were the dominant life form in all habitats (62% of seedlings). The fraction of perennial forb and graminoid seedlings was comparable (19 versus 18%, respectively), and seedlings of woody plants were rare. Density, diversity, and species composition of seed banks varied significantly among the three habitats. Seed banks in grassland and live oak were most dissimilar, and seed banks of Ashe juniper were intermediate in species composition. Early-to-mid-successional species present in grasslands were absent from seed banks of Ashe juniper. Late-successional species of grasses were either absent or few in the seed bank in all habitats. Results indicate that occupation of grasslands by Ashe juniper alters seed banks after a relatively short time, and these changes are distinct from patches of woody plants that have a long-term history of occupation of sites. Approaches to restoration of grasslands that involve removal of Ashe juniper alone cannot rely on the soil seed bank for rapid reestablishment of climax grassland communities.
We explored use of non-invasive track and camera surveys to provide baseline information on distribution, activity, and habitat associations of mammalian carnivores within the Chiricahua and Peloncillo mountains of southeastern Arizona. In total, track and camera stations recorded 241 and 149 detections, respectively, of carnivores and other vertebrates in both mountain ranges. In order of frequency of detections, we recorded gray foxes (112 track and camera detections), white-nosed coatis (33), large skunks (25), ringtails (13), domestic dogs (13), coyotes (9), cougars (7), bobcats (3), and western spotted skunks (2) in both the Chiricahua and Peloncillo mountains, and one American black bear was photographed in the Chiricahua mountains. Other vertebrates detected included cattle (12), deer (10), and a variety of small rodents (83), birds (33), lizards (22), and lagomorphs (12). The combination of track and camera data were effective at detecting a variety of species in a range of habitat types, and emphasized the importance of deciduous riparian habitat for carnivores as well as other vertebrates.
We present here the first record of the velvety fruit-eating bat (Enchistenes hartii; Phyllostomidae) for the state of Morelos, Mexico. Our record gives more insight into the range of the species in Mexico, extending it ca. 52 km into central Mexico, east of the closest reported locality, Malinaltenango, in the state of México. We provide external and cranial measurements of one individual, and information about the habitat where it was captured and other species of bats recorded at the same locality.
We evaluated breeding season and breeding behavior of two populations (Los Angeles and La Perforadora) of the Mexican prairie dog (Cynomys mexicanus) in northeastern Mexico during January–June 2002 and 2003. We observed 18 coteries in each colony. The breeding season began at the end of January and extended into late April for both colonies. Males were sexually active January–March, and females were in estrus in early March. However, 7 and 10 mature females in La Perforadora and Los Angeles, respectively, underwent estrus in mid-February. Gestation lasted from early March to early April, parturition occurred in early April, and weaning occurred in late April. Infanticide was not observed. Mature females and dominant males of each coterie cut fresh vegetation, possibly for construction of the nest inside the burrow. A series of sexual-mounting exercises occurred outside burrows between young of the same coterie. We describe fights that occurred frequently between adults after the young emerged from their burrows.
Texas has five species of alderflies (Sialis). A key to adult males and females and their known distributions in the state is presented. New county records are included, as well as the first state record of Sialis vagans (Ross).
The Iowa darter (Etheostoma exile) was first captured in Little Yampa Canyon, Yampa River, Colorado, by electrofishing in autumn 2003, and abundance of this nonnative species increased during 2004–2007. The Iowa darter also expanded downstream 229 river km, based on captures of young fish in a drift net at the confluence of the Yampa and Green rivers in 2005, and in light traps in the Green River near Jensen, Utah, in 2005–2007. Likely introduction of the Iowa darter via bait-bucket transfer suggests that additional legal deterrents might be needed to reduce further illicit introductions of potentially problematic nonnative fishes in the Colorado River Basin.
We document the jaguar (Panthera onca) in the Sierra Nanchititla (state of Mexico) in pine-oak forest. During October 2002–December 2004, we determined presence of jaguars using three methods: we conducted interviews in local communities, collected scats, and installed automated-camera detection systems. Although no jaguar was mentioned in 86 interviews, three photographs of a male were obtained, and 10 of 132 scats were attributed to P. onca. This represents the first record of P. onca in central Mexico within the Balsas River macro-basin.
Morpho polyphemus, a butterfly whose geographic and temporal distribution in Mexico is relatively well known, is reported for the first time from the state of Zacatecas. This species was observed at El Mezquital, on both sides of a river with riparian subtropical vegetation.