Herbivory by wild ungulates influences the structure and composition of plant communities, but less is known about how such changes affect species richness and abundance of insect herbivores. In Bandelier National Monument, New Mexico, 1999 to 2002, we used ungulate exclosures and reference sites to measure the response of butterflies to herbivory by high numbers of elk (Cervus elaphus) in ponderosa pine (Pinus ponderosa) grassland and aspen-mixed conifer forests. At each site, we measured butterfly abundance, species richness, and selected environmental variables. Butterfly abundance and species richness significantly differed among dates in ponderosa pine-grassland sites and differed significantly for date, treatment, and date*treatment interaction in aspen-mixed conifer sites in 2001, the year of greatest butterfly abundance and richness. Environmental variables differed little between treatments in either habitat, with the exception of the distribution of aspen stem densities, which significantly differed among height classes and treatments in 2001 and 2002. Results of nonmetric, multidimensional scaling ordination indicated that butterfly community composition in late summer was best explained by non-woody biomass, blooming forb species richness and abundance, and aspen saplings excluded from elk in the aspen-mixed conifer sites. Although elk were only excluded for 4 y, our results indicated that, at high densities, they browse non-woody vegetation and young aspen, which in turn has a cascading affect on adult butterfly community composition in some habitats during some years.

I compared the life histories of the invading Catostomus commersoni and the declining native C. plebeius in the upper Rio Grande of northern New Mexico to illuminate the mechanisms by which C. commersoni attains higher abundance than C. plebeius. In the first year of life, the 2 species did not differ in length, but C. plebeius reached greater individual mass. Catostomus plebeius achieved a higher intrinsic reproductive rate by maturing earlier, but C. commersoni attained approximately twice the net reproductive output by living longer, growing larger, and attaining 15-fold higher fecundity. While other factors undoubtedly facilitate the invasion of C. commersoni, I suggest that the high fecundity achieved by large C. commersoni contributes to its dominance in the upper Rio Grande system.

Fire regimes in North America, including the American Southwest, have undergone relatively dramatic shifts in the last century, resulting in novel stand-replacing fires, which are changing landscapes in unprecedented ways. We investigated some possible effects of these landscape changes on a terrestrial plethodontid salamander (Plethodon neomexicanus). We investigated microhabitat temperatures in 4 burn-severity types following recent fires. Temperatures were significantly greater in high-severity and moderate-severity burn areas than in low-severity and unburned areas. We present presence-absence data from 4 burn-severity types that were previously documented as having salamanders present. The proportions of presence and absence were similar for all severity types. Finally, we used data from a 9-year demographic study of P. neomexicanus from 2 locations, where one location was burned in a wildfire halfway through the study, to measure possible effects of fire. We compared salamander size distributions and body condition pre-fire and post-fire within the burned site, and the unburned site was used as a reference location. Salamanders at the burned site had a shift in size distribution, with an increase in observed juveniles and a decrease in observed adults 2 y post-fire relative to itself. No significant changes were measured at the unburned site. We did not observe a significant effect in salamander body condition. Overall, we conclude that salamander surveys are valuable for determining presence-absence, but alone are ineffective and not appropriate for monitoring or measuring populations after a disturbance. We suggest that future studies investigating the effects of disturbance on terrestrial plethodontid salamanders use size distribution and potentially body condition data to monitor for effects within populations, in conjunction with measuring environmental parameters for understanding causal agents.

Cayo Cochino Pequeño is a 0.64-km² Caribbean island in the Cayos Cochinos archipelago, Department of Islas de la Bahía, Honduras. One published report noted the presence of the rainbow whiptail (Cnemidophorus lemniscatus) on Cayo Cochino Pequeño, but nothing is known about the biology of this insular population. During a part of the dry season in July and August 2004, we used drift fences, pitfall traps, and separate observational transects to elucidate the distribution and habitat use of C. lemniscatus on the island. The only population of this species was located in a narrow coastal zone (width to 60 m and length to 450 m) on the southern half of the eastern windward side of the island. We analyzed the percentage of the canopy cover and the percentage of 4 ground coverage types along 2 transects 200 m long in this area to understand the basis of the suitability of the habitat for C. lemniscatus. Descriptively, the area harboring this species on Cayo Cochino Pequeño consisted of the remnants of a coconut palm grove with low-lying herbaceous vegetation and grasses, in which a mosaic of small, open areas of sandy soil and coral fragments, with or without accumulations of debris, were the foci of lizard activities. Also observed in this habitat were 2 individuals of the brown racer (Dryadophis melanolomus), an actively foraging snake and likely predator on C. lemniscatus. Data obtained on rainbow whiptails captured in pitfall traps and subsequently released were used to determine the size and color patterns of hatchlings and adult males and females.

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 colors until they ended activity in July or August, although coloration fluctuated within a season for some individuals. Individual differences in the amount of coloration occurred with some large adults never developing fully bright breeding colors. Females produced multiple clutches in each year, and their breeding colors were not immediately apparent with their first clutch and sometimes faded, but did not disappear, between clutches.

A small resident population of peregrine falcons (Falco peregrinus anatum) in the Big Bend region of Texas has suffered reproductive failures since 1990. To continue our assessment of the effects of environmental contaminants on the peregrine falcon, we collected representative avian prey species during 2001 at Mariscal Canyon, Big Bend National Park. The avian carcasses were analyzed for inorganic and organochlorine contaminants. Concentrations of Se and Hg were present at high levels (up to 11 and 2.2 µg/g dry weight, respectively) in some avian prey and could be implicated in reproductive failures of the peregrine falcon in Big Bend National Park. All other inorganic elements were below concentrations known to affect reproduction or to be associated with other deleterious effects in birds. Of all the organochlorines analyzed, only DDE and total PCBs were present above detection limits in all species, although at low concentrations. Our study provides further support to the hypothesis that contaminants in potential avian prey of the peregrine falcon in the Big Bend region are implicated in the productivity failures observed in this species since 1990.

The western burrowing owl (Athene cunicularia hypugaea) is threatened in Mexico, endangered in Canada, and declining in most of the western United States. Most previous research has focused on burrowing owl breeding biology, and little is known about its winter ecology. We determined characteristics of roost sites used by western burrowing owls in southern Texas during winter. Data on 46 winter roost sites were collected from 15 November 2001 to 15 February 2002. Of these roost sites, 87% were located on agricultural land, 80% were along roads, and 74% were concrete, steel, or cast-iron culverts. Mean diameter (±SE) of roost site openings was 22 ± 1.5 cm. Most roost sites (70%) were located on inaccessible private lands. Bare ground comprised 61% of ground cover within a 10-m radius of roost sites. We recommend that landowners and public-land managers should be encouraged to use smaller-diameter culverts when building roads or replacing old or damaged culverts and to graze livestock or mow around these culverts during winter.

Sex ratios of Myotis velifer populations were studied during 2 hibernating seasons within and among 42 caves across a portion of its geographic range in Oklahoma and Kansas. The number of females to males was significantly different than the expected 1∶1 sex ratio in 25 of 44 visits to hibernacula. The percentage of females at the Selman Cave System, one of the largest hibernacula in Oklahoma, was always greater than the percentage of males throughout the season and in clusters of different sizes. Neither females nor males were any more likely to be found at the center than on the periphery of large clusters. The sex ratio of volant young at a maternity roost did not differ significantly from the expected 1∶1 sex ratio.

Although the swimming behavior of Oryzomys palustris has been described, little is known about how long this species will remain in an area that is inundated by several centimeters of water. This study documents the response of an O. palustris population to habitat inundation in a coastal prairie locality of southeastern Texas. During a mark-recapture study conducted during 2002 and 2003, we live-trapped O. palustris on a grid in an area that experienced prolonged (≥5 mo) inundation during 2 of our 6 quarterly trapping periods. We describe a trapping technique, using foam rafts to support rodent live-traps, that is suitable for use in inundated areas. Despite long-term inundation, little available refuge, and an apparent complete turnover of the population, we estimated population densities of ca. 29 individuals per hectare during inundation, only a moderate decrease from the higher levels encountered before and after inundation.

Based on 13 y of trapping data, captures of the western harvest mouse (Reithrodontomys megalotis) in northeastern Kansas decreased significantly in summer. Reduced rates of capture could have arisen from reduced numbers or behavioral changes. We found a slight decrease in persistence rates in summer, so in June and July 2002, we placed traps on elevated platforms to test whether R. megalotis might be scansorial in summer. Elevated traps were significantly more successful than surface traps. We concluded that apparent disappearance of R. megalotis in summer was attributable to changes in behavior rather than emigration or death.

Burrow systems of 43 individuals representing 7 species of pocket gophers (Geomyidae) in Texas (Geomys breviceps, G. bursarius, G. personatus, G. texensis, Thomomys bottae) and Jalisco, Mexico (Cratogeomys fumosus, Pappogeomys bulleri) were excavated, measured, described, and compared. All burrow systems consisted of a main tunnel with several to many side branches. Burrow systems of most species included chambers serving as nest sites, food caches, and latrines. Vertically oriented spiral tunnels are reported for the first time for G. breviceps, G. texensis, and C. fumosus. Regression analyses revealed that mean tunnel depths and diameters varied significantly by species in direct relation to body size. Mean length of tunnel systems varied significantly by species (longest in G. breviceps and shortest in T. bottae), but variation was not correlated with body size.

The remaining populations of ocelot (Leopardus pardalis albescens) in the United States are reduced to 2 isolated populations in southern Texas, with the next closest populations occurring in central Tamaulipas, Mexico. The species is listed as endangered, and recovery of populations in Texas eventually might require translocations from larger source populations. We sequenced the mitochondrial DNA control region from individuals from Texas and northern Mexico and compared these data to existing sequences derived from ocelots in other parts of its range in southern Mexico, Central America, and South America. Nucleotide diversity was lower in Texas than in Mexico, suggesting a loss of genetic variation as a consequence of fragmentation and increased genetic drift. Phylogenetic analyses showed a close relationship between populations in Texas and northern Mexico that encompass the range of the subspecies L. pardalis albescens. Based on these data, the best source population for a recovery plan involving ocelot translocations would be northern Mexico, because this region seems to form a discrete management unit (both ecologically and phylogenetically) that includes Texas.

Desert bighorn sheep (Ovis canadensis) have been extirpated from much of their historical range in the Chihuahuan Desert. Understanding their dietary preferences in the Chihuahuan Desert is integral to their successful restoration. We evaluated differences (sexual, temporal, and spatial) in the diets of desert bighorn sheep from Elephant Mountain Wildlife Management Area in the Chihuahuan Desert of western Texas by using microhistological analysis of 432 fecal pellet groups (209 rams, 209 ewes, 14 lambs) collected every 2 weeks between September 1998 and August 2000. Ninety-four plant species were identified; bighorn sheep diets consisted of 50% browse, 35% forbs, 11% grasses, and 4% succulents. Diets of rams and ewes did not differ annually. Diets differed seasonally (P < 0.05); forbs prevailed in diets of rams during winter. Diets of bighorn sheep from Elephant Mountain were compared to previously determined diets from the Beach, Baylor, and Sierra Diablo mountains. There were significant differences among female diets between Elephant Mountain and Beach Mountain during winter and the Sierra Diablo Mountains in fall, winter, and summer. Dietary overlap was greatest among desert bighorn sheep at Elephant Mountain and the Sierra Diablo Mountain populations (57.6%), followed by Baylor Mountain (55.7%) and Beach Mountain (52.0%). Dietary overlap among all ranges was highest in the browse component (53%), followed by forbs (23%), grasses (16%), and succulents (8%).

We examined use of vegetation associations by female desert mule deer (Odocoileus hemionus eremicus) and proximity to human developments to determine whether human activity and developments influenced habitat use. We hypothesized that use of habitats in disturbed areas would be reduced with increasing human activity. We radiocollared 14 deer and monitored their distribution from March 1996 to March 1997. Female desert mule deer generally used the mesquite-burroweed (Prosopis velutina-Isocoma tenuisecta) vegetation association more than it was available and the palo verde (Cercidium)-mixed cacti association less than it was available. Female deer were generally closer to housing, roads, permanent water, and the Central Arizona Project than random points. Our prediction that desert mule deer would avoid human activity was not supported.

Faunal remains of 40 vertebrate taxa were recovered from 15, 10-cm levels of Holocene deposits in Big Manhole Cave, New Mexico. Radiocarbon dates were determined for the 8 uppermost levels and ranged from 550 to 4,170 radiocarbon years before the present. Rapid deposition was indicated for levels 6, 7, and 8. Most identified taxa occurred in the immediate area at the time of our study, but the yellow-nosed cotton rat (Sigmodon ochrognathus), eastern cottontail (Sylvilagus cf., S. floridanus), and Mexican packrat (Neotoma mexicana) currently occur only at higher elevations in the region. The Mexican packrat was present in only the upper 4 levels, consistent with indications from other sites that it arrived east of the Rio Grande relatively recently. The extralimital taxa suggest greater effective precipitation, but the suggestion is confounded by our ignorance of pre-European ecological conditions in the area.

I describe the vertical distribution of root biomass and root productivity in a xeric shrubland of central Mexico. The effect of the soil nitrogen on root production was evaluated with a fertilization experiment. The highest percentage of roots was found at a depth of 40 to 60 cm. Monthly variation in root biomass for diameter class was significant. Fine and very fine roots were the most important fraction in terms of biomass and production. The highest production of fine root occurred in native soil versus the other treatments.

Plants growing on rock outcrops are subject to environmental and edaphic extremes compared to nearby forested communities growing in deeper soil. Endemic and other characteristic outcrop species have adapted well to the shallow soil habitat of outcrops, but still might be absent from outcrops physically similar to those on which they occur. Presence can be influenced by the ability of species to tolerate various bedrock chemistries and to compete with other characteristic outcrop plants. To examine the role of soil type tolerance in determining the potential distribution of certain plants, we grew individuals of several species (Sedum nuttallianum, Hypericum gentianoides, and Oenothera linifolia) on a limestone substrate that they do not inhabit naturally, even when limestone outcrops are in close proximity to the variety of other rock outcrops where they do occur. Both H. gentianoides and O. linifolia were strongly intolerant of the limestone soil, indicating that edaphic factors are the dominant force limiting distribution. Growth also was reduced for S. nuttallianum, although the same physiological intolerance symptoms were not present as in the other species. Potentially, competitive interactions with Sedum pulchellum, a similar but larger stonecrop, are more important in limiting S. nuttallianum presence on limestone outcrops than is physiological intolerance to the calcareous substrate.

We examined Characodon audax (n  =  30) and C. lateralis (n  =  27) (Pisces: Goodeidae), endemic freshwater fishes from Durango, Mexico. We recorded 8 helminth species, and metacercariae of Posthodiplostomum minimum had the highest prevalence and highest mean intensity of infection. Specialist species included Salsuginus sp. (an undescribed monogenean) and the intestinal trematode Margotrema bravoae. These 3 species and larvae of the nematode Spiroxys sp. were the most frequent and abundant species. The remaining species were rare and found at low mean intensities. Intestinal helminth communities were comprised primarily M. bravoae, though most host intestines were free of macroscopic parasites. These data confirm the depauperate nature of the helminth communities of Goodeidae fish species in Nearctic Mexico. Helminth host specificity is suggested as an important factor for explaining the observed richness, and host feeding habits and local habitat characteristics are suggested as the main factors contributing to the variability observed in community composition and richness.

We sampled nonnative fishes stranded in isolated pools near Grand Falls in the Little Colorado River (LCR), Arizona, after the river ceased flowing (21 June and 12 July 2005) to evaluate whether nonnative fishes can invade the perennial, lower 21 km of the LCR from upriver sources. The encroachment of nonnative fishes could jeopardize resident populations of endangered humpback chub, Gila cypha, and other native fishes in the lower LCR. We captured red shiner, Cyprinella lutrensis; common carp, Cyprinus carpio; fathead minnow, Pimephales promelas; black bullhead, Ameiurus melas; and plains killifish, Fundulus zebrinus, all of which have been captured >132 km downriver in the lower LCR and >127 km upriver in the closest perennial sources. Moreover, we detected Asian tapeworm, Bothriocephalus acheilognathi, in 9 of 30 common carp examined. Our findings suggest that nonnative fishes, including those hosting parasites, can invade the lower LCR from upriver sources >250 km away during freshets and provide a mechanism for the dispersal of invasive aquatic species in intermittent river systems.

Little is known about the life history and habits, including the reproductive behavior, of Pimephales tenellus. I collected 182 individuals and transferred them into 10 aquaria; of these fish, 18 pairs spawned. Based on my aquarium observations, P. tenellus exhibited the egg-clustering strategy similar to the other species of Pimephales.

The exotic suckermouth armored catfishes are known to be established in Mexico. Pterygoplichthys multiradiatus is established in Campeche, Chiapas, and localities in central and western Mexico. We report the first record of another suckermouth armored catfish established in southeastern Mexico. We captured 7 specimens of Pterygoplichthys pardalis in a freshwater pond near Frontera, Tabasco, on 8 January 2005. Additional records in this region indicated that P. pardalis was spreading in the upper Grijalva-Usumacinta River basin. Further sampling and monitoring is required to assess the ecological impacts of this exotic species on the native fauna.

We placed 24 pairs of adult San Marcos salamanders in small flow-through aquaria with rocks and aquatic moss. Some aquaria had clear marbles within tubes through which water upwelled into each aquarium. Seven clutches (eggs per clutch: mean  =  34.7; range  =  2 to 73) were produced during a 9-month period. Overall hatching success was 29.6%. One breeding pair reproduced 3 times (eggs per clutch: mean  =  44; range  =  27 to 59) at an average of 64-day intervals during a 191-day period. Once mature, a single female potentially could produce 176 eggs per year in captivity.

The desert tortoise (Gopherus agassizii) has undergone significant declines in the past several decades. Thus, many carcasses are present across the desert landscape. Here we report on osteophagy by the desert tortoise, specifically the consumption of bones from deceased desert tortoises. Desert tortoises seem to have an appetite for calcium-rich substances. To our knowledge, this is the first documentation of desert tortoises consuming conspecific skeletal remains.

We detected buff-breasted flycatchers (Empidonax fulvifrons) while conducting surveys in the Rincon Mountains, Arizona, in 2000 (n  =  2), 2004 (n  =  4), and 2005 (n  =  5). Our detections represent the first records of buff-breasted flycatchers in the Rincon Mountains since 1911, suggesting that this rare species has recolonized a portion of its historical breeding range.

The common loon (Gavia immer) has occasionally been reported inland in northern Mexico. The first record in Coahuila, Mexico, was collected at El Tulillo reservoir in November 1986. The present record is more unusual, because it was collected on 12 June 2003, a late date for any location at this latitude. Damage caused by shotgun pellets to the ventral surface of both wings apparently prevented flight. This represents the second record for the state of Coahuila and the first record for the Cuatro Ciénegas Valley.

Studies using artificial nests or remote cameras have documented avian predation by red squirrels (Tamiasciurus hudsonicus). Although several direct observations of avian predation events are known in the northern range of the red squirrel distribution, no accounts have been reported in the southern portion. We observed predation upon a hermit thrush (Catharus guttatus) nestling by the Mount Graham red squirrel (T. h. grahamensis), an endangered subspecies living at the southern terminus of the distribution of the red squirrel.

We examined nest tree preferences of northern flying squirrels (Glaucomys sabrinus) in an old-growth, mixed-conifer forest of Yosemite National Park, California. We tracked 8 individuals to 21 nest trees during July through September 2004. Flying squirrels selected nest trees that were larger in diameter and taller than either large nearest-neighbor or random trees. Flying squirrels showed no tree species preference, but used snags more often than live trees relative to their availability. Nest trees were not closer to perennial creeks than random trees. Results suggest that northern flying squirrels of Yosemite National Park might require large trees and snags, but unlike more xeric parts of the extreme southern Sierra Nevada, they might not be constrained by proximity to perennial streams.

Reports of intraspecific strife among mountain lions (Puma concolor) have been presented in the literature. However, there are no published accounts of an actual field observation of lion behavior during an incidence of intraspecific strife. Here we provide a report of such an incident, in which a female mountain lion was killed by a male mountain lion in rural El Dorado County, California, in 2002. Observations from a field investigation of the site and the results of the necropsy of the female also are presented. The investigation indicated that the female lion was healthy and was not pregnant, lactating, or in estrus. Mortal injury was a skull fracture resulting in brain damage and hemorrhage. We suspect the female might have been killed while defending a deer kill or as prey of the male lion.

We evaluated levels of body fat, body condition scores, live weight, and fetal rates of mule deer (Odocoileus hemionus) compromised by injuries from radiocollars and compared them to non-injured animals before and after those injuries had healed. Compromised animals had lower values for all parameters at the time injuries were discovered, and that pattern repeated itself 4 mo later when subjects again were examined. Investigators must consider ramifications of their activities for research subjects, as well as for research results.