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Mate choice tests provided no evidence of prezygotic reproductive isolation between a population of Physa virgata (Gould, 1855) collected from its type locality in the Gila River of Arizona and Physa acuta (Draparnaud, 1805) from a control site in Charleston, South Carolina. Reared in a no-choice experimental design, 10 outcross Arizona × South Carolina pairs initiated reproduction at approximately the same age as Arizona × Arizona controls, and earlier than South Carolina × South Carolina controls. Parents in the outcross experiment did not differ significantly from either control in their median weekly fecundity across 10 weeks of observation, yielding an F1 generation with significantly improved viability. We detected no evidence of reduction in F1 fertility. Thus, P. virgata, the most widespread freshwater gastropod of the American Southwest, should be considered a junior synonym of the cosmopolitan P. acuta.
Spawning season of the white sucker (Catostomus commersoni) in tributaries of Lake Taneycomo, a coldwater reservoir of the White River system in southwestern Missouri, lasted from early April to late May in 1994 and 1995. Collection of fish larvae and spawning activities of adult white sucker indicated that spawning occurred in all tributaries of the lake. We did not observe evidence of spawning in the lake. White suckers began to mature at age 3 and a total length of 275 mm. A larger proportion of males matured at an earlier age and length, but females lived longer and reached larger sizes. Mortality rates were higher for mature males than females. Both sexes exhibited high mortality after age 8. Females were more abundant than males (1.94 to 6.50: 1 F:M) in the upper lake throughout the year, while males were more abundant in Bull Creek (0.27 to 0.30:1 F:M), a major tributary, during the spawning season. Fecundity increased with fish size, ranging from approximately 5,000 to 59,000 eggs. Growth of white sucker continued throughout life, but slowed dramatically after maturation. Although this southern population in the Lake Taneycomo system spawned earlier than reported for most northern populations, its demographic attributes (age and length at maturity, fecundity, gonadosomatic index, fecundity, condition, and growth rates) were within ranges reported for other white sucker populations.
Hemidactylus turcicus is a small gekkonid lizard native to the Middle East and Asia that is known to exhibit sexual dimorphism in head size. Several potential explanations exist for the evolution and maintenance of sexual dimorphism in lizards. We tested 2 of these competing hypotheses concerning diet partitioning and differential growth. We found no differences in average meal size (volume) or in any single dimension of prey size for similarly sized males and females. Allometric patterns of increases in head size also were measured in males and females. We found that males exhibited a mixture of isometric and positively allometric patterns of head size increase, whereas females exhibited isometric and negatively allometric patterns. Thus, we concluded that sexual dimorphism in head size is not the result of diet partitioning but instead of differential growth patterns following sexual maturity in males and females.
Land-bird density on Espíritu Santo Island, lower Gulf of California, Mexico, was determined bimonthly from November 1998 to October 1999. Bird density was quantified in 4 habitats on the island using the line transect sampling method. Fiftyeight species were recorded, of which 44 were detected in the transects and the other 14 in adjacent sites. The highest bird densities were observed in March and June, coincident with the lowest rainfall months in the neighboring peninsular mainland. Average density (birds/ha) was highest in alluvial fans (18.14) and lowest in mesas (8.08). Migratory bird density on the island was relatively low and commonly less than 10% of the observed total density. The average land-bird density on the island (13.29/ha) was greater than that previously recorded.
We studied habitat preferences of northern harriers (Circus cyaneus) in 4 counties of the Southern High Plains of northwestern Texas from October 1989 to May 1995. Harriers generally arrived in late July and departed in April. They hunted over a variety of habitats in the study area but mainly in Conservation Reserve Program (CRP) grasslands and vegetated playa basins. CRP grasslands, playa basins, and shortgrass prairie were used disproportionately to their availability, whereas winter wheat was used less than its availability. Brown harriers (adult females or subadults of either sex) foraged in CRP about as often as adult males but more frequently in playas and prairies, whereas adult males foraged more in winter wheat. As underground water sources for irrigation continue to be depleted, agricultural practices are likely to change. Depending on how the land is used after irrigation ceases, harriers might benefit if CRP grasslands, vegetated playas, and shortgrass prairies persist. If dominant land use reverts to livestock grazing, however, the harrier population will be negatively affected.
Morphological observations of male genital tracts obtained from wild, adult Mexican big-eared bats (Corynorhinus mexicanus) revealed only one but long annual reproductive cycle showing the existence of temporal asynchrony of its reproductive functions, as is characteristic of temperate-zone vespertilionid and rhinolophid chiropterans. Testes were largest in August, whereas maximum development of epididymides and accessory sex glands complex was observed 1 and 3 months later. High value of relative body condition of individuals was observed from May to June, when testicular enlargement commenced, suggesting that recrudescence of spermatogenesis in the adult bats is dependent on a good body condition.
Abert's squirrels (Sciurus aberti) are reported to be dependent on ponderosa pine (Pinus ponderosa) forests for food, cover, and nest sites. Introduced Abert's squirrels in the Pinaleño Mountains of Arizona, however, occupy forests that contain little to no ponderosa pine. We documented diet and tree use of Abert's squirrels in mixed-conifer forests of the Pinaleño Mountains using observations of marked animals. Individuals ate similar food items as Abert's squirrels in ponderosa pine forests, including seeds, inner bark, buds, and fungi, but 5 conifer species were used as food sources. Douglas-fir (Pseudotsuga menziesii) and southwestern white pine (Pinus strobiformis) were the most frequently eaten conifer species. Abert's squirrels also were observed in all tree species. Our results suggest that the dependence of Abert's squirrels on ponderosa pine is not as strong as previously reported.
We examined scavenging on mule deer (Odocoileus hemionus) carcasses by puma (Puma concolor) in the Peninsular Ranges of San Diego County, California. Between January 2001 and October 2003, we placed 44 deer carcasses at 23 sites and used them to examine scavenging events. We also documented 2 additional deer carcasses, not placed as bait, that were scavenged by puma. Eight to 12 puma (6 males, 2 to 5 females, and 1 of unknown sex) scavenged 20 of 46 deer carcasses (43.5%) at 12 of the 25 sites. Six puma (4 males, 2 females) were captured 7 times at scavenging sites. We identified 7 scavenging puma (5 males, 2 females) through captures and telemetry, and 1 unmarked, scavenging male from a camera trap. The 7 telemetered puma that scavenged ranged in age from 11 months to 9 years, and each individual scavenged on 1 to 6 deer (mean = 2.3). Deer carcasses were found and scavenged by puma from 1 to 14 days (mean = 5 days) after deposition, when carcass conditions ranged from frozen and fresh to rotting and maggot-infested. Puma treated scavenged carcasses as they would their own kills, dragging carcasses to preferred sites, caching, depositing scats, and making scrapes in the area. However, puma did not always attempt to cache tethered carcasses. During fieldwork, we also discovered that 1 telemetered puma repeatedly visited a domestic livestock graveyard and scavenged on surface-discarded horse and cattle carcasses. Puma are known to be opportunistic predators, but our results indicate that they are opportunistic scavengers as well. Due to the propensity of puma to scavenge, it is likely that some perceived kills might be scavenging events. Frequent monitoring and timely field investigation of mortality signals detected from telemetered prey species will help investigators identify those events. Scavenging behavior should be considered when evaluating or predicting the effects of puma predation on prey species.
Seeds collected from coyote scats in southern California were tested for germination. Eighteen of 38 plant species germinated. Native species that germinated included Arctostaphylos glauca, Arctostaphylos sp., Heteromeles arbutifolia, Opuntia littoralis, Prosopis glandulosa, Prunus ilicifolia, and Washingtonia filifera. Exotic species that germinated included Annona cherimola, Cucumis sp., Ficus sp., Lycopersicon esculentum, Panicum miliaceum, Phoenix sp., Prunus sp., and Pyracantha sp. Additional species thought to be exotic that germinated were Fragaria sp., Vitis sp., and an unidentified species. Compared to seeds directly off the plant, O. littoralis germinated significantly more frequently following passage through coyotes, whereas H. arbutifolia germinated significantly less often. Although coyotes are dispersing exotic plant seeds in viable condition, none of the seeds identified in this study were considered invasive.
Large-scale native woodland loss in the Lower Rio Grande Valley of Texas during the 20th century has been reported in the literature. However, no detailed, quantitative study of landscape change in the area has been conducted. This paper presents an example of quantified native woodland loss within this area. Using historical topographic maps and aerial photographs, we were able to map the extent of native woodland areas in Cameron County in the 1930s. The historical native woodland areas were then compared with the 1983 extent of native woodlands as mapped on modern topographic quadrangles. Our results for Cameron County corroborate previous estimates of native woodlands loss in the Lower Rio Grande Valley, though at a slightly lower percentage (91%). Comparisons with recent land-use and land-cover mapping show that much of the loss was a result of agricultural expansion.
Seedlings of Ferocactus wislizeni and Mammillaria grahamii, 2 common cactus species in the northern Sonoran Desert, emerged under protective cages that had been left in place for 6 years after an initial sowing of numerous Carnegiea gigantea and F. wislizeni seeds. Because no seeds were sown in the interim, Mammillaria and Ferocactus seedlings must have emerged from persistent seed banks. Mammillaria seeds evidently survived in or on the soil as long as 6 years, forming a long-term persistent seed bank, and Ferocactus seeds apparently survived up to 3 years, forming a short-term persistent seed bank. No Carnegiea seedlings emerged, confirming that this species has a transient seed bank This is the first evidence for a between-year seed bank in M. grahamii and the first confirmation of a between-year seed bank in F. wislizeni.
The river shiner, Notropis blennius, was collected from Lake Meredith, Texas and outside of its reported native range. This specimen likely represents a bait-bucket release. Within its native range, the river shiner readily acclimates to lentic conditions, increases in abundance, and displaces other riverine fishes following flow regime alterations. Its occurrence and possible establishment might have similar negative impacts on the Canadian River fish assemblage upstream from Lake Meredith, which includes the threatened Arkansas River shiner, Notropis girardi.
We report the first case of unusually frequent abnormal anatomy in Pseudacris streckeri and the first such account for anurans in the state of Texas. We found abnormal digits in 55% of 40 adult males and 26% of 23 adult females in Austin, Texas. In contrast to other studies that reported frequent abnormal limbs and cutaneous fusion, abnormalities were restricted to digits. None of 325 newly metamorphosed juveniles showed abnormal digits, indicating that the abnormalities are formed after metamorphosis, or that the cause of the abnormalities was not active during the sampling period. Abnormalities continued to be found in the adults of this population during the following 3 years.
A description of 3 neonate western long-nosed snakes (Rhinocheilus lecontei lecontei) that hatched from one clutch of eggs is provided. Each individual differed in color pattern. One of the neonates was striped. Standard morphometric data for the hatchlings are provided. The history of color pattern polymorphism in R. l. lecontei is discussed. A similar example of striping in another banded snake taxon is related, substantiating the taxonomic significance of reporting the second known striped specimen of R. l. lecontei.
New evidence is presented that suggests that the single specimen of Elgaria usafa from the Sierra del Nido in Chihuahua is an aberrantly patterned E. kingii. We suggest that E. usafa be considered a junior synonym of E. kingii.
We performed Exploratory Data Analysis on data sets assembled to determine subspecies limits of great horned owls (Bubo virginianus) in Texas; the results revealed unusual patterns of tail measurements. In the subspecies B. v. pallescens, tail lengths of males (206.0 mm) were longer than those of females (202.5 mm). Additionally, tail length was longer in intergrades (males = 209.4, females = 213.5) than for either subspecies (B. v. virginianus males = 206.2, females = 209.0; B. v. pallescens males = 206.0, females = 202.5).
The breeding range of the slate-throated redstart (Myioborus miniatus) stretches from South America to Mexico, where it extends northward along the Sierra Madre Oriental to southeastern Coahuila and along the Sierra Madre Occidental to southern Chihuahua and Sonora. We report the discovery of slate-throated redstarts breeding in the Maderas del Carmen mountains in Coahuila. This represents a range extension of approximately 400 km and is, to our knowledge, the northernmost breeding record for this species.
Nelsonia neotomodon is recorded for the first time for the state of Chihuahua, Mexico. This record extends the distribution of this species 250 km to the north. Morphometric and reproductive information for a sample of N. neotomodon, as well as additional unpublished records, are provided. The data suggest that this species has a continuous distribution in the Sierra Madre Occidental and that there is no significant geographic variation or sexual dimorphism.
The desert bighorn sheep (Ovis canadensis mexicana) population in the Santa Catalina Mountains, Arizona, has declined since the 1920s and was virtually extirpated in the late 1990s. Urban development, human recreation, and changes in habitat conditions due to wildfire suppression have contributed to the decline. Wildfires in 2002 and 2003 burned approximately 46,701 ha in the Santa Catalina Mountains, including areas previously inhabited by desert bighorn sheep. Our objectives were to estimate the amount of potential and historical bighorn sheep habitat in the Santa Catalina Mountains and to determine if the fires improved habitat quality for bighorn sheep. We created a spatial habitat suitability model to estimate the amount of potential and historical habitat available for bighorn sheep in the Santa Catalina Mountains. We then used Burn Severity maps and the Normalized Difference Vegetation Index to examine the impact of recent wildfires on bighorn sheep habitat. We calculated 39,201 and 9,017 ha of potential and historical habitat of desert bighorn sheep, respectively. Historical bighorn sheep habitat in the western Santa Catalina Mountains declined 64% since 1989. Approximately 21% of potential habitat and 24% of historical bighorn sheep habitat were burned during the fires, most of which experienced low burn severity that was not high enough to remove vegetation that decreases habitat quality for desert bighorn sheep. Any consideration of translocation of desert bighorn sheep to the Santa Catalina Mountains should further assess the suitability of the areas identified as potential habitat.
Animals that inhabit vegetative communities where thorns and spines are common should be capable of moving while avoiding injury from thorns and spines. On 21 December 2003, we found that a saguaro cactus (Carnegiea gigantea) spine had penetrated the lacrimal bone into the orbit of a desert bighorn sheep (Ovis canadensis) in south-central Arizona. The animal was observed with clinical infectious keratoconjunctivitis and was blind for 3 weeks prior to death. It is likely that the animal collided with a saguaro cactus after she became blinded by disease.
Collared peccary (Tayassu tajacu) and wild pig (Sus scrofa) exist in sympatry in southern Texas. These species vary in the structure of the digestive system and in adult body size, which might influence digestive performance. Our objective was to assess differences in digestive system efficiency between these species, controlling for body size. Four peccaries and 4 young pigs of similar size were fed a standardized amount of a commercial feed (38% neutral detergent fiber, 12% crude protein) based on metabolic body weight (kg0.75) for 8 days. Feed consumed and feces produced were measured during the last 5 days of the trial. No differences were found for digestive performance between the 2 species, although pigs excreted 95% of chromium-marked fiber sooner than peccaries. Although peccaries have a complex stomach in which fermentation occurs, they apparently do not gain a significant benefit in digestibility of dry matter, energy, or fiber relative to a hindgut fermenter of similar body size when eating similar amounts of food. Peccaries might, however, benefit from microbial products (e.g., vitamins and amino acids) that would not be readily available if fermentation occurred exclusively in the hindgut. Our results do not suggest that either species has a competitive advantage in dry matter digestion of plant material.