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Vegetation recovery following a wildfire in vegetated flats and secondary dunes of Padre Island National Seashore, Texas, was studied from January 2000 to January 2002. Species richness, diversity, evenness, abundance, and importance were evaluated. Species richness, diversity, and evenness were restored quickly in vegetated flats (51 days) and secondary dunes (71 days). The burned secondary dune site had the same dominant species as its non-burned counterpart from the beginning to the end of the study, but it took 106 days for the dominant species to be restored in the burned vegetated flats. No exotic species established in burned sites. Two years post-fire, community similarity was high between burned and non-burned sites in both the vegetated flats and secondary dunes. One year after the fire, cover contributed by live plants was virtually identical on the burned and non-burned secondary dunes. On the vegetated flats, live plant cover on the burned site exceeded live plant cover on the non-burned site. Two years after the fire, the dead plant biomass and standing dead plant cover were still markedly lower on the burned sites in both the vegetated flats and secondary dunes.
Mixed diets can allow generalist insect herbivores to obtain nutritionally balanced resources or dilute toxins from specific foods, but also present the generalist with greater challenges in decision-making and require a greater ability to detoxify a wide range of plant defensive compounds. Young and small generalist larvae can have different nutritional requirements, ability to detoxify compounds, and mobility compared to older and larger larvae. In this field study, I asked how larval size affected performance of the woolly bear (Platyprepia virginalis), a generalist herbivore, on a uniform diet of bush lupine (Lupinus arboreus) compared to a mixed diet including bush lupine. Large larvae had greater survival on the mixed diet treatment compared to the lupine-only diet, but survival of small larvae did not vary with diet. Larval size also influenced growth on each diet, but this effect varied with year. In 1997, large larvae had higher growth on a lupine-only diet compared to a mixed diet, whereas small larvae had equivalent growth on both diets. In 1998, larvae of each size did not differ in their response to diet treatments. In the field, large larvae apparently eat a more diverse diet than small larvae, which contrasts with the growth result for 1997. This suggests that factors other than growth, such as parasitism or predation, might influence choice of host plants.
We compared several external morphological features for determining sex of adult fall-run chinook salmon (Oncorhynchus tschawytscha) migrating to spawning grounds in the Central Valley of California. Adult fish carcasses of known sex were measured at fish hatcheries or during angler surveys. These data were used to develop predictive morphometric discriminant function models for potential incorporation in an automated monitoring system. The best predictor for determining sex of handled fish was snout length to fork length ratio, which correctly classified 96% of individuals tested. In contrast, adipose fin length to fork length ratio was the best predictor of sex when measurements were obtained from video images at a fish passage facility. Of these fish, 86% were correctly identified. Combining both ratios with a third (head length) increased model accuracy to 92% for video images.
We estimated ages of Colorado pikeminnow, Ptychocheilus lucius, by counting annuli in scales, vertebral centra, whole otoliths, and thin otolith sections. Vertebrae provided the most precise estimator of age and the range of ages obtained were highly correlated with total length. Ages estimated from sectioned otoliths were ranked second in precision and strongly correlated with vertebral ages. Ages read from scales underestimated vertebral ages, and ages estimated from whole otoliths were most variable and least related to total length. Ages estimated using all 4 structures from the same individuals revealed a close relationship between ages estimated with vertebrae and sectioned otoliths.
Breeding migrations of the ringed salamander (Ambystoma annulatum) occur in autumn during rainy nights, when adults move in phalanxes toward small, fishless ponds. We intercepted ringed salamanders on their breeding migration in 1997 and 1998 as they crossed a paved road close to their 0.11-ha breeding pond. In 1997, we measured over 100 salamanders and found larger individuals of both sexes moved earlier in the migration, and females averaged larger than males in both weight and length. In 1998, we counted 1,096 salamanders moving towards the pond and 135 post-breeding animals as they emigrated back to their woodland habitat. Males dominated the first migration event of the 1998 season (73%) and females the last major phalanx (72%), but by the end of the migration season sex ratios were equal. A model predicted 9,848 ringed salamanders crossed the road to breed in this pond in 1998. Our sampling accounted for only 12% of post-breeding salamanders moving away from the pond, suggesting emigration is less directed than immigration. We found 61 ringed salamanders dead on the highway in 1998, indicating a 0.62% mortality due to vehicles.
The relict leopard frog (Rana onca) was once thought to be extinct, but has recently been shown to comprise a valid taxon with extant populations. We delineate the minimum historical range of the species based on records from 24 localities, report the extinction of 2 of 7 populations extant in the 1990s, and estimate total population size. The 5 remaining populations occurred in 2 areas: near the Overton Arm of Lake Mead and in Black Canyon along the Colorado River below Lake Mead, Nevada. These 2 areas are only 3.6 and 5.1 km long, respectively. The 5 extant populations inhabited spring systems with largely unaltered hydrology and no introduced American bullfrogs (Rana catesbeiana) or game fishes. In a mark-recapture study conducted in the Overton Arm area, the estimated number of adult frogs averaged 36 over 555 m of stream habitat, and estimated annual survivorship of adults averaged 0.27. A single mark-recapture estimate for the size of the largest population within Black Canyon, at a site approximately 450 m in length, was 637 adult frogs. An estimate for the total number of frogs at all sites, based on mark-recapture data, visual encounter surveys, and extent of habitat, was approximately 1,100 adults (range 693–1,833). The 2 recent population extinctions occurred concomitantly with encroachment of emergent vegetation into pools. We speculate that this occurred as a result of natural processes in one case, and anthropogenic processes in the other.
The late Pleistocene ground sloth Paramylodon harlani was widely distributed across North America, but it is represented in Arizona by only 2 records. These include a nearly complete skeleton from the Richville Gravels near Springerville, Apache County, and a second partial skeleton from Shonto, Navajo County. Both specimens are from reportedly lacustrine deposits and suggest that the species was not adapted to xeric conditions. Thus, its distribution in the Southwest and potential for dispersal might have been determined by the presence of permanent water sources.
A fire history for the Aiken Canyon Nature Conservancy preserve in Colorado is presented. Eighteen cross-sections cut from ponderosa pine recorded 20 fire events for the period spanning 1602 to 1999. An unusually small median fire interval (MFI) of 7.5 years was obtained for the period 1753 to 1935. A significant association was found between El Nino weather patterns and the fires at Aiken Canyon. A shorter MFI was observed in the grasslands, which are at lower elevations. Fires from railroads or cattle ranching might have caused the shorter MFI in the grasslands between 1872 and 1935. After 1935, fire suppression became common.
We assessed the ability to age post oak (Quercus stellata) and blackjack oak (Q. marilandica) reproduction less than 100 cm in height using counts of terminal bud scars. We harvested reproduction from an old-growth Cross Timbers forest in north-central Oklahoma and compared age estimates from bud scar counts with actual age determined from annual ring counts. Approximately 71% of reproduction was accurately aged by counting bud scars. The majority of errors in age estimation were underestimates. We could accurately estimate age to within 2 years of the actual age 96% of the time. Error rates were similar between species and across height classes, but increased with age of reproduction. Damage to the stem from deer browsing or disease also increased age estimation error. This method might be especially applicable to oak forests that have low levels of herbivory and where nondestructive sampling techniques are required.
To examine how fire affects the invasive Argentine ant, Linepithema humile, I used pitfall traps to estimate worker abundance immediately prior to and for approximately 3 months after a controlled burn in a northern California grassland. I found that L. humile abundance per trap was, on average, 75% lower after the fire than before the fire.
Examination of museum records and field observations have included 4 new records for species of crayfish in Oklahoma (Cambarellus puer, Orconectes deanae, O. lancifer, and O. macrus) and a new drainage record for O. neglectus neglectus. These records bring the number of crayfish known in Oklahoma to 28 and emphasize the importance of revisiting aquatic habitats in regions that have been visited previously. Such records can help in determining the conservation status of poorly known taxonomic groups.
Twice monthly collections of young-of-the-year Procambarus clarkii were taken during the months of October 1998 through mid April l999 from a roadside swamp near Colfax, Louisiana. Antennal glands of 465 P. clarkii were removed and examined for presence of the trematode parasite Allocorrigia filiformis. Data on seasonal prevalence of infection suggests that newly recruited members of the P. clarkii population acquired infections during a 5-month period from October through March.
Although amphibians are the dominant vertebrate inhabiting playa wetlands during spring and summer in the Southern Great Plains, little is known about their diet and role in playa trophic structure. Because new metamorphs are more numerous than other terrestrial life stages of amphibians, we describe the diets of recently (<2 weeks) metamorphosed Great Plains toad (Bufo cognatus), barred tiger salamander (Ambystoma tigrinum), and New Mexico spadefoot (Spea multiplicata). Cultivation has greatly altered most playa watersheds (>95%); therefore, we also examined this influence on diets of Great Plains toad metamorphs. Diets of all 3 species were dominated by coleopteran taxa, and diversity of prey taxa did not vary among species. Amount of specific prey consumed varied among species, with Great Plains toads preying more on scarab beetles and formicid ants than New Mexico spadefoots and tiger salamanders. New Mexico spadefoot metamorphs consumed more chrysomelid and elaterid beetles than tiger salamanders or Great Plains toads. Given the high numerical abundance of metamorphs, they likely have a strong influence on secondary production in playas. Great Plains toad metamorphs in playas with grassland watersheds had a much more diverse diet than those using playas with cultivated watersheds. Conservation of amphibians in the Southern Great Plains should focus on preserving playas with native grassland watersheds or restoring those with cultivated watersheds.
The genus Syrrhophus is recorded for the first time from Louisiana due to the discovery of a population of Syrrhophus cystignathoides in Shreveport. The frogs have been documented during 4 years. Calling males and a female with large yolked eggs indicated that this species was reproducing and surviving.
Many Phrynosoma species exhibit blood-squirting behavior, shooting a stream of blood from the ocular area, but not all species are known to exhibit this behavior. I tested blood-squirting responses to Canis familiaris in P. ditmarsi and P. solare, and recorded incidences of this behavior in other Phrynosoma species (P. asio, P. braconnieri, P. cornutum, P. orbiculare, and P. taurus). Phrynosoma ditmarsi squirted blood in 2 of 3 trials with the dog, but no P. ditmarsi showed any sign of blood squirting while handled in the field (n = 17). No P. solare squirted blood while handled (n = 7), but 1 specimen did squirt blood during a predator trial. Phrynosoma asio and P. cornutum both squirted blood more frequently when handled and other species did not squirt blood. This study corroborates previous observations that the behavior is context specific and can be elicited by tactile stimulation. This is the first published account of the blood squirting behavior in P. ditmarsi.
During June and July 2000, we collected regurgitated pellets and uneaten prey remains at 26 nests occupied by ferruginous hawks (Buteo regalis) in northwestern, western, and central New Mexico. Analysis of remains from all nests yielded a minimum of 260 individual prey from at least 18 vertebrate (13 mammals, 3 birds, and 2 reptiles) and 2 arthropod species. The taxa most frequently represented were Botta's pocket gopher (Thomomys bottae), ground squirrels (Spermophilus), Gunnison's prairie dog (Cynomys gunnisoni), and desert cottontail (Sylvilagus audubonii). Western diamondback rattlesnake (Crotalus atrox) and barn owl (Tyto alba) were recorded for the first time as prey of ferruginous hawks.
Information on cowbird parasitism in Mexico is rare. We report the successful fledging of a brown-headed cowbird (Molothrus ater) nestling by black-capped gnatcatchers (Polioptila nigriceps) in the tropical deciduous forest of the Chamela-Cuixmala Biosphere Reserve, western Mexico, in June 2001. We observed 2 additional gnatcatcher pairs feeding a single brown-headed cowbird fledging. Opportunistic observations of nests of other species and few captures of brown-headed cowbirds during 18 months of intensive mistnetting suggested that cowbird abundance and parasitism was low in the reserve.
We designed a mobile anesthesia unit for surgically implanting radio transmitters in birds in the field. This minimizes the amount of time individuals undergoing the procedure are kept from their normal activities. Two units were designed and tested. In 2000, we successfully implanted radio transmitters in 40 white-winged doves in Kingsville, Texas, using a surgical unit carried in the bed of a truck. In 2002, we successfully implanted 39 white-winged doves in Waco, Texas, using a surgical unit carried in the cargo area of a minivan. The success of both trials indicates this method has great potential for use for numerous avian species while minimizing impacts to individuals being studied.
The white-ankled mouse (Peromyscus pectoralis) was previously known only from Carlsbad Caverns National Park and nearby areas in extreme southeastern New Mexico. I discovered 15 new localities for P. pectoralis, which extend its distribution 225 km north-northwest. This new distribution does not represent a recent northward expansion of P. pectoralis in New Mexico but reflects the lack of mammalian surveys in the region and misidentification of museum specimens from past surveys. At present, the distribution of P. pectoralis in New Mexico includes the Guadalupe Mountains and lowland habitats between the Sacramento Mountains and Pecos River.
In southeastern Arizona, brush mice (Peromyscus boylii) are the primary carriers of Sin Nombre virus, the etiologic agent for the disease hantavirus pulmonary syndrome in humans. Due to the lack of available literature on brush mouse movements, we were interested in determining the probability of mice entering human habitations. We examined movements and home range size of radiocollared brush mice on the Santa Rita Experimental Range, 48 km south of Tucson, Arizona (31°50′N, 110°50′W). We compared movements among seasons (i.e., spring, January to April; summer, May to August; winter, September to December), and between sex and animals living near (≤200 m) versus far from human structures (e.g., cabins, sheds). We did not detect any significant differences in movements or home range size among seasons, or between sex or proximity to artificial structures. Brush mice, on average, moved 17.7 m between consecutive locations (≥3 hr apart). Annually, the average size of home range areas was 0.12 ha. On average, brush mice made small-scale movements within their home range. We found little evidence that brush mice sought human dwellings.
Myotis austroriparius and Corynorhinus rafinesquii are rare bats of the southeastern United States that reach the western limit of their range in eastern Texas. Although the presence of both bats in Texas has been known for over 30 years, there is little roosting information on either species. We located 15 roost sites of M. austroriparius in 9 Texas counties and 13 roosts of C. rafinesquii in 5 counties. Maternity roosts for M. austroriparius were located by tracking radiocollared adult females during the maternity season. These efforts resulted in 10 new county records (from 13 to 23 counties) for M. austroriparius and 5 new county records (from 10 to 15 counties) for Corynorhinus rafinefsquii in Texas. In addition to general roosting sites, 6 maternity roosts for M. austroriparius and 4 for C. rafinesquii were identified in 6 eastern Texas counties.