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Results for “Southwestern Naturalist”

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At least 55 records · Page 3Linked to original sources
USGS2013

Home range and use of habitat of western yellow-billed cuckoos on the middle Rio Grande, New Mexico

The western yellow-billed cuckoo (Coccyzus americanus occidentalis) is a Distinct Population Segment that has been proposed for listing under the Endangered Species Act, yet very little is known about its spatial use on the breeding grounds. We implemented a study, using radio telemetry, of home range and use of habitat for breeding cuckoos along the Middle Rio Grande in central New Mexico in 2007 and 2008. Nine of 13 cuckoos were tracked for sufficient time to generate estimates of home range. Overall size of home ranges for the 2 years was 91 ha for a minimum-convex-polygon estimate and 62 ha for a 95%-kernel-home-range estimate. Home ranges varied considerably among individuals, highlighting variability in spatial use by cuckoos. Additionally, use of habitat differed between core areas and overall home ranges, but the differences were nonsignificant. Home ranges calculated for western yellow-billed cuckoos on the Middle Rio Grande are larger than those in other southwestern riparian areas. Based on calculated home ranges and availability of riparian habitat in the study area, we estimate that the study area is capable of supporting 82-99 nonoverlapping home ranges of cuckoos. Spatial data from this study should contribute to the understanding of the requirements of area and habitat of this species for management of resources and help facilitate recovery if a listing occurs.

New Mexico↗
USGS2016

Flow regime effects on mature Populus fremontii (Fremont cottonwood) productivity on two contrasting dryland river floodplains

I compared riparian cottonwood ( Populus fremontii ) productivity-discharge relationships in a relictual stand along the highly regulated Green River and in a naturally functioning stand along the unregulated Yampa River in semiarid northwest Colorado. I used multiple regression to model flow effects on annual basal area increment (BAI) from 1982 to 2011, after removing any autocorrelation present. Each BAI series was developed from 20 trees whose mean size (67 cm diameter at breast height [DBH]) was equivalent in the two stands. BAI was larger in the Yampa River stand except in 2 y when defoliating leaf beetles were present there. I found no evidence for a Yampa flood-magnitude threshold above which BAI declined. Flow variables explained ∼45% of residual BAI variability, with most explained by current-year maximum 90-d discharge (Q M90 ) in the Yampa River stand and by a measure of the year-to-year change in Q M90 in the Green River stand. The latter reflects a management-imposed ceiling on flood magnitude—Flaming Gorge Dam power plant capacity—infrequently exceeded during the study period. BAI in the relictual stand began to trend upward in 1992 when flows started to mimic a natural flow regime. Mature Fremont cottonwoods appear to be ecologically resilient. Their productivity along regulated rivers might be optimized using multiyear environmental flow designs.

Southwestern Naturalist↗
USGS2016

Diet of pumas ( Puma concolor ) in Sonora, Mexico, as determined by GPS kill sites and molecular identified scat, with comments on jaguar ( Panthera onca ) diet

We documented puma ( Puma concolor ) and jaguar ( Panthera onca ) prey consumption in northeastern Sonora, Mexico, by investigating global positioning system cluster sites ( n = 220), and conducting molecular analyses of scat ( n = 116) collected between 2011 and 2013. We used camera trap data ( n = 8,976 camera days) to estimate relative abundances of pumas and jaguars. Deer ( Odocoileus virginianus ) was the most frequent prey for puma found at kill sites (67%) and identified from scat (74%), although based on relative numbers of prey consumed, deer represented 45% and lagomorphs 20% of the proportion of all individuals eaten. A variety of small prey (weighing <15 kg) comprised the majority (52%) of the jaguar kill sites. From prey found at kill sites, jaguars killed calves ( Bos taurus ) at a lower frequency than previously reported, whereas pumas preyed on calves at a higher frequency than previously reported in the same area. In our study area, jaguars preyed on calves at approximately the same rate as pumas (jaguars 3.7 calves per year, pumas 4.9 calves per year). Calculated predation rates were limited only to collared animals within our study area and therefore should not be considered applicable to all pumas and jaguars in Sonora.

Sonora↗
USGS2016

Use of free water by nesting lesser prairie-chickens

The lesser prairie-chicken ( Tympanuchus pallidicinctus ) is a grassland grouse of semiarid regions. Use of free water has been hypothesized as necessary for egg formation during drought. We assessed the use of hydrogen isotopes (deuterium, δ 2 H) to determine if female lesser prairie-chickens use and incorporate free water during egg formation by testing the relationship between isotope ratios in available free water and eggshells. We collected eggshells from 124 nests and 282 free water samples from three sites in Kansas in 2013 and 2014. Eggshells had δ 2 H values similar to free water in the year of severe drought but were dissimilar the year with lessened drought severity. With an established link between lesser prairie-chicken eggshells and free water during severe drought, we have identified a mechanism behind observations of lesser prairie-chicken water use. We have demonstrated that hydrogen isotopes can be used to test research questions related to use of free water.

Southwestern Naturalist↗
USGS2016

Restoring sand shinnery oak prairies with herbicide and grazing in New Mexico

Sand shinnery oak ( Quercus havardii ) prairies are increasingly disappearing and increasingly degraded in the Southern High Plains of Texas and New Mexico. Restoring and managing sand shinnery oak prairie can support biodiversity, specific species of conservation concern, and livestock production. We measured vegetation response to four treatment combinations of herbicide (tebuthiuron applied at 0.60 kg/ha) and moderate-intensity grazing (50% removal of annual herbaceous production) over a 10-year period in a sand shinnery oak prairie of eastern New Mexico. We compared the annual vegetation response to the historical climax plant community (HCPC) as outlined by the U.S. Department of Agriculture Ecological Site Description. From 2 to 10 years postapplication, tebuthiuron-treated plots had reduced shrub cover with twice as much forb and grass cover as untreated plots. Tebuthiuron-treated plots, regardless of the presence of grazing, most frequently met HCPC. Tebuthiuron and moderate-intensity grazing increased vegetation heterogeneity and, based on comparison of the HCPC, successfully restored sand shinnery oak prairie to a vegetation composition similar to presettlement.

New Mexico↗
USGS2016

Phenology of the adult angel lichen moth ( Cisthene angelus ) in Grand Canyon, USA

We investigated the phenology of adult angel lichen moths ( Cisthene angelus ) along a 364-km long segment of the Colorado River in Grand Canyon, Arizona, USA, using a unique data set of 2,437 light-trap samples collected by citizen scientists. We found that adults of C. angelus were bivoltine from 2012 to 2014. We quantified plasticity in wing lengths and sex ratios among the two generations and across a 545-m elevation gradient. We found that abundance, but not wing length, increased at lower elevations and that the two generations differed in size and sex distributions. Our results shed light on the life history and morphology of a common, but poorly known, species of moth endemic to the southwestern United States and Mexico.

Arizona↗
USGS2016

Rare alluvial sands of El Monte Valley, California (San Diego County), support high herpetofaunal species richness and diversity, despite severe habitat disturbance

We characterized the species richness, diversity, and distribution of amphibians and reptiles inhabiting El Monte Valley, a heavily disturbed, alluvium-filled basin within the lower San Diego River in Lakeside, California. This rare habitat type in coastal southern California is designated as a critical sand resource by the state of California and is currently under consideration for a large-scale sand mining operation with subsequent habitat restoration. We conducted field surveys from June 2015 to May 2016 using drift fence lines with funnel traps, coverboard arrays, walking transects, and road driving. We recorded 1,208 total captures, revealing high species richness and diversity, but with marked unevenness in species' abundances. Snakes were the most species-rich taxonomic group (13 species representing 11 genera), followed by lizards (11 species representing 9 genera). After the southern Pacific rattlesnake ( Crotalus oreganus helleri ), the California glossy snake ( Arizona elegans occidentalis ) was the second most frequently detected snake species ( n = 23 captures). Amphibian species richness was limited to only three species in three genera. Despite the relatively limited 12-month sampling period, a longstanding drought, and severe habitat disturbance, our study demonstrates that El Monte Valley harbors a rich herpetofauna that includes many sensitive species.

California↗
USGS2017

Nesting ecology of grassland birds following a wildfire in the southern Great Plains

We studied the response of nesting grassland birds occupying short-grass and mixed-grass prairie sites 2 and 3 y following two, large-scale wildfires that burned ≥360,000 ha in the Texas Panhandle in March 2006. Nest success was greater on burned plots compared to unburned plots, though this varied by species and year. Woody vegetation cover was greater around nests on unburned plots compared to burned plots for Cassin's sparrow ( Peucaea cassinii ) and lark sparrow ( Chondestes grammacus ). Cassin's sparrows and lark sparrows nested in more-woody vegetation than did grasshopper sparrows ( Ammodramus savannarum ), and woody vegetation was reduced following the wildfires. The wildfires appear to have had few if any negative influences on the avian community 3 years postfire. This may be due to grassland breeding birds being adapted to landscapes in which, historically, periodic disturbance (e.g., wildfire, intensive grazing by bison [ Bison bison ]) resulted in vegetation heterogeneity.

Texas↗
USGS2017

Protozoal hepatitis in a western burrowing owl ( Athene cunicularia hypugaea )

A western burrowing owl ( Athene cunicularia hypugaea ) found dead in southern California had many light-colored lesions visible grossly on its liver, and histopathology revealed extensive necrosis throughout the hepatic parenchyma. Single-celled organisms were seen in clear spaces within the areas of necrosis. The owl was diagnosed with protozoal hepatitis.

Southwestern Naturalist↗
USGS2017

Subsequent-year recaptures at winter sites in three species of shrubland sparrows (Emberizidae)

The tendency by individual birds to return to winter sites in subsequent years can be important in assessing the potential influence of habitat changes during the nonbreeding period. We recaptured five Brewer's ( Spizella breweri ), seven sagebrush ( Artemisiospiza nevadensis ), and three black-throated ( Amphispiza bilineata ) sparrows from 1–3 subsequent years at the same winter location following their initial capture. Two Brewer's and one sagebrush sparrow returned to the same winter location at least 4 years after their initial capture. Levels of feather deuterium indicated that birds captured together on winter sites had different breeding ranges. Although individuals of these species returned to specific sites used in previous years, the low recapture rate suggests that wintering individuals may use an itinerant strategy adapted to seasonal food resources.

Arizona, California, Colorado, Nevada, New Mexico,↗
USGS2017

Survival of the endangered Pima pineapple cactus: Does clearing before prescribed fire alter survival postfire?

Federal land managers and ranchers often use prescribed fire as a tool to reduce invading woody plants within desert grasslands of the arid southwestern United States. Managers must evaluate the threat of the burn toward the health and survival of plants of concern including how preemptive clearing before prescribed fire might benefit these species. One example is the endangered Pima pineapple cactus ( Coryphantha scheeri var. robustispina ), a small hemispheric cactus of desert scrublands and grasslands of south-central Arizona and northern Sonora, Mexico. In 2014, we examined survival of Pima pineapple cactus documented in 2009 or 2010 within grasslands of Buenos Aires National Wildlife Refuge in Arizona. Of the 72 sites observed, 35 had no burn after documentation and 37 experienced prescribed fire. Refuge staff removed vegetation between 0.3 and 3.0 m from the cactus preburn. We found that Pima pineapple cacti in areas subjected to prescribed fire and with preemptive clearing had the same survival statistically as cacti from sites that were not burned.

Arizona↗
USGS2018

Long-Term Movement and Estimated Age of a Paddlefish (Polyodon spathula) in the Arkansas River Basin of Oklahoma

We report the age and distance moved for an individual paddlefish ( Polyodon spathula ) that was tagged March 1998 in the Cimarron River Arm of Keystone Lake, Oklahoma, and snagged by an angler in April 2016 downstream of Eufaula Dam, Oklahoma. The fish was part of a cohort spawned in 1995. At the time of initial capture, the fish measured 795 mm eye–fork length, was estimated to be 3 y old, and 18 y had elapsed before its recapture by an angler in 2016, indicating this fish was 21 y old at recapture. Although paddlefish as old as 27 have been estimated in the Grand River basin of Oklahoma, this is the oldest fish known in the Arkansas River basin of Oklahoma. At the place of its recapture, this fish would have traveled approximately 235 km, passing downstream through three dams before moving upstream to Eufaula Dam.

Oklahoma↗
USGS2017

Population expansion of Humpback chub in western Grand Canyon and hypothesized mechanisms

Humpback chub, Gila cypha , is an endangered warm water fish endemic to the Colorado River basin of southwestern North America. In Grand Canyon National Park, cold hypolimnetic water-release temperatures from Glen Canyon Dam have largely precluded successful spawning and recruitment of humpback chub in the mainstem Colorado River. Therefore, the species has utilized the warmer, more saline, and free-flowing Little Colorado River for its primary spawning habitat and continued existence. Based on long-term fish sampling efforts, we document local recruitment and population expansion of humpback chub in the western Grand Canyon and hypothesize that this is a result of recent warmer mainstem water temperatures. Continued recruitment and population expansion of humpback chub in the western Grand Canyon could potentially reduce extinction risk by providing population redundancy and less reliance upon the Little Colorado River for the species survival in the Grand Canyon.

Arizona↗
USGS2019

Winter and spring diet of the orangebelly darter, Etheostoma radiosum, among tributaries of the Lower Mountain Fork River

Little is known about prey use by the orangebelly darter, Etheostoma radiosum , and what is known has been described from relatively large river systems. We examined prey use by orangebelly darters from first- and second-order tributaries in the Lower Mountain Fork River of southeastern Oklahoma. Adult darters ( n = 141) were captured from five tributaries in 2015, and stomach contents were examined to determine prey use. Aquatic isopods were the most frequently consumed organism. This differs notably from previous reports that insects, primarily dipterans, were the predominant prey for the species.

Oklahoma↗
USGS2019

Viability of Razorback-Flannelmouth Sucker hybrids

Razorback sucker ( Xyrauchen texanus ) and flannelmouth sucker ( Catostomus latipinnis ) live in sympatry in the Colorado River basin. Although morphological intermediates have been described since 1889, hybrids were seemingly rare. Rarity of hybrids was likely attributed to razorback suckers' ability to find conspecific mates throughout the basin. Dams have segmented the Colorado River, altering habitat and isolating native fish populations. As a result, razorback suckers became endangered. Razorback suckers are uncommon in the Colorado River and hybridization could increase because of limited conspecific mates. To understand the impacts of hybridization on recovery of the razorback sucker, information on hybrid viability is needed. We compared hatch success and larval survival of artificially spawned razorback sucker, flannelmouth sucker, and their hybrids. We were able to successfully spawn and rear all combinations, implying that there are limited pre- and postzygotic isolation mechanisms, and hybrids are likely to survive in the wild.

Arizona, Baja California, California, Colorado, Ne↗
USGS2020

Co-occurence of Chiricahua leopard frogs (Lithobates chiricahuensis) with sunfish (Lepomis)

Invasive species are a major threat to the persistence of native species, particularly in systems where ephemeral aquatic habitats have been replaced by permanent water and predators, such as fish, have been introduced. Within the Altar Valley, Arizona, the invasive American bullfrog, Lithobates catesbeianus (formerly Rana catesbeianus ), has been successfully eradicated to help recover Chiricahua leopard frogs ( Lithobates chiricahuensis ). However, other nonnative predators including sunfish ( Lepomis ) are present in some permanent water bodies. During four consecutive years (2014–2017), we detected both the federally threatened Chiricahua leopard frog and sunfish at one permanent water body in the Altar Valley. This suggests that despite the potential negative effect of predatory fish on amphibians, there may be conditions where the Chiricahua leopard frog can co-occur with this nonnative predator. A better understanding of rare situations of co-occurrence with nonnative predators may contribute to our understanding of why co-occurrence happens in some, but not all, systems and whether conservation strategies can be developed in situations where eradication of nonnative predators is infeasible.

Arizona↗
USGS2020

Reproduction and denning by San Clemente Island Foxes: Age, sex, and polygamy

Channel Island foxes ( Urocyon littoralis ) live on six of the eight California Channel Islands, and each island is inhabited by a distinct subspecies. Until recently, four of these subspecies were listed under the Endangered Species Act as endangered. Although three of the four subspecies have been delisted, and one subspecies was downlisted to threatened, all subspecies are still vulnerable because of small population sizes and potential threats from predation and disease. Consequently, information on reproductive behavior for each subspecies, including the San Clemente Island fox ( Urocyon littoralis clementae ), is important for understanding fox population dynamics. We determined reproductive status of 28 island foxes through observations of radio collared yearlings and adults with or without juveniles between 25 February and 8 October 2009. We found a greater number of adult foxes than yearling foxes and a greater number of female foxes than male foxes observed with juveniles. Also, there was a significantly greater probability of observing adult female foxes with juveniles than yearling males with juveniles. Only 1 of 28 radio collared foxes exhibited either polygamous or “helper” behaviors. Parturition started approximately 2 months earlier than historically recorded for other Channel Island fox subspecies. Our results suggest that in future studies of reproductive success more effort should be placed on monitoring adult females than yearling males. If emergence from dens continues to occur earlier than previously recorded, the current recommended time period for trapping (20 June–31 January) might need revision to exclude January to reduce stress to pregnant females. If all foxes have similar probabilities of transmitting disease on a given contact with juveniles, our data suggest that it may be appropriate to focus more vaccination efforts on females than males and adults than yearlings because they contact juveniles more frequently.

California↗
USGS2021

Augmentation of natural prey reduces cattle predation by puma (Puma concolor) and jaguar (Panthera onca) on a ranch in Sonora, Mexico

Retaliatory killing of large carnivores due to livestock predation is one of the major threats for the conservation of many declining populations of predators. According to empirical observations, there is a higher incidence of livestock predation when native prey abundance is low. In this study, we applied a treatment consisting of augmentation of prey abundance by translocation of peccaries ( Pecari tajacu ) and placement of four feed stations for white-tailed deer ( Odocoileus virginianus ) on a cattle ranch in Sonora, Mexico, with verified calf predation by puma ( Puma concolor ) and jaguar ( Panthera onca ). We quantified and compared consumed prey over two periods—phase I (8 months before the augmentation of prey) and phase II (8 months after the augmentation of prey)—through investigation of kill sites from Global Positioning System–collared jaguar and puma, prey identification from analyzed scat using molecular DNA techniques, and opportunistic discoveries of recently killed animal remains by either predator. We calculated the relative abundance of species (17 mammals [one species with two distinct age classes] and 1 bird species) through camera traps and for the most relevant prey species for this study (deer, calf, and peccary), we also estimated prey use by the predator, based on their availability during each period (prey preference). In the prey composition analyses of scat, we observed a significant reduction in the consumption of bovids and a significant increase in the consumption of peccaries during phase II. In the analyses of prey use, during phase I, predators consumed peccaries and calves at a higher proportion in relation to their availability. During phase II, consumption of calves declined from being preferred, to being consumed at the same proportion as their availability. Application of these results can contribute to the decrease of livestock predation and therefore conservation of pumas and jaguars.

Sonora↗