Geology topics

Evan P. Tanner

Publications and source records attributed to Evan P. Tanner.

9 recordsLinked to original sources

USGS2026

Biological and environmental drivers of early life fawn survival in a declining pronghorn population

Pronghorn Antilocapra americana occupy only a portion of their historical range and in Oklahoma occur at the eastern edge of the species' contemporary distribution. Monitoring has suggested pronghorn populations in Oklahoma have declined in recent years. We captured and collared 125 adult females across two winters, monitored them for signs of parturition during each subsequent spring, and then captured and radio-collared 70 fawns ≤ 4 days old. We assessed cause-specific mortality, estimated proportional survival, and visualized survival of fawns through 60 days of life with Kaplan–Meier curves. Nearly 87% of fawn mortalities were attributed to predation, with > 77% of predations attributed to coyotes Canis latrans . Our results indicated that fawn survival was lowest during the first 15 days of life, with 33% of fawns surviving to 15 days and 12% surviving to 60 days. We used known-fate models to evaluate the influence of biological factors (i.e. sex, mass, birth timing), environmental factors (i.e. ambient temperature, precipitation, vegetation), and temporal variation on the probability of early life (i.e. the first 15 days) survival. For each adult female with a collared fawn, we used female space-use patterns for 30 days before and 15 days after parturition to collect environmental covariates. Early life probability of survival was lower for larger fawns, those born earlier in the parturition period (i.e. earlier in the year relative to the range of parturition days), and those with higher pre-parturition temperatures; daily probability of survival decreased with time-since-parturition within the first 15 days of life. Our results indicate poor fawn survival, highlight a potential limitation of population growth, and can inform population management by identifying factors influencing early life fawn survival.

Oklahoma↗

USGS2025

Sentinel-2 based estimates of rangeland fractional cover and canopy gap class for the western United States

Rangelands are extensive ecosystems, providing important ecosystem services while undergoing continuous change. As a result, improved monitoring technologies can help better characterize vegetation change. Satellite remote sensing has proven effective in this regard, tracking vegetation dynamics at broad and fine scales. We leveraged the spatial, spectral, and temporal resolution of Sentinel-2 satellites to estimate fractional cover and canopy gap across rangelands of the western United States. We produced annual, 10 m spatial resolution estimates of fractional cover and canopy gap size class for years 2018 to 2024. Fractional cover estimates include that of common plant functional types (annual forb and grass, bareground, littler, perennial forb and grass, shrub, tree) and select genera (including invasive annual grass species, pinyon-juniper species, and sagebrush species); canopy gap size classes include gap sizes 25 to 50, 51 to 100, 101 to 200, and greater than 200 cm. We make these data available as Cloud Optimized GeoTIFFs, organized as 75 × 75 km tiles covering the 17 western states of the United States.

western United States↗

USGS2025

Harmless tags or hazardous ads? Investigating the potential for ear tags to increase predation on neonatal ungulates

Studies involving individually marked animals provide insights predicated on the assumption marked individuals are accurate models of their unmarked counterparts. Taxa-specific and marker-specific examinations are needed to determine if marked animals are suitable models for the parameter(s) being measured. Our objective was to determine if brightly colored ear tags influenced the probability of predation for neonatal ungulates. We captured 94 neonatal pronghorn (Antilocapra americana (Ord, 1815)), fitted each neonate with a tracking collar, and attached a yellow ear tag to 49 (52.1%) of the captured neonates. We monitored the survival of each neonate during 2023–2024 in Oklahoma, USA. Predation was the leading cause of mortality during our monitoring period and accounted for 29 (82.9%) of the 35 mortalities with a known cause. Coyotes (Canis latrans Say, 1823) were the predominant predator of neonatal pronghorn in our study area. Presence of a yellow ear tag seemingly did not influence the probability of predation, even though coyotes can distinguish yellow objects from most natural backgrounds. A larger sample size may be needed to validate our results, but neonatal ungulates with an ear tag appear to be accurate models of neonatal ungulates without an ear tag when examining predation risk.

Oklahoma↗

USGS2025

Predator-induced injury of a neonatal pronghorn cues abandonment of current reproductive investment

Evolutionary theory predicts that parental care is favored when the fitness benefits outweigh the costs of providing care (Klug et al., 2012 ). In mammals, parental care is generally provided by females, who provide nourishment through lactation, protection from predators, aid in juvenile movement, or otherwise facilitate offspring survival (Balshine, 2012 ; Lent, 1974 ). However, in capital breeding species that rely on stored energy reserves for reproduction, increased investment can reduce the female's body condition and the number of offspring produced in subsequent years (Balme et al., 2017 ; Cook et al., 2013 ; Stephens et al., 2009 ). Unlike income breeders, which produce offspring from concurrent energy uptake, capital breeders deplete energy stores during reproduction, and lactation hinders the recovery of these stores (Clutton-Brock et al., 1983 ; Cook et al., 2013 ; Stephens et al., 2009 ). Consequently, iteroparous mammals face a trade-off between investing in current offspring and investing in maintenance or future offspring (Hamel et al., 2010 ; Stearns, 1989 ; Williams, 1966 ).

Ecology↗

USGS2025

Sentinel-2 based estimates of rangeland fractional cover and canopy gap class for the western United States

Rangelands are extensive ecosystems, providing important ecosystem services while undergoing continuous change. As a result, improved monitoring technologies can help better characterize vegetation change. Satellite remote sensing has proven effective in this regard, tracking vegetation dynamics at broad and fine scales. We leveraged the spatial, spectral, and temporal resolution of Sentinel-2 satellites to estimate fractional cover and canopy gap across rangelands of the western United States. We produced annual, 10 m spatial resolution estimates of fractional cover and canopy gap size class for years 2018 to 2024. Fractional cover estimates include that of common plant functional types (annual forb and grass, bareground, littler, perennial forb and grass, shrub, tree) and select genera (including invasive annual grass species, pinyon-juniper species, and sagebrush species); canopy gap size classes include gap sizes 25 to 50, 51 to 100, 101 to 200, and greater than 200 cm. We make these data available as Cloud Optimized GeoTIFFs, organized as 75×75 km tiles covering the 17 western states of the United States.

BioRxiv↗

USGS2023

Using fiber-optic distributed temperature sensing in fisheries applications: An example from the Ozark Highlands

Studies of thermal selection by organisms, including fishes, are common and provide data that are useful for conservation and management. Advances in temperature sensing technology have improved these studies; however, the benefits of new technology (e.g., increased accuracy and greater deployment flexibility) should be carefully considered and compared to disadvantages (e.g., higher costs and training requirements). Fiber-optic distributed temperature sensing (FO-DTS) has become more common in aquatic applications and may provide a novel and useful method of relating thermal patchiness to habitat selection by fishes or other aquatic organisms. We present a case study using FO-DTS to conduct a microhabitat-scale resource selection study using stream fishes of the Ozark Highland ecoregion in the south-central United States. We describe the setup and deployment of FO-DTS and how it was integrated into traditional microhabitat survey methods at three stream sites that were repeatedly surveyed over consecutive days. We successfully used FO-DTS to characterize thermal selection by Neosho Bass Micropterus velox at our sites and conclude that the technology would be applicable to similar, microhabitat-scale evaluations. We then compare costs, benefits, and disadvantages of FO-DTS to other sensing methods that could have been used to complete our study. We found that FO-DTS provided accurate measures and greater coverage compared to most alternatives but that equipment costs were far greater. We provide suggestions for additional fisheries applications where FO-DTS may be useful while acknowledging that in some instances, the upfront costs of the technology may outweigh the potential benefits.

Fisheries Research↗

USGS2016

Northern bobwhite breeding season ecology on a reclaimed surface mine

Surface coal mining and subsequent reclamation of surface mines have converted large forest areas into early successional vegetative communities in the eastern United States. This reclamation can provide a novel opportunity to conserve northern bobwhite ( Colinus virginianus ). We evaluated the influence of habitat management activities on nest survival, nest-site selection, and brood resource selection on managed and unmanaged units of a reclaimed surface mine, Peabody Wildlife Management Area (Peabody), in west-central Kentucky, USA, from 2010 to 2013. We compared resource selection, using discrete-choice analysis, and nest survival, using the nest survival model in Program MARK, between managed and unmanaged units of Peabody at 2 spatial scales: the composition and configuration of vegetation types (i.e., macrohabitat) and vegetation characteristics at nest sites and brood locations (i.e., microhabitat). On managed sites, we also investigated resource selection relative to a number of different treatments (e.g., herbicide, disking, prescribed fire). We found no evidence that nest-site selection was influenced by macrohabitat variables, but bobwhite selected nest sites in areas with greater litter depth than was available at random sites. On managed units, bobwhite were more likely to nest where herbicide was applied to reduce sericea lespedeza ( Lespedeza cuneata ) compared with areas untreated with herbicide. Daily nest survival was not influenced by habitat characteristics or by habitat management but was influenced by nest age and the interaction of nest initiation date and nest age. Daily nest survival was greater for older nests occurring early in the breeding season (0.99, SE < 0.01) but was lower for older nests occurring later in the season (0.08, SE = 0.13). Brood resource selection was not influenced by macrohabitat or microhabitat variables we measured, but broods on managed units selected areas treated with herbicide to control sericea lespedeza and were located closer to firebreaks and disked native-warm season grass stands than would be expected at random. Our results suggest the vegetation at Peabody was sufficient without manipulation to support nesting and brood-rearing northern bobwhite at a low level, but habitat management practices improved vegetation for nesting and brood-rearing resource selection. Reproductive rates (e.g., nest survival and re-nesting rates) at Peabody were lower than reported in other studies, which may be related to nutritional deficiencies caused by the abundance of sericea lespedeza. On reclaimed mine lands dominated by sericea lespedeza, we suggest continuing practices such as disking and herbicide application that are targeted at reducing sericea lespedeza to improve the vegetation for nesting and brood-rearing bobwhite.

Kentucky↗

USGS2015

Habitat manipulation influences northern bobwhite resource selection on a reclaimed surface mine

More than 600,000 ha of mine land have been reclaimed in the eastern United States, providing large contiguous tracts of early successional vegetation that can be managed for northern bobwhite ( Colinus virginianus ). However, habitat quality on reclaimed mine land can be limited by extensive coverage of non-native invasive species, which are commonly planted during reclamation. We used discrete-choice analysis to investigate bobwhite resource selection throughout the year on Peabody Wildlife Management Area, a 3,330-ha reclaimed surface mine in western Kentucky. We used a treatment-control design to study resource selection at 2 spatial scales to identify important aspects of mine land vegetation and whether resource selection differed between areas with habitat management (i.e., burning, disking, herbicide; treatment) and unmanaged units (control). Our objectives were to estimate bobwhite resource selection on reclaimed mine land and to estimate the influence of habitat management practices on resource selection. We used locations from 283 individuals during the breeding season (1 Apr–30 Sep) and 136 coveys during the non-breeding season (1 Oct–Mar 31) from August 2009 to March 2014. Individuals were located closer to shrub cover than would be expected at random throughout the year. During the breeding season, individuals on treatment units used areas with smaller contagion index values (i.e., greater interspersion) compared with individuals on control units. During the non-breeding season, birds selected areas with greater shrub-open edge density compared with random. At the microhabitat scale, individuals selected areas with increased visual obstruction >1 m aboveground. During the breeding season, birds were closer to disked areas (linear and non-linear) than would be expected at random. Individuals selected non-linear disked areas during winter but did not select linear disked areas (firebreaks) because they were planted to winter wheat each fall and lacked cover during the non-breeding season. Individuals also selected areas treated with herbicide to control sericea lespedeza ( Lespedeza cuneata ) throughout the year. During the breeding season, bobwhites avoided areas burned during the previous dormant season. Habitat quality of reclaimed mine lands may be limited by a lack of shrub cover and extensive coverage of non-native herbaceous vegetation. Managers aiming to increase bobwhite abundance should focus on increasing interspersion of shrub cover, with no area >100 m from shrub cover. We suggest disking and herbicide application to control invasive species and improve the structure and composition of vegetation for bobwhites.

Kentucky↗

USGS2015

Impact of experimental habitat manipulation on northern bobwhite survival

Habitat management for northern bobwhite ( Colinus virginianus ) should affect vital rates, but direct linkages with survival are not well documented; therefore, we implemented an experiment to evaluate those responses. We conducted our experiment on a reclaimed surface mine, a novel landscape where conditions were considered sub-optimal because of the dominance of non-native vegetation, such as sericea lespedeza ( Lespedeza cuneata ), which has been reported to provide marginal habitat for northern bobwhite and may negatively affect survival. Nonetheless, these areas have great potential for contributing to bobwhite conservation because of the amount of early successional cover they provide. Our study site, a 3,330-ha reclaimed surface mine in western Kentucky, consisted of 2 tracts (Sinclair and Ken, 1,471 ha and 1,853 ha, respectively) that served as replicates with each randomly divided into a treatment (i.e., habitat manipulation through a combination of disking, burning, and herbicide application) and an undisturbed control ( n  = 4 experimental units). Habitat treatments were applied October 2009 to September 2013. We used radio telemetry to monitor northern bobwhite ( n  = 1,198) during summer (1 Apr–30 Sep) and winter (1 Oct–31 Mar), 2009–2013. We used the known-fate model in Program MARK to evaluate treatment effects on seasonal survival rates. We included biological, home-range, landscape, and microhabitat metrics as covariates to help improve model sensitivity and further elucidate experimental impacts. Survival varied annually, ranging from 0.139 (SE = 0.031) to 0.301 (SE = 0.032), and seasonally (summer, 0.148 [SE = 0.015]; winter, 0.281 [SE = 0.022]). We found a treatment effect ( β  = 0.256, 95% CI = 0.057–0.456) with a seasonal interaction ( β   = −0.598, 95% CI = −0.898 to −0.298) with survival being higher in summer (0.179 [SE = 0.022] vs. 0.109 [SE = 0.019]) and lower in winter (0.233 [SE = 0.025] vs. 0.355 [SE = 0.035]) on treatment than control units. Among habitat covariates, litter depth ( β  = −0.387, 95%CI = −0.5809 to −0.1930) was the most influential effect (negative) on survival. Additional experiments across a wider range of habitat conditions may be required to determine management intensity or duration thresholds required to elicit greater changes in survival for northern bobwhite populations.

Kentucky↗