Geology topics

Sarah King

Publications and source records attributed to Sarah King.

4 recordsLinked to original sources

USGS2024

Resource availability and heterogeneity affect space use and resource selection of a feral ungulate

Animals adjust their habitat use patterns in response to changes in their physiological needs and environmental conditions. Understanding the mechanisms underlying resource selection and space use across time and space reveals effects of the environment on animals' decisions. We explored the effects of habitat availability and heterogeneity on the seasonal and annual space use and resource selection of two free-roaming feral burro ( Equus asinus ) populations in the United States within distinct climate and habitat conditions: the Sonoran Desert and the Colorado Plateau. As an introduced yet protected species in the United States, understanding burros' interactions with habitat elements is important for their conservation and management, as well as the conservation of sympatric wildlife. We used GPS locations of female burros (72 animals across both study areas) to delineate annual and seasonal ranges and resource selection patterns. We evaluated effects of mean and CV of habitat covariates, including forage, distance to water, and topography, representing availability and heterogeneity of resources, on seasonal and annual range size of burros. Moreover, we explored how burro seasonal and annual resource selection patterns were affected by availability and heterogeneity of resources. In the Sonoran Desert study area, burros had smaller seasonal and annual ranges and constant resource selection patterns across a year, likely due to a freshwater lake in the area, making water a nonlimiting resource. Human presence was the greatest factor affecting range size and resource selection in the Sonoran Desert, where burros selected for areas near roads and human recreation. In the Colorado Plateau study area, where resources were more seasonal, we found larger range sizes and fluctuating resource selection patterns compared to the Sonoran Desert population. Spatial variation in forage, water, and topography significantly affected range size of burros inhabiting the Colorado Plateau study area. Productive habitats with available water support smaller ranges and a more consistent pattern of resource selection. Our results highlight the positive effect of habitat heterogeneity and the negative effect of habitat productivity on range size of animals. Our findings contribute to an improved understanding of habitat requirements for free-roaming burros that currently live under various climate and habitat conditions globally.

Arizona, Utah↗

USGS2024

Effects of telemetry collars on two free-roaming feral equid species

There are two species of free-roaming feral equids in North America: horses ( Equus caballus ) and donkeys or “burros” ( E . asinus ). Both species were introduced as domestic animals to North America in the early 1500s and currently inhabit rangelands across the western United States, Canada, and all continents except Antarctica. Despite their global distribution, little is known about their fine scale spatial ecology. Contemporary research tools to assess space use include global positioning system (GPS) tracking collars, but older models were problematic due to stiff collar belting causing poor fit. We tested modern designs of GPS collars on n = 105 horses and n = 60 burros for 4 years in five populations (3 horse, 2 burro) across the western United States, to assess whether collars posed welfare risks to horses or burros. We found no difference in survival of collared versus uncollared mares and jennies, and no difference in survival of their foals. In 4036 of 4307 observations for horses (93.7%) and 2115 of 2258 observations for burros (93.6%), collars were observed symmetrical, maintaining proper fit on the neck. Fur effects from collars (sweaty neck, indented fur, broken fur) were seen in 3% of horse observations and 25% of burro observations. Superficial effects (chafes and marks on skin surface) were seen in 2% of horse observations and 11% of burro observations; no severe effects from collars were seen. Body condition was not affected by collars; mean body condition of collared horses was 4.70 ± 0.54 (mean ± s.d) and 4.71 ± 0.65 for collared burros. Behavior results indicated minimal effects; collared horses stood slightly more than uncollared, and collared burros stood and foraged more in one population, but not in the other. For 6.3% of observations of horses and 6.4% of observations of burros, we found an effect of time wearing a collar on the cumulative sum of fur effects which increased over time (burros: r s = 0.87, P = <0.0001; horses: r s = 0.31, P = 0.002). Burros also showed an increase over time in the number of superficial effects, but horses did not. Collars occasionally moved into the wrong position, shifting forward over the ears; we observed this on 19 horses and 1 burro. Of those, most collars went over the ears in summer ( n = 12). All collars were equipped with a remote release mechanism as well as a timed-release mechanism for redundancy, thus removed when observed in wrong position to avoid rubbing or discomfort. Our finding of no consequential physical effects in 98% of horse observations, and 89% of burro observations suggests the consequences of collars on free-roaming equid welfare and survival is biologically insignificant, although collars should be monitored regularly and continue to be equipped with a remote release mechanism to remove a collar if needed. With frequent welfare-driven, visual monitoring, collaring of free-roaming equids can be a safe and useful tool to increase our understanding of their spatial ecology, demography, habitat use, behavior, and interactions with other wildlife.

Arizona, Utah, Wyoming↗

USGS2024

Toxicity of crude oil-derived polar unresolved complex mixtures to Pacific herring embryos: Insights beyond polycyclic aromatic hydrocarbons

Crude oil toxicity to early life stage fish is commonly attributed to polycyclic aromatic hydrocarbons (PAHs). However, it remains unclear how the polar unresolved complex mixture (UCM), which constitutes the bulk of the water-soluble fraction of crude oil, contributes to crude oil toxicity. Additionally, the role of photomodification-induced toxicity in relation to the polar UCM is not well understood. This study addresses these knowledge gaps by assessing the toxicity of two laboratory generated polar UCMs from Cook Inlet crude oil, representing the readily water-soluble fraction of crude oil and photoproduced hydrocarbon oxidation products (HOPs), to Pacific herring ( Clupea pallasii ) embryos. A small-scale semi-static exposure design was utilized with a range of polar UCM concentrations (0.5–14 mg/L) in nonvolatile dissolved organic carbon (NVDOC) units, quantifying the entire polar UCM. Compositional analyses revealed a photochemical-driven shift toward more complex aromatic compositions, naphthenic acids, and no detectable levels of PAHs (above 0.3 μg/L). Exposure to the dark polar UCM resulted in higher mortality than exposure to the light polar UCM. Both dark and light polar UCMs induced developmental abnormalities commonly attributed to the PAH fraction, including edema, reduced heart rate, body axis defects, and decreased body lengths, with these effects observed at the lowest dose group (0.5 mg/L NVDOC). These responses suggest photomodification-induced toxicity is driven by exposure to increased concentrations of dissolved HOPs rather than photochemical induced compositional changes. Gene expression analyses focusing on xenobiotic metabolism and cardiac morphogenesis yielded results consistent with previous studies examining the biological mechanisms of crude oil toxicity. In summary, these phenotypic and genotypic responses in Pacific herring embryos indicate that the polar UCM is a significant driver of crude oil toxicity. These findings emphasize the importance of considering the polar UCM in future studies, metric reporting, and risk assessments related to crude oil toxicity.

Science of the Total Environment↗

USGS2023

Browsers or Grazers? New insights into feral burro diet using a non-invasive sampling and plant DNA metabarcoding approach

By selecting certain plants for consumption, ungulates (hoofed mammals) shape ecosystems and influence which plant species are present in their habitats. We investigated the summer diets of non-native feral burros in two ecosystems: a subtropical Sonoran Desert in Arizona and a temperate juniper shrubland in Utah, the United States. In June and July of 2019, we gathered 50 fecal samples from both locations and analyzed plant DNA in the samples to identify which plants the burros were eating. Our findings revealed that during our summer sampling period, the burros in the Sonoran Desert predominantly consumed woody browse, whereas the burros in the juniper woodland consumed a wide range of flowering herbaceous plants (forbs) and grasses. The burros in the temperate system had to consume a more diverse diet to meet their nutritional needs, while the burros in the Sonoran Desert could rely on two major forage species, mesquite and grasses from the Poaceae family; as a result, their diet had a lower degree of diversity. Feral burros are descended from the African wild ass and exhibit a similar mixed feeding strategy to their ancestors in which they can adapt their diet in different ecosystems to meet their nutritional requirements.

Animals↗