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1. Biotic and abiotic factors affecting Atlantic ghost crab (Ocypode quadrata) spatiotemporal activity at an important shorebird nesting site in Virginia

   https://doi.org/10.1371/journal.pone.0307821  

   Call, Mikayla N; Pongnon, Rasheed S; Wails, Christy N; Karpanty, Sarah M; Lapenta, Kristy C; Wilke, Alexandra L; Boettcher, Ruth; Alvino, Camille R; Fraser, James D (August 2024, PLOS ONE)

   Romanach, Stephanie S (Ed.)

   Atlantic ghost crabs (Ocypode quadrata) are predators of beach-nesting shorebird nests and chicks on the United States’ Atlantic and Gulf coasts. Ghost crabs may also disturb birds, altering foraging, habitat use, or nest and brood attendance patterns. Shorebird conservation strategies often involve predator and disturbance management to improve reproductive success, but efforts rarely target ghost crabs. Despite the threat to shorebird reproductive success, ghost crabs are a poorly understood part of the beach ecosystem and additional knowledge about ghost crab habitat selection is needed to inform shorebird conservation. We monitored ghost crab activity, defined as burrow abundance, throughout the shorebird breeding season on Metompkin Island, Virginia, an important breeding site for piping plovers (Charadrius melodus) and American oystercatchers (Haematopus palliatus). We counted burrows at shorebird nests and random locations throughout the breeding season and investigated whether ghost crab activity was greater at nest sites relative to random locations without shorebird nests. While we observed burrows at all nest sites (n= 63 nests), we found that burrow counts were lower at piping plover nests with shell cover, relative to random locations with no shell cover. Ghost crabs may avoid piping plover nest sites due to anti-predator behaviors from incubating adults or differences in microhabitat characteristics selected by piping plovers. We also investigated the effects of habitat type, date, and air temperature on the abundance of ghost crab burrows. We found that while crab burrows were present across the barrier island landscape, there were more burrows in sandy, undisturbed habitats behind the dunes, relative to wave-disturbed beach. Additionally, ghost crab activity increased later in the shorebird breeding season. Understanding when and where ghost crabs are most likely to be active in the landscape can aid decision-making to benefit imperiled shorebird populations. 

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2. Stability of kangaroo rat burrows in the Sonoran Desert: Evidence of biocementation

   https://doi.org/10.1139/cgj-2024-0225  

   Tirkes, Sera; Aydin, Duygu; Thompson, Madison; Collins, Clint E; Beyenal, Haluk; Akin, Idil Deniz (October 2024, Canadian Geotechnical Journal)

   Kangaroo rats (Dipodomys deserti) construct complex burrow systems in loose desert sand that survive temperature and relative humidity fluctuations and storms. Animals that burrow in desert sand typically burrow in compacted sand, near plant roots, or when the soil is unsaturated. However, these processes are insufficient to explain tunnel stability of kangaroo rats. Our goal is to understand how kangaroo rat burrows remain stable in loose desert sand, intending to translate this knowledge to geotechnical engineering. A kangaroo rat habitat in the dunes of The Sonoran Desert, AZ, was selected for the study. Dynamic cone penetrometer tests performed at active, abandoned, and no-burrow sites demonstrated that the animals prefer loose sand for burrow construction. Soil samples collected from the burrows' ceilings, subsurface, and surface were characterized. Brazilian tensile strength test results showed that burrow soil has approximately 3 times greater tensile strength than the rest at dry state, which indicates increased interparticle attractive stress in burrow ceilings due to biocementation. Laboratory experiments, scanning electron microscopy, and confocal microscopy images showed that fungal and microbial biofilms provided 17 kPa increase in interparticle attractive stress at less than 1% biomass concentration, indicating potential to be used in soil improvement applications. 

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3. The structure of the thermal landscape determined behavioural and physiological responses to simulated predation risk

   https://doi.org/10.1111/1365-2435.14429  

   Rusch, Travis W; Sears, Michael W; Angilletta, Michael J (November 2023, Functional Ecology)

   Although predators can deter an animal from regulating its body temperature by basking or shuttling, this response to predation should depend on the spatial distribution of thermal resources. By simulating predation risk, we showed that movement, thermoregulation and corticosterone of male lizards Sceloporus jarrovi depended on the spatial distribution of shade. Simulated risk caused lizards to move less, thermoregulate worse and circulate more corticosterone than they did without risk. However, a patchier distribution of shade enabled lizards to move more, thermoregulate better and circulate less corticosterone when exposed to a simulated predator. In the absence of simulated risk, lizards in patchier environments moved less, thermoregulated better and circulated less corticosterone, indicating the distribution of shade also affected the energetic cost of thermoregulation. This study provides the first test of a spatial theory of thermoregulation under the perceived risk of predation. 

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4. Terrain Features and Architecture of Wolverine (Gulo gulo) Resting Burrows and Reproductive Dens on Arctic Tundra

   https://doi.org/10.14430/arctic75576  

   Glass, Thomas W.; Breed, Greg A.; Laird, Cristina R.; Magoun, Audrey J.; Robards, Martin D.; Williams, Cory T.; Kielland, Knut (September 2022, ARCTIC)

   Burrowing species rely on subterranean and subnivean sites to fulfill important life-history and behavioral processes, including predator avoidance, thermoregulation, resting, and reproduction. For these species, burrow architecture can affect the quality and success of such processes, since characteristics like tunnel width and chamber depth influence access by predators, thermal insulation, and energy spent digging. Wolverines (Gulo gulo) living in Arctic tundra environments dig burrows in snow during winter for resting sites and reproductive dens, but there are few published descriptions of such burrows. We visited 114 resting burrows and describe associated architectural characteristics and non-snow structure. Additionally, we describe characteristics of 15 reproductive den sites that we visited during winter and summer. Although many resting burrows were solely excavated in snow, most incorporated terrain structures including cliffs, talus, river shelf ice, thermokarst caves, and stream cutbanks. Burrows typically consisted of a single tunnel leading to a single chamber, though some burrows had multiple entrances, branching tunnels, or both. Tunnels in resting burrows were shorter than those in reproductive dens, and resting chambers were typically located at the deepest part of the burrow. Reproductive dens were associated with snowdrift-forming terrain features such as streambeds, cutbanks on lake edges, thermokarst caves, and boulders. Understanding such characteristics of Arctic wolverine resting and reproductive structures is critical for assessing anthropogenic impacts as snowpack undergoes climate-driven shifts. 

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5. Autonomic perspiration in 3D-printed hydrogel actuators

   https://doi.org/10.1126/scirobotics.aaz3918  

   Mishra, Anand K.; Wallin, Thomas J.; Pan, Wenyang; Xu, Patricia; Wang, Kaiyang; Giannelis, Emmanuel P.; Mazzolai, Barbara; Shepherd, Robert F. (January 2020, Science Robotics)

   In both biological and engineered systems, functioning at peak power output for prolonged periods of time requires thermoregulation. Here, we report a soft hydrogel-based actuator that can maintain stable body temperatures via autonomic perspiration. Using multimaterial stereolithography, we three-dimensionally print finger-like fluidic elastomer actuators having a poly- N -isopropylacrylamide (PNIPAm) body capped with a microporous (~200 micrometers) polyacrylamide (PAAm) dorsal layer. The chemomechanical response of these hydrogel materials is such that, at low temperatures (<30°C), the pores are sufficiently closed to allow for pressurization and actuation, whereas at elevated temperatures (>30°C), the pores dilate to enable localized perspiration in the hydraulic actuator. Such sweating actuators exhibit a 600% enhancement in cooling rate (i.e., 39.1°C minute −1 ) over similar non-sweating devices. Combining multiple finger actuators into a single device yields soft robotic grippers capable of both mechanically and thermally manipulating various heated objects. The measured thermoregulatory performance of these sweating actuators (~107 watts kilogram −1 ) greatly exceeds the evaporative cooling capacity found in the best animal systems (~35 watts kilogram −1 ) at the cost of a temporary decrease in actuation efficiency. 

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