Ecological drivers of ultraviolet colour evolution in snakes.

Ultraviolet (UV) colour patterns invisible to humans are widespread in nature. However, research bias favouring species with conspicuous colours under sexual selection can limit our assessment of other ecological drivers of UV colour, like interactions between predators and prey. Here we demonstrate widespread UV colouration across Western Hemisphere snakes and find stronger support for a predator defence function than for reproduction. We find that UV colouration has evolved repeatedly in species with ecologies most sensitive to bird predation, with no sexual dichromatism at any life stage. By modelling visual systems of potential predators, we find that snake conspicuousness correlates with UV colouration and predator cone number, providing a plausible mechanism for selection. Our results suggest that UV reflectance should not be assumed absent in "cryptically coloured" animals, as signalling beyond human visual capacities may be a key outcome of species interactions in many taxa for which UV colour is likely underreported.

The Batrachian Barf Bowl: An authentic research experience using ecological data from frog diets.

Authentic research experiences (AREs) are a powerful strategy for inspiring and retaining students in science, technology, engineering, and math (STEM) fields. However, recent demand for virtual learning has emphasized the need for remote AREs that also foster a sense of community and interpersonal connections among participants. Here, we describe an ARE activity that leverages digitized diet data from natural history collections to provide students with collaborative research experience across any learning environment. Using magnified photographs of frog stomach contents collected in the Peruvian Amazon, we designed an open-source "bowl game" competition that challenges students to identify, measure, and compare diet items across vouchered frog specimens ("Batrachian Barf Bowl"). To demonstrate learning outcomes, we ran this activity with 39 herpetology class students from the University of Notre Dame and the University of Michigan. We used pre- and post-activity assessments to evaluate effectiveness, scientific accuracy of results, and impact on student well-being. With minimal preparation and training in invertebrate identification, students were successful in identifying hundreds of frog diet items to taxonomic order, although accuracy varied among clades (global accuracy ~70%). While we found no difference in science identity, community, or self-efficacy between the two institutions at either time point (pre- and post-activity), we found that well-being was significantly higher for both sets of students after the activity. Overall, this approach offers a model for combining active learning with museum collections to provide experiential research opportunities that highlight the power of scientific collaboration.

Climatic factors impacting thermoregulatory behaviours of coastal and inland rattlesnakes.

Conspecific animals living in multiple habitats may utilize different behaviours to survive and thrive in their environments. The Pacific rattlesnake (Crotalus oreganus), a generalist pit viper species, lives in a myriad of habitat types. We hypothesized that populations inhabiting hot, inland habitats and those in cool, coastal habitats would exhibit different behavioural strategies, especially those related to thermoregulation. Additionally, we determined whether environmental factors could be used as predictors of certain behaviours. We recorded environmental and behavioural data while radio-tracking adult, male rattlesnakes from two inland sites and two coastal sites throughout their active season. We found significant differences in thermoregulatory behaviour, with coastal snakes found more frequently above ground and in an active state than inland snakes. Additionally, wind, cloud cover, and air temperature were significant predictors of several snake behaviours. These results suggest that rattlesnakes exhibit plasticity in thermoregulatory behaviour.

Thermal ecology and baseline energetic requirements of a large-bodied ectotherm suggest resilience to climate change.

Most studies on how rising temperatures will impact terrestrial ectotherms have focused on single populations or multiple sympatric species. Addressing the thermal and energetic implications of climatic variation on multiple allopatric populations of a species will help us better understand how a species may be impacted by altered climates.We used eight years of thermal and behavioral data collected from four populations of Pacific rattlesnakes (Crotalus oreganus) living in climatically distinct habitat types (inland and coastal) to determine the field-active and laboratory-preferred body temperatures, thermoregulatory metrics, and maintenance energetic requirements of snakes from each population.Physical models showed that thermal quality was best at coastal sites, but inland snakes thermoregulated more accurately despite being in more thermally constrained environments. Projected increases of 1 and 2°C in ambient temperature result in an increase in overall thermal quality at both coastal and inland sites.Population differences in modeled standard metabolic rate estimates were driven by body size and not field-active body temperature, with inland snakes requiring 1.6× more food annually than coastal snakes.All snakes thermoregulated with high accuracy, suggesting that small increases in ambient temperature are unlikely to impact the maintenance energetic requirements of individual snakes and that some species of large-bodied reptiles may be robust to modest thermal perturbations under conservative climate change predictions. ​.

Thermal ecology of the federally endangered blunt-nosed leopard lizard (Gambelia sila).

Recognizing how climate change will impact populations can aid in making decisions about approaches for conservation of endangered species. The blunt-nosed leopard lizard (Gambelia sila) is a federally endangered species that, despite protection, remains in extremely arid, hot areas and may be at risk of extirpation due to climate change. We collected data on the field-active body temperatures, preferred body temperatures and upper thermal tolerance of G. sila. We then described available thermal habitat using biophysical models, which allowed us to (i) describe patterns in lizard body temperatures, microhabitat temperatures and lizard microhabitat use; (ii) quantify the lizards' thermoregulatory accuracy; (iii) calculate the number of hours they are currently thermally restricted in microhabitat use; (iv) project how the number of restricted hours will change in the future as ambient temperatures rise; and (v) assess the importance of giant kangaroo rat burrows and shade-providing shrubs in the current and projected future thermal ecology of G. sila. Lizards maintained fairly consistent daytime body temperatures over the course of the active season, and use of burrows and shrubs increased as the season progressed and ambient temperatures rose. During the hottest part of the year, lizards shuttled among kangaroo rat burrows, shrubs, and open habitat to maintain body temperatures below their upper thermal tolerance, but, occasionally, higher than their preferred body temperature range. Lizards are restricted from staying in the open habitat for 75% of daylight hours and are forced to seek refuge under shrubs or burrows to avoid surpassing their upper thermal threshold. After applying climatic projections of 1 and 2°C increases to 2018 ambient temperatures, G. sila will lose additional hours of activity time that could compound stressors faced by this population, potentially leading to extirpation.