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.

Functional diversity of snake locomotor behaviors: A review of the biological literature for bioinspiration

Organismal solutions to natural challenges can spark creative engineering applications. However, most engineers are not experts in organismal biology, creating a potential barrier to maximally effective bioinspired design. In this review, we aim to reduce that barrier with respect to a group of organisms that hold particular promise for a variety of applications: snakes. Representing >10% of tetrapod vertebrates, snakes inhabit nearly every imaginable terrestrial environment, moving with ease under many conditions that would thwart other animals. To do so, they employ over a dozen different types of locomotion (perhaps well over). Lacking limbs, they have evolved axial musculoskeletal features that enable their vast functional diversity, which can vary across species. Different species also have various skin features that provide numerous functional benefits, including frictional anisotropy or isotropy (as their locomotor habits demand), waterproofing, dirt shedding, antimicrobial properties, structural colors, and wear resistance. Snakes clearly have much to offer to the fields of robotics and materials science. We aim for this review to increase knowledge of snake functional diversity by facilitating access to the relevant literature.

Sound garden: How snakes respond to airborne and groundborne sounds

Evidence suggests that snakes can hear, but how snakes naturally respond to sound is still unclear. We conducted 304 controlled experiment trials on 19 snakes across five genera in a sound-proof room (4.9 x 4.9 m) at 27ºC, observing the effects of three sounds on individual snake behavior, compared to controls. We quantified eight snake behaviors (body movement, body freezing, head-flicks, tongue-flicks, hissing, periscoping, head fixation, lower jaw drop) in response to three sounds, which were filtered pink-noise within the following frequency ranges: 0-150Hz (sound 1, which produced ground vibrations, as measured by an accelerometer), 150-300Hz (sound 2, which did not produced ground vibrations), 300-450Hz (sound 3, which did not produced ground vibrations). All snake responses were strongly genus dependent. Only one genus (Aspidites, Woma Pythons) significantly increased their probability of movement in response to sound, but three other genera (Acanthophis (Death Adders), Oxyuranus (Taipans), and Pseudonaja (Brown Snakes)) were more likely to move away from sound, signaling potential avoidance behavior. Taipans significantly increased their likelihood of displaying defensive and cautious behaviors in response to sound, but three of the five genera exhibited significantly different types of behaviors in sound trials compared to the control. Our results highlight potential heritable behavioral responses of snakes to sound, clustered within genera. Our study illustrates the behavioral variability among different snake genera, and across sound frequencies, which contributes to our limited understanding of hearing and behavior in snakes.

Description of the antipredatory head-wobble behaviour in Chilean rear-fanged snakes Tachymenis peruviana Wiegmann, 1835 and Tachymenis chilensis coronellina Werner, 1898 (Serpentes, Dipsadidae)

In this work, we describe the first records of head-wobble behaviour for Tachymenis peruviana and T. chilensis coronellina. We analyse this behaviour (occurrence, frequency) and accompanying displays in both species. Of particular note is that T. ch. coronellina exhibited more frequent head-wobbling than T. peruviana and, in both records, wind activity was observed during this antipredatory behaviour.

Virtual Expeditions Facilitated By Open Source Solutions Broaden Student Participation in Natural History Research

From its genesis in the Victorian era as an activity for the elite to today's emphasis on “Big Data” and continuous monitoring, natural history has a prominent role in scientific discoveries for many fields. However, participation in field expeditions is limited by funding, space, accessibility, and safety constraints. Others have detailed the active exclusion of minoritized groups from field expeditions and harm/discrimination faced by the few who do participate, but we provide one solution to broaden opportunities for participation in natural history: Virtual Expeditions. Virtual Expeditions are broadly defined as open source, web-facilitated research activities designed to analyze bulk-collected digital data from field expeditions that require visual human interpretation. We show two examples here of their use: an independent research-based analysis of snake behavior and a course-based identification of invertebrate species. We present a guide to their appropriate design, facilitation, and evaluation to result in research grade data. We highlight the importance of open source technology to allow for longevity in methodology and appropriate quality control measures necessary for projects that include dozens of researchers over multiple years. In this perspective, we specifically emphasize the prominent role that open source technology plays in making these experiences feasible and scalable. Even without explicit design as broadening participation endeavors, Virtual Expeditions allow for more inclusive participation of early career researchers with specific participatory limitations. Not only are Virtual Expeditions integral to the large-scale analysis necessary for field expeditions that generate impossibly enormous datasets, but they can also be effective facilitators of inclusivity in natural history research.

Concepts and contentions of coral snake resemblance: Batesian mimicry and its alternatives

Venomous coral snakes and non-venomous coral snake lookalikes are often regarded as a classic example of Batesian mimicry, whereby a harmless or palatable organism imitates a harmful or less palatable organism. However, the validity of this claim is questionable. The existing literature regarding coral snake mimicry presents a divisive stance on whether Batesian mimicry is occurring or whether the similarity between snakes is attributable to alternative factors. Here, we compile available literature on coral snake mimicry and assess the support for Batesian mimicry. We find that most of the recent relevant literature (after approximately 2000) supports the Batesian mimicry hypothesis. However, this is not strongly supported by empirical evidence. Potential considerations addressed here for both the Batesian and alternative hypotheses include the function of the colour pattern, predatory learning and the biogeographical distribution of similar snakes. The analyses performed previously by mimicry researchers show that the interpretation of the conditions for mimicry is not consistent throughout the scientific community when applied to coral snake systems. This review focuses on this division and stresses the need to reach an agreement about the adaptive significance of New World coral snakes and their lookalikes.