Are they arboreal? Climbing abilities and mechanics in the red‐backed salamander (Plethodon cinereus)

Abstract

While red‐backed salamanders (Plethodon cinereus) are most often observed in terrestrial forested areas, several studies report arboreal substrate use and climbing behavior. However, salamanders do not have any of the anatomical features commonly observed in specialized climbing species (e.g., claws, setae, suction cups). Instead, salamanders cling to surfaces using the shear and adhesive properties of their mucous layer. In this study, we explore the capabilities and spatiotemporal gait patterns of arboreal locomotion in the red‐backed salamander as they move across twelve substrate conditions ranging in diameter, orientation, and roughness. On arboreal substrates, red‐backed salamanders decreased locomotor speed, stride frequency, phase and stride length, and increased duty factor and stride duration. Such responses have been observed in other non‐salamander species and are posited to increase arboreal stability. Furthermore, these findings indicate that amphibian locomotion, or at least the locomotor behavior of the red‐backed salamander, is not stereotyped and that some locomotor plasticity is possible in response to the demands of the external environment. However, red‐backed salamanders were unable to locomote on any small‐diameter or vertically‐oriented coarse substrates. This finding provides strong evidence that the climbing abilities of red‐backed salamanders are attributable solely to mucous adhesion and that this species is unable to produce the necessary external “gripping” forces to achieve fine‐branch arboreal locomotion or scale substrates where adhesion is not possible. The red‐backed salamander provides an ideal model for arboreal locomotor performance of anatomically‐unspecialized amphibians and offers insight into transitionary stages in the evolution of arborealism in this lineage.

Three toes and three modes: Dynamics of terrestrial, suspensory, and vertical locomotion in brown‐throated three‐toed sloths (Bradypodidae, Xenarthra)

“…Brown‐throated three‐toed sloths employed slow gaits (speed pooled across locomotor modes: 0.07 ± 0.04 m/s) kinematically equivalent to walking (duty factor pooled across locomotor modes: 67.64 ± 9.42%), regardless of substrate condition. Relative to other sampled tetrapods (e.g., Karantanis et al, 2017a,b; Granatosky et al, 2019b, 2021; Hanna et al, 2022), B. variegatus exhibits a remarkably slow terrestrial gait. Both quadrupedal crawling and suspensory walking mirrored each other in numerous gait characteristics ( e.g ., similar stride durations, stride frequencies, and contact times; Table 1), and the difference in speed between these two modes is only attributable to a slight increase in stride length during suspensory walking (Figure 3).…”

“…Brown-throated three-toed sloths employed slow gaits (speed pooled across locomotor modes: 0.07 ± 0.04 m/s) kinematically equivalent to walking (duty factor pooled across locomotor modes: 67.64 ± 9.42%), regardless of substrate condition. Relative to other sampled tetrapods (e.g., Karantanis et al, 2017a,b;Granatosky et al, 2019bGranatosky et al, , 2021Hanna et al, 2022) stride durations, stride frequencies, and contact times; Table 1), and the difference in speed between these two modes is only attributable to a slight increase in stride length during suspensory walking (Figure 3). Stride frequency and stride length both contribute to increasing speed during terrestrial and suspensory locomotion in B.…”

Locomotor characteristics of the ground‐walking chameleonBrookesia superciliaris

“…To address the aims of this study, we collected kinematic and spatiotemporal gait data from four adult brown leaf chameleons (B. superciliaris; see Table 2 The experimental procedures described below follow protocols adapted from previous works exploring gait patterns associated with arboreal locomotion (Granatosky et al, 2021;Hanna et al, 2022;Karantanis et al, 2015Karantanis et al, , 2017a. Briefly, videographic data was collected from B. superciliaris as they walked across two simulated terrestrial and two arboreal runways of varying widths and diameters.…”

“…They will adopt gait patterns that maximize the portion of the stride where the limbs are positioned as a wide polygon of support on thin substrates, such as lateral-sequence diagonal couplet (LSDC) gaits (Cartmill et al, 2002(Cartmill et al, , 2020Wimberly et al, 2021). In LSDC gaits, the forefoot directly follows the hindfoot on the same side of the body (lateral sequence), and footfalls on opposite sides of the body are coupled in time (diagonal couplet); Schmidt and Fischer (2010), Karantanis et al (2015Karantanis et al ( , 2017a2017b), Granatosky et al (2019Granatosky et al ( , 2021, Granatosky andMcElroy (2022), andHanna et al (2022).…”

“… Source : Table 1 adapted from Hanna et al (2022) and functional hypotheses derived from Schmidt and Fischer (2010), Karantanis et al (2015, 2017a; 2017b), Granatosky et al (2019, 2021, 2022), Granatosky and McElroy (2022), and Hanna et al (2022). …”