The effect of substrate diameter and incline on locomotion in an arboreal frog

Abstract

SUMMARYFrogs are characterized by a unique morphology associated with their saltatory lifestyle. Yet, arboreal species show morphological specializations relative to other ecological specialists allowing them to hold on to narrow substrates. However, almost nothing is known about the effects of substrate characteristics on locomotion in frogs. Here, we quantified the 3D kinematics of forelimb movement for frogs moving across branches of different diameters (1 and 40mm) and two different inclines (horizontal and 45deg uphill). Our results show that grip types differ while moving across substrates of different diameters and inclines. The kinematics of the wrist, elbow and shoulder as well as the body position relative to the substrate also showed significant effects of individual, diameter and incline. Kinematic differences involved duration, velocity of movement and angular excursions. Differences were most pronounced for the proximal joints of the forelimb and effects for substrate diameter were greater than for incline. Interestingly, the effects of diameter and incline on both grip type and kinematics are similar to what has been observed for lizards and primates, suggesting that the mechanics of narrow substrate locomotion drive the kinematics of movement independent of morphology and phylogeny.

When the going gets rough – studying the effect of surface roughness on the adhesive abilities of tree frogs

“…Despite these limitations, tree frogs are still able to generate large forces when landing on a horizontal wooden rod with just one or two toe pads following a jump [49]. They can also climb the narrow twigs and branches of their natural environment by combining adhesion/friction with the ability to grasp even very small twigs [50]. We are thus building up a good understanding of both the underlying mechanisms and the ecology of tree frog adhesive mechanisms.…”

Effects of support diameter and compliance on common marmoset (Callithrix jacchus) gait kinematics

“…Though faster speeds may facilitate dynamic stability, particularly in the rolling plane (Bruijn et al, 2009), fast travel also reduces agility (Hyams et al, 2012;Wheatley et al, 2015;Wynn et al, 2015) and increases peak force production (Weyand et al, 2000) -both of which may compromise stability when moving on a precariously narrow support. Indeed, substrate narrowness has previously been shown to be associated with slower travel speeds in many arboreal tetrapods, including tree frogs (Herrel et al, 2013), anoles (Losos and Sinervo, 1989; Losos and Irschick, 1996; Mattingly and Jayne, 2004;Hsieh, 2016), fence lizards (Sinervo and Losos, 1991), marsupial gliders (Karantanis et al, 2015), opossums (Lammers and Biknevicius, 2004;Shapiro et al, 2014), mice (Hyams et al, 2012), squirrels (Schmidt, 2011) and strepsirrhine primates (Stevens, 2007). Other gait adjustments were subtler, often displaying a complex interaction with speed.…”

The effects of substratum on locomotor performance in lacertid lizards

“…Over recent decades, significant attention has been paid to how variation in incline and substrate diameter affects locomotor capacity in a variety of vertebrate taxa (Huey & Hertz, 1984;Irschick & Jayne, 1998;Schmitt, 2003;Higham & Jayne, 2004;Spezzano & Jayne, 2004;Vanhooydonck, Herrel & Irschick, 2006;Foster & Higham, 2012;Hyams, Jayne & Cameron, 2012;Herrel et al, 2013). By contrast, how variation in substrate texture or roughness affects locomotion remains rather poorly understood (Vanhooydonck et al, 2005;Tulli, Abdala & Cruz, 2012;Cabezas-Cartes, Kubisch & Ibarg€ uengoyt ıa, 2014).…”