Asymmetrical gait kinematics of free-ranging callitrichines in response to changes in substrate diameter and orientation

Abstract

Arboreal environments present considerable biomechanical challenges for animals moving and foraging among substrates varying in diameter, orientation and compliance. Most studies of quadrupedal gait kinematics in primates and other arboreal mammals have focused on symmetrical walking gaits and the significance of diagonal sequence gaits. Considerably less research has examined asymmetrical gaits, despite their prevalence in small-bodied arboreal taxa. Here, we examined whether and how free-ranging callitrichine primates adjust asymmetrical gait kinematics to changes in substrate diameter and orientation, as well as how variation in gait kinematics affects substrate displacement. We used high-speed video to film free-ranging Saguinus tripartitus and Cebuella pygmaea inhabiting the Tiputini Biodiversity Station, Ecuador. We found that S. tripartitus used bounding and half-bounding gaits on larger substrates versus gallops and symmetrical gaits on smaller substrates, and also shifted several kinematic parameters consistent with attenuating forces transferred from the animal to the substrate. Similarly, C. pygmaea shifted from high-impact bounding gaits on larger substrates to using more half-bounding gaits on smaller substrates; however, kinematic adjustments to substrate diameter were not as profound as in S. tripartitus. Both species adjusted gait kinematics to changes in substrate orientation; however, gait kinematics did not significantly affect empirical measures of substrate displacement in either species. Because of their small body size, claw-like nails and reduced grasping capabilities, callitrichines arguably represent extant biomechanical analogs for an early stage in primate evolution. As such, greater attention should be placed on understanding asymmetrical gait dynamics for insight into hypotheses concerning early primate locomotor evolution.

Gait mechanics of a blind echolocating rodent: Implications for the locomotion of small arboreal mammals and proto‐bats

“…Arguably on large diameter substrates, where balance no longer becomes a biomechanical concern, switching to asymmetrical half‐bounds confer a reduction in inter‐cycle variability (Diedrich & Warren, 1995; Granatosky, Bryce, et al, 2018), and energetic expenditure (Hoyt & Taylor, 1981; Reilly et al, 2007). While the use of asymmetrical gaits often comprises a substantial portion of the locomotor repertoire of many small‐bodied arboreal mammals (Dunham et al, 2020; Karantanis et al, 2017a, 2017b; Lammers & Biknevicius, 2004; Lammers & Zurcher, 2011; Nyakatura & Heymann, 2010; Nyakatura et al, 2008; Shapiro & Young, 2010; Young, 2009), an understanding of the biomechanical advantages/disadvantages of these gait types remains elusive.…”

“…Asymmetrical gaits, including gallops, half‐bounds, and bounds, are commonly used by mammals at high speeds and frequently include a whole‐body aerial phase (Dunham et al, 2020; Granatosky, 2018b; Herbin et al, 2004; Hildebrand, 1977). Asymmetrical gaits are especially prevalent in small‐bodied arboreal mammals, and often represent a substantial portion of their locomotor repertoire (Dunham et al, 2020; Karantanis et al, 2017a, 2017b; Lammers & Biknevicius, 2004; Nyakatura & Heymann, 2010; Nyakatura et al, 2008; Shapiro & Young, 2010; Young, 2009).…”

“…Asymmetrical gaits, including gallops, half‐bounds, and bounds, are commonly used by mammals at high speeds and frequently include a whole‐body aerial phase (Dunham et al, 2020; Granatosky, 2018b; Herbin et al, 2004; Hildebrand, 1977). Asymmetrical gaits are especially prevalent in small‐bodied arboreal mammals, and often represent a substantial portion of their locomotor repertoire (Dunham et al, 2020; Karantanis et al, 2017a, 2017b; Lammers & Biknevicius, 2004; Nyakatura & Heymann, 2010; Nyakatura et al, 2008; Shapiro & Young, 2010; Young, 2009). It has been proposed that asymmetrical gaits may be preferable over symmetrical gaits during faster locomotion as they lower inter‐cycle variability (Brisswalter & Mottet, 1996; Diedrich & Warren, 1995) and may optimize metabolic costs, at least at the trot‐gallop transition (Hoyt & Taylor, 1981; Reilly et al, 2007; Vilensky et al, 1991).…”

“…It has been proposed that asymmetrical gaits may be preferable over symmetrical gaits during faster locomotion as they lower inter‐cycle variability (Brisswalter & Mottet, 1996; Diedrich & Warren, 1995) and may optimize metabolic costs, at least at the trot‐gallop transition (Hoyt & Taylor, 1981; Reilly et al, 2007; Vilensky et al, 1991). For small arboreal mammals, asymmetrical gaits further confer advantages in stability by limiting center of mass oscillations (Dunham et al, 2020; Karantanis et al, 2017a, 2017b; Schmidt & Fischer, 2011; Young, 2009). However, data on the use of asymmetrical gaits during arboreal locomotion in small mammals is limited.…”

Robust locomotor performance of squirrel monkeys (Saimiri boliviensis) in response to simulated changes in support diameter and compliance

“…Animals tend to reduce speed on narrower substrates (e.g., Dunham et al, 2020; Granatosky et al, 2021; Herrel et al, 2013; Hsieh, 2016; Lammers & Biknevicius, 2004; Losos & Irschick, 1996; Stevens, 2008; Young et al, 2016), and squirrel monkeys repeat this pattern on compliant supports, although not on stable supports. Though there are relatively few studies to compare the effect of compliance on stride speed, we predicted that squirrel monkeys would similarly reduce speed on more compliant substrates because of the animal's reduced capacity to control CoM trajectory (MacLellan & Patla, 2006).…”