Jumping mechanics of desert kangaroo rats

As animals get smaller, their ability to generate usable work from muscle contraction is decreased by the muscle’s force–velocity properties, thereby reducing their effective jump height. Very small animals use a spring-actuated system, which prevents velocity effects from reducing available energy. Since force–velocity properties reduce the usable work in even larger animals, why don’t larger animals use spring-actuated jumping systems as well? We will show that muscle length–tension properties limit spring-actuated systems to generating a maximum one-third of the possible work that a muscle could produce—greatly restricting the jumping height of spring-actuated jumpers. Thus a spring-actuated jumping animal has a jumping height that is one-third of the maximum possible jump height achievable were 100% of the possible muscle work available. Larger animals, which could theoretically use all of the available muscle energy, have a maximum jumping height that asymptotically approaches a value that is about three times higher than that of spring-actuated jumpers. Furthermore, a size related “crossover point” is evident for these two jumping mechanisms: animals smaller than this point can jump higher with a spring-actuated mechanism, while animals larger than this point can jump higher with a muscle-actuated mechanism. We demonstrate how this limit on energy storage is a consequence of the interaction between length–tension properties of muscles and spring stiffness. We indicate where this crossover point occurs based on modeling and then use jumping data from the literature to validate that larger jumping animals generate greater jump heights with muscle-actuated systems than spring-actuated systems.

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“…(2006); Picker et al. (2012); Schwaner et al. (2018); Sutton and Burrows (2011); and Mendoza (2018).…”

Section: Methodsmentioning

confidence: 99%

Why do Large Animals Never Actuate Their Jumps with Latch-Mediated Springs? Because They can Jump Higher Without Them

Sutton

Mendoza

Azizi

et al. 2019

Integrative and Comparative Biology

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“…The phrase that describes a quantity equal to the increase in muscle force, ground reaction force or joint moment divided by the time interval of that increase. In our previous study, kangaroo rats jumped over a vertical barrier from a standing posture (Schwaner et al, 2018). The GRF vector (red arrow) was measured using a force plate.…”

Section: Rate Of Force Developmentmentioning

confidence: 99%

“…More specifically, in movements that involve leaving the ground, such as jumping or leaping, takeoff velocity needs to be maximized to achieve the greatest distance (Garcia-Ramos et al, 2015). We have been studying vertical jumping mechanics in kangaroo rats, which are capable of vertically jumping to 10 times their standing hip height (Biewener and Blickhan, 1988;Schwaner et al, 2018) (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Yank: the time derivative of force is an important biomechanical variable in sensorimotor systems

Lin

McGowan

Blum

et al. 2019

Journal of Experimental Biology

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The derivative of force with respect to time does not have a standard term in physics. As a consequence, the quantity has been given a variety of names, the most closely related being 'rate of force development'. The lack of a proper name has made it difficult to understand how different structures and processes within the sensorimotor system respond to and shape the dynamics of force generation, which is critical for survival in many species. We advocate that ∂F/∂t be termed 'yank', a term that has previously been informally used and never formally defined. Our aim in this Commentary is to establish the significance of yank in how biological motor systems are organized, evolve and adapt. Further, by defining the quantity in mathematical terms, several measurement variables that are commonly reported can be clarified and unified. In this Commentary, we first detail the many types of motor function that are affected by the magnitude of yank generation, especially those related to timeconstrained activities. These activities include escape, prey capture and postural responses to perturbations. Next, we describe the multiscale structures and processes of the musculoskeletal system that influence yank and can be modified to increase yank generation. Lastly, we highlight recent studies showing that yank is represented in the sensory feedback system, and discuss how this information is used to enhance postural stability and facilitate recovery from postural perturbations. Overall, we promote an increased consideration of yank in studying biological motor and sensory systems.

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“…Owing to the high power outputs calculated in the study, these authors found support for the use of elastic energy during jumping. Studies of bipedal rodents [lesser Egyptian jerboas (Moore et al, 2017b), banner-tailed kangaroo rats (Biewener & Blickhan, 1988) and desert kangaroo rats (Schwaner et al, 2018)], however, have not found evidence for power amplification via elastic energy storage; these species rely solely on power production by their enlarged hindlimb muscles during jumps. Because of this, bipedal rodents are capable of faster jumps with higher force production and accelerations.…”

Section: Discussionmentioning

confidence: 99%

Escape dynamics of free-ranging desert kangaroo rats (Rodentia: Heteromyidae) evading rattlesnake strikes

Freymiller

Whitford

Higham

et al. 2019

Biological Journal of the Linnean Society

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Many animals exhibit morphological specializations driven by the extreme selective pressure of predation, and understanding how such specializations shape escape behaviours can elucidate the evolutionary context of these morphologies. We examined the kinematics of the evasive leaps of desert kangaroo rats (Dipodomys deserti) during strikes from sidewinder rattlesnakes (Crotalus cerastes) to understand the potential importance of predator evasion in shaping bipedalism in desert rodents. We found that kangaroo rats escaping from snake strikes relied on rapid response times to initiate effective evasions. During jumps, their enlarged hindlimbs propelled vertical leaps that were multiple body lengths into the air, and these leaps were often accompanied by mid-air kicks and other manoeuvres that deterred snakes. Although we found high levels of variability in kinematic factors, all kangaroo rats that successfully evaded attacks escaped in a path away from the snake and thus did not have random/protean escape trajectories. In general, our findings support the idea that bipedalism, which has evolved independently in several desert rodent lineages, might be favoured because it allows for rapid and powerful vertical leaps that are crucial for avoiding ambush predators, such as vipers and owls.

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Jumping mechanics of desert kangaroo rats

Cited by 29 publications

References 32 publications

Why do Large Animals Never Actuate Their Jumps with Latch-Mediated Springs? Because They can Jump Higher Without Them

Why do Large Animals Never Actuate Their Jumps with Latch-Mediated Springs? Because They can Jump Higher Without Them

Yank: the time derivative of force is an important biomechanical variable in sensorimotor systems

Escape dynamics of free-ranging desert kangaroo rats (Rodentia: Heteromyidae) evading rattlesnake strikes

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