Elastic Energy in Our Movements
Elastic Energy in Our Movements

Elastic Energy in Our Movements

Kangaroos, snakes, snd so also do we store elastic energy — in ligaments and tendons when we run, in fascia in much we do, etc.

In “Hot or cold, venomous vipers still quick to strike: Cold weather makes rattlesnakes more vulnerable — but not much” (UV Riverside News, 23 July 2020), Jules Bernstein writes

“We expected their strike to be about half as fast for every 10-degree drop in temperature, but they’re still able to uncoil and strike fairly rapidly, even at our lowest test temperatures,’ said SDSU ecologist and research team member Rulon Clark.

At most, the snakes were about 25 percent slower at the lowest temperature. The finding means that pit vipers, the type of rattlesnake studied, are slightly more vulnerable to real or perceived threats in colder temperatures but not by a lot.

This might help explain how rattlesnakes can thrive even in cooler climates like southern Canada. It also suggests that the snakes are using a mechanism other than just muscles in order to strike, as muscle movement becomes more difficult in the cold.

Kangaroos use tendons like elastic bands to bounce and hop without using much energy, the way that humans use a bow and arrow. The findings suggest that snakes may also be storing elastic energy somehow.

And in “Rattlesnakes are extremely fast and variable when striking at kangaroo rats in nature: Three-dimensional high-speed kinematics at night” by Higham, Clark, Collins, Whitford. and Freymiller, they say in the abstract:

Predation plays a central role in the lives of most organisms. Predators must find and subdue prey to survive and reproduce, whereas prey must avoid predators to do the same. The resultant antagonistic coevolution often leads to extreme adaptations in both parties. Few examples capture the imagination like a rapid strike from a venomous snake. However, almost nothing is known about strike performance of viperid snakes under natural conditions. We obtained high-speed (500 fps) three-dimensional video in the field (at night using infrared lights) of Mohave rattlesnakes (Crotalus scutulatus) attempting to capture Merriam’s kangaroo rats (Dipodomys merriami). Strikes occurred from a range of distances (4.6 to 20.6 cm), and rattlesnake performance was highly variable. Missed capture attempts resulted from both rapid escape maneuvers and poor strike accuracy. Maximum velocity and acceleration of some rattlesnake strikes fell within the range of reported laboratory values, but some far exceeded most observations. Thus, quantifying rapid predator-prey interactions in the wild will propel our understanding of animal performance.

And in the Discussion:

The escape response and behavior of the kangaroo rats were equally impressive, and we provide some of the first data regarding escape performance of small mammals during natural interactions. The average response time, from the onset of snake movement to the first observable motion of the kangaroo rat, was 61.5 ± 10.6 ms, which is at the lower end of the mammalian startle response40. Thus, the performance of the prey in our study can be considered extremely high. Compared to Pacific jumping mice (Zapus trinotatus)41, the D. merriami in our study were larger and reached velocities that were almost 50% greater (Table 1). Given that Z. trinotatus is assumed to amplify power by storing elastic energy in their distal tendons, and that we found higher levels of performance in the kangaroo rats in our study, we predict that the kangaroo rats are likely exhibiting power amplification via elastic energy storage. This is in contrast to steady locomotion in kangaroo rats, which does not involve elastic energy storage,

We propose that the rattlesnake-kangaroo rat system is a model system for studying the dynamics of high-power predator-prey interactions, given that they can be observed (with some effort) under completely natural conditions. This system could be used to test a number of important questions about predation success and prey escape responses in nature. Given the extreme performance on the part of the snakes and kangaroo rats, it is very likely that elastic energy storage is important for both species in circumventing the limits of neuromuscular function. Future studies should address this possibility. Finally other species of rattlesnake (e.g. C. cerastes) consume other species of kangaroo rat (e.g. D. deserti), opening up the possibility of a comparative study across predators and prey.

The original study, referenced by the Bernstein article.

The effects of temperature on the defensive strikes of rattlesnakes” by Malachi D. Whitford, Grace A. Freymiller, Timothy E. Higham, Rulon W. Clark.

The Abstract

Movements of ectotherms are constrained by their body temperature owing to the effects of temperature on muscle physiology. As physical performance often affects the outcome of predator–prey interactions, environmental temperature can influence the ability of ectotherms to capture prey and/or defend themselves against predators. However, previous research on the kinematics of ectotherms suggests that some species may use elastic storage mechanisms when attacking or defending, thereby mitigating the effects of sub-optimal temperature. Rattlesnakes (Crotalus spp.) are a speciose group of ectothermic viperid snakes that rely on crypsis, rattling and striking to deter predators. We examined the influence of body temperature on the behavior and kinematics of two rattlesnake species (Crotalus oreganus helleri and Crotalus scutulatus) when defensively striking towards a threatening stimulus. We recorded defensive strikes at body temperatures ranging from 15–35°C. We found that strike speed and speed of mouth gaping during the strike were positively correlated with temperature. We also found a marginal effect of temperature on the probability of striking, latency to strike and strike outcome. Overall, warmer snakes are more likely to strike, strike faster, open their mouth faster and reach maximum gape earlier than colder snakes. However, the effects of temperature were less than would be expected for purely muscle-driven movements. Our results suggest that, although rattlesnakes are at a greater risk of predation at colder body temperatures, their decrease in strike performance may be mitigated to some extent by employing mechanisms in addition to skeletal muscle contraction (e.g. elastic energy storage) to power strikes.

And in the Introduction:

Temperature has large impacts on muscle-driven movements (Bennett, 1985). In general, the contractile rates of skeletal muscle doubles with a 10°C increase in temperature (i.e. a Q10 value of ∼2), and the effects of temperature on the capacity for many ectothermic species to perform muscle-driven movement has been well documented (Angilletta et al., 2002; Bennett, 1985; Peplowski and Marsh, 1997). This strong correlation between muscle physiology and performance is often deleterious, as it can hinder the ability of ectotherms to capture prey and flee from predators at lower body temperatures (Kruse et al., 2008). As a result, many ectotherms have mechanisms that act to mitigate the deleterious effects of low temperature on performance (Anderson et al., 2014; Deban and Richardson, 2011; Deban and Scales, 2016; Higham and Irschick, 2013; Scales et al., 2016). For example, chameleons project their tongue by using muscles to stretch and store energy in elastic structures which, upon release, rapidly propel the tongue forward (Anderson and Deban, 2010). Temperature has less influence on performance traits that rely on energy stored in elastic structures because the rate of recoil is a product of the material property of the elastic structure (Roberts and Azizi, 2011). Elastic recoil mechanisms similar to the one used by chameleons have been found repeatedly in animals that use ballistic movements to capture prey or flee predators (Burrows, 2009; Deban and Lappin, 2011; Patek et al., 2011, 2004; Van Wassenbergh et al., 2008).

Vipers (family Viperidae) are a near globally distributed family of venomous snakes that can be highly abundant mesopredators in tropical and temperate environments. Relative to many other snake families, vipers tend to be heavy-bodied (Feldman and Meiri, 2013; Pough and Groves, 1983), relying on crypsis and defensive displays to dissuade attacks by predators, rather than rapid flight (Araujo and Martins, 2006; Shine et al., 2002). The defensive displays of vipers are bolstered by their potential to inflict a painful and potentially harmful bite on an attacking predator. As vipers are active across a wide range of temperatures (Ayers and Shine, 1997; Putman and Clark, 2017), a strong positive correlation between defensive strike performance and temperature would indicate that they experience a higher risk of predation when confronted by an endothermic predator at colder temperatures. However, recent studies suggest vipers may have mechanisms to diminish the effects of temperature on strike performance. Young (2010) conducted an electromyographic study of puff adder (Bitis arietans) musculature and found that they contracted their dominant epaxial musculature prior to, but not during, defensive strikes. This pattern suggests that the adders may be stretching and storing energy in elastic structures prior to the strike, and then using the stored energy to propel their heads forward rather than relying primarily on temperature-dependent muscle contractions. As the storage and release of energy from elastic structures is controlled by the material properties of the structure and not chemical energy – unlike a muscle contraction – the strike performance of heavy-bodied vipers, such as puff adders and rattlesnakes, may be relatively resistant to change in temperature.

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