Flexibility in locomotor-feeding integration during prey capture in varanid lizards: effects of prey size and velocity

Abstract

SUMMARYFeeding movements are adjusted in response to food properties, and this flexibility is essential for omnivorous predators as food properties vary routinely. In most lizards, prey capture is no longer considered to solely rely on the movements of the feeding structures (jaws, hyolingual apparatus) but instead is understood to require the integration of the feeding system with the locomotor system (i.e. coordination of movements). Here, we investigated flexibility in the coordination pattern between jaw, neck and forelimb movements in omnivorous varanid lizards feeding on four prey types varying in length and mobility: grasshoppers, live newborn mice, adult mice and dead adult mice. We tested for bivariate correlations between 3D locomotor and feeding kinematics, and compared the jaw-neck-forelimb coordination patterns across prey types. Our results reveal that locomotor-feeding integration is essential for the capture of evasive prey, and that different jaw-neck-forelimb coordination patterns are used to capture different prey types. Jaw-neck-forelimb coordination is indeed significantly altered by the length and speed of the prey, indicating that a similar coordination pattern can be finely tuned in response to prey stimuli. These results suggest feed-forward as well as feed-back modulation of the control of locomotor-feeding integration. As varanids are considered to be specialized in the capture of evasive prey (although they retain their ability to feed on a wide variety of prey items), flexibility in locomotor-feeding integration in response to prey mobility is proposed to be a key component in their dietary specialization.

Patterns of variation in feeding strike kinematics of juvenile ghost praying mantis (Phyllocrania paradoxa): are components of the strike stereotypic?

“…Based on the above results, there does not seem to be consistent consensus on whether the feeding strikes of animals are, or should be, stereotyped or flexible. Our results, along with some others (Reilly, 1995;Rice and Westneat, 2005), suggest stereotypy in components of feeding strikes, whereas others highlight the amount of variability (Kagaya and Patek, 2016;Montuelle et al, 2012), even in stereotypic motor activation patterns.…”

“…3A). Even though our prey were alive and moved in front of the mantises, they were not as evasive as other studies of feeding kinematics (Longo et al, 2016;Montuelle et al, 2012;Oufiero et al, 2012). Therefore, changes in the velocity of the prey of the praying mantis may elicit more variation in the stereotyped kinematic traits we observed.…”

“…Similarly, Reilly (1995), found little change in the feeding kinematics of salamanders (Salamandra salamandra) across ontogeny. Conversely, Montuelle et al (2012) found flexibility in the strikes of a varanid lizard, with mobile prey such as live crickets and adult mice eliciting similar kinematics compared with strikes on non-mobile prey.…”

“…This may limit the range of positions a predator can strike within to be successful. Conversely, if a predator has the ability to modulate or exhibit flexibility in one part of the integrated system, this may allow for a greater range of attack (Corrette, 1990;Montuelle et al, 2012;Nemeth, 1997). Although many of these relationships have been examined in vertebrate feeding systems, such as suction feeding among fish, there are fewer examples from invertebrate predators (Corrette, 1990;deVries et al, 2012;Kral et al, 2000;Patek et al, 2004).…”

A combination of gyroscope and accelerometer for identifying alternative feeding behaviours in fish

“…Graham et al, 2001;Montuelle et al, 2012;Nemeth, 1997). In addition to jaw motion, body motions such as body posture, angular velocity and forward velocity were found to be different between prey types in these animals.…”