Prey speed influences the speed and structure of the raptorial strike of a ‘sit-and-wait’ predator

Abstract

Predators must often employ flexible strategies to capture prey. Particular attention has been given to the strategies of visual predators that actively pursue their prey, but sit-and-wait predators have been largely overlooked, their strategies often characterized as stereotyped. Praying mantids are primarily sit-and-wait predators that often employ crypsis to catch their prey using a raptorial strike produced by their highly modified forelimbs. Here, we show that the raptorial strike of the Madagascan marbled mantis ( Polyspilota aeruginosa ) varies in duration from 60 to 290 ms due to the tibial extension alone; slower strikes involve slower tibial extensions that may also be interrupted by a pause. The success of a strike is independent of its duration or the presence of these pauses. However, prey speed affects the duration of tibial extension and the probability of a pause occurring, both increasing at slower prey speeds. Adjusting the duration of the tibial extension according to prey speed allows mantids to time the final downward sweep of the tibia to their prey's approach. The use of visual inputs to adjust the motor pattern controlling forelimb movements shows that not all aspects of the strike are stereotyped and that sit-and-wait predators can produce behavioural flexibility.

Braking slows passive flexion during goal-directed movements of a small limb

“…The total duration of the reach is achieved by adjusting the durations of distinct movement phases. This contrasts with raptorial strikes produced by the forelimbs, the duration of which is primarily adjusted through tibial extension, 17 and walking movements of other insects, where the step duration is adjusted by regulating only one of two behavioral phases while the duration of the other stays largely constant. 27 The difference between reaching and raptorial strikes or walking suggests that reaches are not merely modified steps or strikes but require a higher degree of flexibility.…”

“…Thus, the duration of each of the phases (draw, throw, and sweep) of reaches/searches could be adjusted, contrasting with the mantids' raptorial strike, the duration of which is primarily adjusted through tibial extension. 17 We compared FTi joint movements during the sweep phase of a sample of missed reaches and searches (Figure S2, Table S2). There was no significant difference in the duration of sweeps (Wilcoxon rank-sum test, W = 230, p = 0.342) or the angular range (Student's t test, t(38) = 1.88, p = 0.067) between reaches and searches.…”

“…The mantid forelimb exhibits several morphological features consistent with its raptorial function. 31 Mantid reaches span a similar angular range to those of the raptorial strike, 12,17 and the flexion of the FTi joint is a key component of prey capture and restraint. [31][32][33] Thus, it is possible that the small resting angle of the FTi joint and the fast passive flexion produced by the flexor tibiae muscle-apodeme complex is primarily an adaptation for the strike.…”

“…[31][32][33] Thus, it is possible that the small resting angle of the FTi joint and the fast passive flexion produced by the flexor tibiae muscle-apodeme complex is primarily an adaptation for the strike. Many insect limbs are versatile, and perform a range of different behaviours, [7][8][9][10][11][12][13][14][15][16][17]24,[28][29][30] but how they adapt fixed passive properties to behaviors requiring high accuracy is largely unknown. The active braking of the mantid's passively driven tibial flexion during reaches slows the tarsus prior to contact.…”

Frontiers in quantifying wildlife behavioural responses to chemical pollution

“…propulsion in swimming fish; Johansen et al ., 2017), and in the air (e.g. honeybee flight paths; Guiraud, Roper & Chittka, 2018), as well as feeding performance of predators (Rossoni & Niven, 2020), and escape performance of prey (e.g. Jonsson et al ., 2019).…”