Overcoming a 'forbidden phenotype': The parrot's head supports, propels, and powers tripedal locomotion

No vertebrate, living or extinct, is known to have possessed an odd number of limbs. Despite this ″forbidden phenotype″, gaits that utilize odd numbers of limbs (e.g., tripedalism or pentapedalism) have evolved in both avian and mammalian lineages. Tripedal locomotion is commonly employed by parrots during climbing, who utilize their beaks as an additional support. However, it is unclear whether the beak functions simply as a stabilizing hook, or as a propulsive limb. Here, we present data on kinetics of tripedal climbing in six rosy –faced lovebirds (Agapornis rosiecollis). Our findings demonstrate that parrots utilize cyclical tripedal gaits when climbing and the beak and hindlimbs generate comparable propulsive and tangential substrate reaction forces and power. Propulsive and tangential forces generated by the beak are of equal or greater magnitudes to those forces generated by the forelimbs of humans and non –human primates during vertical climbing. We conclude that the feeding apparatus and neck musculature of parrots has been co–opted to function biomechanically as a third limb during vertical climbing. We hypothesize that this exaptation required substantive alterations to the neuromuscular system including enhanced force–generating capabilities of the neck musculature and modifications to limb central pattern generators.

Comparison of Environmental Conditions on Summits of Mount Everest and K2 in Climbing and Midwinter Seasons

(1) Background: Today’s elite alpinists target K2 and Everest in midwinter. This study aimed to asses and compare weather at the summits of both peaks in the climbing season (Everest, May; K2, July) and the midwinter season (January and February). (2) Methods: We assessed environmental conditions using the ERA5 dataset (1979–2019). Analyses examined barometric pressure (BP), temperature (Temp), wind speed (Wind), perceived altitude (Alt), maximal oxygen uptake (VO2max), vertical climbing speed (Speed), wind chill equivalent temperature (WCT), and facial frostbite time (FFT). (3) Results: Most climbing-season parameters were found to be more severe (p < 0.05) on Everest than on K2: BP (333 ± 1 vs. 347 ± 1 hPa), Alt (8925 ± 20 vs. 8640 ± 20 m), VO2max (16.2 ± 0.1 vs. 17.8 ± 0.1 ml·kg−1·min−1), Speed (190 ± 2 vs. 223 ± 2 m·h−1), Temp (−26 ± 1 vs. −21 ± 1°C), WCT (−45 ± 2 vs. −37 ± 2 °C), and FFT (6 ± 1 vs. 11 ± 2 min). Wind was found to be similar (16 ± 3 vs. 15 ± 3 m·s−1). Most midwinter parameters were found to be worse (p < 0.05) on Everest vs. K2: BP (324 ± 2 vs. 326 ± 2 hPa), Alt (9134 ± 40 vs. 9095 ± 48 m), VO2max (15.1 ± 0.2 vs. 15.3 ± 0.3 ml·kg−1·min−1), Speed (165 ± 5 vs. 170 ± 6 m·h−1), Wind (41 ± 6 vs. 27 ± 4 m·s−1), and FFT (<1 min vs. 1 min). Everest’s Temp of −36 ± 2 °C and WCT −66 ± 3 °C were found to be less extreme than K2’s Temp of −45 ± 1 °C and WCT −76 ± 2 °C. (4) Conclusions: Everest presents more extreme conditions in the climbing and midwinter seasons than K2. K2’s 8° higher latitude makes its midwinter BP similar and Temp lower than Everest’s. K2’s midwinter conditions are more severe than Everest’s in the climbing season.

Ardipithecus hand provides evidence that humans and chimpanzees evolved from an ancestor with suspensory adaptations

The morphology and positional behavior of the last common ancestor of humans and chimpanzees are critical for understanding the evolution of bipedalism. Early 20th century anatomical research supported the view that humans evolved from a suspensory ancestor bearing some resemblance to apes. However, the hand of the 4.4-million-year-old hominin Ardipithecus ramidus purportedly provides evidence that the hominin hand was derived from a more generalized form. Here, we use morphometric and phylogenetic comparative methods to show that Ardipithecus retains suspensory adapted hand morphologies shared with chimpanzees and bonobos. We identify an evolutionary shift in hand morphology between Ardipithecus and Australopithecus that renews questions about the coevolution of hominin manipulative capabilities and obligate bipedalism initially proposed by Darwin. Overall, our results suggest that early hominins evolved from an ancestor with a varied positional repertoire including suspension and vertical climbing, directly affecting the viable range of hypotheses for the origin of our lineage.

The obstacle-surmounting analysis of a pole-climbing robot

Surmounting obstacles during continuously climbing in a complex environment is an important issue for pole-climbing robots. An obstacle-surmounting strategy is presented for a pole-climbing robot. The force and moment applied on the pole-climbing robot in static status were analyzed, and the analysis of pole-climbing robot’s upward vertical climbing was conducted. The climbing execution has four steps: loosening the lower gripper, curling up, striding forward, and clamping the upper gripper. To obtain the information of obstacle crossing accurately, the obstacle-surmounting conditions were analyzed in detail. We modeled the striding linkage with thickness and obtained the Denavit–Hartenberg coordinates of each vertex. The model of the grippers with thickness was proposed and the Denavit–Hartenberg coordinates of each vertex of the grippers were obtained. Then single-step negotiating an obstacle and multistep negotiating an obstacle were proposed. Experiments were conducted to verify the effectiveness of the obstacle-surmounting strategy.

Analysis of the Vertical Driving Performance of Multiple Connected Pipe-Climbing Microrobots with Magnetic Wheels

In this study, we analyzed the vertical driving performance of multiple connected magnetic wheel-driven microrobots when moving up and down a small cylinder that simulated a pipe. The dynamics of pipe climbing by the magnetic wheel-driven microrobot were analyzed considering the magnetic attraction force and slip; a vertical climbing simulator was developed considering the hoop force and external force from the adjacent microrobots to determine the magnetic attraction force required for multiple connected microrobot pipe climbing. A prototype of an independent vertical climbing microrobot, 5 mm long, 9 mm wide, and 6.5 mm high, and prototypes of 10 microrobots were manufactured to evaluate the vertical driving performance. The usefulness was verified by showing that three driving microrobots can move seven non-driving microrobots comprising 60% of their own weight up and down along a small cylinder.

Inverted and vertical climbing of a quadrupedal microrobot using electroadhesion

The ability to climb greatly increases the reachable workspace of terrestrial robots, improving their utility for inspection and exploration tasks. This is particularly desirable for small (millimeter-scale) legged robots operating in confined environments. This paper presents a 1.48-gram and 4.5-centimeter-long tethered quadrupedal microrobot, the Harvard Ambulatory MicroRobot with Electroadhesion (HAMR-E). The design of HAMR-E enables precise leg motions and voltage-controlled electroadhesion for repeatable and reliable climbing of inverted and vertical surfaces. The innovations that enable this behavior are an integrated leg structure with electroadhesive pads and passive alignment ankles and a parametric tripedal crawling gait. At a relatively low adhesion voltage of 250 volts, HAMR-E achieves speeds up to 1.2 (4.6) millimeters per second and can ambulate for a maximum of 215 (162) steps during vertical (inverted) locomotion. Furthermore, HAMR-E still retains the ability for high-speed locomotion at 140 millimeters per second on horizontal surfaces. As a demonstration of its potential for industrial applications, such as in situ inspection of high-value assets, we show that HAMR-E is capable of achieving open-loop, inverted locomotion inside a curved portion of a commercial jet engine.