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Birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact

Birds land on a wide range of complex surfaces, yet it is unclear how they grasp a perch reliably. Here, we show how Pacific parrotlets exhibit stereotyped leg and wing dynamics regardless of perch diameter and texture, but foot, toe, and claw kinematics become surface-specific upon touchdown. A new...

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Detalles Bibliográficos
Autores principales: Roderick, William RT, Chin, Diana D, Cutkosky, Mark R, Lentink, David
Formato: Online Artículo Texto
Lenguaje:English
Publicado: eLife Sciences Publications, Ltd 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6684272/
https://www.ncbi.nlm.nih.gov/pubmed/31385573
http://dx.doi.org/10.7554/eLife.46415
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author Roderick, William RT
Chin, Diana D
Cutkosky, Mark R
Lentink, David
author_facet Roderick, William RT
Chin, Diana D
Cutkosky, Mark R
Lentink, David
author_sort Roderick, William RT
collection PubMed
description Birds land on a wide range of complex surfaces, yet it is unclear how they grasp a perch reliably. Here, we show how Pacific parrotlets exhibit stereotyped leg and wing dynamics regardless of perch diameter and texture, but foot, toe, and claw kinematics become surface-specific upon touchdown. A new dynamic grasping model, which integrates our detailed measurements, reveals how birds stabilize their grasp. They combine predictable toe pad friction with probabilistic friction from their claws, which they drag to find surface asperities—dragging further when they can squeeze less. Remarkably, parrotlet claws can undergo superfast movements, within 1–2 ms, on moderately slippery surfaces to find more secure asperities when necessary. With this strategy, they first ramp up safety margins by squeezing before relaxing their grasp. The model further shows it is advantageous to be small for stable perching when high friction relative to normal force is required because claws can find more usable surface, but this trend reverses when required friction shrinks. This explains how many animals and robots may grasp complex surfaces reliably.
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spelling pubmed-66842722019-08-09 Birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact Roderick, William RT Chin, Diana D Cutkosky, Mark R Lentink, David eLife Evolutionary Biology Birds land on a wide range of complex surfaces, yet it is unclear how they grasp a perch reliably. Here, we show how Pacific parrotlets exhibit stereotyped leg and wing dynamics regardless of perch diameter and texture, but foot, toe, and claw kinematics become surface-specific upon touchdown. A new dynamic grasping model, which integrates our detailed measurements, reveals how birds stabilize their grasp. They combine predictable toe pad friction with probabilistic friction from their claws, which they drag to find surface asperities—dragging further when they can squeeze less. Remarkably, parrotlet claws can undergo superfast movements, within 1–2 ms, on moderately slippery surfaces to find more secure asperities when necessary. With this strategy, they first ramp up safety margins by squeezing before relaxing their grasp. The model further shows it is advantageous to be small for stable perching when high friction relative to normal force is required because claws can find more usable surface, but this trend reverses when required friction shrinks. This explains how many animals and robots may grasp complex surfaces reliably. eLife Sciences Publications, Ltd 2019-08-06 /pmc/articles/PMC6684272/ /pubmed/31385573 http://dx.doi.org/10.7554/eLife.46415 Text en © 2019, Roderick et al http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/This article is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use and redistribution provided that the original author and source are credited.
spellingShingle Evolutionary Biology
Roderick, William RT
Chin, Diana D
Cutkosky, Mark R
Lentink, David
Birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact
title Birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact
title_full Birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact
title_fullStr Birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact
title_full_unstemmed Birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact
title_short Birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact
title_sort birds land reliably on complex surfaces by adapting their foot-surface interactions upon contact
topic Evolutionary Biology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6684272/
https://www.ncbi.nlm.nih.gov/pubmed/31385573
http://dx.doi.org/10.7554/eLife.46415
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