Evidence map›Paper›PMID 40013580›Full record

ArticleThe Journal of experimental biology2025

Free-ranging squirrels perform stable, above-branch landings by balancing using leg force and nonprehensile foot torque.

Sebastian D Lee, Stanley Wang, Duyi Kuang, Eric K Wang, Justin K Yim, Nathaniel H Hunt, Ronald S Fearing, Hannah S Stuart, Robert J Full

Abstract read
PubMed Full text at PMC Publisher
In one paragraph

Article in The Journal of experimental biology, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.

0numbers the graph read from it
0cells of the map it votes in
2citing papers in PubMed
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

2 citing papers in PubMed.

  1. A spinal substrate for modular control of natural behavior.bioRxiv : the preprint server for biology · 2026
    Article
  2. Article
4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

9 authors.

Sebastian D LeeDepartment of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720-1740, USA.ORCID 0000-0002-3260-2167
Stanley WangDepartment of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
Duyi KuangDepartment of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
Eric K WangDepartment of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Justin K YimDepartment of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
Nathaniel H HuntDepartment of Biomechanics, University of Nebraska Omaha, Omaha, NE 68182, USA.
Ronald S FearingDepartment of Electrical Engineering and Computer Science, University of California at Berkeley, Berkeley, CA 94720-1740, USA.
Hannah S StuartDepartment of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720-1740, USA.
Robert J FullDepartment of Integrative Biology, University of California at Berkeley, Berkeley, CA 94720-1740, USA.ORCID 0000-0001-8435-5279

Funding

Army Research Office ARO #W911NF-1810327 and ARO #W911NF-17-S-002Army Research Office W911NF-1810327
6 · The paper itself

Abstract

For gap-crossing agility, arboreal animals require the ability to stabilize dynamic landings on branches. Despite lacking a prehensile grip, squirrels achieve stable landings using a palmar grasp. We investigated the landing dynamics of free-ranging fox squirrels (Sciurus niger) to uncover strategies for stable, above-branch landings. Using high-speed video and force-torque measurements in the sagittal plane, we quantified landing kinetics across gap distances. Squirrels rapidly managed >80% of the landing energy with their forelimbs. With larger gaps, peak leg force and foot torque increased. Alignment between forelimbs, velocity and force also increased, likely reducing joint moment. We tested control hypotheses based on an extensible pendulum model used in a physical, hopping robot named Salto. Squirrels stabilized off-target landings by modulating leg force and foot torque. To correct for undershooting, squirrels generated pull-up torques and reduced leg force. For overshooting, squirrels generated braking torques and increased leg force. Embodying control principles in leg and foot design can enable stable landings in sparse environments for animals and robots alike, even those lacking prehensile grasps.

Indexed as

FootLocomotionSciuridaeAnimalsBiomechanical PhenomenaForelimbHindlimbTorqueArborealBalance controlJumpingLandingLocomotionSciurus niger

Identifiers

PMID40013580
PMCPMC11993264

What OpenQuestion holds

Textmetadata
LicenceCC BY
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.