{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T09:02:58Z","timestamp":1789722178254,"version":"4.0.1"},"reference-count":50,"publisher":"The Company of Biologists","issue":"9","license":[{"start":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T00:00:00Z","timestamp":1789689600000},"content-version":"vor","delay-in-days":3,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0"}],"funder":[{"name":"Biotechnology and Biological Sciences Research Council","award":["BB\/H005838\/1"],"award-info":[{"award-number":["BB\/H005838\/1"]}],"id":[{"id":"https:\/\/ror.org\/00cwqg982","id-type":"ROR","asserted-by":"crossref"}]},{"name":"National Science Foundation","award":["NSF-DBI 2319710"],"award-info":[{"award-number":["NSF-DBI 2319710"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,9,15]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>Terrestrial gaits are usually treated as discrete categories, yet the criteria that define them disagree in ground birds, which use grounded-running, bouncing dynamics without an aerial phase, over much of their speed range. We asked whether the rotation sense of the center-of-mass velocity loop, the hodograph, resolves gait-transition speeds in guinea fowl (Numida meleagris). We reconstructed center-of-mass motion from ground reaction forces over 2580 level overground steps (dimensionless speed range: 0.14 to 3.27). Hodograph rotation sense reverses from pendular to bouncing at a crossover speed of 0.58, close to 0.56 from kinetic-potential energy congruity and well below 1.06 at which aerial phases appear. Six established gait descriptors show the same structure: one principal component explains 50% of their variance and describes a pendular-to-bouncing continuum, and clustering agrees with hodograph rotation sense on 87.7% of steps. Gait in guinea fowl is a continuum whose most meaningful division is walking to grounded running, which can be determined based on one signed scalar per cycle from the velocity trajectory. The approach requires no measurement of height, making it less sensitive to integration drift, which may open opportunities for comparative gait studies in freely ranging animals equipped with inertial sensors.<\/jats:p>","DOI":"10.1242\/bio.062880","type":"journal-article","created":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T08:31:00Z","timestamp":1789720260000},"source":"Crossref","is-referenced-by-count":0,"title":["A velocity-loop view of avian gait: hodograph rotation sense characterizes the walking-to-running continuum in guinea fowl"],"prefix":"10.1242","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8584-2052","authenticated-orcid":false,"given":"Monica A.","family":"Daley","sequence":"first","affiliation":[{"name":"University of California, Irvine 1 Department of Ecology and Evolutionary Biology , , Irvine , CA 92697 ,","place":["USA"]},{"name":"University of California 2 Department of Biomedical Engineering, Henry Samueli School of Engineering , , Irvine, Irvine, CA 92697 ,","place":["USA"]},{"name":"University of California 3 Department of Mechanical and Aerospace Engineering, Henry Samueli School of Engineering , , Irvine, Irvine, CA 92697 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2633-006X","authenticated-orcid":false,"given":"Aleksandra","family":"Birn-Jeffery","sequence":"additional","affiliation":[{"name":"University of Essex 4 School of Sport, Rehabilitation and Exercise Sciences , , Colchester CO4 3SQ ,","place":["UK"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"237","published-online":{"date-parts":[[2026,9,18]]},"reference":[{"key":"2026091804305691200_BIO062880C1","doi-asserted-by":"publisher","first-page":"2668","DOI":"10.1242\/jeb.027581","article-title":"Redirection of center-of-mass velocity during the step-to-step transition of human walking","volume":"212","author":"Adamczyk","year":"2009","journal-title":"J. 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