Here’s how geckos (al­most) walk on wa­ter

Sun.Star Pampanga - - SCIENCENEWS! -

High-speed video re­veals the physics of how the an­i­mals move al­most as fast in wa­ter as on land

Add wa­ter aer­o­bics to the list of the ag­ile gecko’s ath­letic ac­com­plish­ments.

In ad­di­tion to stick­ing to smooth walls and swing­ing from leaves, geckos can skit­ter along the sur­face of wa­ter. By slap­ping the wa­ter with all four limbs to cre­ate air bub­bles and ex­ploit­ing the sur­face ten­sion of wa­ter, the rep­tiles can travel at speeds close to what they can achieve on land, ac­cord­ing to a new anal­y­sis of high-speed video footage de­scribed De­cem­ber 6 in Cur­rent Bi ol ogy.

In the world of wa­ter walk­ers, geckos oc­cupy an awk­ward in­ter­me­di­ate turf, says study coau­thor Jas­mine Nirody, a bio­physi­cist at Rock­e­feller Univer­sity in New York City and the Univer­sity of Ox­ford. Small in­sects like wa­ter strid­ers use sur­face ten­sion, cre­ated by wa­ter mol­e­cules stick­ing to­gether, to stay afloat. Big­ger an­i­mals like basilisk lizards slap the sur­face of the wa­ter, cre­at­ing air pock­ets around their feet that re­duce drag and keep the lizards mostly above the wa­ter’s sur­face. But an an­i­mal needs to be fairly large to gen­er­ate enough force to hold it­self out of the wa­ter us­ing that st r at egy.

“Geckos fall smack-dab in the mid­dle” size-wise, Nirody says. “They shouldn't re­ally be able to do this at all.” And yet, when her col­league Ar­dian Jusufi of the Max Planck In­sti­tute for In­tel­li­gent Sys­tems in Stuttgart, Ger­many, was on a re­search trip in Sin­ga­pore, he no­ticed small geckos skit­ter­ing across the sur­face of pud­dles.

Back in the lab, the team filmed eight flat­tailed house geckos (Hemi­dacty­lus platyu­rus) cross­ing a tank of wa­ter, then slowed the footage to get a closer look at the ac­tion.


ON THE MOVE This com­pos­ite im­age tracks the gait of a gecko as it crosses a tank of wa­ter, stay­ing at the sur­face by slap­ping the wa­ter with its feet and get­ting some ex­tra help from sur­face ten­sion.

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