ArticlePDF Available

How Cats Lap: Water Uptake by Felis catus

Authors:
Pedro M Reis
Pedro M Reis
Pedro M Reis
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Sunghwan Jung at Cornell University
Sunghwan Jung
Jeffrey M Aristoff
Jeffrey M Aristoff
Jeffrey M Aristoff
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Roman Stocker at ETH Zurich
Roman Stocker
Download full-text PDF
Read full-text
Download citation

Abstract and Figures

Lap Cats We all know that domestic cats lap milk, but perhaps fewer of us have thought about how they do this. Reis et al. (p. 1231 , published online 11 November; see the cover) have discovered that cats curl their tongues so that the top surface touches the water. Then, by lifting their tongues rapidly, a column of liquid grows by inertia until gravity induces its breakage and the cats close their jaws to capture the liquid. Lapping frequency is tuned to maximize the volume ingested, depending on the animal's mass; a relationship that holds as true for tabby cats as it does for lions.
The lapping kinematics. (A) Vertical position of the tip of the tongue of Felis catus over 11 lapping cycles. (B) Vertical position (red circles) and velocity (blue squares) of the tongue's tip during a typical lapping cycle, obtained by averaging 11 cycles. The dashed line (red) represents a fitted error-function profile for vertical position. The dotted line (blue) is its temporal derivative and represents upward speed, which yielded U MAX = 78 ± 2 cm s 1 .
The lapping kinematics. (A) Vertical position of the tip of the tongue of Felis catus over 11 lapping cycles. (B) Vertical position (red circles) and velocity (blue squares) of the tongue's tip during a typical lapping cycle, obtained by averaging 11 cycles. The dashed line (red) represents a fitted error-function profile for vertical position. The dotted line (blue) is its temporal derivative and represents upward speed, which yielded U MAX = 78 ± 2 cm s 1 .
… 
Liquid column dynamics in the physical model and observed lapping frequency of felines. (A) Position of the disk at pinch-off, Z P , versus Fr*, for four disk radii R (solid squares), and position of the disk when the column achieves maximum volume, Z MaxVol , versus Fr*, for R = 5 mm (open squares). (B) Time course of the liquid column volume, V, for different speeds U MAX . Black open squares indicate the pinchoff time relative to the moment when the disk started moving (16). The maximum column volumes (0.12 to 0.26 ml) are of the same order as the volume per lap ingested by Felis catus (0.14 ± 0.04 ml). The inset shows the volume as a function of relative disk height (solid circles) and the prediction from a scaling argument for low heights (black line, Z/H << 1). At greater heights, drainage reduces the volume and then pinchoff occurs. (C) Lapping frequency as a function of animal mass for eight species of felines. Solid symbols represent data acquired at the Zoo New England, open symbols represent data from YouTube videos (16). The line of best fit (dashed red) has slope ––0.181 ± 0.024. The solid black line has slope ––1/6.
Liquid column dynamics in the physical model and observed lapping frequency of felines. (A) Position of the disk at pinch-off, Z P , versus Fr*, for four disk radii R (solid squares), and position of the disk when the column achieves maximum volume, Z MaxVol , versus Fr*, for R = 5 mm (open squares). (B) Time course of the liquid column volume, V, for different speeds U MAX . Black open squares indicate the pinchoff time relative to the moment when the disk started moving (16). The maximum column volumes (0.12 to 0.26 ml) are of the same order as the volume per lap ingested by Felis catus (0.14 ± 0.04 ml). The inset shows the volume as a function of relative disk height (solid circles) and the prediction from a scaling argument for low heights (black line, Z/H << 1). At greater heights, drainage reduces the volume and then pinchoff occurs. (C) Lapping frequency as a function of animal mass for eight species of felines. Solid symbols represent data acquired at the Zoo New England, open symbols represent data from YouTube videos (16). The line of best fit (dashed red) has slope ––0.181 ± 0.024. The solid black line has slope ––1/6.
… 
Figures - uploaded by Sunghwan Jung
Author content
All figure content in this area was uploaded by Sunghwan Jung
Content may be subject to copyright.
Content uploaded by Sunghwan Jung
Author content
All content in this area was uploaded by Sunghwan Jung
Content may be subject to copyright.
!
!"!###$%&'()&(*+,(%%$-,.!"!//!0-1(23(,!45/5!"!67.(!/!"!/5$//48"%&'()&($//9:;4/!
!
Animals have developed a range of drinking strategies
depending on physiological and environmental
constraints. Vertebrates with incomplete cheeks use their
tongue to drink; the most common example is the lapping
of cats and dogs. We show that the domestic cat (Felis
catus) laps by a subtle mechanism based on water
adhesion to the dorsal side of the tongue. A combined
experimental and theoretical analysis reveals that Felis
catus exploits fluid inertia to defeat gravity and pull liquid
into the mouth. This competition between inertia and
gravity sets the lapping frequency and yields a prediction
for the dependence of frequency on animal mass.
Measurements of lapping frequency across the family
Felidae support this prediction, which suggests that the
lapping mechanism is conserved among felines.
<(,,(%=,'7>!7)'27>%!?71(!(1->1(@!@'1(,%(!2(7)%!=-!7&AB',(!
#7=(,C!')&>B@').!73%-,+='-)!=?,-B.?!=?(!%D')!E1F!-,!(*=,7&='-)!
-G!2-'%=B,(!G,-2!G--@!E2FC!3B=!2-%=!,(>H!-)!@,')D').!E3I12F$!
J,')D').!+,(%()=%!7!&?7>>().(!=-!>7)@!1(,=(3,7=(%C!3(&7B%(!
G,(%?#7=(,!-&&B,%!27')>H!7%!?-,'K-)=7>!>'AB'@!%B,G7&(%C!%B&?!
7%!+B@@>(%C!+-)@%C!>7D(%C!-,!%=,(72%C!7)@!7)'27>%!2B%=!
@'%+>7&(!#7=(,!B+#7,@!7.7')%=!.,71'=H!=-!@,')D!'=$!L,B&'7>!')!
=?(!@,')D').!+,-&(%%!'%!=?(!,->(!-G!=?(!=-).B(C!#?'&?!')!
1(,=(3,7=(%!'%!B%(@!')!=#-!@'%=')&=>H!@'GG(,()=!#7H%$!
M(,=(3,7=(%!#'=?!&-2+>(=(!&?((D%C!%B&?!7%!+'.%C!%?((+C!7)@!
?-,%(%C!B%(!%B&='-)!=-!@,7#!>'AB'@!B+#7,@!7)@!B%(!=?(',!
=-).B(!=-!=,7)%+-,=!'=!')=,7-,7>>H!E13C!14F$!N)!&-)=,7%=C!
1(,=(3,7=(%!#'=?!')&-2+>(=(!&?((D%C!')&>B@').!2-%=!
&7,)'1-,(%C!7,(!B)73>(!E7G=(,!#(7)').F!=-!%(7>!=?(',!2-B=?!
&71'=H!=-!.()(,7=(!%B&='-)!7)@!2B%=!,(>H!-)!=?(',!=-).B(!=-!
2-1(!#7=(,!')=-!=?(!2-B=?!E13F$!O?()!=?(!=-).B(!%#((+%!=?(!
3-==-2!-G!7!%?7>>-#!+B@@>(C!=?(!+,-&(%%!'%!&7>>(@!>'&D').!E4F$!
O?()!=?(!+B@@>(!'%!@((+(,!=?7)!=?(!=-).B(!(*&B,%'-)!')=-!=?(!
>'AB'@C!'=!'%!&7>>(@!>7++').!E15F$!P(,(!#(!,(+-,=!-)!=?(!>7++').!
2(&?7)'%2!-G!=?(!@-2(%='&!&7=!EFelis catusF$!
Q>2-%=!(1(,H-)(!?7%!-3%(,1(@!7!@-2(%='&!&7=!>7+!2'>D!-,!
#7=(,$!R(=C!&7%B7>!-3%(,17='-)!?7,@>H!&7+=B,(%!=?(!(>(.7)&(!
7)@!&-2+>(*'=H!-G!=?'%!7&=C!7%!=?(!=-).B(S%!2-='-)!'%!=--!G7%=!
=-!3(!,(%->1(@!3H!=?(!)7D(@!(H($!O(!B%(@!?'.?T%+((@!'27.').!
=-!&7+=B,(!=?(!2-='-)!-G!3-=?!=?(!=-).B(!7)@!>'AB'@!@B,').!
>7++').!UV'.$!/!7)@!2-1'(!W/!E16FX$!O'=?!=?(!&7=S%!G7&(!
-,'()=(@!@-#)#7,@C!=?(!=-).B(!(*=()@%!G,-2!=?(!Y7#!EV'.$!
/QF!7)@!'=%!='+!&B,>%!%?7,+>H!&7B@7>>H!EV'.$!/ZF$!Q=!=?(!>-#(%=!
+-%'='-)!-G!=?(!=-).B([%!='+C!'=%!@-,%7>!%'@(!,(%=%!-)!=?(!>'AB'@!
%B,G7&(C!#'=?-B=!+'(,&').!'=!EV'.$!/ZF$!O?()!=?(!&7=!>'G=%!=?(!
=-).B(C!>'AB'@!7@?(,').!=-!=?(!@-,%7>!%'@(!-G!=?(!='+!'%!@,7#)!
B+#7,@C!G-,2').!7!&->B2)!EV'.$!/LF$!<?'%!>'AB'@!&->B2)!'%!
GB,=?(,!(*=()@(@!3H!=?(!=-).B([%!B+#7,@!2-='-)!EV'.$!/JFC!
=?'))').!')!=?(!+,-&(%%!EV'.$!/\FC!7)@!'%!G')7>>H!+7,='7>>H!
&7+=B,(@!B+-)!Y7#!&>-%B,(!EV'.$!/C!\!7)@!VF$!N)%'@(!=?(!2-B=?C!
&71'='(%!3(=#(()!=?(!+7>7=([%!,B.7(!7)@!=?(!=-).B(!7&=!7%!7!
)-),(=B,)!@(1'&(!7)@!=,7+!>'AB'@!B)='>!'=!'%!').(%=(@!(1(,H!]!=-!
/^!&H&>(%!E15F$!
<?'%!%(AB()&(!-G!(1()=%!,(1(7>%!=#-!'2+-,=7)=!7%+(&=%!-G!
?-#!Felis catus!>7+%$!V',%=C!>7++').!@-(%!)-=!,(>H!-)!
_%&--+').`!#7=(,!')=-!=?(!2-B=?!7%!')!@-.%!ECanis lupus
familiarisF$!Q>=?-B.?!=?(!@-.[%!=-).B(!7>%-!&B,>%!&7B@7>>H!')!7!
&B+>'D(!%?7+(C!'=!+()(=,7=(%!=?(!>'AB'@!%B,G7&(!7)@!%&--+%!B+!
=?(!#7=(,!=?7=!G'>>%!'=%!1()=,7>!%'@($!N)!&-)=,7%=C!=?(!&7=S%!=-).B(!
@-(%!)-=!@'+!')=-!=?(!>'AB'@!EV'.$!/ZF!7)@!=?(!&71'=H!-)!'=%!
1()=,7>!%'@(!,(27')%!(2+=H!EV'.$!/C!Z!7)@!LFC!7%!7>%-!
,(&-.)'K(@!')!7!/9;5!a%&7,T#'))').!%?-,=!G'>2!E17F$!W(&-)@C!
-)>H!=?(!='+!-G!=?(!=-).B(!'%!B%(@!G-,!>7++').$!<?(!='+!'%!G,((!
-G!G'>'G-,2!+7+'>>7(!E18F!EV'.$!/bFC!=?(!%(2','.'@!?7',>'D(!
%=,B&=B,(%!=?7=!.'1(!7!&7=S%!=-).B(!'=%!&?7,7&=(,'%='&!,-B.?)(%%$!
<?B%C!+7+'>>7(!7++(7,!=-!?71(!)-!GB)&='-)!')!>7++').$!
<?(!2-1'(%!7>>-#(@!B%!=-!AB7)='GH!=?(!>7++').!D')(27='&%$!
<?(!+-%'='-)!-G!=?(!='+!-G!=?(!=-).B(!#7%!=,7&D(@!-1(,!-)(!
>7++').!(1()=!EV'.$!4QF!7)@!71(,7.(@!-1(,!//!&H&>(%!EV'.$!
4ZF$!<?(!=-).B(S%!1(,='&7>!+-%'='-)!@B,').!B+#7,@!2-='-)!'%!
#(>>!@(%&,'3(@!3H!7)!(,,-,TGB)&='-)!+,-G'>(C!ZEtF!c!
dHe/f(,GEUgQht¥ʌ"HFiC!#?(,(!H!c!]$5!&2!EV'.$!4ZC!,(@F!'%!
=?(!=-=7>!1(,='&7>!@'%+>7&(2()=C!UgQh!'%!=?(!27*'2B2!%+((@C!
7)@!t!'%!=?(!='2(!2(7%B,(@!#'=?!,(%+(&=!=-!ZEtc5F!c!H"4C!=?(!
How Cats Lap: Water Uptake by Felis catus
6(@,-!g$!j('%C/C4k!WB).?#7)!lB).C]k!l(GG,(H!g$!Q,'%=-GGC;k!j-27)!W=-&D(,/km!
/J(+7,=2()=!-G!L'1'>!7)@!\)1',-)2()=7>!\).')((,').C!g7%%7&?B%(==%!N)%='=B=(!-G!<(&?)->-.H!EgN<FC!L723,'@.(C!gQ!54/]9C!
nWQ$!4J(+7,=2()=!-G!g(&?7)'&7>!\).')((,').C!gN<C!L723,'@.(C!gQ!54/]9C!nWQ$!]J(+7,=2()=!-G!\).')((,').!W&'()&(!7)@!
g(&?7)'&%C!M',.')'7!6->H=(&?)'&!N)%='=B=(!7)@!W=7=(!n)'1(,%'=HC!Z>7&D%3B,.C!MQ!4;58/C!nWQ$!;J(+7,=2()=!-G!g(&?7)'&7>!7)@!
Q(,-%+7&(!\).')((,').C!6,')&(=-)!n)'1(,%'=HC!6,')&(=-)C!0l!5o:;;C!nWQ$!
kQ>>!7B=?-,%!&-)=,'3B=(@!(AB7>>H!=-!=?'%!#-,D$!
m<-!#?-2!&-,,(%+-)@()&(!%?-B>@!3(!7@@,(%%(@$!\T27'>p!,-27)%q2'=$(@B!
!
!"!###$%&'()&(*+,(%%$-,.!"!//!0-1(23(,!45/5!"!67.(!4!"!/5$//48"%&'()&($//9:;4/!
!
?7>GT?('.?=$!Q%!7!,(%B>=C!=?(!1(,='&7>!1(>-&'=H!?7%!7)!
7++,-*'27=(>H!b7B%%'7)!+,-G'>(!EV'.$!4ZC!3>B(Fp!<?(!=-).B(!
7&&(>(,7=(%!7%!'=!>(71(%!=?(!#7=(,!%B,G7&(C!7==7')%!7!,(27,D73>(!
27*'2B2!%+((@!-G!UgQh!c!^o!r!4!&2!%í/C!=?()!@(&(>(,7=(%!7%!
'=!()=(,%!=?(!2-B=?$!j(&-,@').%!-G!/5!7@B>=!')@'1'@B7>%!E16F!
H'(>@(@!7!>7++').!G,(AB()&H!f!c!]$:!r!5$;!%í/!7)@!7)!').(%=(@!
1->B2(!+(,!>7+!V!c!5$/;!r!5$5;!2>$!
<-!?(>+!B)@(,%=7)@!=?(!2(&?7)'%2!-G!>7++').C!#(!
+(,G-,2(@!+?H%'&7>!(*+(,'2()=%!')!#?'&?!7!.>7%%!@'%D!-G!
,7@'B%!R!E,(+,(%()=').!=?(!=-).B([%!='+FC!')'='7>>H!+>7&(@!-)!7!
#7=(,!%B,G7&(C!#7%!+B>>(@!1(,='&7>>H!B+#7,@!EV'.$!]F$!<?(!='2(!
%(,'(%!-G!=?(!@'%D!+-%'='-)!#7%!%(=!3H!7!&-2+B=(,T&-)=,->>(@!
%=7.(!7)@!+,-.,722(@!=-!?71(!=?(!-3%(,1(@!(,,-,TGB)&='-)!
+,-G'>(!EV'.$!4ZFC!#?(,(!#(!&-B>@!&-)=,->!=?(!>7++').!?('.?=!
H!7)@!%+((@!UgQh$!<?(!?H@,-+?'>'&!)7=B,(!-G!.>7%%!E%=7='&!
&-)=7&=!7).>(!c!/;sF!2'2'&D(@!=?(!#(=)(%%!-G!=?(!=-).B($!
P'.?T%+((@!'27.').!,(1(7>(@!=?(!G-,27='-)!7)@!(*=()%'-)!-G!
7!#7=(,!&->B2)C!7%!')!>7++').!EV'.$!]C!Q!=-!b!7)@!2-1'(%!W4!
7)@!W]F!E16F$!<?(!&->B2)S%!7%&()=!#7%!(1()=B7>>H!')=(,,B+=(@!
3H!+')&?T-GGC!>(71').!7!+()@7)=>'D(!@,-+!-)!=?(!>-#(,!%B,G7&(!
-G!=?(!@'%D!EV'.$!]C!V!=-!PF$!
\%='27='-)!-G!=?(!G-,&(%!')1->1(@!%B..(%=%!=?7=!=?(!G>B'@!
@H)72'&%!-G!>7++').!7,(!.-1(,)(@!3H!')(,='7!7)@!.,71'=HC!
#?(,(7%!1'%&-B%!7)@!&7+'>>7,H!G-,&(%!7,(!)(.>'.'3>(!E16F$!
N)(,='7>!()=,7')2()=!@,7#%!>'AB'@!B+#7,@!')=-!7!&->B2)C!#?'>(!
.,71'=H!7&=%!=-!&->>7+%(!'=$!n>='27=(>HC!.,71'=H!+,(17'>%!7)@!=?(!
&->B2)!+')&?(%!-GG$!J'2()%'-)7>!7)7>H%'%!,(1(7>%!=?7=!=#-!
@'2()%'-)>(%%!+7,72(=(,%!&-)=,->!>7++').p!=?(!V,-B@(!
)B23(,C!V,!c!UgQh"EgRF/"4C!2(7%B,').!=?(!,(>7='1(!'2+-,=7)&(!
-G!')(,='7!7)@!.,71'=H!Eg!'%!=?(!.,71'=7='-)7>!7&&(>(,7='-)FC!7)@!
=?(!7%+(&=!,7='-C!H"R$!\*+(,'2()=%!#(,(!=?(,(G-,(!&-)@B&=(@!
-1(,!7!,7).(!-G!V,!7)@!H"R!17>B(%!E16FC!G-,!7!G'*(@!>7++').!
?('.?=C!H!c!]!&2C!@(=(,2')(@!G,-2!-3%(,17='-)%!EV'.$!4ZF$!
<?(!>7==(,!'%!+-%%'3>H!@'&=7=(@!3H!3'->-.'&7>!&-)%=,7')=%C!%B&?!
7%!=?(!)((@!=-!D((+!#?'%D(,%!@,H!=-!27')=7')!=?(',!%()%-,H!
+(,G-,27)&(!E19F!-,!=-!27*'2'K(!+(,'+?(,7>!1'%'-)!#?'>(!
@,')D').$!
<-!=(%=!=?(!+,-+-%'='-)!=?7=!=?(!&->B2)!@H)72'&%!7,(!%(=!3H!
7!&-2+(='='-)!3(=#(()!')(,='7!7)@!.,71'=HC!#(!&-2+7,(@!=?(!
?('.?=!-G!=?(!@'%D!EZF!7=!+')&?T-GGC!Z6C!#'=?!=?7=!+,(@'&=(@!
G,-2!-B,!%&7>').!7)7>H%'%$!O(!G')@!E16F!=?7=!Z6"H!t!V,k!G-,!
V,k!u!/!7)@!Z6"H!t!/!-=?(,#'%($!P(,(!V,k!c!ER"HFV,4"]!'%!=?(!
,7='-!-G!=?(!='2(!%&7>(!G-,!=?(!.,71'=7='-)7>!&->>7+%(!-G!=?(!
&->B2)C!t6!c!ER"UgQhFV,4"]C!7)@!=?(!='2(!%&7>(!G-,!=?(!B+#7,@!
2-='-)!-G!=?(!@'%DC!H"UgQh$!\*+(,'2()=%!&-)G',2(@!=?(!
(*'%=()&(!-G!=#-!,(.'2(%!EV'.$!;QF$!V-,!%27>>!@'%D%!ER!c!4$:!
7)@!:!22FC!Z6"H!')&,(7%(@!>')(7,>H!#'=?!V,kC!#?(,(7%!>7,.(!
@'%D%!ER!c!/5!7)@!/4$^!22F!,(7&?(@!=?(!G')7>!?('.?=!3(G-,(!
+')&?T-GG!EZ6"H!c!/F$!<?(-,H!7>%-!%B&&(%%GB>>H!+,(@'&=%!=?7=!
+')&?T-GG!-&&B,%!&>-%(!=-!=?(!@'%D!EV'.$!]F$!
L-)%(AB()=>HC!=?(!37>7)&(!3(=#(()!')(,='7!7)@!.,71'=H!
@'&=7=(%!=?(!>7++').!G,(AB()&HC!fC!3H!&-)=,->>').!=?(!='2(!-G!
+')&?T-GG$!<-!27*'2'K(!').(%=(@!1->B2(C!#?'&?!'%!7%%B2(@!
=-!3(!+,-+-,='-)7>!=-!=?(!&->B2)S%!1->B2(!VC!=?(!>7++').!='2(C!
/"fC!%?-B>@!27=&?!=?(!+')&?T-GG!='2(C!t6C!3(&7B%(!G7%=(,!
>7++').!G7'>%!=-!27*'2'K(!')(,='7>!()=,7')2()=C!#?(,(7%!
%>-#(,!>7++').!,(%B>=%!')!3(>7=(@!2-B=?!&>-%B,(!=?7=!2'%%(%!
2-%=!-G!=?(!&->B2)$!<?'%!+,(@'&=%!f!t!EgHF/"4"R!-,C!3(&7B%(!f!t!
UgQh"HC!=?7=!V,k!'%!-G!-,@(,!-)($!V-,!@-2(%='&!&7=%C!#(!G')@!
=?7=!V,k!'%!')@((@!-G!-,@(,!B)'=H!E5$;FC!B%').!=?(!
(*+(,'2()=7>>H!2(7%B,(@!17>B(%!UgQh!c^o!&2!%í/!7)@!H!c!]!
&2!EV'.$!4ZF!7)@!7!=-).B(!%'K(!-G!R!§!:!22!EV'.$!/bF$!
<?(!.,-#=?!@H)72'&%!-G!=?(!&->B2)S%!1->B2(!EV'.$!;ZF!
E16F!+,-1'@(!GB,=?(,!(1'@()&(!=?7=!=?(!>7++').!G,(AB()&H!'%!%(=!
3H!=?(!')=(,+>7H!3(=#(()!')(,='7!7)@!.,71'=H$!O?()!=?(!@'%D!'%!
&>-%(!=-!=?(!37=?!EZ!uu!HFC!=?(!&->B2)!'%!&H>')@,'&7>!7)@!V!
')&,(7%(%!7%!V"R]!c!ʌZ"R!EV'.$!;Z!')%(=F$!b,71'=HT@,'1()!
@,7')7.(!=?()!,(@B&(%!=?(!,7=(!-G!1->B2(!')&,(7%(C!7)@!V!'%!7=!
7!27*'2B2!#?()!.,71'=H!7)@!')(,='7!37>7)&(!EV'.$!;ZF$!Q!
%&7>').!7,.B2()=!+,(@'&=%!7!27*'2B2!1->B2(!#?()!=?(!@'%D!
?('.?=!,(7&?(%!Zg7*M->"H!t!V,k!E16F,!')!(*&(>>()=!7.,((2()=!
#'=?!-3%(,17='-)%!EV'.$!;QF$!<?'%!7>%-!%B++-,=%!-B,!
7%%B2+='-)!=?7=!V!'%!27*'2B2!&>-%(!=-!=?(!='2(!-G!+')&?T-GG$!
N)!G7&=C!V!7>#7H%!+(7D%!%?-,=>H!3(G-,(!+')&?T-GG!E/5!=-!^5!2%F!
EV'.$!;ZFC!#?'&?!%B..(%=%!=?7=!2-B=?!&>-%B,(!%?-B>@!7>%-!
-&&B,!YB%=!3(G-,(!+')&?T-GG!=-!27*'2'K(!&7+=B,(@!1->B2($!
a3%(,17='-)%!-G!@-2(%='&!&7=%!%?-#(@!=?7=!2-B=?!&>-%B,(!
')@((@!=H+'&7>>H!+,(&(@(@!+')&?T-GG!E2-1'(!W/F!E16F$!
<?(!37>7)&(!-G!')(,='7!7)@!.,71'=H!H'(>@%!7!+,(@'&='-)!G-,!
=?(!>7++').!G,(AB()&H!-G!-=?(,!G(>')(%$!Q%%B2').!'%-2(=,H!
#'=?')!=?(!V(>'@7(!G72'>H!E'$($C!=?7=!>7++').!?('.?=!H!%&7>(%!
>')(7,>H!#'=?!=-).B(!#'@=?!R!7)@!7)'27>!27%%!M!%&7>(%!7%!
R]FC!=?(!G')@').!=?7=!V,k!'%!-G!-,@(,!-)(!=,7)%>7=(%!=-!=?(!
+,(@'&='-)!f!t!R!I/"4!t!M!I/"8$!N%-2(=,H!-,!27,.')7>>H!+-%'='1(!
7>>-2(=H!72-).!=?(!V(>'@7(!?7%!3(()!@(2-)%=,7=(@!G-,!%DB>>!
E20C!21F!7)@!>'23!3-)(%!E22F$!Q>=?-B.?!17,'73'>'=H!3H!
GB)&='-)!&7)!>(7@!=-!@(+7,=B,(%!G,-2!'%-2(=,H!')!')=(,%+(&'G'&!
%&7>').%!E23FC!,(+-,=(@!17,'7='-)%!#'=?')!=?(!V(>'@7(!E23C!24F!
-)>H!2')'27>>H!7GG(&=!=?(!+,(@'&=(@!%&7>').!f!t!M!I/"8$!O(!
=(%=(@!=?'%!I/"8!+-#(,T>7#!@(+()@()&(!3H!2(7%B,').!=?(!
>7++').!G,(AB()&H!G-,!('.?=!%+(&'(%!-G!G(>')(%C!G,-2!1'@(-%!
7&AB',(@!7=!=?(!v--!0(#!\).>7)@!-,!717'>73>(!-)!R-B<B3(!
E16F$!<?(!>7++').!G,(AB()&H!#7%!-3%(,1(@!=-!@(&,(7%(!#'=?!
7)'27>!27%%!7%!f!c!;$8!M!I5$/o/!r!5$54;!Ef!')!%í/C!M!')!D.F!EV'.$!
;LFC!&>-%(!=-!=?(!+,(@'&=(@!MI/"8$!<?'%!&>-%(!7.,((2()=!
%B..(%=%!=?7=!=?(!@-2(%='&!&7=S%!')(,='7T!7)@!.,71'=HT&-)=,->>(@!
>7++').!2(&?7)'%2!'%!&-)%(,1(@!72-).!G(>')(%$!
<?(!>7++').!-G!Felis catus!'%!+7,=!-G!7!#'@(,!&>7%%!-G!
+,-3>(2%!')!3'->-.H!')1->1').!.,71'=H!7)@!')(,='7C!%-2(='2(%!
,(G(,,(@!=-!7%!V,-B@(!2(&?7)'%2%$!V-,!(*72+>(C!=?(!#7=(,T
,B))').!73'>'=H!-G!=?(!Z7%'>'%D!>'K7,@!@(+()@%!-)!=?(!.,71'=HT
@,'1()!&->>7+%(!-G!=?(!7',!&71'=H!'=!&,(7=(%!B+-)!%>7++').!=?(!
#7=(,!%B,G7&(!#'=?!'=%!G((=$!<?(!@(+=?!=-!#?'&?!=?(!>'K7,@[%!>(.!
+()(=,7=(%!=?(!%B,G7&(!@(+()@%!-)!=?(!V,-B@(!)B23(,C!#?'&?!
!
!"!###$%&'()&(*+,(%%$-,.!"!//!0-1(23(,!45/5!"!67.(!]!"!/5$//48"%&'()&($//9:;4/!
!
')!=B,)!+,(%&,'3(%!=?(!2')'2B2!%>7++').!G,(AB()&H!E25F$!<?(!
V,-B@(!)B23(,!'%!7>%-!,(>(17)=!=-!%#'22').C!G-,!(*72+>(!
%(==').!=?(!27*'2B2!+,7&='&7>!%#'22').!%+((@!')!@B&D%!
E26F,!7)@!=-!=(,,(%=,'7>!>(..(@!>-&-2-='-)$!N)!=?'%!,(%+(&=C!'=!'%!
')=(,(%=').!=-!)-=(!=?7=!=?(!=,7)%'='-)!G,-2!=,-=!=-!.7>>-+!-3(H%!
)(7,>H!=?(!%72(!%&7>').!-G!G,(AB()&H!#'=?!27%%!7%!>7++').C!f!c!
;$:!M!í5$/;!Ef!')!%í/C!M!')!D.F!E27F$!
<?(!%B3=>(!B%(!-G!=?(!=-).B(!')!=?(!@,')D').!+,-&(%%!-G!
Felis catus!'%!,(27,D73>(C!.'1()!=?(!=-).B([%!>7&D!-G!%D(>(=7>!
%B++-,=!E28F$!L-2+>(*!2-1(2()=!')!=?(!73%()&(!-G!,'.'@!
&-2+-)()=%!'%!7!&-22-)!G(7=B,(!-G!2B%&B>7,!?H@,-%=7=%C!
#?'&?!')!7@@'='-)!=-!=-).B(%!')&>B@(!(>(+?7)=!=,B)D%!7)@!
-&=-+B%!7,2%!E28C!29F$!<?(!GB)&='-)7>!@'1(,%'=H!7)@!?'.?!
&-2+>'7)&(!-G!=?(%(!%=,B&=B,(%!&-)=')B(!=-!')%+',(!=?(!@(%'.)!
-G!%-G=!,-3-=%!E29F!7)@!7!GB)@72()=7>!B)@(,%=7)@').!-G!=?(',!
GB)&='-)7>'=H!&7)!>(7@!=-!)(#!@(%'.)!&-)&(+=%!7)@!'%!(%%()='7>!
=-!')G-,2!3'-2(&?7)'&7>!2-@(>%!E29C!30F$!
References and Notes
/$!6$!l$!Z()=>(HC!<$!R-,'-C!J. Exp. Biol.!79C!;/!E/9^9F$!
4$!J$!Q==()3-,-B.?C!The Living Planet: a Portrait of the
Earth!EL->>')%!7)@!Z,'='%?!Z,-7@&7%=').!L-,+-,7='-)C!
w-)@-)C!/9o;F$!
]$!l$!P('@#('>>(,C!l$!Q$!17)!w--)C!b$!Q$!v#((,%C!
Zoomorphology!111C!/;/!E/994F$!!
;$!l$!Q$!O$!g$!O('Y)()C!Neurosci. Biobehav. Rev.!22C!^:/!
E/99oF$!!
:$!O$!L$!J'>.(,C!')!Roots of BehaviorC!\$!w$!Z>'%%C!\@$!
EP7,+(,C!0(#!R-,DC!/984FC!++$!]:I;^$!
8$!g$!6,7D7%?C!J$!xBy,yC!l$!O$!g$!ZB%?C!Science!320C!9]/!
E455oF$!!
^$!W$!O$!W$!bB%%(D>--C!j$!b$!Z-B=C!J. Exp. Biol.!208C!]]9:!
E455:F$!!
o$!<$!w$!J7)'(>C!l$!b$!z').%->1(,C!\$!g(H?{G(,C!Oecologia!79C!
88!E/9o9F$!!
9$!l$!b$!z').%->1(,C!<$!w$!J7)'(>C!Oecologia!60C!4/;!E/9o]F$!!
/5$!J$!LB)@7>>C!J. Exp. Biol.!203C!4/^/!E4555F$!
//$!l$!P('@#('>>(,C!b$!Q$!v#((,%C!Condor!92C!/!E/995F$!!
/4$!l$!b$!g$!z-->--%C!b$!Q$!v#((,%C!J. Morphol.!199C!]4^!
E/9o9F$!!
/]$!Q$!l$!<?(*=-)C!Q$!O$!L,-2+=-)C!j$!v$!b(,27)C!J. Exp.
Zool.!280C!]4^!E/99oF$!!
/;$!z$!g$!P''(27(C!Q$!O$!L,-2+=-)C!')!Functional
Vertebrate MorphologyC!g$!P'>@(3,7)@C!J$!Z,723>(C!z$!
w'(2C!J$!Z$!O7D(!\@%$!EZ(>D)7+!-G!P7,17,@!n)'1$!6,(%%C!
L723,'@.(C!gQC!/9o:FC!++$!484I495$!
/:$!Q$!l$!<?(*=-)C!l$!J$!g&b7,,'&DC!Arch. Oral Biol.!33C!]]/!
E/9ooF$!!
/8$!g7=(,'7>%!7)@!2(=?-@%!7,(!717'>73>(!7%!%B++-,=').!
27=(,'7>!-)!Science!a)>')($!
/^$!Quicker Xn a Wink!Eg(=,-Tb->@#H)Tg7H(,!W=B@'-%C!w-%!
Q).(>(%C!LQC!/9;5F$!!
/o$!z$!aY'27C!V$!g'=%B?7%?'C!g$!07%BC!R$!WBKBD'C!Ann. Anat.!
182C!;^!E4555F$!!
/9$!Q$!W$!Q?>C!Vet. Res. Commun.!10C!4;:!E/9o8F$!!
45$!6$!L?,'%='7)%()C!l$!W$!Q@->G%%()C!J. Zool. Ew-)@-)F!266C!
/]]!E455:F$!!
4/$!Q$!6$!jB%%(>>C!P$!0$!Z,H7)=C!b$!w$!6-#(>>C!j$!w7,-'H7C!J.
Zool. Ew-)@-)F!236C!/8/!E/99:F$!!
44$!l$!g(7&?()TW72B(>%C!Z$!M7)!M7>D()3B,.?C!J. Morphol.!
270C!^49!E4559F$!!
4]$!g$!J-B3(C!Q$!O'D=-,-#'&KTL-),-HC!6$!L?,'%='7)%()C!l$!j$!
PB=&?')%-)C!W$!W?(G(>3')(C!PLoS ONE!4C!(;^;4!E4559F$!!
4;$!w$!g$!J7HC!Z$!L$!l7H)(C!J. Exp. Biol.!210C!8;4!E455^F$!!
4:$!l$!O$!b>7%?(()C!<$!Q$!g&27?-)C!J. Exp. Biol.!199C!48//!
E/998F$!
48$!P$!J$!6,7).(C!z$!W&?2'@=T0'(>%()C!J. Exp. Biol.!53C!^8]!
E/9^5F$!
4^$!0$!L$!P(.>B)@C!L$!j$!<7H>-,C!<$!Q$!g&g7?-)C!Science!
186C!///4!E/9^;F$!!
4o$!z$!z$!W2'=?C!O$!g$!z'(,C!Am. Sci.!77C!4o!E/9o9F$!
49$!J$!<,'1(@'C!L$!J$!j7?)C!O$!g$!z'(,C!N$!J$!O7>D(,C!Appl.
Bionics Biomech.!5C!99!E455oF$!!
]5$!P$!l$!L?'(>C!6$!L,7.-C!l$!g$!g7)%-B,C!z$!P7=?'C!Biol.
Cybern.!67C!;5]!E/994F$!!
]/$!Q>>!,(%(7,&?!#'=?!7)'27>%!&-2+>'(@!#'=?!7)@!#7%!
7++,-1(@!3H!gN<S%!Q)'27>!j'.?=%!L-22'==(($!O(!=?7)D!l$!
6'7KK7!7)@!=?(!%=7GG!7=!v--!0(#!\).>7)@!G-,!?(>+!#'=?!
G'>2').!G(>')(%|!g$!j-&DC!Q$!z())(@HC!7)@!=?(!
g7%%7&?B%(==%!W-&'(=H!G-,!=?(!6,(1()='-)!-G!L,B(>=H!=-!
Q)'27>%!EgW6LQF!G-,!?(>+!#'=?!G'>2').!@-2(%='&!&7=%|!b$!
g&z')>(H!G-,!B%(!-G!?'%!V'W\j!%=7.(|!Q$!L,-2+=-)C!Q$!
<?(*=-)C!O$!z'(,C!l$!Z7>(%C!l$!ZB%?C!Z$!Q)@,(-=='C!l$!Z'&-C!
J$!M(>>7C!7)@!Q$!Z-B@7-B@!G-,!@'%&B%%'-)%!7)@!&-22()=%|!
7)@!Q$!l-)(%C!\$!W727?7C!j$!<-27%C!7)@!O$!l7,Y-B'!G-,!
=(&?)'&7>!7%%'%=7)&($!W$l$C!6$j$C!7)@!j$W$!@(%'.)(@!,(%(7,&?|!
W$l$C!6$j$C!j$W$C!7)@!l$Q$!+(,G-,2(@!(*+(,'2()=%!7)@!
7)7>HK(@!@7=7|!W$l$C!l$Q$C!7)@!j$W$!@(1(>-+(@!%&7>').%!7)@!
=?(-,H|!6$j$C!j$W$C!W$l$C!7)@!l$Q$!#,-=(!=?(!+7+(,$!!
!
Supporting Online Material!
###$%&'()&(27.$-,."&.'"&-)=()="GB>>"%&'()&($//9:;4/"JL/!
g7=(,'7>%!7)@!g(=?-@%!
g-1'(%!W/!=-!W]!
j(G(,()&(%!
4/!lB>H!45/5|!7&&(+=(@!45!a&=-3(,!45/5!
6B3>'%?(@!-)>')(!//!0-1(23(,!45/5|!
/5$//48"%&'()&($//9:;4/!
Fig. 1. <?(!>7++').!+,-&(%%$!EA!=-!FF!W)7+%?-=%!%?-#').!=?(!
2-1(2()=!-G!=?(!=-).B(!-G!Felis catus!7)@!=?(!@H)72'&%!-G!
=?(!>'AB'@!&->B2)!@B,').!7!>7++').!&H&>($!w7++').!-&&B,%!3H!
!
!"!###$%&'()&(*+,(%%$-,.!"!//!0-1(23(,!45/5!"!67.(!;!"!/5$//48"%&'()&($//9:;4/!
!
G>B'@!7@?(%'-)!=-!=?(!@-,%7>!+7,=!-G!=?(!=-).B(S%!='+!7)@!3H!
>'G=').!7!>'AB'@!&->B2)!=?,-B.?!=?(!=-).B(S%!B+#7,@!2-='-)C!
3(G-,(!Y7#!&>-%B,($!<'2(!(>7+%(@!G,-2!=?(!G',%=!G,72(!'%!.'1()!
')!=?(!=-+!>(G=!&-,)(,!-G!(7&?!G,72($!EGF!6?-=-.,7+?!-G!=?(!
@-,%7>!%'@(!-G!=?(!=-).B(!-G!Felis catusC!7&AB',(@!B)@(,!
7)(%=?(%'7!E16F$!a)>H!=?(!%2--=?!='+!'%!B%(@!')!>7++').$!
Fig. 2. <?(!>7++').!D')(27='&%$!EAF!M(,='&7>!+-%'='-)!-G!=?(!
='+!-G!=?(!=-).B(!-G!Felis catus!-1(,!//!>7++').!&H&>(%$!EBF!
M(,='&7>!+-%'='-)!E,(@!&',&>(%F!7)@!1(>-&'=H!E3>B(!%AB7,(%F!-G!
=?(!=-).B(S%!='+!@B,').!7!=H+'&7>!>7++').!&H&>(C!-3=7')(@!3H!
71(,7.').!//!&H&>(%$!<?(!@7%?(@!>')(!E,(@F!,(+,(%()=%!7!G'==(@!
(,,-,TGB)&='-)!+,-G'>(!G-,!1(,='&7>!+-%'='-)$!<?(!@-==(@!>')(!
E3>B(F!'%!'=%!=(2+-,7>!@(,'17='1(!7)@!,(+,(%()=%!B+#7,@!%+((@C!
#?'&?!H'(>@(@!UgQh!c!^o!r!4!&2!%í/$!
Fig. 3. 6?H%'&7>!2-@(>!-G!>7++').$!Q!@'%D!-G!,7@'B%!R!'%!@,'1()!
1(,='&7>>H!B+#7,@C!%B&?!=?7=!=?(!(>(17='-)!-G!=?(!@'%DC!ZEtFC!
G,-2!=?(!>'AB'@!')=(,G7&(!E@7%?(@!>')(C!Z!c!5FC!?7%!7)!(,,-,T
GB)&='-)!+,-G'>(!E16F$!w-#(,&7%(!z!@()-=(%!=?(!@'%=7)&(!-G!7!
.()(,'&!>'AB'@!>7H(,!G,-2!=?(!@'%D$!<?(!%(AB()&(!'>>B%=,7=(%!
=?(!G-,27='-)!EA!=-!EF!7)@!+')&?T-GG!EFF!-G!=?(!>'AB'@!&->B2)$!
QG=(,!+')&?T-GGC!+7,=!-G!=?(!&->B2)!&->>7+%(%!')=-!=?(!37=?!
EGFC!#?'&?!>(71(%!7!+()@7)=>'D(!@,-+!7==7&?(@!=-!=?(!@'%D!EHF$!
<?(!G')7>!?('.?=!-G!=?(!@'%D!'%!Z!c!H$!<'2(!'%!2(7%B,(@!
,(>7='1(!=-!=?(!2-2()=!=?(!@'%D!,(7&?(%!?('.?=!Z!c!H"4!c!/$:!
&2$!<?'%!%(AB()&(!&-,,(%+-)@%!=-!R!c!/4$^!22C!H!c!]!&2C!
UgQh!c!:5!&2!%í/!EV,!c!/$;4|!V,k!c!5$85F$!
Fig. 4. w'AB'@!&->B2)!@H)72'&%!')!=?(!+?H%'&7>!2-@(>!7)@!
-3%(,1(@!>7++').!G,(AB()&H!-G!G(>')(%$!EAF!6-%'='-)!-G!=?(!
@'%D!7=!+')&?T-GGC!Z6C!1(,%B%!V,kC!G-,!G-B,!@'%D!,7@''!R!E%->'@!
%AB7,(%FC!7)@!+-%'='-)!-G!=?(!@'%D!#?()!=?(!&->B2)!7&?'(1(%!
27*'2B2!1->B2(C!Zg7*M->C!1(,%B%!V,kC!G-,!R!c!:!22!E-+()!
%AB7,(%F$!EBF!<'2(!&-B,%(!-G!=?(!>'AB'@!&->B2)!1->B2(C!VC!G-,!
@'GG(,()=!%+((@%!UgQh$!Z>7&D!-+()!%AB7,(%!')@'&7=(!=?(!+')&?T
-GG!='2(!,(>7='1(!=-!=?(!2-2()=!#?()!=?(!@'%D!%=7,=(@!2-1').!
E16F$!<?(!27*'2B2!&->B2)!1->B2(%!E5$/4!=-!5$48!2>F!7,(!-G!
=?(!%72(!-,@(,!7%!=?(!1->B2(!+(,!>7+!').(%=(@!3H!Felis catus!
E5$/;!r!5$5;!2>F$!<?(!')%(=!%?-#%!=?(!1->B2(!7%!7!GB)&='-)!-G!
,(>7='1(!@'%D!?('.?=!E%->'@!&',&>(%F!7)@!=?(!+,(@'&='-)!G,-2!7!
%&7>').!7,.B2()=!G-,!>-#!?('.?=%!E3>7&D!>')(C!Z"H!uu!/F$!Q=!
.,(7=(,!?('.?=%C!@,7')7.(!,(@B&(%!=?(!1->B2(!7)@!=?()!+')&?T
-GG!-&&B,%$!ECF!w7++').!G,(AB()&H!7%!7!GB)&='-)!-G!7)'27>!
27%%!G-,!('.?=!%+(&'(%!-G!G(>')(%$!W->'@!%H23->%!,(+,(%()=!@7=7!
7&AB',(@!7=!=?(!v--!0(#!\).>7)@C!-+()!%H23->%!,(+,(%()=!
@7=7!G,-2!R-B<B3(!1'@(-%!E16F$!<?(!>')(!-G!3(%=!G'=!E@7%?(@!
,(@F!?7%!%>-+(!I5$/o/!r!5$54;$!<?(!%->'@!3>7&D!>')(!?7%!%>-+(!
I/"8$!
!
... Dipping brush-like structures is also a strategy adopted by some nectarivores to feed on nectar [27,28]. Indeed, collecting a viscous fluid at small scales prevents the use of methods employed by other animals [29], like using gravity (humans) or fluid inertia to overcome gravity (lapping for cats [30], ladling for dogs [31,32]). To deal with capillary and viscous forces dominat-ing at small scale, many nectarivores have developed highly specialized mouthparts adapted to their feeding method [33,34]: hollow tubular proboscis/tongue for suction (butterfly [35], sunbird [36,37]) or tongue decorated by numerous outgrowths resembling a brush for dipping (bees [13,38], honeyeaters [39,40], bats [41]). ...
... At small retraction speed, their expression are given by Eq. (29) and Eq. (30). At large speed, they both tend to 1. ...
Optimal rigid brush for fluid capture
Preprint
Full-text available
  • Nov 2024
Parallel assemblies of slender structures forming brushes are common in our daily life from sweepers to pastry brushes and paintbrushes. This type of porous objects can easily trap liquid in their interstices when removed from a liquid bath. This property is exploited to transport liquids in many applications ranging from painting, dip-coating, brush-coating to the capture of nectar by bees, bats and honeyeaters. Rationalizing the viscous entrainment flow beyond simple scaling laws is complex due to its multiscale structure and the multidirectional flow. Here, we provide an analytical model, together with precision experiments with ideal rigid brushes, to fully characterize the flow through this anisotropic porous medium as it is withdrawn from a liquid bath. We show that the amount of liquid entrained by a brush varies non-monotonically during the withdrawal at low speed, is highly sensitive to the different parameters at play and is very well described by the model without any fitting parameter. Finally, an optimal brush geometry maximizing the amount of liquid captured at a given retraction speed is derived from the model and experimentally validated. These optimal designs open routes towards efficient liquid manipulating devices.
View
... It has been extensively developed over the last hundred years. The phenomenon of fluid frequently flows out from capillary tubes in various industrial and natural environments [3,4]. Due to the universality and importance of the free interfacial evolution process of liquid droplets, it has attracted the attention of many researchers. ...
... Actual i − mean of the observer data 2 (4) It determines how close the predicted data values are to the regression line. If the R 2 value tends to 1, it means that the regression model is perfect, and if R 2 is 0, it means that the regression model is a complete failure, i.e., no variance is explained by the regression. ...
A Machine Learning Approach to Predict Fluid Viscosity Based on Droplet Dynamics Features
Article
Full-text available
  • Apr 2024
In recent years, machine learning has made significant progress in the field of micro-fluids, and viscosity prediction has become one of the hotspots of research. Due to the specificity of the application direction, the input datasets required for machine learning models are diverse, which limits the generalisation ability of the models. This paper starts by analysing the most obvious kinetic feature induced by viscosity during flow—the variation in droplet neck contraction with time (hmin/R∼τ). The kinetic processes of aqueous glycerol solutions of different viscosities when dropped in air were investigated by high-speed camera experiments, and the kinetic characteristics of the contraction of the liquid neck during droplet falling were extracted, using the Ohnesorge number (Oh=μ/(ρRσ)1/2) to represent the change in viscosity. Subsequently, the liquid neck contraction data were used as the original dataset, and three models, namely, random forest, multiple linear regression, and neural network, were used for training. The final results showed superior results for all three models, with the multivariate linear regression model having the best predictive ability with a correlation coefficient R2 of 0.98.
View
... The necessity to manipulate flow and transport liquids is primitive to many biophysical processes such as embryonic growth and development 1,2 , mucus transport in bronchial tree 3-5 , the motion of food within intestine 6,7 , animal drinking 8,9 . Engineered systems also rely on efficient liquid transport such as in heat sinks and exchangers for integrated circuits 10,11 , micropumps 12,13 , and lab-on-a-chip devices 14 . ...
... The necessity to manipulate flow and transport liquids is primitive to many biophysical processes such as embryonic growth and development 1,2 , mucus transport in bronchial tree [3][4][5] , the motion of food within intestine 6,7 , animal drinking 8,9 . Engineered systems also rely on efficient liquid transport such as in heat sinks and exchangers for integrated circuits 10,11 , micropumps 12,13 , and lab-on-a-chip devices 14 . ...
Optimal free-surface pumping by an undulating carpet
Article
Full-text available
  • Nov 2023
Examples of fluid flows driven by undulating boundaries are found in nature across many different length scales. Even though different driving mechanisms have evolved in distinct environments, they perform essentially the same function: directional transport of liquid. Nature-inspired strategies have been adopted in engineered devices to manipulate and direct flow. Here, we demonstrate how an undulating boundary generates large-scale pumping of a thin liquid near the liquid-air interface. Two dimensional traveling waves on the undulator, a canonical strategy to transport fluid at low Reynolds numbers, surprisingly lead to flow rates that depend non-monotonically on the wave speed. Through an asymptotic analysis of the thin-film equations that account for gravity and surface tension, we predict the observed optimal speed that maximizes pumping. Our findings reveal how proximity to free surfaces, which ensure lower energy dissipation, can be leveraged to achieve directional transport of liquids.
View
... There are two fundamental modes of fluid transport: pressure-driven (Poiseuille) and boundary-driven (Couette) flows [32][33][34]. Most animals employ a pressure-driven mechanism (suction) using a confined oral structure, while a few species (mostly carnivoran mammals) employ boundary-driven flow (lapping) [35][36][37]. For small animals, capillary-driven flows can be used, which can be categorized as pressure-driven flow to some extent [38][39][40][41]. ...
Upper bill bending as an adaptation for nectar feeding in hummingbirds
Article
Full-text available
Observations of maxillary (upper bill) bending in hummingbirds have been considered an optical illusion, yet a recent description of out-of-phase opening and closing between their bill base and tip suggests a genuine capacity for bill bending. We investigate bill kinematics during nectar feeding in six species of hummingbirds. We employed geometric morphometrics to identify bending zones and combined these data with measurements of bill flexural rigidity from micro-computed tomography scans to better understand the flexing mechanism. We found that the mandible remains in place throughout the licking cycle, while the maxilla undergoes significant shape deformation, such that the distal portion of the upper bill bends upwards. We propose that bill bending is a key component of the drinking mechanism in hummingbirds, allowing the coordination of bill function (distal wringing and basal expansion) and tongue function (raking/squeegeeing) during intra-oral transport. We present a fluid analysis that reveals a combination of pressure-driven (Poiseuille) and boundary-driven (Couette) flows, which have previously been thought to represent alternative drinking mechanisms. Bill bending allows for separation of the bill tips while maintaining a tightly closed middle section of the bill, enabling nectar exploitation in long and narrow flowers that can exclude less efficient pollinators.
View
... There are two fundamental modes of fluid transport: pressure-driven (Poiseuille) and boundary-driven (Couette) flows [32][33][34]. Most animals employ a pressure-driven mechanism (suction) using a confined oral structure, while a few species (mostly carnivoran mammals) employ boundary-driven flow (lapping) [35][36][37]. For small animals, capillary-driven flows can be used, which can be categorised as pressure-driven flow to some extent [38][39][40][41]. ...
Upper bill bending as an adaptation for nectar feeding in hummingbirds
Preprint
  • Oct 2024
Observations of maxillary (upper bill) bending in hummingbirds have been considered an optical illusion, yet a recent description of out-of-phase opening and closing between their bill base and tip suggests a genuine capacity for bill bending. We investigate bill kinematics during nectar feeding in six species of hummingbirds. We employed geometric morphometrics to identify bending zones and combined these data with measurements of bill flexural rigidity from microCT scans to better understand the flexing mechanism. We found that the mandible remains in place throughout the licking cycle, while the maxilla undergoes significant shape deformation, such that the distal portion of the upper bill bends upwards. We propose that bill bending is a key component of the drinking mechanism in hummingbirds, allowing the coordination of bill function (distal wringing and basal expansion) and tongue function (raking/squeegeeing) during intraoral transport. We present a fluid analysis that reveals a combination of pressure-driven (Poiseuille) and boundary-driven (Couette) flows, which have previously been thought to represent alternative drinking mechanisms. Bill bending allows for separation of the bill tips while maintaining a tightly closed middle section of the bill, enabling nectar exploitation in long and narrow flowers that can exclude less efficient pollinators.
View
... The breakup is intrinsically due to Rayleigh-Plateau instability, leading to a characteristic timescale that mainly depends on the ligament radius for low-viscosity liquids [26]. It has been reported that the breakup time decreases with the increasing of axial stretching velocities or accelerations [27][28][29][30]. We have recently showed that the breakup of stretched ligaments are determined by the competition between contractions sequentially dominated by ductility and capillarity [31]. ...
Exit dynamics of a sphere launched underneath a liquid bath surface
Article
  • May 2024
In this paper, we investigate the exit dynamics of a sphere launched underneath a liquid bath surface at a prescribed impact velocity. Spheres with radii approximate or smaller than the capillary length are considered. Following our previous work of a ligament drawn of a liquid bath [J. Fluid Mech. 922, A14 (2021)], a two-dimensional model is applied to describe the liquid dynamics, and the whole exit dynamics up to the descent or the pinch-off moments is considered. The process can be sequenced into a partial exit stage that forms a coated layer and a full exit stage with an attached ligament. A bouncing-off regime, a lower pinch-off penetration regime, and an upper pinch-off penetration regime are identified, separating by a penetration Weber number and a switching Weber number. The phase diagram is revealed, where the two critical Weber numbers are functions of the Bond number. By considering the energy evolutions, we show that the impact energy is mainly converted into the surface energy and the gravitational potential energy for the low- and large-gravity cases, respectively. The coated layer is mainly formed in the partial exit stage, whose maximum volume increases with the impact velocity but decreases with gravity effect. Stretching motion is shown to have negligible influence on the local pinch-off behavior, while it determines the appearance and the location of pinch-off. Our results can help to understand the exit behaviors of aquatic animals, and the design of microamphibious aircraft or energy collection devices.
View
... Tegu lizards, V Bels 2023, personal observation) and (vii) generation of water columns by inertia produced by lapping action of the adhesive curled tongue again gravity (e.g. lorikeets, V Bels 2017, personal observation), as in cats [46] and dogs [47]. In all of the mechanisms used by the tongue to gather the liquid, the tongue acts to produce a continuous water/nectar movement from uptake through the buccal cavity to the pharynx, regardless of the jaw (and rhamphotheca) plus lingual morphologies. ...
Food transport in Reptilia: a comparative viewpoint
Article
Full-text available
  • Oct 2023
Reptilia exploit a large diversity of food resources from plant materials to living mobile prey. They are among the first tetrapods that needed to drink to maintain their water homeostasis. Here were compare the feeding and drinking mechanisms in Reptilia through an empirical approach based on the available data to open perspectives in our understanding of the evolution of the various mechanisms determined in these Tetrapoda for exploiting solid and liquid food resources. This article is part of the theme issue ‘Food processing and nutritional assimilation in animals’.
View
Vampire bat’s tongue-inspired superhydrophilic flexible origami channel for directional and spontaneous liquid manipulation
Article
  • Jan 2024
Achieving continuous, directional fluid manipulation without external energy input is promising in current systems. However, designing a spontaneous fluid manipulating system with the ability of simplified fabrication, deformation, and integration...
View
Dynamical wetting transition of a stretched liquid bridge
Article
Full-text available
The liquid bridge is an important model problem in printing processes. We report the experimental results of stretching a highly viscous liquid bridge between two parallel plates. Depending on the stretching speed, a thin liquid bridge exhibits two representative flow regimes. At low stretching speeds, the liquid bridge deforms in a quasi-static manner and no liquid films are observed. When the stretching speed exceeds a critical value, the contact line fails to follow the retracting meniscus, resulting in the deposition of liquid films on the plate. The entrained film is characterized by an annular rim that retracts and grows by collecting the liquid in the film. It is found that the velocity of the receding contact line is weakly decreasing, and the growth of the rim is characterized by a width of w rim ∼ C a 1 / 3 t 1 / 2, where the capillary number Ca is defined by the stretching velocity and t is the time. The film may not be fully absorbed into the bulk of the liquid bridge before its eventual breakup at high stretching speeds, leading to variations in the liquid transfer ratio of the two plates.
View
Bio-inspired sustained entrainment in immiscible liquid–liquid systems for collecting floating oil
Article
  • Jan 2024
Entrainment, where a solid object in a liquid bath moves towards the air phase, is common in industry and daily-life.
View
Do Frogs Drinks?
Article
Full-text available
  • Apr 1979
View
View
Scaling relationships within the maxillary tooth row of the Felidae, and the absence of the second upper premolar in Lynx
Article
Full-text available
Suggestions that short-faced members of the Felidae tend to lack the second upper premolar (P2) imply a possible shift in scaling associated with the palate and maxillary tooth row in Lynx, which lacks P2, as compared to felids that retain it. This hypothesis is tested using a scaling model that relates the lengths of the palate, and the upper tooth row and its components, to post-palatal skull length in the small to moderately large felids Felis catus (domestic cat), L. canadensis (Canada lynx), F. pardalis (ocelot), and F. concolor (cougar). Scaling relationships of both palate and tooth row length to post-palatal skull length do not differ significantly from isometry in all four species. However, ocelots have a significantly shorter palate and tooth row than lynxes over their overlapping ranges of post-palatal skull length, suggesting that the absence of P2 is not correlated with the length of the face in these species. CI, P3 and P4 tend to be relatively longer in larger felids; none the less, ocelots have a relatively small P3 and lynxes have a proportionately large P4. Because both lynxes and ocelots have a relatively small gap between CI and P3, the absence of P2 is not correlated with available space within the tooth row in adults. However, lynxes also appear to have a relatively long dP3 that almost obliterates the diastema within the deciduous tooth row. The absence of P2 in Lynx may be an engineering artefact that is associated with a shift in proportions within the deciduous toothrow, resulting in inhibition of the development of P2 and dP2 early in ontogeny. Despite the variable occurrence and polymorphism associated with P2 in the Felidae, this character has systematic value within this clade and is a synapomorphy for Lynx.
View
Soft Robotics: Biological Inspiration, State of the Art, and Future Research
Article
Full-text available
  • Dec 2008
Traditional robots have rigid underlying structures that limit their ability to interact with their environment. For example, conventional robot manipulators have rigid links and can manipulate objects using only their specialised end effectors. These robots often encounter difficulties operating in unstructured and highly congested environments. A variety of animals and plants exhibit complex movement with soft structures devoid of rigid components. Muscular hydrostats (e.g. octopus arms and elephant trunks) are almost entirely composed of muscle and connective tissue and plant cells can change shape when pressurised by osmosis. Researchers have been inspired by biology to design and build soft robots. With a soft structure and redundant degrees of freedom, these robots can be used for delicate tasks in cluttered and/or unstructured environments. This paper discusses the novel capabilities of soft robots, describes examples from nature that provide biological inspiration, surveys the state of the art and outlines existing challenges in soft robot design, modelling, fabrication and control.
View
Do Frogs Drink?
Article
  • Apr 1979
Drinking in response to dehydration and exposure to saline solutions was measured in adult Rana pipiens, Bufo marinus and Xenopus laevis, and tadpoles of Rana catesbeiana. These animals normally occupy quite different types of environments where the possible advantages of drinking may differ. Small amounts of the external media were swallowed by all the animals and the quantity usually increased when they were placed in hyperosmotic NaCl solution. However, no relationship between the oral intake of water and the particular conditions, such as the degree of dehydration, was observed. Usually 80–90% of the total water uptake occurred by absorption across the skin. Thus although ‘secondary’ type drinking takes place, ‘primary’ drinking did not appear to occur. These results directly confirm the general popular impression that amphibians, in contrast to other tetrapods and marine teleosts, do not drink in order to rehydrate.
View
View
Drinking Mechanisms in the Zebra Finch and the Bengalese Finch
Article
  • Feb 1990
Two kinds of drinking behavior were studied by film and radiogram analysis of tip down drinking Zebra Finches (Poephila guttata) and tip up drinking Bengalese Finches (Lonchura striata) which use similar scooping tongue motions to carry water into the mouth. Water transport through the pharynx differs: the Zebra Finch uses a scooping motion of the larynx that reoccurs in every motion cycle, while the beak is kept down. The Bengalese Finch elevates the head allowing water to flow downward due to gravity and pharyngeal properistalsis. Extensive analyses show the anatomy of the species to be highly similar. The Zebra Finch is able to drink by a double scoop mechanism, because--unlike the Bengalese Finch--reflexes for glottis closure and esophageal peristalsis are used. Integration of these reflexes and a shift in timing of the larynx-scoop has modified tip up into tip down drinking. Thus, tip down is more complex than tip up drinking, since here actions from different cycles and patterns are integrated in one motion cycle. Increased kinematic complexity is, apart from any historical scenario, an argument that tip down is derived from tip up drinking in Estrildidae. An evolutionary scenario is presented in which developments of scooping anatomical elements are seen as preadaptations. These developed by selection on elements serving the highly specialized kind of feeding on seeds of Gramineae under high predator pressure in open fields, and allowed a wide secondary extension of the feeding area.
View
Mechanics of drinking in the mallard (Anas platyrhynchos, Anatidae)
Article
  • Mar 1989
  • J MORPHOL
Water drinking in the mallard is accomplished by a fine-tuned set of movements of upper and lower jaw and of the tongue. During immersion of the tips of the bill, the oral cavity is formed into smaller volumes containing water and into connecting tubes. Two mechanisms serve the water transport: (1) lingual and jaw movements press water from the water-containing spaces into the tubes; (2) a quantitative simulation of the shape of the oral cavity during immersion shows that the two tubes are so narrow that capillary action also contributes to water transport. Thereafter, the tips of the bill are raised until they point upward. In this “tip-up” position, water flows into the esophagus because of gravity. We conclude that, in addition to normal tip-up drinking observed in almost all Passeriformes and Galliformes, a second type of tip-up drinking may be distinguished in Anseriformes. The integration of the drinking mechanism, keeping the water inside the mouth, and the straining mechanism, expelling the water along the beak rims, is effected by specific actions of the elaborate lingual apparatus.
View
View
Bite forces, canine strength and skull allometry in carnivores (Mammalia, Carnivora)
Article
Skull variables were analysed for allometry patterns in 56 species of extant carnivores. As previously reported, many skull variables scale near isometrically with either skull length or lower jaw length. The maximal gape angle scales insignificantly (P<0.05) with skull size, but the clearance between the canines shows a significant relationship with skull size and scales near isometrically. Maximal bite forces were estimated from geometrical cross-sectional areas of dried skulls, and the bending strength of the canines was computed by modelling the canines as a cantilevered beam of solid, homogeneous material with an elliptical cross section. Previous hypotheses of large taxon differences in canine bending strengths, so that felids have stronger canines than canids, are corroborated when actual bite forces at the upper canine are ignored. Incorporation of bite force values, however, nullifies the differences in canine bending strength among felids and canids, and ursids seem to have stronger canines than felids. This is probably because of the significantly longer canines of felids compared to canids and ursids, and the generally high bite forces of felids.
View