<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.2900.3698" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT face=Arial size=2></FONT><BR> </DIV><FONT face=Arial size=2>
<DIV class=articleTitle><FONT size=3><STRONG>Journal of Animal
Ecology</STRONG></FONT></DIV>
<DIV id=publishedOnlineDate>Article first published online: 14 OCT 2010</DIV>
<DIV id=doi>DOI: 10.1111/j.1365-2656.2010.01760.x</DIV>
<DIV class=articleTitle><FONT size=4></FONT> </DIV>
<DIV class=articleTitle><FONT size=4>Scaling of swim speed in breath-hold
divers</FONT></DIV>
<DIV id=cr1><FONT size=3><SUP>Yuuki Y. Watanabe1,*, </SUP><SUP>Katsufumi Sato2,
</SUP><SUP>Yutaka Watanuki3, </SUP><SUP>Akinori Takahashi1, </SUP><SUP>Yoko
Mitani4, </SUP><SUP>Masao Amano5, </SUP><SUP>Kagari Aoki2, </SUP><SUP>Tomoko
Narazaki2, </SUP><SUP>Takashi Iwata1, </SUP><SUP>Shingo Minamikawa6,
</SUP><SUP>Nobuyuki Miyazaki7</SUP></FONT></DIV>
<DIV class=affiliation><SUP>1</SUP> National Institute of Polar Research,
Tachikawa, Tokyo 190-8518, Japan<SUP>2</SUP> International Coastal Research
Center, Atmosphere and Ocean Research Institute, The University of Tokyo,
Otsuchi, Iwate 028-1102, Japan<SUP>3</SUP> Graduate School of Fisheries
Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan<SUP>4</SUP>
Field Science Center for Northern Biosphere, Hokkaido University, Hakodate,
Hokkaido 041-8611, Japan<SUP>5</SUP> Faculty of Fisheries, Nagasaki University,
Nagasaki-shi, Nagasaki 852-8521, Japan<SUP>6</SUP> National Research Institute
of Far Seas Fisheries, Fisheries Research Agency, Yokohama, Kanagawa 236-8648,
Japan</DIV>
<DIV class=affiliation><SUP>7</SUP> Atmosphere and Ocean Research Institute, The
University of Tokyo, Kashiwa, Chiba 277-8564, Japan.*Correspondence: Yuuki Y.
Watanabe, E-mail: <!--TODO: clickthrough URL--><A title="Link to email address"
href="mailto:watanabe.yuuki@nipr.ac.jp" shape=rect><FONT
color=#007e8a>watanabe.yuuki@nipr.ac.jp</FONT></A></DIV>
<DIV>
<H3>Summary</H3>
<DIV class=para>
<P><B>1.</B> Breath-hold divers are widely assumed to descend and ascend at the
speed that minimizes energy expenditure per distance travelled (the cost of
transport (COT)) to maximize foraging duration at depth. However, measuring COT
with captive animals is difficult, and empirical support for this hypothesis is
sparse.</P></DIV>
<DIV class=para>
<P><B>2.</B> We examined the scaling relationship of swim speed in free-ranging
diving birds, mammals and turtles (37 species; mass range,
0·5–90 000 kg) with phylogenetically informed statistical methods and
derived the theoretical prediction for the allometric exponent under the COT
hypothesis by constructing a biomechanical model.</P></DIV>
<DIV class=para>
<P><B>3.</B> Swim speed significantly increased with mass, despite considerable
variations around the scaling line. The allometric exponent (0·09) was
statistically consistent with the theoretical prediction (0·05) of the COT
hypothesis.</P></DIV>
<DIV class=para>
<P><B>4.</B> Our finding suggests a previously unrecognized advantage of size in
divers: larger animals swim faster and thus could travel longer distance, search
larger volume of water for prey and exploit a greater range of depths during a
given dive duration.</P></DIV>
<DIV class=para>
<P><B>5.</B> Furthermore, as predicted from the model, endotherms (birds and
mammals) swam faster than ectotherms (turtles) for their size, suggesting that
metabolic power production limits swim speed. Among endotherms, birds swam
faster than mammals, which cannot be explained by the model. Reynolds numbers of
small birds (<2 kg) were close to the lower limit of turbulent flow
(∼3 × 10<SUP><FONT size=1>5</FONT></SUP>), and they swam fast possibly
to avoid the increased drag associated with flow
transition.</P></DIV></FONT></DIV><BR></BODY></HTML>