There was an error published in J. Exp. Biol.218, 440-450.

In Fig. 5 of this paper, there was a mistake in the theoretical calculation of the average slip angle, . The corrected calculations show that rises more sharply for low mean relative curvatures and approaches 90 deg. This change does not affect the conclusions set forth in the original paper, and shows better agreement with the experimental findings.

Fig. 5.

Granular resistive force theory (RFT) predictions of mean slip angle ($β¯s$) with changing mean relative curvature ($κλ¯s$), average number of undulations along the body ($ξ¯$), body length to width ratio (L/w) and effective friction. Force relationships were established from empirical drag data in loosely packed (LP) media. The color of the curves and experimental data correspond to different $ξ¯$ (where dark blue is $ξ¯$=0, dark red is $ξ¯$=5). Solid curves are predictions for an undulatory swimmer with a L/w=7.1 and body–particle friction, μs, of 0.17. The dotted-dashed curves show the theoretical predictions with L/w=33.5 and μs=0.17. The dashed curves are the predictions for L/w=33.5 and half the tangential force (which occurs when there is a 50% decrease in body–particle friction, i.e. μs of 0.085; see supplementary material Fig. S1). Experimental data are shown for sandfish (gray cross with red center) and snake (gray cross with blue center) trials in CP and LP media. Horizontal and vertical lines are centered on $κλ¯s$ and $β¯s$, respectively, with span representing ±1 s.d. The diagram above the main panel illustrates waves with different $κλ¯s$.

Fig. 5.

Granular resistive force theory (RFT) predictions of mean slip angle ($β¯s$) with changing mean relative curvature ($κλ¯s$), average number of undulations along the body ($ξ¯$), body length to width ratio (L/w) and effective friction. Force relationships were established from empirical drag data in loosely packed (LP) media. The color of the curves and experimental data correspond to different $ξ¯$ (where dark blue is $ξ¯$=0, dark red is $ξ¯$=5). Solid curves are predictions for an undulatory swimmer with a L/w=7.1 and body–particle friction, μs, of 0.17. The dotted-dashed curves show the theoretical predictions with L/w=33.5 and μs=0.17. The dashed curves are the predictions for L/w=33.5 and half the tangential force (which occurs when there is a 50% decrease in body–particle friction, i.e. μs of 0.085; see supplementary material Fig. S1). Experimental data are shown for sandfish (gray cross with red center) and snake (gray cross with blue center) trials in CP and LP media. Horizontal and vertical lines are centered on $κλ¯s$ and $β¯s$, respectively, with span representing ±1 s.d. The diagram above the main panel illustrates waves with different $κλ¯s$.

The corrected figure is reproduced below:

The authors apologise for any inconvenience this may have caused.