Figure 2.

Negative density-dependence in cockle flesh mass caused a hump-shaped functional response for knots (a type IV functional response). (a) A cockle's relative ash-free dry mass of the flesh (AFDM_flesh) plotted against cockle density (m⁻²). The regression line reflects the statistical model presented in electronic supplementary material, table S1a. (b) The predicted energy functional response of knots foraging on 7 mm long cockles (thick black line), which includes the negative density-dependence in relative cockle AFDM_flesh (short-dashed line with units on the right y-axis). We also plotted the Holling's type II functional response without the negative density-dependence among cockles (long-dashed line). For reference, we included the threshold intake rate that knots need to acquire energy balance (grey horizontal line, [34]).