Figure 1.
Functional response of year-1 blue king crabs (P. platypus) to year-0 blue king crabs density in sand (closed circles) and shell (open circles) habitat: (A) proportional predation and (B) number of prey crabs eaten.
Points are the average (± SE) at each density and are offset slightly. Lines represent the best fit functional response model for each habitat. Parameter estimates (± SE) for sand are: b = 0.039 (0.023), c = −0.068 (0.19), Th = 0.84 (0.19), and for shell are: r = 0.016 (0.003).
Table 1.
Ranking of functional response models in sand and shell habitats using AICc.
Figure 2.
Average (± SE) prey crab crypsis index at five densities with (solid circles) and without (open circles) predator presence.
The lines represent linear regressions for when predators were present (closed circles; crypsis = 0.732−(0.0134×density), R2 = 0.172) and absent (open circles; crypsis = 0.551−(0.00971×density), R2 = 0.106).
Figure 3.
The number of prey crabs eaten as a function of predator size (carapace length) in sand (closed circles) and shell (open circles) habitat.
Lines represent linear regression. Equations are: 1) sand: prey eaten = −23.926 + (1.883×carapace length), R2 = 0.895; and, 2) shell: prey eaten = 1.373 + (0.00155×carapace length), R2 = 0.0000568.
Figure 4.
Average (± SE) predator crab activity in sand and shell habitat.
We define “motionless” as crabs not moving, “walking” as crabs moving laterally, and “foraging” as crabs consuming prey or crabs with repeated movements of chelae from the substrate to the mouth. Different letters indicate statistical significance between habitats for each behavior (t test, p≤0.05).
Table 2.
ANCOVAs for crypsis and the number of prey eaten.