Juvenile horseshoe crab behaviour - foraging

This post documents the behaviour of juvenile horseshoe crabs (Tachypleus tridentatus) based on observations made at an inter-tidal mudflat at Ha Pak Nai, Deep Bay, New Territories, Hong Kong.

All observable juvenile horseshoe crab activity on the mudflat appears to be synchronized with the tides. Before the tide comes in, the juveniles bury themselves in the substrate. When the tide recedes, they emerge to forage.

In terms of horseshoe crab locomotion, two principal types of locomotion are observed – foraging in the substrate and walking on the substrate. This post covers foraging activity.

Prosoma used like a “snow plough”

Juveniles forage at different depths in the sediment. These are photographs of various foraging juveniles. Observations suggest that some of the prosoma design and ornamentation on juveniles is used to reduce surface tension and separate the sediment that is being foraged through.

Spiral foraging trails

These are the spiral trails left as a result of foraging activity. Such “disoriented” trails constitute normal behavior and are the norm, not the exception!