Juvenile horseshoe crab behaviour – self righting

This post documents the behaviour of a juvenile horseshoe crab (Carcinoscorpius rotundicauda) at an inter-tidal mudflat at Luk Geng, New Territories, Hong Kong.

This photograph was taken just as the tide was receding and shows a juvenile C. rotundicauda on its back trying to self-right itself using its tail. The tail marks left by the animal’s actions can clearly be seen in the muddy substrate (if horseshoe crabs end up on their backs, they use their tail as a lever to self-right themselves).

Juvenile horseshoe crab behaviour - burrowing

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. When the tide comes in, the juveniles bury themselves in the substrate. When the tide recedes, they emerge to forage.

The following photographs show two instances of juvenile T. tridentatus burrowing on the exposed mudflat:

Burrowing 1

Juvenile T. tridentatus sprints across the mudflat, then burrows into the sandy substrate.

Burrowing 2

Juvenile T. tridentatus burrowing into sandy substrate

Comment

Understanding the way that tidal cycles dictate the foraging and burrowing activities of juvenile horseshoe crabs may help in the interpretation of the palaeo-environment of other localities with horseshoe crab fossils, such as Mazon Creek.

Juvenile horseshoe crab behaviour – walking, wandering and sprinting

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.

The following are examples of walking, wandering and sprinting behaviour, either after the tide has receded, or after foraging activity has taken place.

Wandering as the tide is receding

This video is of a juvenile T. tridentatus wandering from pool to pool in a well developed seagrass bed, just as the tide is receding, perhaps searching for a new foraging area:

http://www.youtube.com/watch?v=CKdfHu1Wjas

Olympic sprint

These photographs show a juvenile T. tridentatus running at high speed across an exposed area of mudflat and quickly burying itself:

Transition from foraging to walking

The following series of photographs shows the sequence of trails left by a juvenile T. tridentatus as it transitions from foraging to walking:

Pool on sandy area of beach where the photographs below were taken.

Foraging horseshoe crab(s)

Transition from foraging to walking trail (walking starts with tail marks)

Walking horseshoe crab

Juvenile horseshoe crab behaviour – marginal spine marks

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. When the tide comes in, the juveniles bury themselves in the substrate. When the tide recedes, they emerge to forage.

In terms of juvenile horseshoe crab locomotion, two principal types of locomotion are observed – foraging in the substrate and walking on the substrate. This post covers both foraging and walking activity, which result in marginal spine impressions being left in the substrate.

Juvenile horseshoe crab behaviour – tail (telson) marks

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. When the tide comes in, the juveniles bury themselves in the substrate. When the tide recedes, they emerge to forage.

In terms of juvenile horseshoe crab locomotion, two principal types of locomotion are observed – foraging in the substrate and walking on the substrate. This post covers both foraging and walking activity, which result in tail mark impressions being left in the substrate.

An examination of many of these marks highlights the importance of the tail (telson) in navigation, showing how the tail is used in changing direction and turning.

Even a juvenile (1.5 cm prosoma width) with a reduced tail can leave a substantial tail mark, highlighting the important role the tail has in turning. See below:

Images to highlight the role of the tail in turning. See below: 

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!