Predator-induced selection on urchin activity level depends on urchin body size.

Area of Science:

• Marine Ecology
• Behavioral Ecology
• Predator-Prey Interactions

Background:

• Individual differences in behavior influence ecological processes.
• Predation is a key factor shaping marine communities.
• Kelp forests are vital ecosystems threatened by ecological shifts.

Purpose of the Study:

• To investigate how individual variation in prey behavior (activity level, covering) and size affects survival against a predator.
• To test if slow-moving and covering purple sea urchins (Strongylocentrotus purpuratus) survive better than active ones when preyed upon by California spiny lobsters (Panulirus interruptus).

Main Methods:

• Confirmed temporal consistency in individual urchin activity and covering behaviors.
• Monitored urchin survival over 108 hours in mesocosms with a single lobster predator.
• Analyzed the relationship between urchin traits (activity, covering, size) and survival rates.

Main Results:

• Individual urchins displayed consistent differences in activity and covering behaviors.
• Higher urchin activity levels were significantly associated with lower survival rates.
• Urchin size and covering behavior did not independently affect survival, but activity's negative impact was stronger for smaller urchins.

Conclusions:

• Urchin activity level and body size interact to determine predation susceptibility by lobsters.
• Predation on specific sea urchin phenotypes by recovering lobster populations may alter kelp forest stability.
• Understanding these individual-level traits is crucial for predicting ecosystem dynamics.