Questions for “Urchin mobs can literally dis-arm a predator”

photo of a red/pink sea star

A common sun star (Crossaster papposus), seen here, was found mangled in an aquarium. In a classic reversal of predator and prey, it had been attacked by dozens of starving sea urchins.

Jeff Clements

To accompany “Urchin mobs can literally dis-arm a predator


Before Reading:

1.  What is a sea urchin and where does it live? What does it eat?

2.  What’s another name for a sea star? Where do these animals live and what do they eat?

During Reading:

1.  In what way might one think of sea urchins as underwater lawnmowers?

2.  What happened back in 2018 when Jeff Clements put a sea star in a tank with a lot of its prey?

3.  In follow-up trials, what did they see urchins do when Clements’ team put a starfish in a tank with them?

4.  What is “urchin pinning”?

5.  What is the normal role of urchins in kelp forests? Why does Clements argue that his team’s new discovery could suggest that a switch to meaty meals could “delay the recovery” of overgrazed kelp forests?

6.  Megan Dethier says that the urchin attacks on starfish can’t be intentional. What support does she make for that claim?

After Reading:  

1.  There still are a number of open questions about the nature of what Clements’ team witnessed and what it might mean for ocean ecosystems. Identify one of those questions and describe how you think scientists might go about answering it. Be as specific as you can.