SearchResearch Challenge (3/6/24): How do animals fake each other out, and why?

While strolling on a Northern California beach one day... 

... I spied a large colony of mussels.  (See above.)  The mussels in the top pic are around 1 inch across (2.5 cm), but they vary widely in size (see bottom pic).  

By mussel I mean bivalves of the marine family Mytilidae, most of which live on exposed shores in the intertidal zone, attached to rocks and stable platforms by means of their strong byssal threads (which are, by the way, incredibly strong).  

Interestingly, marine mussels have a wide range of predators--they're eaten by humans, starfish, seabirds, dog whelks. Likewise, freshwater mussels are eaten by muskrats, otters, raccoons, ducks, baboons, humans (again), and geese.

For an animal that's been around for nearly 500 million years (early precursor bivalves evolved during the middle of the Cambrian era, around 100 million years before trees evolved on land!), they seem pretty static.  I mean, look at them--they just hang around and filter feed for most of their life.  

As I was standing in the tidepools looking at them I couldn't help but wonder if such a long-lived creature had something else up its behavioral sleeve. 

We know that many creatures go to great lengths to create fake displays.  Here's one that I saw while scuba diving--the fabled frogfish, which looks and acts a lot like a sponge, until a small fishy swims too close to its mouth, and then learns the hard way that it's not a sponge! 

Frogfish in Bonaire.  P/C  dive buddy Megaaan. 
You can see the mouth on the lower left, with the eye right above.

So this brings up our SearchResearch Challenge for this week.  

BUT... this is going to be slightly different than normal. I've got 3 SRS Challenges that I'll release one-at-a-time over the next few days. (I'm doing it like this to make a kind of cliff-hanger experience.  You'll see why...)  

Here's the first Challenge: 

1. Given that mussels are fairly quiet and sessile creatures, do they ever try to do some kind of fakery in their appearance?  If so, why?   

Once you figure that out, I'll post SRS Challenge #2 about mussel fakery.  It will all become clear in a bit. 

Let us know how you found the answer!  

Keep searching.