Olivia and Tim, in the comments on that post, came up with a few more scenarios. The logs could have been washed up from some other source; the hermits could have massacred the snails after all (they have been known to do that in a pinch); or it could be a seasonal thing.
I'll have to start paying closer attention to numbers, dates, proportions, demographic ratios.
And I have more data to add; here goes.
As usual, I examined my hermits in a bowl of water before I added them to the tank. Three were quite tiny, and one was in a different shell, not from a mudsnail. I took its photo, before I settled it down in its new home.
|Orange hermit in a matching shell, possibly an olive snail's shell.|
Hairy hermits crabs have green and white banded antennae, dark, hairy legs with variable white and/or blue markings.
|Small hairy hermit in pretty moonsnail shell.|
|Two of the orange hermits. The larger one is in a mudsnail shell.|
By the time I'd discovered this, the 5 new hermits had mingled with the old-timers. I looked for them in the tank, and discovered one of the tinies in an awkward position:
|Caught on the back leg of a big shore crab.|
|None the worse for wear.|
And sure enough, this one has the orange-tipped pincers and antennae, too.
The other common species, the grainyhand hermit, has orange antennae, but otherwise is quite different:
|Bluish-green to brown legs and pincers, all covered with blue warts. These are larger hermits, up to 2 cm. They prefer big shells, like this whelk.|
This adds to the questions I have. Were all those hermits on the logs greenmarks? Why have I not seen any before? Do they, tiny as they are, kill snails?
We must go back and examine those logs properly.