The reason I only have 3 of the 4 left is because I had a pair in one tank, and the smaller one of that pair apparently eventually became dinner.
All my experience says that this is entirely typical crawdad behavior.
And of course, the "sooner or later" part: also applies to any comparably sized fish you might have co-habiting with the crawdads ... they gradually disappear over time too. Best to keep them with fish that aren't too precious to you and are easily replaced ... exactly the kind of thing I have going in my "common local fish community tank."
The other absolutely typical behavior I've seen is that pretty much any crawdad over 1 ½" long can ... and will ... uproot every plant in a tank, and if he/she is ambitious, snip them to pieces as well. So in my mind there's a big flashing sign that says "Warning: Crayfish - incompatible with nicely planted tank." However, mine seem to be very happy with killie-keeper type "yarn-mops" serving as artificial plants and cover.
The best of all worlds IMO with crawdads is to catch 'em locally when they're ½" long. Then when they get to be 1" long proto-trouble-makers, take 'em back you got 'em, pitch 'em back in (or use them as bait, bass love them), and have the fun of re-stocking up on more of the very small ones.
.02
Doug Dame
Interlachen FL
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