And as I've gotten to know them, I noticed that even when set to take 30 second videos, they'd occasionally take really short ones instead. 1 second, or 2, and even fractions of seconds.
Then I had that dumb "aha!" moment - I noticed it only happened when the cams ran out of batteries in the field. I.e., they were from the last gasps of nearly dead batteries on the threshold of being able to power the camera.
- animal walks in front of camera and gets detected by the motion-sensor
- controller turns on the video cam, which powers up and starts shooting footage
- the power up and video mode quickly draw the weak batteries down, and the camera automatically goes into its "batteries low, shutting down..." mode.
But once off, after a bit of rest, or perhaps after getting cold, the batteries can come back up a little in voltage. And thus the short video triggering can happen multiple times over multiple days, as the batteries bounce above and below the threshold.
And while that sounds frustrating, I just learned that you can sometimes get a glimpse of goodness on one of those final days - that a truly dead camera might otherwise have missed.
Such as this masked mustelid that popped out of an old badger burrow in the Santa Cruz Mountains during one of these HD video cam trap's last 1.4 second gasps:
Here are 3 stills from the vid:
The other possibility: this particular cam trap is allergic to cute.
But in either case, I think I'm going to use a bigger battery.