...Looking at the photograph got me to think about another relevant feature of the mouth that might contribute to the success of capture. Its that tounge. Its there for a purpose and I think that purpose is to push prey to rear of the mouth. It may be used in conjuction with the roof pads for constraining prey motion. What are your thoughts Al? Would the tounge affect the measurement of effective gape?
I'm not sure, but the abrasions on the palette make me think it's part of the process by either holding or helping swallow the forage.
4.75" is the more conservative number, and what I would go by here. Having said that, LMB are opportunistic feeders, so their diet is probably determined primarily by availability as much as anything.
EDIT: I didn't take the tongue into account for 2 reasons. One, the vertical gape is the most common and easily determined choice for forage sizing, and two, I was unable to manipulate the LMB's mouth into a true flared opening, so any numbers I had would get would probably be sketchy at best.
Sometimes LMB make poor choices based on that availability.
