A streak is series of catches, of the same mouse in a row. A FTA, FTC or catch of another type of mouse breaks a streak.
For every multiple of 3 in a streak, you cause two extra mice to 'retreat' (they are removed from your wave). Streaks do not appear to apply to Theurgy Wardens, which makes sense as they are the only thing in wave 4 other than the Warmonger, lol.
For example, if you catch three desert archers in a row, two desert archers retreat. If you then immediately go on to catch three more desert archers, four more desert archers retreat. At this point, you have a streak of six desert archers and a total of six more desert archers have retreated, for a total of 12 desert archers removed from the 35 original desert archers that was your goal. If you then go on to catch another three desert archers with no FTAs, FTCs, or catches of other mice, making a streak of nine, six more desert archers will retreat, for a total of 9 catches + 12 retreats = 21 removed from your goal.
Note, however, that you can have a streak of 4 or 5. This fact is important when considering the effect of catching a Crimson Commander.
By capturing a Crimson Commander Mouse I demoralized the remaining mice in this wave! My current streak was 8. 8 of each mouse have retreated!
When you capture a Crimson Commander, wherever you are in a streak, that number of each mouse retreats. We had early reports of catching a Crimson Commander without the demoralizing effect taking place, but none in quite some time, so perhaps that was a glitch. It is possible to clear the rest of a mouse this way (if you have 7 Sentinals left to go and 8 of each mouse retreat you are done with Sentinals.) Ever wonder what would happen if a Crimson Commander is the first mouse you encounter? Lisa R. found out for us; 1 of each mouse retreats.
Crimson Commanders can be encountered at any time, although the probability appears to be quite low. Using sb+ increases the chances of encountering a Crimson Commander.
Strength in numbers! After I failed to catch a Caravan Guard Mouse, members of my hunting party were able to prevent the mouse reinforcements from arriving!
If you fail to catch a Caravan Guard and you are hunting solo (no friends online), reinforcements will arrive (your target mouse count will increase.) How many reinforcements? Good question! See Caravan Guards for more information.
Your main protection from this dastardly fate is to hunt with friends: if you miss your Caravan Guard, your chances of reinforcements arriving are smaller the more friends you have online. Using sb+ as bait also reduces the chances of attracting Caravan Guards, although it does not eliminate it.
Fearing that I was gaining the upper hand, the Warmonger released a Gargantuamouse, putting an end to my streak.
After seven catches in a row, the Warmonger releases the Gargantuamouse in an attempt to slow you down. You have an increasing probability of encountering the Gargantuamouse, until after the ninth catch when it is extremely likely. The chances of encountering Gargantua increase by a polynomial equation (not exponential) as the streak progresses. No hard limit is set on the length of a streak: if you can keep dodging Gargantuas, you can keep going! (For more on Gargantuamice, see the Gargantuamouse entry in the strategy guide.