The traps are the easy part. The day goes wrong in the twelve hours before them, almost every time.

The day before is the actual work

Tell everyone who feeds that colony to stop. This sinks more trap days than everything else put together. You withhold food for about a day so the cats are hungry enough to walk into a box, and then one kind neighbor who has been putting out kibble for three years quietly tops up the bowl at six in the evening, and in the morning your traps sit empty. Find out who else feeds that colony. There is almost always someone else feeding that colony.

Count your traps by touching them. A trap stacked in a shed since spring is not the same thing as a trap that latches. Test every trigger plate with your hand. Doors hang, trip plates bend, and you will find this out either tonight in your driveway or tomorrow at dawn with a cat walking away from it.

Confirm the number you gave the clinic, the night before, not three days before. Two cats you were counting on can stop showing up to a feeding station in seventy-two hours.

Trap-day morning

Set later than feels right. Traps set at first light sit open and warming for hours, which is bad for the first cat in and bad for your nerves. Set close to the hour those cats actually expect food.

Label the trap, not your memory. Masking tape and a marker: where it came from, what time it fired, anything you noticed. Standing in a parking lot at six in the morning with eleven traps out, you will be completely certain you will remember which one came from behind the church. You will not.

Cover a trap the second it fires. A covered cat goes quiet and stays that way. An uncovered cat throws itself at the door and arrives at surgery already hurt.

Never open a trap to check on anything. Not to look, not to adjust, not to give water. That is the one rule with no exception in it, and the day somebody breaks it is the day a cat is loose in a van.

What actually goes wrong, and what to do about it

• You catch a cat that is already fixed. Check for an ear tip before you count it toward your surgery slots. Then let it go and note where it came from, because a fixed cat in your trap means your colony map is out of date in that spot.
• You catch a nursing mother. Do not decide this one alone. Call the clinic and tell them what you have, because whether they will spay her that day depends on her condition and on how old the kittens are, and that is their judgment to make and not yours.
• You catch a possum, a skunk, or somebody’s outdoor cat. Cover it, carry it somewhere calm, open the door, and stand behind it. Nobody needs a story about this. It happens to everyone.
• You catch fewer than you booked. Call the clinic the moment you know, not when you arrive. An hour of warning is the difference between an empty slot and a cat from somebody else’s colony getting fixed today.

Write it down while you are standing there

Not tonight, when you are tired and everything blurs. While you are standing in the lot with tape on your hand.

Which cats, from where, already-tipped or not, who was too smart for the trap this time. That last one especially. The cat who watched you set every trap and ate nothing is the cat you will be back for in three weeks, and the only version of that information that survives until then is the one you wrote down.

That is the part Purralytics is built to hold: cat-level history on the colony, including who is already fixed, free for your first three colonies, so the next trap day starts from what you learned on this one instead of from memory.