Where there is one, there is more. Rats are not a "singular" species.
+1 on the electric trap. We developed a rat issue last year, because we started feeding our dog outside in the evenings, and she sometimes did not eat all her food every night. We too have a deck that sits pretty low and that is where we thought they came from/were staging their attack from.
Ratschwitz. May not be PC, but that's what we started calling our electric trap. They got around the conventional ones, and the glue traps would just disappear. But Ratschwitz nailed 3 in under 30 minutes one night. Trick is to leave it off, and bait it for a couple of days. They get used to going in an eating (we baited with) peanut butter. Then bait again and turn it on. Check it every hour or two the first night on. I bet you get several. We thought we had one or two. We fried 8. Have left it sit, with the glues as a check for almost a year now and nothing. We also pick up the outside dog feed every night to prevent further issues.
Happy frying.