[tareqak]

I was trying to answer "Dogs are much better at killing rats yet we don't let dogs roam around outside willy nilly.", but I was not as precise as I could be in retrospect.

The objective function that most human beings use is not "what animal kills rodents most efficiently", but "what animal kills rodents most efficiently and poses little harm to human beings most of the time". In my experience, most stray cats will likely run away from children and most stray cats will likely not initiate attacks against children. On the other hand, most stray dogs are more likely to do both of those things. As a result, cats get a pass for being less efficient rodent killers than dogs because they are also less likely to harm human beings.

[darkpuma]

> The objective function that most human beings use is not "what animal kills rodents most efficiently", but "what animal kills rodents most efficiently and poses little harm to human beings most of the time".

See, I disagree. I do not believe that killing rodents is a serious consideration for most modern cat owners. There are cheaper, more efficient and lower maintenance methods of exterminating rodents than cats. Most cat owners own their cat as a pet and think nothing of letting it terrorize the neighborhood birds because it's cute. Talk of rodent extermination is a post-hoc justification for their behavior.

[tareqak]

Oh, I agree with that: most people who have cats have them for companionship, and they don't think about the things that said choice externalizes. However, the same can be said for people who have dogs for companionship. Some dogs routinely lunge at people passing by. In addition, despite the best efforts of those who walk their dogs, there are smears of dog feces on sidewalks. Both situations are examples how keeping a dog has externalities.

[jessaustin]

On a cycle path that was closed by floodwaters earlier this week, already last night there was dog feces. Dog owners DGAF.