Not to start another thread about the benefits/evils of dog parks, but does anyone else suspect that much of the dog-on-dog aggression today could be traced back to this?
I don't know what the shelter population is like in your area, but in Philly, most of the shelter dogs are pit bulls or pittie mixes, and not infrequently they come from breeders who are intentionally trying to select for dog aggression (because they're trying to breed fighting dogs and/or just conflate all types of aggression and think it makes for a better guard dog, more macho displays on the street, or whatever).
That has an influence on the shelter population, especially over time as responsible owners spay/neuter their dogs and the shelter population tilts ever more toward what the least responsible segment of the city's dog owners are doing.
It has absolutely nothing to do with dog parks. I wouldn't be surprised if there's been an increase in Philly's dog park usage over the same time period, but it's a completely separate trend driven mostly by gentrifying yuppies and hipsters, and it has no connection to the increased rates of dog-dog aggression. The dog-park dogs aren't breeding and mostly aren't getting dumped at the shelters. The trend is completely coincidental.
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