I don’t now much about this topic except that in southern California cities and suburbs rats have reached very large populations. Our feral cats are being wiped out by coyotes. Is it reasonable to expect that some kind of predator will eventually fill the niche that kills rats.
I can't think of very many potential predators that could be introduced to an urban landscape and establish themselves in large enough numbers to be effective. The great horned owl or possible the European stone martin are about the only ones I can think of.
People will kill every snake they see. Maybe some education here might help and we could start releasing rat snakes.
The coyotes themselves, very likely.
They kill some rats for sure but only at ground level. I don’t think they are effective as rat controllers. They prefer cats, dogs and backyard fruits
Way back in the day (80s?) I remember reading about programs to introduce peregrine falcon populations into cities to hunt the pigeons. I have no idea if it was successful or if they or another daytime raptor could fill the role. I don’t think that urban rats are especially nocturnal that you’d need owls.
We have a Coopers hawk who frequents our backyard & they are supposed to eat rats—but the only prey we’ve ever seen him catch are birds (at our feeder :mad:). And great horned owls already live here, though I’ve never seen one, so their numbers may be low. I only know they live here because everyone on my Nextdoor feed is always complaining that the owls eat the koi in their ponds. I’d love to see their populations increase, with extra nutrition from all those gross rats.
The peregrine breeding program and reintroduction has had pretty good success but for some reason the coopers hawks have also enjoyed a huge increase in populations and they feed on pigeons primarily.
I think rats are at least 90% nocturnal
The peregrine falcons in Cleveland are thriving. Redtailed hawks are even more numerous, though I think they mostly target rodents rather than pigeons.
You got raccoons a-plenty down there in Torrance. I’ll bet they are doing a number on rats and small vermin.
I’d question their veracity there. Most owls don’t eat fish. If they’re losing koi overnight, I’d be liable to blame night-herons. Black-crowned Night Heron Identification, All About Birds, Cornell Lab of Ornithology
The coyotes have killed most of the raccoons as well. Raccoons are not that great at ratting.
Yeah I doubt they really know what ate their koi, but great horned owls definitely live in the South Bay. One neighbor posted a picture of a great horned owl sitting at her koi pond - during the day. They are nocturnal so it was probably sick and she said animal control came and got it. That post may have triggered everyone to believe that owls were the culprit, but it could be anything, even raccoons.
We need to bring in some mountain lions to keep the coyote population in check.
I know someone who has a pet Great Horned Owl. It had a wing broken somehow, and was picked up by a rescue, and survived, but could no longer fly to hunt (it can flutter up to perches, but it can’t soar). Anyway, S adopted it. She feeds it turkeyburger, some veggies & fruits, and mice purchased at the pet store where they sell them for snakes (they are already a part of history).
Boris has become a day-walker. She keeps the lights where he is low, but even though at first, she would put his food out at 8pm or so, and had him in a habitat (she lives way out with a few other rescue animals, dogs she trains for obedience trials, and puppies she trains for Seeing-Eye, Inc.) She swears up and down that she did not try to get him to adapt to a day schedule, but he did. He has become very domesticated-- it’s actually a thing that’s been observed in other injured wild animals. Anyway, now Boris comes into the house, and even goes to her for petting. It’s pretty funny to see this owl strutting around like his name is on the lease. She has cats, and he doesn’t bother them, probably because he’s well-fed, and I suspect at this point, older than most wild owls ever get to be.
My point is, that if owls were in an area where the best food source was around during the day, I think they would adapt.
Raccoons are the big koi killers around the South Bay
Gray hounds hunting behind a bait dog will get the job done.
They are not supposed to eat rats, at least not primarily. They are bird specialists like most accipiters. Any rodent added to the diet would be a nice supplement at best.
Barn owls and great horned owls definitely will adapt to suburbs and cities with large enough city parks. I work evenings and see both regularly in the East Bay - Berkeley, Oakland, Richmond. Even short-eared owls once in awhile in shoreline parks in Richmond and Hayward. But, yeah density won’t be super-high at least partly due to territoriality and partly limitations in nesting sites. Owls can only take so many rats and in urban areas there are a lot of rats…
I think you’re almost certainly correct night herons are the most likely culprit.
However that said, it isn’t impossible a great horned owl might take an easy koi meal. They have been known to take fish. In fact they’ll eat damn near anything they can kill and they can kill a lot of stuff. They’re pretty much the ultimate generalists in North America - I believe they have the widest documented prey list of any predator on the continent. Including a lot of other raptors and corvids, snatched off their perches at night.
Huh, if you asked me to guess the widest diet range of any North American predators, I would never have guessed any owl.
Honestly, I’m surprised it’s not coyotes to begin with …
In downtown Chicago, the peregrines were doing fine as of 10 yrs ago when I worked there. A pair nested on the bldg. behind mine, and I saw them regularly.
I live in the western burbs. There are plenty of coyotes - in fact, over the past couple of weeks a coyote bit a kid in downtown Chicago. Foxes too.
We used to have great horned owls in our neighborhood. And currently, barred owls are expanding in the forest preserves.
The folk behind my sister’s house had their koi pound decimated by great blue herons. Was an amazing sight to see 10-12 of those big birds bellying up to the bar! 