[jonathonlui]

There's a ~$90 million wildlife crossing that started construction earlier this year in Agoura Hills, CA [1] where apparently many mountain lions try to cross.

It wouldn't have helped P22 since there's many roads and freeways in the 30 miles between Griffith Park, where P22 lived, and Agoura Hills but there's some progress in helping mountain lions in the area.

[1] https://en.wikipedia.org/wiki/Wallis_Annenberg_Wildlife_Cros...

[rqtwteye]

I feel this is suffering from the typical US problem that public infrastructure does either not get built at all or in a super expensive way. There must be ways to build these crossings way cheaper than 90 million and place them in more locations. They only have to hold animals that at best weight a few hundred pounds.

[krisoft]

> They only have to hold animals that at best weight a few hundred pounds.

Uhm. I think there is some misunderstanding here. These wildlife crossings are more than just a plank going over the road. They are basically a bridge with a small patch of forest on them (or whatever vegetation matches the surrounding area).

> To encourage use by wildlife, the bridge will have lush but drought-tolerant vegetation with matte materials to deflect bright headlights and insulation to quiet the roar of cars. Fencing at each end will help funnel them onto the crossing.

I don’t know what is the fair price of a 165-foot-wide (50 m) and 200-foot-long (61 m) overpass holding up a small forest, but I know that the additional weight of the animals crossing is not a significant factor in it at all.

Now obviously if we could convince wildlife to use something much narrower and simpler built like a pedestrian bridge maybe we could drive down the costs, i’m not sure if that has been tested or not.

[Someone]

It has but not for mountain lions. The likes of toads and hedgehogs only need a small below-ground tube (https://en.wikipedia.org/wiki/Davis,_California#Toad_Tunnel), squirrels and marters can be helped with an above-ground rope (https://en.wikipedia.org/wiki/Squirrel_bridge)

One issue with narrow passages is that predators may learn to take advantage of them, eventually driving other wildlife away.

[kodah]

$90M sounded big until I looked up the budget: https://lao.ca.gov/Publications/Report/4628What

It's measured in billions.

[willnonya]

This trend of spending millions on sinple projects is not a US problem so much as a California, New York etc problem.

[unsignedchar]

Banff has quite a few of them so sounds like LA should be able to afford more than one

https://canadiangeographic.ca/articles/as-banffs-famed-wildl...

[WirelessGigabit]

People on NextDoor are complaining about their children and tiny pets. Afraid that the Mountain Lion will come for them. I send them real estate links in DTLA...

[WalterBright]

Putting a culvert under the highway would do well and it'd be cheap.

[Xylakant]

I don‘t think it‘s as trivial. I‘m definitely no wildlife expert, but the wildlife crossing that are built over here are wide bridges with a lot of greenery growing on it, so that it feels more like a small hill with a tunnel through it. And I‘d assume that there‘s reasons to build them that way - other than „all wildlife experts agree that it‘s more beautiful.“ I can imagine that some species of wildlife just don‘t crawl through culverts - or even may not fit. Can you imagine a deer getting on it‘s knees and squeeze through, antlers and all? I can‘t.

[WalterBright]

Culverts come in all sizes, even 10 foot diameter ones.

The problem with throwing $90 million dollars to build one is you cannot build very many at those prices. That means that predators will know they can hang around them picking off any herbivores that try to cross.

Culverts of various sizes can be placed - animals come in various sizes.

[saagarjha]

It's good to be curious on Hacker News, but I have to ask if you have experience in this area or are just saying things that sound reasonable to you? Despite not being an expert, I happened to hear the opposite a while back, and doing a little bit of research seems to agree that predators do not actually do this: https://www.nature.com/articles/s41598-020-67340-8. I understand the concern of "why could this possibly take $90 million, the animals don't care anyways" but I am sure that more thought has been put into this than just sticking corrugated metal culverts every so often.

[WalterBright]

The bit about predators hanging around the only access across a highway I saw in a documentary. Mountain lions would hang around under a bridge over a stream. It's the same reason predators hang around water holes, etc. They aren't stupid.

> I am sure that more thought has been put into this

I am not. Sometimes it takes someone outside the industry to see the obvious. And besides, SpaceX figured out how to launch rockets at what, 10% of the cost of NASA?

I saw a documentary once on one of those zillion dollar animal crossings, and the activists and designers simply went ape over it like they were building the Taj Mahal.

Highways are built over culverts all the time. They know how to do it. It doesn't cost $100,000,000 to do it. They don't even have to raise the highway - the highway is often raised up already on a berm of dirt to keep it from flooding.

[WalterBright]

My dad in the AF once saw that engineers devised an elaborate draining system so a highway could be built across a swamp. He suggested instead they bulldoze a berm and build the highway on that.

That reduced the cost by about 95%, and they adopted it.

Note that the civil engineers working on it all failed to see the simpler, vastly cheaper option.

[saagarjha]

Yes, it happens, and we love to see it here when it does. But I'm not sure that really qualifies what appears to be musings as anything beyond that.