Why is such a tunnel needed?

funny@lemmus.org to Ask Lemmy@lemmy.world – 701 points –

I found such a photo on the Internet and became interested in what function such a structure could perform.

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These are great for wildlife as they provide a safe crossing over high-speed highways. They are usually design to be in already existing migration paths where moving a proposed highway may not work and not disrupting migration paths is of importance.

So they're literally building the mountain next year. Neat.

They dug it out before. Later they rebuild it. But if they wait for a year, nature suffers much.

Looks like a nice choke point for a predator to hang about.

Possibly but I’d think it’s still safer than vehicles and less disruptive to overall migration for a given species.

I wonder if there’s been any studies showing how effective, if at all, these are.

There have been study's, these crossing are usually design to feel like open fields in a sense, so most animals will cross quick and on high alert to get through the "opening" in the field.

Are there any predators smart enough to strategize like this? I know that some use water holes as hunting grounds, but that's probably more instinctive than actual strategy.

Are there any predators smart enough to strategize like this?

it is the predators that build such passages. Have you ever seen any construction company building them? Even in the first photo that is under construction, there is not any human worker in sight

That under construction pit is the pit of the manlion. It's similar to the pit of the antlion, except for construction workers.

They always have to deal with the manlion before they start building. Often by pouring concrete over it.

So you're telling me lions and tigers built that tunnel and that natural bridge? okay.

Would they need to be that smart? Ambush predators that stay in roughly one area, for example, could naturally grow their numbers in the area around such a chokepoint simply by virtue of the ones in that area having more food available and therefore better survival chances.

I think that these human-made structures provide such a different environment (loud sounds from cars, moving/flashing lights etc.) that previous instinctual adaptations wouldn't trigger.

They can track other species by smell at least. If that path is used by too many and smells like a farm, they would probably get used to hang around it naturally.

Maybe canines? Idk

I just think it would be dope to drive under as a dramatic fight between an elk and wolves tumbled off the side onto my vehicle. Killing all of us instantly. What a way to go!

I know octopi have been escaping their aquarium enclosures and covering their tracks that humans would see. Just to take one at a time pray from their tank. If I recall correctly even killer wailes have been taking down human boats. In conclusion there are for Shure aquatic predators that use genuine strategy. Granted with my killer waile example is a similar case of is it strategy or instinct.

After seeing an aerial view of an African wild dog hunt, a coyote hanging out by a bottleneck doesn't seem outlandish. (here)

I don't imagine it would be a major problem though maybe it would let them get one or two easy meals but predators don't hunt unless they're hungry. So once they've taken down one prey animal they'll ignore the rest. On a species level it's probably not a major issue.

As opposed to roads which will kill lots of animals.

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It's taken into consideration of the design of these crossings.

I'd like to read about that,understand how it's done. it's a thought I have whenever I see them but of course the professionals designing them would have thought about it.

There was a documentary I watch years ago where they went into great detail into this, as well as the design of these things. Can't remember where i saw this documentary though.

Anyways, researchers setup cameras trigger by movement and body heat to watch these overpasses and found no evidence of higher predetor active.

They also went into detail about how these things are design with extra width and gentle slopes to make them as "friendly" as possible depending on the specific species that will be migrating in the area, as different wildlife species prefer different types of crossing structures.

For example:

Grizzly bears and wolves

Wary animals like grizzly bears and wolves there is a "learning curve", it may take up to five years before they feel secure using newly built crossings. Grizzly bears, elk, moose and deer prefer wildlife crossings that are high, wide and short in length, including overpasses

Cougars and black bears

Cougars and black bears prefer long, low and narrow crossings such as underpasses.

Elk

Elk are usually the first large species to use the new crossings, even using some while they are still under construction!

Here are some articles that talk about some of the studies:

https://wildlife.org/wild-cam-do-predators-ambush-at-underpasses/

https://www.nature.com/articles/s41598-020-67340-8

Yea elk don't give a fuck about much really. We have a few herds where I live and they don't even move when we walk our dogs nearby. I even have a video of one coming right up to the fence around my property, both my great pyrenees were losing their minds with the elk less than a foot away, the elk seemed more curious about the noisy little things ("little" relative to a full grown elk that is) than anything else.

It is like that playground game, but with less violence since only one player gets hurt at a time.

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It's also amazing visually! Forget regular highways! Let's have buried highways! That's especially good for if our country is invaded because we can install physical barriers to logistical supply lines against us!

Buried highways would be insanely expensive, and in the case of invasion, one well placed shot would completely kill logistics for the defenders as much as it would for the invaders, so probably not the best idea to rely on those

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