While California is seeing more wildlife crossings, researchers say some animals may be afraid to use them

As Californians mourn the death of celebrity mountain lion P-22, the work goes on a massive wildlife crossing bridge in Los Angeles County that will connect two natural landscapes intersected by one of the nation’s busiest highways.

Perhaps the lasting legacy of the cougar, which was captured and euthanized by California Fish and Wildlife officials after his health began to rapidly decline, the attention his story has brought to the plight of animals that find themselves trapped on all sides by urban sprawl.

That is why in September 2022, Gov. Gavin Newsom signed legislation to require the state to identify locations where animals have barriers that separate them from moving freely and prioritize building or converting existing infrastructure to allow them to cross more safely.

The decision was praised by animal welfare groups, but researchers say special care is needed to ensure wildlife transitions make sense for the animals that will use them.

A recently published study by researchers at UCLA found that some animals may actually be afraid of using wildlife crossings, so designers will have to take that into account when planning new crossings.

“We know that species use them, but sometimes they have to be kind of designed for specific species, because different species look at open areas or the habitat at intersections differently,” said Dan Blumstein, a UCLA professor of ecology and evolutionary biology.

Blumstein’s team studied a wildlife crossing in Alberta, Canada, to see how animals used it, if at all.

Videos of that wildlife crossing showed some deer and elk looking for food at the wildlife crossing after being frightened or fleeing completely when cars passed. Animals that appeared to be more fearful or more alert were less likely to use the crossing.

Other animals, including some rodents, would likely cross over without giving it a second thought.

Ultimately, what they found was that there was no universal set of behaviors for animals, so there is no one-size-fits-all solution to designing a wildlife transition.

“At the end of the day, we found that the animals that were foraging seemed to be less concerned about traffic than those that were more vigilant and that kind of says that individuals behave differently at these wildlife intersections,” Blumstein said.

The researcher said that part of it comes down to whether the specific animal sees the habitat structure as protective or obstructive. Animals that consider things like bushes and shrubs to be safe places will use cover, but other animals may think of the same obstacles as dangerous.

“On these wildlife crossings, different species behave differently, and we need to think about designing crossings, as other people have already realized, we need to think about designing crossings to be as good as the species you’re dealing with, Blumstein said.

Even closely related species – in his example, wallabies and kangaroos – will interpret different landscapes and vegetation in opposite ways. Wallabies value coverage; kangaroos prefer open space.

Although there won’t be any kangaroos crossing the 101 Freeway, the logic remains the same: animals perceive different things as safe or dangerous.

He added that the architects and researchers who design wildlife crossings need to have a good understanding of what species they are trying to get and then design a structure that is “attractive to multiple species.”

As for the Wallis Annenberg Wildlife Crossing in Agoura Hills, Blumstein said the project’s size could allow for multiple “microhabitats” to suit the needs of multiple species.

Blumstein called it a brave idea to try to reconnect fragmented habitats, one that comes with a hefty price.

The transition from Los Angeles County will come at a price tag of more than $90 millionbut not the building also has a cost.

“We know there are costs to isolation, we can see that with genetic mutations and inbred animals and with mountain lions in Los Angeles. And you know, some will use this and this will lead to gene flow and this will be a good thing ,” Blumstein said. “We mess with mother nature at our own risk and the solutions are often expensive, but wildlife crossings and wildlife corridors have been very successful in other places, and I expect on a certain level, will be successful here.”

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