The Learning Process

During the years since the wildlife crossings were built, Jack observed patterns of crossings use indicative of a learning process. The underpasses were utilized very quickly by terrestrial mammals, with species such as collared peccary (Pecari tajacu) using them even while they were still under construction, while other species took longer to make use of them. It took over a year for arboreal species to start using the aerial overpasses, with the white-faced capuchin monkeys being the first species to venture out on the bridges. However, once accustomed to crossing the bridges, it appeared that many species were able to quickly generalize their learned behavior to incorporate the use of new structures such as the rope bridges.
The placement of tunnels and bridges at known crossing points along the highway no doubt accelerated the learning and habitation process. This points to the critical importance of road design engineers and ecologists collaborating with local people—landowners and tour guides, for example—to ensure that the crossing structures are strategically placed at customary wildlife-crossing points.
Video of collared peccaries (Pecari tajacu) in one of the underpass tunnels
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White-faced capuchin monkey crossing on one of the overpass bridges
Photo credit:
Jack Ewing
White-faced capuchin monkey (Cebus capucinus) crossing on one of the overpass bridges
Some wildlife took a long time to learn to use the wildlife crossings. It appeared that groups of female white-nosed coatis (Nasua narica) with young had stopped moving back and forth between the highlands and lowlands until 2023, when they were finally observed to use the underpass tunnels for the first time! It is well known that coati males (“coatimundis”) are almost always solitary, whereas the females travel in groups of 10–20 with their young. Male coatis have often been sighted crossing through the tunnels and over the highway bridges, but until 2023 the females had not been observed using either, and no coatis have been killed on the highway. Perhaps the males have more motivation to cross the road in search of females to mate with?
SOMETHING TO THINK ABOUT…
  1. Collared peccaries, capuchin monkeys, and female coati are all highly social species, and yet they differed dramatically in how quickly they learned to use the crossings. What other factors might influence their learning process? (Hint: there is no right or wrong answer to this!)
See below for more information before moving to the next page
Female and young coati
Photo credit:
evandroanjos/Pixabay
Female coatis (Nasua narica) with young are now using the underpasses to cross the road
Male coati crossing through an underpass tunnel
Photo credit:
Jack Ewing
Male coati (Nasua narica) crossing through an underpass tunnel
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Just as with anything new, adding overpasses and underpasses to highways raise a host of unanswered questions and concerns. For example, some people worry that predators might learn about prey species using the crossing structures and could then alter their behavior and exploit the crossings in order to detect and capture prey. This is known as the “predation-trap hypothesis”. At Hacienda Baru, predators such as ocelots, jaguarundis (Herpailurus yaguarondi), and tayras (Eira barbara) have been observed passing through the tunnels, raising questions about the risk they pose to other mammals that use the tunnels to cross the road. Fortunately, there has never been any indication that these predators wait at the tunnel entrances for prey. Furthermore, the scientific literature records few reports of predation by wild predators near crossing structures. In fact, the majority of studies conclude that the empirical evidence for the predation-trap hypothesis is scant, largely anecdotal, and indicates infrequent opportunistic behavior rather than regular patterns of predation.
There is also concern about human predators because illegal hunters have occasionally used the tunnel entrances at Hacienda Baru as ambush points. Fortunately, this has not been a regular occurrence, perhaps because it requires waiting a long time. However, illegal hunters have sometimes stolen or vandalized the cameras in an attempt to destroy evidence of their presence. This points to the importance of including environmental education at the community level whenever wildlife crossing structures are introduced. Because hunting in this area is done for recreation rather than subsistence, it would be important to communicate the benefits to be gained from protecting wildlife (e.g., economic benefits of ecotourism).
Ocelot crossing through an underpass tunnel at Hacienda Baru
Photo credit:
Jack Ewing
Ocelot (Leopardus pardalis) crossing through an underpass tunnel at Hacienda Baru
Illegals hunters caught with a camera trap hunting with dogs at night
Photo credit:
Mike Mooring
Illegals hunters caught with a camera trap hunting with dogs at night
Next: Wildlife-friendly Roads in Costa Rica