Study Finds that When Roads Appear Jaguars Decline

I have just read a study by Espinosa, Celis, and Branch that was published last year in PLOS ONE. It examined the effects of road development on jaguar (Panthera onca) conservation in Ecuador, and found, not surprisingly, that more roads equal fewer jaguars.

Background and Study Area

Espinosa et al.’s study took place in Ecuador’s Yasuní Biosphere Reserve, which includes Yasuní National Park and the Waorani Ethnic Reserve. When added together, these areas occupy 18,000 km² of land, which the study authors collectively labeled “Yasuní.”

As with many protected areas, some portions of Yasuní are more accessible than others. This is linked to the presence of roads, which make it easier for hunters to enter the forest, and facilitate the construction of human settlements within Yasuní.

To determine how accessibility in general – and roads in particular – impacted jaguars, Espinosa et al. measured the abundances of the cats and their prey at multiple sites within Yasuní.

Methods

The authors recorded wildlife densities by placing networks of 23-26 camera traps at four sites in Yasuní that varied in their distances to roads, rivers, and settlements – all of which influence accessibility.

Espinosa et al. let their camera traps run for 90 days in a row at each site. They then used mathematical formulas to convert the images they captured into data, and to generate estimates of jaguar and jaguar prey densities at each location.

Results

The authors found that the more accessible sites had fewer jaguars. While poaching could be part of the problem, Espinosa et al. believed that the jaguar declines they observed were more directly linked to the overhunting of their prey.

Espinosa et al. monitored the abundances of eight jaguar prey species, and seven of them were more scarce at the sites that were closest to roads and settlements; ungulates (hoofed creatures) like peccaries, tapirs, and red-brocket deer were especially hard-hit.

The loss of their prey severely affected jaguars, which were 6-18 times more abundant in the least accessible site than in the most accessible one.

Conclusion

Espinosa et al. had two major conclusions:

1. Conservationists and local governments need to work together to avoid building roads in areas that are crucial for jaguars. This includes not only large reserves like Yasuní, but also the corridors that jaguars use to move throughout their range.
2. To ensure jaguars’ long-term survival, we need to safeguard their prey. This is why jaguars are “umbrella species:” their conservation requires the strengthening of entire ecosystems.

More Information

This post is but a small summary of Espinosa et al.’s study. Click below to read the original paper for free!