- In a 17-year study, Chilean researchers observed that Andean condors (Vultur gryphus) use landfills as supplemental food sources when natural food is scarce.
- The researchers found that females and juveniles lower in the pecking order are more likely to scavenge in landfills than older males.
- While this food subsidy could help Andean condors when times are tight, it may also put them at an increased risk of poisoning.
Fifty kilometers north of Santiago, Chile, sits Loma Los Colorados, a sprawling landfill that receives more than 60% of the capital city’s domestic waste. Day after day, heavy machinery buries tons of household garbage, industrial waste, construction material and more. Far removed from Chile’s unspoiled national parks and mountain peaks, it may seem an unlikely place for wildlife. But after 17 years of careful observation, researchers have found that the country’s largest landfill is more than just the final destination for human trash — it’s also a popular grub hub for imperiled Andean condors (Vultur gryphus).
Tipping the scales at more than 30 pounds and measuring up to 4 feet in length, the Andean condor is one of the world’s largest flying birds. Unfortunately, it’s also one of the most imperiled. A 2020 assessment estimates that a mere 6,700 mature individuals remain in their native range of western South America. As they fight to survive a multitude of existential threats including hunting, illegal wildlife trade and poisonings, these resilient scavengers have turned to landfills as an important food source. A paper recently published in the Journal of Raptor Research finds that a significant number of Andean condors flock to Loma Los Colorados landfill to feed on organic waste when natural food sources are in short supply.
Researchers say this food subsidy is particularly appealing to raptors lower in the pecking order: A large proportion of condors at the landfill were juveniles and females, two groups more likely to be chased off from other food sources (like a tasty cow carcass) by older males.
“Landfills are a barometer that provides valuable information regarding the situation of condors on a broad territorial scale — for example, regarding their abundance or food supply … the relationship of condors with landfills is a very important aspect to study and monitor,” says lead author Eduardo Pavez with the NGOs Bioamérica Consultores and Union de Ornitólogos de Chile.
Over the course of this long-term study conducted from 2005 to 2022, scientists uncovered another pattern: The number of Andean condors at the landfill was directly linked to food abundance in the surrounding landscape. Between 2005 and 2013, condor sightings at the landfill steadily climbed. At one point, observers counted a staggering 131 condors scavenging at the landfill’s workfront, the active part of the landfill where new trash is buried. But, between 2013 and 2019, landfill scavenging decreased when more dead cattle and rabbits (important natural food sources) became available due to drought and disease.
Despite this variation, the scientists say the landfill’s place as a food subsidy is, much like our garbage, probably here to stay.
“Today, the main source of food for condors is carrion derived from extensive livestock farming. For social and economic reasons, this type of traditional livestock farming is rapidly disappearing, and with it the food for the condors is decreasing,” Pavez says. “Food sources will continue to reduce, and landfills will continue to be an option for condors.”
Currently listed as vulnerable by the IUCN Red List, scientists say they believe extra sources of food may be beneficial. According to the new study, food subsidies could keep low-status individuals from going hungry when carrion pickings are slim. Previous research shows that when condor populations are strong, the environment benefits because, like their cousins in California, Andean condors are natural sanitarians. By feeding on dead and decaying animal carcasses, they clean up potential sources of pathogens and disease.
But their janitorial skills aren’t the only reason to prioritize their conservation.
“The condor is very relevant for the Indigenous peoples throughout the entire Andes Mountains,” Pavez says. “For them, it is a sacred species.”
Soaring through alpine peaks on wingspans more than 10 feet in length, this iconic species has long represented power in the region. It’s a national symbol for seven different South American countries and is firmly rooted in regional mythology and culture.
While generally admired by the public, human activity continues to threaten this species’ existence. Andean condors regularly succumb to habitat loss, shootings and poisonings. Due to human-wildlife conflict, poisoning poses the greatest threat. In an effort to protect their herds and livelihoods, ranchers have been known to dump livestock carcasses deliberately poisoned with pesticides or other lethal chemicals to deter predators such as wild dogs and pumas. Andean condors get caught up in the carnage by feeding on the poisoned carrion, usually dying shortly after.
Landfills aren’t safe either, potentially exposing condors to familiar threats.
In the long-term study, researchers gave medical treatment to 14 condors that were poisoned after consuming organic material containing organophosphorus, a common pesticide. Eight of these condors perished. Other individuals were regularly observed consuming plastic bags. Although incidents like these may not always be lethal, they highlight the negative consequences of scavenging in human refuse.
According to Pavez, a lack of food also reduces condors’ reproductive rate, so a food subsidy like the landfill may benefit their reproduction. However, a parent’s regurgitated garbage may not be ideal for a new chick.
“The greatest risk for the chicks is with the food that their parents … regurgitate for them,” he explains in an email correspondence. “Fragments of garbage may be present (for example, plastic), which does not cause harm to the adults but can kill the chicks.”
While the future is often unclear, some things will likely remain true: Andean condors will continue to scavenge, and humans will continue to produce shockingly large quantities of garbage. These two truths present landfill management companies with a unique opportunity to turn trash into treasure, at least from a condor’s perspective. Researchers of the long-term study write that landfill companies may be able to help the Andean condor capitalize on food subsidies by exploring and adopting measures that reduce the risk. One recommendation is to establish dedicated feeding stations, areas at landfill facilities managed specifically for condor scavenging.
“What makes the condor so particular is its charisma, and with it the possibility to work for the conservation of nature in a broad sense, presenting the condor as a flagship species and an umbrella species,” Pavez says. “Under its large wings, an entire ecosystem can be protected.”
Citations:
Pavez, E. F., Pascual, P., & González, B. A. (2023). Landfill use by andean condors in central Chile. Journal of Raptor Research, 57(4). doi:10.3356/jrr-22-00051
Zambrano-Monserrate, M. A. (2020). The economic value of the andean condor: The national symbol of South America. Journal for Nature Conservation, 54, 125796. doi:10.1016/j.jnc.2020.125796
Restrepo-Cardona, J. S., Parrado, M. A., Vargas, F. H., Kohn, S., Sáenz-Jiménez, F., Potaufeu, Y., & Narváez, F. (2022). Anthropogenic threats to the vulnerable andean condor in northern South America. PLOS ONE, 17(12), e0278331. doi:10.1371/journal.pone.0278331