The Lure of Landfills: How Garbage Changes Animal Behavior

Our leftovers can be dangerous in the wrong hands, paws, or beaks.

Gulls scavenge at a Connecticut landfill. Evan Schneider, UN Photo/Flickr

One-third of the food we produce globally winds up in a landfill. That’s everything from fugly-looking vegetables that never even make it to store shelves to last night’s forgotten leftovers. And while throwing moldy bread and stale chips in the trash seems like the end of their story, it’s only the beginning.

Food doesn’t stop being food when it hits a landfill. And all sorts of animals are all too happy to swoop down and gorge themselves on our scraps. Our waste has the power to disrupt animal reproduction and create population booms. It can remake ecosystems and upend social structures. Food for thought, the next time you throw away a soggy sandwich.

Global municipal waste is expected to double by the year 2025. And while the developed world is responsible for the lion’s share of that mountain of garbage, there’s one thing the rich and the poor have in common: Most of that waste will never see a compost heap or recycling facility. Indeed, more than two-thirds of the world’s trash is destined for a dump or landfill.

To get a better sense of how waste management plays into the lives of wildlife, here are five stories from the animal kingdom about what happens when our trash becomes part of their menu.

A white stork wanders past an enticing trash pile in Spain. Paul Vallejo/Flickr

Lazy Storks

Since at least the Middle Ages, white storks (Ciconia ciconia) have split their year between breeding grounds in Europe, Asia, and northern Africa and wintering grounds as far south as South Africa. Their long migration is a spectacle made even more striking by the bird’s size. The largest white storks can stand up to four feet in height and boast wingspans comparable to the NBA’s largest ballers.

But lately scientists have been noticing a disturbing trend. According to a study published in March in the journal Movement Ecology, one population of white storks is deciding to stay behind, seemingly canceling its migratory flight south in favor of gorging on rotting food found in Portuguese landfills.

It’s unclear what long-term effects the mountains of refuse might have on the birds, but right now, these easy meals are creating a stork bonanza. Birds that nest near the dump show markedly higher fledgling rates, and the overall resident population has exploded from just under 2,000 animals in 1995 to a whopping 14,000 today. Only time will tell if the garbage is actually “good” for the birds, as dump-diving could lead the animals to accidentally ingest all sorts of plastic, toxins, and other hazardous material. Similarly, studies have yet to be conducted on the potential ecological impacts of the birds’ ditching their southern haunts.

In any event, the smorgasbord will eventually come to an end. The European Union Landfill Directive is gradually replacing open-pit trash sites with more environmentally friendly covered-waste processing facilities that storks can’t access. Here’s hoping those birds remember where to go when those trash sites disappear.

Beer Goggles

Australian jewel beetles don’t have great eyesight. In fact, when males go out looking to mate, they identify females by touch: Lady beetles have rows of brown bumps on their backsides. Think of it like beetle braille. For dating.

This tactile type of courting worked just fine for the bugs until the 1980s, when some Australian beer companies, such as Swan Brewery, began using brown bottles to hold their brew. Adorning the glass containers were with bumps surprisingly similar to those found on a female jewel beetle’s rump. Soon, scientists started noticing male jewel beetles trying to mate with beer bottles.

Scientists published an actual paper on beetle bottle bonking and the threat it posed to the insect’s overall population. After all, if too many male beetles spend a significant amount of energy trying to impregnate a piece of litter, the survival of the species could be in jeopardy. This is what biologists refer to as an evolutionary trap, when a beneficial trait (such as the insects’ dogged persistence to reproduce) becomes a disadvantage for the species’s survival. You see, once male jewel beetles find a bottle, they don’t let go, even when the consequence is baking to death beneath the Australian sun or becoming dinner for marauding ants.

Cheers are in order, however, for the beer companies’ taking pity on the insects. They simply changed their bottle designs so their products would no longer interfere with the bugs’ courtship. After all, losing an entire species over a few bumps on a bottle of suds would be tragic.

Argentinean kelp gulls have a nasty habit of dive-bombing whales for a taste of blubber. Dario Rodriguez/Flickr

A Hitchcockian Nightmare

News stories about whales getting entangled in fishing gear or beaching because of plastic in their guts seem to pop up every week. But for the southern right whales off the coast of Península Valdés, Argentina, garbage isn’t nearly as deadly as what it attracts: thousands and thousands of merciless, voracious kelp gulls—birds that apparently aren’t afraid to go up against a whale.

When whales surface to breathe or feed their calves, kelp gulls take the opportunity to peck into the mammals’ exposed flesh and strip away nutrient-rich blubber.

This wouldn’t be much of a problem if only a few gulls were doing this. But a 2011 study found that in just 15 years, Argentina’s gull population grew by 37 percent and colonized 10 new breeding sites. One possible explanation for this boom is the country’s growing fishery industry, which dumps all its discarded guts in open-pit landfills. With easy pickings from the landfill, gull parents were able to feed more chicks that survived to adulthood. Not all gulls feed on whales, but more gulls in total may simply mean more birds with a taste for blubber.

In the 1970s, just 2 percent of Argentina’s right whale mother-calf pairs showed evidence of gull-inflicted wounds. By 1990, the carnage had increased to 38 percent. By the 2000s, 99 percent of the pairs exhibited the pockmarks and gashes indicative of seagull strikes.

You may be thinking a few chunks missing here and there might not be a big deal when you are a 91-ton whale. Well, some scientists suspect the attacks are linked to stranding deaths. But perhaps more troubling is that the gulls target mother-calf pairs, probably because the young whales can’t hold their breath as long and spend more time at the surface. Scientists worry the biting could stress the calves so much that they become less likely to survive to sexual maturity. Other potential impacts include dehydration, impaired thermoregulation, and energy loss as a result of the need to constantly heal new wounds.

Fortunately for the right whales, whale watching is a huge moneymaker for the people of Península Valdés, and there’s an enormous amount of public pressure to solve the problem. Some landfills have already been closed by the outcry, but those that remain may need to implement new strategies, such as reducing the amount of the time the fish guts are available to the scavengers. Other proposed anti-gull countermeasures include playing gull distress calls and using other avian deterrents such as pyrotechnics, dogs, and propane cannons at the dumps.

A grizzly bear eagerly waits for a garbage truck to unload a feast at Yellowstone's Trout Creek dump in 1970. National Park Service

Yellowstone’s “Bear Shows”

Go to Yellowstone National Park today, and you’ll be lucky to spot a bear ambling along in the distance. Just a few decades ago, you could have seen hundreds at once—right at the park’s on-site landfill.

From 1890 to the beginning of World War II, one of Yellowstone’s most popular attractions was the nightly “bear show” down at the park dump. After decades of habituation, both grizzly and black bears would emerge from the woods each evening to feast on the rubbish generated by tourists. Park officials not only encouraged people to watch this fiasco of wildlife mismanagement, but they even constructed wooden bleachers for better viewing. Some nights, as many as 250 bears would show up to paw through trash in relative tolerance of the people around them.

I say “relative“ because incidents did occur. As the bears got used to humans, they got more gutsy. If they smelled food in a car, they busted in. If they thought a kid might cough up his or her candy bar, they made a swipe for it. Basically, the bears acted like bears.

The problem is, once a bear learns that humans are sources of food, the animal is set on a collision course with people that often ends tragically. The animal gets progressively less afraid of humans and more daring. Sometimes the bear stops caring about the picnic basket altogether and starts going after the person holding it. Then wildlife management has to come trap and relocate the animal or, worse, euthanize it. “A fed bear is a dead bear,” as they say.

By 1969, there were an average of 48 bear-inflicted injuries each year, and more than 100 instances of property damage. Finally, the park decided enough was enough and looked for ways to fix the destructive relationship between visitors and bears and get the animals back to eating berries and other natural foods. In 1970, Yellowstone closed its last dump, converted every garbage can and Dumpster to bear-proof models, and, perhaps most important, made it illegal for tourists to feed bears.

As a result, bear-inflicted injuries on people plummeted to around one per year. Best of all, the reduction in incidents led to a dramatic decline in the number of bears that had to be euthanized—from 33 black and four grizzly bears each year in the 1960s to an average of 0.4 black bear and 0.1 grizzly per year in the 2000s.

A baboon grooms its troop-mate in Kenya's Masai Mara National Reserve. RayMorris1/Flickr

The Baboon Revolution

Life in a baboon troop can be violent and tense. Dominant males run the show, and anything that displeases or threatens them is met with aggression. Their behavior sets the tone for the rest of the baboons.

But a curious thing happened in Kenya in the 1980s. When a tourist lodge started dumping its food scraps in a pile in the bush, the delicious heap created fierce competition among the local troop’s top males. Each day, the dominant baboons gathered to battle over the leftovers—that is, until some spoiled meat infected the males with tuberculosis, killing them off in one fell swoop.

Only those baboons that never had the chance to dine at the dump (subordinate males, females, and the young) survived, and interestingly, with the bullies now gone, nobody aggressively stepped up to fill the power vacuum, as one might have expected. Instead, the troop started to become really chill. According to the New York Times, “threats, swipes, and bites” were replaced with “affection and mutual grooming.” Also, new males were able to join the troop without risking death and dismemberment, and the newbies began behaving in a more peaceful manner too. What’s more, blood tests revealed lower levels of stress hormones in the lowest-ranking baboons when compared with lowly baboons from more traditional troops. Perhaps most remarkable of all, this cultural shift continues to this day, three decades later.

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Suffice to say, our garbage creates long-lasting and disruptive behavioral change in animals. The World Bank estimates that by 2025 we’ll produce 4.8 trillion pounds of it every year—and that’s just in cities. That is, unless we undergo a serious and long-overdue behavioral change of our own.


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