Waste Not

Last week, we dug into the season of decay, specifically as it relates to trees and the turning of their leaves here in the Northern Hemisphere. Elsewhere in the world, spring is in bloom—a reminder that life is always hanging in the balance between growth and decomposition. Nowhere is that more readily apparent than in the food web, what we call the cycle in which energy and matter move through organisms all over our planet. This week, we’re looking at an integral and often overlooked group that helps maintain that web: scavengers.

Scavengers are organisms whose diets consist mostly of rotting biomass. Most scavengers that we’re familiar with are carnivores, meaning they feast primarily on carrion (decaying meat). Birds, mammals, insects, and even sea dwellers can be scavengers. They play an important role in the trophic system by ensuring that their habitats do not fill up with disease-ridden carcasses, instead digesting and recycling them back into nutrients that ultimately benefit their ecosystems. What others deem dead and unsuitable, scavengers see as life-giving and far from lost.

Some scavengers, like vultures, feast exclusively on carrion because it’s easier to come by. And evolution has granted them a number of extraordinary means to do so. Most of these birds possess exceptional senses of sight and smell so that they can detect deteriorating matter while soaring safely in the sky. Bearded vultures eat mostly bones, dropping them from the sky so they break apart. And if you’ve ever wondered why vultures are bald, it’s so that infected flesh they feast on doesn’t end up in their feathers where they might cause harm. Through every biological adaptation, they have learned to nourish themselves without suffering.

Speaking of disease and infection, that’s what makes these creatures so marvelous: their ability to remain unscathed when feasting on the dead. Vultures have highly potent digestive acids in their stomachs—ten times as powerful as ours—which kill most of the harmful pathogens they ingest. Scientists don’t yet understand how they survive the initial ones that slip through, but they’ve observed that the more exposure these birds have to them, the more immunity they build. The more they encounter that which might harm them, the stronger they become.

Meanwhile, burying beetles have developed their own unique approach to eating carrion and keeping themselves safe in the process. As their names suggest, these insects bury small, dead vertebrates such as birds and rodents underground, where their larvae can safely feast on them. And rather than their digestive enzymes protecting them from bacteria after ingestion like vultures, burying beetles coat their prey in antibacterial microbes before eating them. From the putrid, they are able to protect the health and vitality of generations to follow. 

Other animals that scavenge, such as hyenas, wolves, and lions, do not dine solely on the dead. While they prefer fresh meat, they supplement their hunting with scavenging in order to widen their food sources and ensure that they are always fed. The fact that these creatures live in packs presents another benefit as well. As they socialize by grooming, playing, and sharing food, they pass along small doses of germs, which help them develop herd immunity to the types of toxins they may encounter from scavenging. Reducing waste doesn’t just help one, but the many. 

I don’t think it’s a coincidence that there’s such a stigma around carrion creatures in a culture where we are unwilling to think about waste. We fill our dead with chemicals, depriving our ecosystems of vital nutrients, and shy away from staggering statistics of species decline. We throw our garbage to some mythical “away,” including uneaten food that corrodes and produces methane in landfills. We deem perfectly viable materials unfit for use, an excuse to consume more. Scavengers might just be the most important teachers we have now: living reminders of how resourceful nature can be, and how much we can still unspool from the rotten.