For many urban dwellers, large animals like bears or tigers are only glimpsed during a visit to the local zoo. Or they’re viewed on the zoo’s live camera doing tame activities like sunning themselves or enjoying an icy treat on a warm day.
As they aren’t part of everyday life for many people, the idea that these animals could be man-eating predators can seem hard to fathom. One anthropologist described it as a “bizarre realization” for people to consider they aren’t always at the top of the food chain.
Humans aren’t often prey, but that doesn’t mean we occupy the top spot on the food chain. Instead, scientists have been using global data to analyze typical consumption habits. They’re finding that not only are humans not at the top of the hierarchy — we aren’t even close.
The basic idea of the food chain is a who-eats-who type of mapping with the ultimate predator at the top of the hierarchy. Starting in the 1940s, scientists began developing a more complex system involving trophic levels that divided all plant and animal life into distinct categories of plant life, herbivores, primary and secondary carnivores.
The study of trophic levels (called trophodynamics) allowed scientists to think about the relationship between these various groups, how they functioned and whether one group would flourish or fail without the others.
In recent years, the use of sophisticated software has allowed scientists to develop a deeper understanding of trophic levels. Most consumers eat more than one type of prey, and new approaches to analysis have allowed scientists to keep these varied diets in mind.
Scientists now consider how various food chains are connected to form food webs. In some instances, different trophic levels have greater dependencies with each other. But what matters in some food chains might not be significant in others.
And what dominates in some food webs might not be present in others. These complexities help explain why humans aren’t very high up in the food chain.
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Humans are not in the same category as fierce hunters like orcas and polar bears. We’re actually at the same trophic level as anchovies and pigs.
In general, scientists typically use five trophic levels to describe food chains.
Trophic level one (primary producers) is reserved for living creatures that produce their own energy and don’t consume others. Plants, for example, would be in category one because they use sun and water to create their own energy.
Level two (primary consumers) would be creatures that eat level-one life forms. Cows, for example, munch exclusively on plant matter. Level two also includes omnivores that have a diverse diet involving fruits, vegetables, grains as well as some meat. Humans, bears, raccoons and pigs would all be examples of level-two eaters.
Trophic levels are incremental, which helps explain how humans can eat pigs yet exist in the same category in the food web. Those increments range from 1 to 5.5. Even though humans eat pigs, our substantial need for non-meat items means we are also categorized in level two, albeit higher than exclusive herbivores.
Secondary consumers are typically carnivores or omnivores, meaning they primarily eat other animals, though they may also consume some plant material. This category would include raptors that feed on birds in level two.
Tertiary consumers represent the next stage in the food chain hierarchy, and they include carnivorous species that prey on other carnivores, such as killer whales. Orcas, for instance, are tertiary consumers known for hunting seals and sea lions, which are carnivores that feed on fish, squid and octopuses.
The highest level, known as quaternary consumers, is reserved for apex predators like polar bears or orcas who do not have natural predators within their typical habitat. This doesn’t mean, however, that an apex predator might not be consumed by another. The incremental quality of trophic levels ranks these animals at a 5.5 to describe instances in which apex predators branch outside their typical diet and consume another creature at the top of the food chain.
Humans are sometimes called apex predators, which means they occupy the top position in the food chain and have no natural predators. While humans often exhibit characteristics of apex predators, some scientists do not classify them as such.
In 2013, a team of French scientists set out to answer where exactly humans were on the food chain or what was the human trophic level. They used the standard definition of trophic levels that ranged from one to five.
The research team found that humans are rungs below apex predators. They used national data from the U.N. to look at the food supply for 98.1 percent of the world’s population from the years 1961 to 2009.
Humans depend on a varied diet, including fruits, vegetables, grains and proteins. Proteins typically come from level-two animals such as chickens, cows, fish and pigs. As a result of this variety, humans aren’t that much more above the level two items we consume. The research team found the human trophic level ranged from 2.04 to 2.57, with an average of 2.21.
A score of 2.21 puts humans at a similar numerical level as anchovies and pigs. Even countries such as Iceland, which had a higher meat consumption than other places, still had a score well below three.
Although a person might look at zoo animals and think a lion or a bear is at the top of the food chain, these large predators don’t exist in many ecosystems. Thus, the top of the food chain is relative to a specific ecosystem.
Starfish, for example, do not live in freshwater and aren’t part of a trophic level in ecosystems like the Great Lakes.
Similarly, human development and agriculture have disrupted some ecosystems’ food chains. In urban and suburban areas, the displacement of top predators has allowed other animals to claim the top spot. Raptors, for example, are often the primary predators.
So even though humans aren’t close to the top of the food chain, they also tend to live in ecosystems where man-eaters are only found in zoos or webcams.