Living off something else

1. 1

   Stop 1 of 5. Ecology

   Start with the version everyone pictures

   Begin here because the popular image of predation is the thing the rest of the route has to be measured against — and because it is already wrong in a useful way. A hunt is a sequence, most attempts fail, and the interesting part of being a predator is not the kill but the cost of everything before it. Getting that straight makes the later categories legible: they are all different answers to the same problem of getting energy from something that would rather keep it.

   Read PredationWhere hunts have actually been counted, most of them fail. The famous capabilities — the speed, the venom, the bite — are rarely what decides it.
2. 2

   Stop 2 of 5. Fungi

   Then remove the animal from the predator

   Second, because it breaks the assumption before it hardens. Soil fungi hunt: they detect nematodes by intercepting the pheromones the worms use on each other, build traps only when prey is about — including a ring that inflates in a tenth of a second — and digest what they catch. No muscles, no nerves, no sense organs. Predation is a relationship, not an animal behaviour, and reading this early stops the rest of the route being about teeth.

   Read Predatory fungiA fungus with no muscles closes a ring around a worm in a tenth of a second — and it knew to build the ring because it was listening to the worms talk.
3. 3

   Stop 3 of 5. Ecology

   Now sort the categories properly

   This is the page the route is built around. Predation, parasitism, parasitoidism, herbivory and scavenging differ in how many others are used and what becomes of them — not in severity — and the parasitoid is the case that proves it, belonging to neither of its neighbours. The page also puts two famous manipulators side by side: the jewel wasp, which genuinely operates on a cockroach’s brain and is barely known, and the zombie-ant fungus, which is not in the ant’s brain at all and is famous everywhere.

   Read Parasitism and predationA predator eats many and kills fast. A parasite keeps its host alive. A parasitoid does one of each, which is why it needed its own word.
4. 4

   Stop 4 of 5. Ecology

   Take the work instead of the body

   Fourth, because it is the category that shares a word and shares almost nothing else. Nothing lives in the host’s body; what is taken is the incubation and the weeks of feeding. That changes the defences from immune responses into decisions — and the decisions turn out to be good ones. A host accepting a well-matched egg is usually described as fooled, and rejecting risks destroying its own egg, so where cuckoos are rare, accepting is the choice that pays.

   Read Brood parasitismA host that accepts a well-matched egg is not necessarily fooled. Rejecting risks destroying its own — and where cuckoos are rare, that is the bigger mistake.
5. 5

   Stop 5 of 5. Ecology

   End where both sides gain, and neither is being kind

   Finish here because it is the relationship the other four make sense of. Mutualism is not cooperation: the cleaner wrasse would rather eat its client’s mucus than its parasites, so the partners want different terms and honest behaviour has to be produced rather than assumed. What produces it, at least in part, is the queue — cleaners behave better when another client is watching. After four relationships defined by what the other organism loses, the useful surprise is that the one where it loses nothing still contains a conflict.

   Read MutualismA cleaner fish would rather eat its client’s mucus than its parasites. Mutualism is not friendship — it is an arrangement that needs holding in place.

Last reviewed 2026-09-04. All guided journeys