Key Traits of Master Manipulators

What some humans and microbes have in common.

Posted Oct 10, 2020

These days one can't help but feel that we are under siege from an onslaught of external manipulation. This got me thinking about whether exploring manipulation in other species could provide any insights on how to buffer oneself from being unwittingly exploited.

Parasites are perhaps the greatest master manipulators in nature. Even though they are tiny, they wallop other species with their influence. The primary objective of a parasite is to increase its numbers and accomplishing this goal requires successfully manipulating its host. One of the easiest ways to do this is to induce behavioral changes that increase transmission of the parasite from one individual to another. For the host, this often results in some very odd behaviors while remaining completely unaware that its actions and brain are being hijacked.

Lxowle CC BY 3.0
Source: Lxowle CC BY 3.0

We tend to think danger is obvious but the reality is that it is often lurking just beneath the surface. A parasite called Toxoplasma gondii is one of the most ubiquitous, with infection rates ranging from 38-70% of animals such as bears, deer, domestic chickens, cattle, sheep, sea otters, and rabbits, to name a few. The easiest way to catch it is by consuming undercooked meat.

It is thought that one of the reasons this protozoan is so successful is that it causes unusual changes in behavior. For example, rats infected with this parasite lose their natural fear of new objects, new foods, and approach a predator instead of fleeing. The parasite needs them to get to its next host. The poor rat has no idea it has lost its ability to discern danger from safety. The precision of the parasite to change the behavior of rats has to do with brain lesions centered on the amygdala, which you can think of as the fear center of the brain. In this way, humans who excel at manipulation also prey on our sensitivities, fears, and emotions. They work hard at precisely undermining your confidence and make you responsible for their actions. 

But toxoplasmosis infection is just the tip of the iceberg when it comes to behavioral manipulation. There is a little worm that causes crickets and grasshoppers to behave very strangely indeed. The hairworm lives as a youngster inside arthropods (insects, spiders, etc.), but is free-living as an adult in rivers, lakes, and streams. It reproduces in water environments, but develop inside non-aquatic invertebrates. This sets up a conundrum: How to transition from one environment to the other without dying? It seems the clever solution is to make their non-water seeking insect host desperately search for water and dive right in. This is in direct opposition to the best interest and survival of the cricket or grasshopper because they can't swim. It is vital that the hairworm succeeds, otherwise it will wither and die. This is also a trait often found in people that manipulate others: They need you to satisfy all their needs.

Things get stranger and stranger as we look at moths—gypsy moths in particular. This is really the stuff of nightmares and science fiction. Imagine an evil virus laughing sadistically in the background. Like butterflies, moths go through several stages of development. The first is as an egg placed on the underside of a host plant leaf. But gypsy moths are less particular: They will lay their eggs on tree trunks, tree branches, anywhere that provides the tiniest bit of shelter. The eggs are laid in clusters and the larvae hatch in the spring. Once they hatch, the larvae go through several stages, molting (shedding their outer covering) as they grow. This larval stage is what we know as caterpillars. When they are ready to pupate it can take several days to two weeks—but this wonderful process is rudely interrupted in those individuals unfortunate enough to catch a virus. A baculovirus, to be exact.

Moth larvae infected with this type of virus become like zombies on a mission to climb and climb to the treetops. This phenomenon is well known and was described in silkworms as wilting disease. The phrase “Wipfelkrankeit," or tree-top disease, has also been used. Why are they induced to perform this odd behavior? Apparently they climb to the tops of the trees just before they die and begin to liquefy. Yes, you read that correctly, liquefy. The end result is excellent dispersal for the virus by raining down on the unfortunate caterpillars below. In the ‘liquid’ of the infected, now deceased, caterpillar, are millions and millions of virus particles. We are also not immune to others who are being exploited and manipulated. Human manipulators cultivate and create scenarios, drama, and hostility between others to ensure dispersal of their toxic messaging and distract from the behavioral control they are exerting.

There are numerous ways that parasites can infect, manipulate, and control their host. The crickets, grasshoppers, moths, and rats become simply vehicles for the parasites to achieve their goal. We humans should pay attention to whether we are being used to further someone else's agenda. 

João Araújo CC BY 2.0
Source: João Araújo CC BY 2.0

Unlike this poor ant that, when infected with a fungus, becomes a zombie, walks away from the safety of its nest, climbs up along a leaf, and grips it with a locked jaw until the fungus explodes out of its brain, we can question our beliefs, re-examine our positions, and integrate new information. If you find yourself infected with beliefs that run counter to your survival and that of your fellow humans, you may discover upon closer inspection that you have been expertly manipulated by a human parasite.

Facebook image: FunKey Factory/Shutterstock


Berdoy, M., Webster, J., and Macdonald, D. 2000. Fatal attraction in rats infected with toxoplasma gondii. Proceedings Royal Society B. 267:1591–1594.

Biron, D.G., Marché, L., Ponton, F., Loxdale, H.D., Galéotti, N., Renault, L., Joly, C., and Thomas, F. 2005. Behavioural manipulation in a grasshopper harbouring hairworm: a proteomics approach. Proceedings Royal Society B. 272:2117-2126 (doi:10.1098/rspb.2005.3213).

Hughes, D.P., Andersen, S.B., Hywel-Jones, N.L., Himaman, W., Billen, J., and Boomsma, J.J. 2011. Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection. BMC Ecology 11:13 (doi:10.1186/1472-6785-11-13).