I watched the World War Z movie on Friday, and there were a couple of scenes which got be thinking about how zombies know where people are. I won’t discuss the scenes themselves in case you haven’t seen it yet (and I’d definitely recommend doing so), but I think this is an interesting question and it’s one I’ll explore in this post. As humans, we are primarily visual animals and, for most of us, our eyesight is the main sense we use to find out about the world around us. To a lesser extent, we also use sound while our remaining senses, smell, taste and touch, are usually only used once we’re already aware of what’s going on.
With zombies, things might be different, but this will depend on the type of zombies we’re talking about. If we’re talking about living humans infected with some sort of disease, sight and sound will still be the primarily senses by which they will detected uninfected humans. The more traditional risen-from-the-dead type zombies, however, will be differ. While in some cases, it appears that these dead zombies can still use their sight, as a rule they seem to be less visual creatures. In particular, in many cases the eyes are specifically portrayed as being clouded over (as an indicator of death), meaning that such zombies are probably limited to seeing changes in light intensity rather than any actual images. This means the best they can probably do visually is detect movement and orient towards it. In contrast, sound seems to be a much more important sense for dead zombies, and in almost all zombie scenarios, it’s unintended noises which alert zombies to the presence of humans. There’s the possibility that such zombies might also rely more on other senses such as smell to tell if humans are nearby but given the limitations of the human nose, this will, at best, be an imperfect mode of detection.
However, when it comes to zombies knowing where you are, there’s more to this than just whether zombies can tell you are there or not. In particular, there’s the question of how zombies tell the difference between normal humans and their fellow undead, since almost every scenario presented in films and books suggests that zombies don’t attack each other. Well, I think there’s two options here. The first is through something like smell. If we’re talking about infected type zombies, many diseases cause humans to give off specific odours, and indeed this is the basis for diagnosis in some cases, while if we’re talking about dead zombies, they may also smell different because of decomposition. This means zombies could tell who’s normal and who isn’t by their scent. This possibility is the basis of the scene from The Walking Dead where the characters cover themselves in rotting flesh from dispatched zombies to allow them to walk through the undead which surround them. However, this would only work across small distances and it seems even over longer distances, zombies can tell the difference between their brethren and normal humans, pursuing the former while ignoring the latter. This suggests zombies can also tell the differences through movements. In almost all cases, zombies, whether fast or slow, and humans move in very different ways and these differences may allow zombies to identify their prey from a great distance. This possibility is the basis of the scene in Shaun of the Dead, where the eponymous hero and his friends cover the last few yards to the Winchester through a mass of zombies by mimicking their movements.
Yet, this still leaves some apparent problems. For a start, zombies seem to be able to know where humans are from greater distances than they could possibly see, hear or smell them, and they seem to be drawn towards areas of human habitation from great distances and across landscapes where lines of sight are limited. How else could you explain the hordes of zombies which tend to descend on and surround the safe houses where humans are hiding? Well, I think the answer here is what I’ll call the ‘vulture’ effect. Vultures hunt by soaring on thermals and scanning the ground below them searching for dead or dying animals. Yet, they don’t devote all their attention to what is going on below; they also watch the other vultures in the skies around them. When one detects food and starts to dive towards the ground, those around them know what this means and do the same, and so do the ones around them and so on. This means hundreds of vultures spread over great distances can descend on a potential food supply within minutes. Zombies, I suspect, would operate in a very similar way and when they hear or see other zombies reacting as if they’ve detected humans, they will be drawn towards the same point. This means that once one zombie detects your presence, you are likely to find yourself inundated within a very short space of time as all the zombies within the local area follow each other towards your location. Interestingly, this concept is depicted in the World War Z book, where they drop soldiers into a location, have them form a square and keep shooting until all the zombies which are drawn to the location from all over the place by other zombies are dead.
So what does all this mean for your survival if you’re unlucky enough to find yourself caught up in a zombie apocalypse? Well, firstly, if even one zombie detects that you are there, the vulture effect is likely to come into play, and many other zombies are likely to be drawn to you very quickly. This means you will only have a very short space of time to escape before you’re surrounded on all sides by hordes of flesh-munchers intent on tearing you limb from limb. If you can’t get away fast enough, there’s an outside possibility that you might be able to disguise yourself in some way so that the zombies can’t tell you are a normal human. You could try mimicking their movements or covering up your scent, but without knowing exactly how they are telling human from zombie this will always be a very risky strategy. In addition, this will probably only work for dead-type zombies and it’s unlikely that the infected type will be fooled so easily. In this way, infected-type zombies are probably more difficult to evade than the dead ones. Either way, however, your best chance of survival is to make sure the zombies don’t find out you’re there in the first place, so keep quiet and keep still!
From the author of For Those In Peril On The Sea, a tale of post-apocalyptic survival in a world where zombie-like infected rule the land and all the last few human survivors can do is stay on their boats and try to survive. Now available in print and as a Kindle ebook. Click here or visit www.forthoseinperil.net to find out more. To download a preview of the first three chapters, click here.
To read the Foreword Clarion Review of For Those In Peril On The Sea (where it scored five stars out of five) click here.