During this five week blogging period, we have discussed insects with cognitive maps and landmarks, birds with magnetoreception, mammals with path integration in the absence of landmarks, and fish with hydrostatic pressure. For our final blog post, we will be taking a look at the similarities and differences between all these different species and their navigation types, and how they relate to each other.
Our first post discussed various insects and their ability to form cognitive maps using the locations of specific nearby objects (also known as landmarks) to find their way to a food source or back to their nest. As stated before, some insects like ants do not have a very large optic lobe, so they do not use landmarks. Bees and wasps are the most well known sight oriented insects that use this ability. One thing that was not mentioned in this post, but is obvious to any person who has ever been in an unfamiliar place, is that humans also have this ability. How many times have you looked at a specific building, tree, body of water, or really anything, and used the location of that object to know where you are? That is the exact same ability the sight oriented insects are using! However, unlike insects, humans (along with other mammals) are able to navigate without the use of landmarks, and instead only the motion of oneself, using the ability discussed in the fourth post, known as path integration. As path integration is generally controlled by the hippocampus, it is obvious that insects do not have a hippocampus developed like that of mammals in order to have this ability. Most insects do not have the appropriate “place cells” or “place fields” that allow mammals to use path integration. The only insect that has been shown to use path integration is the honeybee, with its famous “waggle dance” that communicates the location of a food source to other members of the hive.
This doesn’t necessarily mean humans and other mammals are the “best” at navigation. Two of our blog posts discussed navigational abilities that humans do not have; magnetoreception and hydrostatic pressure sensing. The main reason for humans lacking these is not so much neural as it is anatomical. Magnetorecepting birds have structures made of magnetite crystals located in their beaks, which are widely theorized as being responsible for their ability to sense the Earth’s magnetic field, and therefore use it to navigate. As you are probably aware, humans do not have beaks, or any sort of magnetite crystal structures to sense magnetic fields with. The same applies to hydrostatic pressure sensing. Fish have an organ called a swim bladder, which not only keeps them buoyant, but enables them to sense pressure changes, which they use in order to measure their depth in the water. Humans and most mammals (besides whales and dolphins) are not aquatic, and therefore do not have a swim bladder, so they have no organ that can sense the pressure changes, besides feeling pain when they are crushed under large amounts of water if they dive too deep, which rarely happens to any animal, besides humans that are trained divers.
From an evolutionary point of view, most mammals survive long enough to reproduce without the need to dive deep enough to sense pressure or use magnetic fields to navigate. This doesn’t mean any of these animals, be it the birds, fish, insects, or mammals, are any less or more “advanced” than one another. They are all equally adapted to their environments and niches. All in all, animals have many amazing and unique methods of navigation.
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