And We Meet Again!
As you read the words I have typed, we are engaging in a type of communication. Due to technology, we have many forms of communication that were unfathomable to our ancestors such as text messages, emails, and online blogs such as these. Inarguably, communication is extremely important for our everyday lives and the continuation of our species. Other animals, too, depend on successful communication with each other and have varying systems of communication. While walking to class we may hear birds chirping and not realize the importance of their songs. In fact, forms of communication are not as simple as one may assume. Many factors come into play that allows the environment of a species to guide the evolutionary history of a particular system of communication.
Endler sums up communication nicely saying that animal communication systems have evolved so that individuals can make decisions based upon the behavior, physiology or morphology of others (Endler, 215). However, what are the factors that guide the evolution of such systems? In my blog, I will discuss the following factors in more detail: those that affect the quality of the received and processed signal, those that affect how the signal is generated and emitted, and those that affect how it fares through transmission through the medium. In essence, the “factors that affect signals [. . .] constrain or bias the direction of evolution of signals and signaling systems” (Endler, 215). The phylogenetic history of a species works hand in hand with the geological time a clade spends in the signaling environment to produce a specific type of signaling design.
I argue that the production of a communication signal is of most importance. Why? Because regardless the quality of the receiving system, if the signal produced is not of good quality, then the effectiveness of communication is automatically destroyed. For example, if you have excellent ears but I cannot form coherent sentences, the information does not get past my lips no matter how well you can hear. Many things affect the generation of a signal such as the physics, biophysics and chemistry of the producing signals for example. If it becomes physically impossible for a signal to be produced, then that mode of signaling will not be successful and therefore will not be selected for. Instead, the physical structure of the signal evolves to increase the efficacy of transmission of the message between emitter and receiver (Endler, 215). Efficacy, however, is not as clear cut as it may seem. If a signal is energetically costly, one may assume that that form of communication will be lost or weakened. However, if there are beneficial trade-offs between the present and future fitness for that species, then there can instead be a bias for things like the time, place, or age of the signaling, and that form of communication can exist and continue to evolve.
There is another trade off that is important: that between the amount of information in a signal and the clarity of the signal. (The two components together are referred to as the “quality” of a signal.) An increase in information is usually achieved via an increase in signal complexity or density. However, as the complexity increases, it becomes difficult to prevent “noise” or confusion with both the production and interpretation of the signal. This brings us to the topic of transmission through the medium through which the signal travels. Environmental constraints can favor signaling during times and places at which things like distortion, attenuation, blocking, absorption, reflection, and refraction are minimized. These effects are exacerbated if the signal is complex with a high information density, or when information is transmitted at a high rate (Endler 217).
The environment can affect signaling both in a direct or an indirect manner. For example, the spatial and temporal variation of predation, or climatic and microenvironmental conditions can directly favor signals that maximize emission and transmission of communication signals (Endler, 216). What I find interesting, however, are the indirect effects environment can have. Endler exemplifies this nicely, “some environmental factors do not directly affect the signals but do affect the evolution of the breeding system [. . .] If the breeding [is] limited to a small range of environmental conditions, then this will bias the evolution of signals and signaling behavior to work better under those more specific conditions (Endler, 216).
The reception of a signal is also not as straightforward as it seems. The current adaptive state of the individuals receptor play a huge role in what can and cannot be received. For example, the present state of an animal’s eyes and the information sent to the brain depends on how much light is in the environment. If the animal is in a microenvironment with high light intensity, its visual system will be less effective at distinguishing between darker pattern elements than between lighter pattern elements (Endler, 218). However, if an animal is in a dark microenvironment, it will be less able to distinguish between lighter pattern elements than between darker pattern elements (Endler 218). In essence, “a given receptor does not always transduce signals into neural outputs in the same way,” and instead depends on the environment the signal is sent through.
According to Endler, “the evolution of a communication system involved three suites of traits: the signals, the sensory and cognitive systems used to receive the signals, and the behavior associated with the signaling” (Endler, 220). Because they are all interrelated, they tend to coevolve, and an effect on one will cause an effect on the other two. Communication is not just about one factor or the other. Instead, it is a network that balances these three main components. To sum up this blog post, “the direction of this joint evolution [is] set by the biophysical and energetic conditions of signal emission, environmental conditions which favor clarity of reception, neural conditions which favor the processing of certain kinds of signals or signal components, and the strategies behind signal emission, detection, discrimination, and decision making” (Endler, 222).
This post is just an introduction to animal communication, to provide context and a better understanding of the following blogs. As the quarter unfolds, what was discussed in this blog should be kept in the back of the mind. Animal communication may be taken for granted, however, just in this introduction, we’ve learned that it is far from simple. Its many intricacies must be appreciated when learning about the communication form in different species. Each communication system had an advantage for the species and the environment that species evolved in.
The following is a table of different modes of communication that animals are known to participate in:
The following is a table of some factors that affect the efficacy of communication systems:
Endler, A. J. (1993). The evolution and design of animal signaling systems. Biological Sciences, 340(1292), 215-225.