In the animal world, which includes people, there are many methods for transmitting information to each other. It can be an energetic dance, like the birds of paradise, talking about the male’s readiness for procreation; it can be a bright color, like the Amazon tree frogs, talking about their toxicity; it can be a smell like a dog’s, marking the boundaries of the territory. But the most common for most developed animals is acoustic communication, that is, the use of sounds. We even teach our children from the cradle who and how they say: a cow – moo-moo-mu, a dog – woof-woof, etc. For us, verbal, that is, acoustic communication, is an integral aspect of socialization. The same can be said of other representatives of the fauna. Scientists from Hainan University (China) decided to look into the past to understand the evolution of acoustic communication. How widespread is acoustic communication among animals when it originated and why became the dominant method of transmitting information? We learn about this from the report of the researchers. Go.
At this stage of evolutionary development, many representatives of the fauna have completely introduced acoustic signals into their rhythm of life. The sounds made by animals are used to attract a partner (birdsong, croaking toads, etc.), to detect or disorient the enemy (a scream from a jay informing the predator that it has been detected and the ambush will not work, so it’s better to retreat), to transmit information about the availability of food (hens, finding food, make a characteristic sound to attract the attention of their offspring), etc.
Male One-Bell Ringer (Procnias albus) emits a mating cry of 125 dB (jet engine – 120-140 dB), while being the loudest bird on the planet.
The study of acoustic signals and their evolution has been carried out for a long time. The data obtained during such works contribute to a better understanding of how people use sounds and, therefore, how different languages were formed in different regions of the planet. However, such studies did not affect the very origin of acoustic communication as a phenomenon. One of the fundamental questions that no one has answered so far is – why did acoustic communication arise?
There are many questions that need answers. Firstly, what environmental factors influenced the emergence and formation of this type of information transfer? Secondly, was acoustic communication related to speciation, i.e. Does it help in spreading the species and in preventing its extinction? Thirdly, is the presence of acoustic communication evolutionarily stable after its development? And finally, did the acoustic connection develop in different groups of animals in parallel, or does it have a common ancestor for all creatures?
The answers to these questions, according to the scientists themselves, are important not only for understanding the acoustic connection as such, but also for understanding the evolution and behavioral changes in animals. For example, there is a theory that the habitat strongly affects sexual selection and communication in some animal species. It is difficult to say whether this theory is applicable to signal generation, but it is quite real. Scientists also recall that Darwin also said that it is sound signals that play an important role in the formation of pairs in some species. Consequently, acoustic signals affect speciation.
In this work, the researchers decided to consider the evolution of sound signals in tetrapods, using the phylogenetic approach (identifying the relationship between different species). The main emphasis is placed on the origin of acoustic communication, and not on its form or functions. The study used data from 1799 different species, also took into account the factor of daily behavior (species with day and night activity). In addition, a study was conducted of the relationship between acoustic communication and the degree of diversification of species, i.e. their prevalence through a speciation-extinction model. Phylogenetic conservatism was also tested in the presence of an acoustic connection between species.
Among tetrapods, most amphibians, mammals, birds, and crocodiles have acoustic communication, while most scaly and turtles do not. In amphibian ranks, this type of information transfer is absent in Cecilia (Caecilian), but some species have salamanders and most frogs (39 of the 41 species under consideration). Also, acoustic communication is absent in snakes and in all families of lizards, except for two – Gekkonidae (gecko), Phyllodactylidae. In the order of turtles, only 2 out of 14 families have acoustic communication. It is expected that among the considered 173 species of birds, acoustic communication was in all. 120 of 125 mammalian families have also demonstrated this feature.
Salamanders have an amazing regeneration and are able to regrow not only the tail, but also the paw; salamanders, unlike many of their relatives, do not lay eggs, but are viviparous; one of the largest salamanders – Japanese gigantic – weighs 35 kg.
Summing up these data, we can say that acoustic transmission of information is present in 69% of representatives of tetrapods.
Table No. 1: percentage of owners of acoustic information transfer among the four-legged species under consideration.
Having established the approximate distribution of acoustic communication among species, it was necessary to understand the relationship between this skill and animal behavior (night or day).
Among several models describing this relationship for each species, a model was selected that is suitable for the average description of the relationship of acoustics and behavior for all species. This model (table No. 2) shows all the possible pros and cons of a similar skill for both animal behaviors.
Table 2: Analysis of the relationship between acoustic communication and animal behavior (day / night).
A clear dependence of acoustic communication on behavior was established, as well as a balanced interdependence. However, curiously, no inverse relationship was found – behavior on acoustic coupling.
Phylogenetic analysis showed a close conjugation of acoustics and nightlife (table No. 3).
Table 3: Phylogenetic analysis of the relationship between acoustic communication and day / night lifestyle.
An analysis of the data also showed that the presence of acoustic coupling did not affect the rate of diversification in the phylogeny of tetrapods. Thus, the average diversification indicators (speciation – extinction; r = 0.08 events per million years) were the same for species lines with acoustic coupling, and for lines without this skill. Therefore, it can be assumed that the presence / absence of acoustic communication had practically no effect on the prevalence of a particular species or on events associated with its formation or extinction.
Image No. 1: a graph of the evolution of acoustic communication among various tetrapods.
Scientists suggest that acoustic communication most likely developed independently in each major group of tetrapods, but its origin was ancient in many major treasures (~ 100-200 million years ago).
For example, acoustic communication developed quite early in the phylogeny of the order of tailless amphibians (Anura), but it is completely absent in the sister group for all other living frogs from treasures containing families Ascaphidae (tailed frogs) and Leiopelmatidae (liopelms).
Liopelms are endemic to New Zealand and are considered long-livers among frogs – males live up to 37 years, and females up to 35 years.
In mammals, as in frogs, acoustic communication arose about 200 million years ago. Some species lost this skill during evolution, however, the vast majority brought it to our days. An exception can be considered birds, which, apparently, are the only ones who did not part with acoustic communication throughout the entire period of evolution.
It was found that acoustic communication was present both in the most recent ancestor of living birds and in the most ancient ancestor of living crocodiles. Each of these ancestors is about 100 million years old. It can be assumed that acoustic communication was also present in the common ancestor of these two treasures, that is, another 250 million years ago.
some species of gecko-like can make the most unexpected sounds for a lizard – barking, clicking, tweeting, etc.
In scaly ones, acoustic communication is rare enough, which may be due to a more narrowly directed appearance exclusively in creatures with a nocturnal lifestyle, such as gecko-like (Gekkota). Relatively recent evolutionary changes have led to the emergence of acoustic communication in some phylogenetically isolated species of salamanders and turtles.
Summarizing all the above results, it is possible to state with almost complete certainty that the development of acoustic communication is in one way or another connected with the night lifestyle. This confirms the theory of the influence of ecology (the environment) on the evolutionary features of the species. However, the presence of acoustic communication has virtually no effect on the diversification of the species on a large time scale.
The researchers also found that sound communication appeared about 100-200 million years ago, and some species of tetrapods carried this ability throughout this time with virtually no changes.
It is worth noting that the presence of acoustic communication for nocturnal creatures, although it is a clear plus, it does not have a negative effect on the transition to a daytime lifestyle. This simple fact is confirmed by the fact that many previously nocturnal species, having switched to the daily way of life, have not lost this ability.
Sound communication according to this study can be called the most stable evolutionary trait. When this ability manifested itself, it almost never disappeared during evolution, which cannot be said about other types of signal transmission, such as bright color or unusual body shape, plumage or coat.
According to the researchers, their analysis of the relationship between acoustic communication and the environment can be applied to other evolutionary traits. It was previously believed that the environmental impact on signal transmission methods is limited by differences between closely related species. However, based on the above work, it can be confidently stated that the fundamental types of signal transmission also change in accordance with changes in the environment of the animal.
A great demonstration of the incredible variety of sounds that make different types of birds.
Sometimes animals make very unusual and funny sounds.
Thank you for your attention, stay curious and have a great weekend everyone, guys! 🙂
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