A visit to the brass department

This week we get an insight to a section of the orchestra that is close to my heart, the native Australian Marsupials. Marsupials have a variety of amazing vocalisations that are completely unique and unusual in their own way. From the bellow of the male koala to the vocalisations of the Northern quolls, these animals are definitely a show stopper and the orchestra would not be the same without them.

Firstly the northern quolls, these animals have different frequencies in their calls (Atikin, 1994). A study was conducted on these animals which recorded the different vocalisations of the animals and then they used these recordings to record the response of other quolls to the initial recording (Atikin, 1994). This study found that the vocalisations of a common adult have the most energy at the lower end of the hearing range for these animals and that the frequencies that are dominant in the isolation calls of the pouch-young lies close to the best frequency of hearing (Atikin, 1994). They found that one role of the low frequency part of their hearing concerns the recognition of adult conspecifics (Atikin, 1994). They found that the mid- frequency range is most important for the detection of the pouch- young and the upper range frequencies may be concerned with predator/prey detection (Atikin, 1994).

Like the quolls, the koalas have a range of vocalisations which are used in different circumstances and at different stages of life.  The koala vocalisations are classified as follows: a squeak, the basic call of the joey; squawk, a sign of mild distress or aggression; low grunt, the response to very weak stimulus; harsh grunt, used by males when fighting (Smith, 1980). There are a couple of vocalisations which are made by the female and they include; the snarl, wail and scream (Smith, 1980). The bellow is the most common call for a male in breeding season as it is their mating call and it consists of a long series of deep, snoring inhalations and belching exhalations (Smith, 1980). The females produce their own version of this mating call but I generally more softly (Smith, 1980). To hear the extent of a males mating call, take a look at this video.

https://www.youtube.com/watch?v=FsOxk_ThKio

This group of animals has a lot more musicians that I have not mentioned here today and they too have an amazing range of vocalisations.

Works Cited

Atikin, L., 1994. Hearing, vocalisation and the external ear of a marsupial, the northern quoll. comparative neurology , 349(3), pp. 377-388.

Smith, m., 1980. Behaviour of koala: vocalisations. australian wildlife research , 7(1), pp. 13-34.

Mammal Vocalisations and the Mechanisms Behind them

Before we enter the word of mammal sound and rhythm we need to understand the workings of how they make the sound and the rhythm. All of mammal vocalizations can be understood with the framework of nonlinear dynamics (Wilden, 1998). This nonlinear process is laryngeal sound production (Wilden, 1998).The driving force of a mammal’s vocalization is airflow which generally comes from the lungs and which is then relayed to the larynx via the bronchi and trachea (Wilden, 1998). When the vocal folds are set into vibrations by the combined effect of subglottal pressure this is known as a phonation (Wilden, 1998). In having a great variety of sounds there can also be complex interactions of aerodynamic and biomechanical forces can be induced (Wilden, 1998). Basically, the fold tissues and the vocal fold collisions create the essential nonlinear characteristics of the sound generating system (Wilden, 1998). To understand the complexities in nonlinear process, a brief look into the linear systems will help with the understanding.

In a linear process only damped oscillations are possible (Wilden, 1998). There is already a manifestation of nonlinear behaviour which is sustained by self-sustained vibrations of vocal folds (Wilden, 1998). The nonlinear system can generate complex outputs without any random external input into the vocal apparatus (Wilden, 1998). In contrast, a linear system, any irregularity must be assigned to random components (Wilden, 1998).

Now back to nonlinear systems and its dynamics. Within the dynamics of the nonlinear system there are two major components; Attractors and bifurcations. The attractor can be defined as the sound generation at constant parameters (Wilden, 1998).So the vibrations of the vocal folds are very fast with periods in order of milliseconds (Wilden, 1998).  The variation in the muscle tensions and lung pressures are much slower, therefore the parameters can be seen as constant during a steady sound generation (Wilden, 1998). The attractors are the corresponding geometric object in phase space (Wilden, 1998).  There are three attractor types; steady state, limit cycle and Torus (Wilden, 1998). The other component is Bifurcations.

The bifurcations are essentially the transitions due to varying parameters (Wilden, 1998). The bifurcations are also defined as the abrupt changes of attractors for varying parameters (Wilden, 1998). There are a couple of bifurcations which are most relevant to mammal vocalizations; Hopf bifurcation, Subharmonic Bifurcation and secondary Hopf Bifurcation (Wilden, 1998). These nonlinear dynamics are the basis that can be used to understand and interpret the phenomena in mammal vocalization (Wilden, 1998). With the basic understanding of the mechanics behind mammal vocalization we can now explore the world of sound in the mammal world.

Works Cited

Wilden, I., 1998. Subharmonics Biphonation, and Deterministics Chaos in Mammal Vocalisation. Bioacoustics: the international journal of Animal sound and its recording , 9(3), pp. 171-196.

Reptiles can make Sound too

Generally, when people think about sounds that animals make them immediately think of the cute and cuddly animals as well as generally the elaborate sounds of a bird but no one really thinks about the reptiles. This could be because they are not as memorable as some of the other animals or I could also be because people rarely associate sound with these animals. Now in actual fact certain reptiles do in fact make sounds like the rest of the animal kingdom.  Turtles and tortoises are two members of the reptilian world who produce sound.

Several studies have shown that one particular tortoise’s species produce roars and bellows as a part of their mating and courtship rituals (Campbell, 1967).  It has also been noted that several other species produces sounds during courtship and under other circumstances (Campbell, 1967). The sea turtle in particular has been credited with a ‘mercy cry’, which is like a piping sound, roars and grunts of anger in times of distress (Campbell, 1967). Other authors have also noted that three species make a grunting sound while mating and one of those species has also been recorded with making a “low piteous cry” and a “short rasping call” (Campbell, 1967). These are just some examples they in particular, our turtle and tortoises species, have been recorded to be making sounds in one aspect of their life or another. Now our snake friends do actually make noise, just not in the most conventional sense.

Our snake friends, the rattle snake are the most notorious snake for making an amazing sound with its tail. These 6 species of rattlesnake all show some species variation in their rattle patterns (Fenton, 1990). The snake individuals there is a variation in the low frequencies and the actual bandwidth of the snakes tail (Fenton, 1990). There has been an evolution of the snake’s medium frequency rattling and the broad band sounds over time (Fenton, 1990).  The purpose of the rattling is a signal which has been designed to attract the attention of other animals whose response will reflect the hearing characteristics and pervious experience of that animal (Fenton, 1990).  To see the rattle snake in action, take a look at this video: https://www.youtube.com/watch?v=XkyKliH1X3c. As you have seen here there is actually a lot of sound which occurs in the reptile world and their sounds should be admired as much as any other animals sound.

Works Cited

Campbell, H., 1967. Sound production in two species of tortoises. Herpetologica , 23(3), pp. 204-209.

Fenton, B., 1990. Why Rattle Snake ?. Herpetology , 24(3), pp. 274-279.

The Evolution of a City Birds Song

Communication is an important part of any animal’s life and a study has shown that birds which now live in suburban areas are starting to change their tune (Brumm, 2006). Many people today complain about the increase in the surrounding noise, but what people do not realise is that the noise is of just an annoyance to them but it also affects the animals as well (Brumm, 2006). This increasing urbanised area and the noise associated with it is becoming problematic for the wildlife around (Brumm, 2006).

The noise of an urbanised area is a problem for bird communication as their signals are being asked by this noise and thus prohibiting the exchange of important information (Brumm, 2006). The major problem for birds is that in cases such as mateship where the male uses their song to attract females and defend their territory is becoming harder with the addition of this noise (Brumm, 2006). There was a study on the urban nightingales which found that the males adjusted their sound level depending on the sound level of the traffic around them (Brumm, 2006). Birds do have one advantage.

The traffic of the urbanised area is generally from automotive vehicles which although they are all different they have one thing in common, they are all low frequency noises (Brumm, 2006). Birds have a high-pitched song which comes at the bird’s advantage in this area as their songs become less masked by the surrounding noises of the area (Brumm, 2006). As a result, city birds have a higher minimum frequency than forest birds (Brumm, 2006).

Even though it looks like this change only occurs in urbanized areas, this characteristic change has also occurred in bird species which live in woodlands close to natural noise sources such as waterfalls and rapids (Brumm, 2006). No matter whether the noise comes from a natural or man-made sound, the birds in the surrounding area have evolved to survive in that particular area. 

For another example of this amazing evolution in the birds song, take a look at this David attenborough video of the lyrebird. 

 https://www.youtube.com/watch?v=mSB71jNq-yQ

Works Cited

Brumm, H., 2006. Animal Communication: City birds have changed their tune. Current Biology , 16(23).

Courtship Songs of the Birds

Have you ever wondered why the birds that fill the air around us today use their beautiful singing voices? Courtship songs are one of the most common uses for these creatures amazing singing abilities. Different bird species use this singing ability in different ways and some even add other hidden surprises to the mix to complete their courtship ritual. I could write pages upon pages on the mountain of different bird species and their courtship techniques but to save a bit of time I will simply be looking at a few examples. The satin bowerbird, zebra finch and long-tailed manakin show unique approaches to courtship in the avian world.

A male satin bowerbird courts with a female at specialized structures called bowers (Lofredo, 1985). The courtship includes a complex pattern of vocalisations which is followed by a broad-band; mechanical-sounding song is followed by mimicry (Lofredo, 1985). Studies show that the older male birds produce a longer and higher quality vocalisation which leads to females choosing the older males more often over the younger males (Lofredo, 1985).

The zebra finches courtship song is joined by a type of dance as well. This display includes a song which they have learned, as well as movements of their body, head and beak (williams, 2001). Each bird has a different sequence of beak movements but it is said that there is resemblance between the father and sons movements (williams, 2001). It is thought that a father teaches his son his courtship song and dance then the son makes slight changes to it to make the routine recognised as their own (williams, 2001).

Finally the long-tailed manakin, these birds complete their courtship routine in pairs (trainer, 1995). This partnership consists of the dominating alpha male and his beta male (trainer, 1995). The pair complete this performance together in unison in order to attach females to the area (trainer, 1995). This way of courtship ritual allows the female to see how well the male partners with another male, looking for a cooperative long-term partner (trainer, 1995).

The courtship song and dance is only one aspect of the birds life which they use their singing and dancing capabilities. Next week we will explore more into the avian world.

Works Cited

Lofredo, C., 1985. Male courtship vocalisations as cues for mate choice in the satin bowerbird. AUK, Volume 103, pp. 189- 195.

trainer, J., 1995. Singing preformance, frequence matching and courtship sucess of long--tailed manakins. Behaviour ecology scoial biology , Volume 37, pp. 249-254.

williams, H., 2001. Choreography of song, dance and beak movements in the zebra finch. The journal of Experimental biology, Volume 204, pp. 3497 - 3506.