Singing Animals

Question 1

What is singing in humans?

Answer 1

Utter words with musical modulations especially according to a set tune, thus produce vocal melody

Question 2

What is song in non-human animals?

Answer 2

The musical phrases uttered by some animals, typically forming a recognizable and repeated sequence

Question 3

Why do animals sing?

Answer 3

● territorial defence
● aggression
● submission
● attracting mates
● synchronising mating behaviour 
● alarm
● parent-infant interactions

Question 4

Costs/downsides to singing in animals?

Answer 4

● conspicuous to predators

● energy involved in singing

● loss of time for other activities

Question 5

What affects the production and nature of a song?

Answer 5

Animals hormonal state of both singer and hearer.

Diff animals have diff mechanisms to produce sound.

Current situations of singer and recipient: Age, season etc.

Hearing ability of recipient.

Question 6

Difference between frequency and sound?

Answer 6

Frequency is in kHz (1000 cycles per second). Shown on sonogram (graph against time)

Pitch is the sensation resulting from the frequency of a sound

Question 7

Larynx use in frogs?

Answer 7

Larynx lies below the glottis. In frogs, sound level increases by vocal sac. Inflated during calling.

Larynx lies in same plane as extensions of the hyoid bone.

It consists of 2 cartilages instead of usual 3 in humans:
Arytenoids: - spoon shaped, meet together in midline to form a hemisphere

Cricoids: - form a complete or almost complete ring which supports laryngeal structures

• attach the larynx to hyoid bone which has processes projecting on either side of the larynx. No thyroid cartilage in frogs.

Question 8

Vocal cords in frogs?

Answer 8

• formed from extensions of the membrane covering the arytenoids.
• partially attached to cricoid and stretched when arytenoids move apart
• not muscular.
• NOT equivalent to mammalian vocal cords

Question 9

Sets of muscles involved in frog sound production?

Answer 9

• dilator laryngis – arises from a process of hyoid and inserts on medial edge of arytenoids
• musculus hyo-laryngeus – constrictor muscle has origin on hyoid and inserts on opposite m. hyo-laryngeus
• posterior and anterior sphincter muscles – arise on arytenoids (some say hyoids) and insert on opposite muscle of each pair

Sound produced when:
• arytenoids part
• vocal folds swung into airstream
• pulmonary pressure is sufficient to cause the vocal folds (and arytenoids) to vibrate

Arytenoids brought together when: constrictors and sphincter muscles contract and slide over the arytenoids

Question 10

Mating call in frogs?

Answer 10

Mating call of Coqui frog has two parts:
• constant frequency ‘Co’-1000Hz
• frequency sweep /qui’ – 1800-2200Hz

Females are more responsive to qui part due to more neurons responsive to this.

Question 11

Mating call in mice and rats?

Answer 11

Studied using sonograms. They produce ultrasound call that we are unable to hear to to very high freq, more than 20khz

Rats: rapid frequency changes, may be alternate with frequency drifts

male mouse songs similar to bird song:
Songs show several syllable types organised into phrases and motifs:
• syllable: a unit of sound separated by silence from other sounds
• phrase: sequence of syllables uttered in rapid succession
• motif: sequence of syllables of one or more syllable types where the entire sequence is observed repeatedly in vocalisation

Question 12

Effect of helium on human voiced sounds?

Answer 12

• helium lighter than air
• vibrating structures, so the fundamental frequency of human voice not affected
• but resonant frequencies of the vocal tract cavities are increased as sound travels faster than in air
• higher harmonics enhanced,
• formants shifted upwards to give higher pitched voice

Question 13

How is ultrasound produced differently in mice and rats?

Answer 13

Initial suggestion:
vocal cords and ‘false vocal cords’, the vestibular folds, are held rigid during ultrasound production.
Air passing through first hole hits edges of second – produce sound. Hole-tone mechanism. Do not vibrate during ultrasonic vocalisation

Contested suggestion:
modification of thyroid cartilage to include a ventral pouch. vocal folds attach to thyroid via this protruberance. small portion of thyroarytenoid (TA) muscles attaches to projecting endpoints of alar cartilage.

contraction of TA could change shape of ventral pouch. suggested that air from trachea passes through glottis and hits alar cartilage.

Ventral pouch then could act as resonator

Question 14

What structure is used in sound production in birds?

Answer 14

Syrinx:
Different structures used for sound production, not larynx.

At base of trachea at bifurcation point of two bronchi. Surrounded by interclavicular air sac

Some adjacent cartilaginous rings are incomplete or absent - replaced by thin membranes called tympaniform membrane.

Question 15

Medial Tympaniform Membrane (MTM) theory for sounds production in birds?

Answer 15

Contraction of Extrinsic muscles → changes tension on tracheae and bronchi, buckling MTMs into air flow.

Fleshy labia on opposite walls rotated into the airstream, with above reduces aperture and so ↑ pressure within the syrinx.

Interclavicular air sac pressure also causes ↑ air pressure in syrinx.

↑ air pressure in syrinx tends to force MTM out of air stream,
but ↑ air flow in system tends to suck it back in

So membrane vibrates

Question 16

Labial theory in song production in birds?

Answer 16

Soft tissues masses, the Medial and Lateral Labia rotated into air stream. Labia have been shown to vibrate in endoscopies. MTM may act to change tension on labia.