vocal sac
C1/C2Technical (primarily biology, zoology)
Definition
Meaning
A flexible membrane of skin on the throat or neck of a male frog or toad that inflates to amplify mating calls.
In a figurative sense, it can refer to any anatomical structure used for vocal amplification, though this usage is rare and mostly metaphorical.
Linguistics
Semantic Notes
This is a highly specialized compound noun. The term is almost exclusively used in herpetology and general biology contexts. It is a concrete, countable noun (plural: vocal sacs).
Dialectal Variation
British vs American Usage
Differences
No significant lexical or spelling differences. The term is identical and used with the same frequency in both scientific communities.
Connotations
Purely technical and descriptive in both varieties. No additional connotations.
Frequency
Extremely low frequency in general discourse. Usage is confined to academic, educational, and wildlife documentary contexts.
Vocabulary
Collocations
Grammar
Valency Patterns
The [male frog] [inflates] its vocal sac.The [call] is [amplified] by the vocal sac.A [single/paired] vocal sac is [present/visible].Vocabulary
Synonyms
Strong
Neutral
Weak
Usage
Context Usage
Business
Not used.
Academic
Primary context. Used in biology textbooks, research papers, and lectures on amphibian anatomy and behaviour.
Everyday
Virtually never used. Might appear in nature documentaries or advanced educational materials.
Technical
The standard term in herpetology and zoology for this specific anatomical feature.
Examples
By Part of Speech
verb
British English
- The male toad will vocal-sac inflate to attract a mate. (Note: highly technical, compound-verb usage is rare and non-standard.)
American English
- The frog vocal-sac-inflated during the call. (Note: highly technical, compound-verb usage is rare and non-standard.)
adjective
British English
- The vocal-sac display was impressive. (Note: hyphenated compound adjective.)
American English
- Researchers noted the vocal-sac inflation rate. (Note: hyphenated compound adjective.)
Examples
By CEFR Level
- The frog has a big throat that blows up like a balloon when it croaks.
- During mating season, you can see the male frog inflate the loose skin under its chin, called a vocal sac, to make its call louder.
- The species is easily identified by its distinctive paired lateral vocal sacs, which it inflates to produce a resonant, far-carrying mating call.
Learning
Memory Aids
Mnemonic
Think: A frog's VOCAL performance needs a SAC to amplify the sound, like a built-in loudspeaker.
Conceptual Metaphor
A NATURAL LOUDSPEAKER or AMPLIFICATION CHAMBER.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid direct calques like '*вокальный мешок*' which sounds unnatural. The standard Russian biological term is '*резонатор*' or '*голосовой мешок*'.
- Do not confuse with 'vocal cords' ('голосовые связки').
Common Mistakes
- Misspelling as 'vocal sack' (incorrect).
- Using it as a general term for any animal throat pouch (it is specific to anurans—frogs and toads).
- Incorrect pluralisation: 'vocal sacs' is correct, not 'vocal sac' for plural.
Practice
Quiz
What is the primary function of a vocal sac in anurans (frogs and toads)?
FAQ
Frequently Asked Questions
No, not all species possess them. Vocal sacs are primarily a feature of male frogs and toads (anurans) used for calling, but their presence, size, and structure vary significantly between species.
They are related but not always identical. 'Gular sac' is a more general term for a throat pouch, seen in some birds and reptiles. In frog biology, 'vocal sac' specifies the gular sac used specifically for vocalization.
It is extremely rare. In the vast majority of frog species, vocal sacs are a secondary sexual characteristic of males.
The frog forces air from its lungs over its vocal cords and into the sac, causing the thin, elastic membrane to inflate. This acts as a resonator, amplifying the sound and projecting it over longer distances.