| 11. | Males have subgular vocal sacs with a slit-like opening in the floor of the mouth.
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| 12. | The male has a pair of vocal sacs which are used during the mating season.
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| 13. | Air is then expelled from the lungs, through the larynx, and into the vocal sac.
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| 14. | This indicates the development of a vocal sac and thus an ability to commence calling behaviour.
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| 15. | The male has a median subgular vocal sac.
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| 16. | Males have internal vocal sacs and oval flat glands on the inner side of their arms.
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| 17. | An alternative use of the vocal sac is employed by the frogs of the Rhinodermatidae family.
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| 18. | They also possess a white vocal sac that can be used to produce sounds for mating.
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| 19. | Muscles within the body wall force the air back and forth between the lungs and vocal sac.
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| 20. | Male with an internal subgular vocal sac.
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