THE ANIMAL FILES

American bullfrog

Aquarana catesbeiana

A pond chorus is a moving social scene.

American bullfrogs are recognized by a deep call, but a calling group is not a permanent gathering. Males join and leave choruses, while eggs and tadpoles use shallow-water habitats.[1]

Follow the evidence ↓
American bullfrog
Image: Katja Schulz from Washington, D. C., USA · Commons · CC BY 2.0
Sound
Males assemble in calling choruses[1]
Visible feature
An exposed eardrum behind the eye[1]
Young
Aquatic tadpoles before metamorphosis[1]

The circle behind the eye

The tympanum is a visible eardrum behind each eye. In males it is larger than the eye; in females it is about the same size as the eye. Comparing these proportions provides a more useful clue than green colour alone.[1]

A chorus changes membership

Calling groups can form, disperse and re-form elsewhere. Males within them compete, move and occupy different positions. A loud patch of pond is therefore not a fixed social unit. The source also discusses costs of calling and competition, reminding us that a display uses energy and time that cannot simultaneously be spent on other tasks.[1]

Not simply a small adult

Tadpoles have tails, gills and feeding structures unlike those of adults. They use aquatic habitats before metamorphosis reorganizes the body. Development time varies with conditions, including temperature. Finding a large tadpole consequently does not tell you that a frog is about to emerge immediately; developmental context matters as well as size.[1]

A COMMON MIX-UP

Does a chorus contain the same males every night?

Not necessarily. The source describes dynamic groups with individuals moving between locations and gatherings.[1]

TRY A LITTLE REASONING

Why could two visits to the same noisy pond suggest different group sizes?

Reveal the explanation

Group membership and locations change. A single visit samples the activity present at that time rather than a permanent census.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Aquarana catesbeiana (adapted and translated; exact revision)
  2. NCBI Taxonomy — Aquarana catesbeiana (identity and game lineage)

Last fact check:

One discovery leads to another

Marsh frogThe tadpole’s menu is not the adult frog’s menu.Pelophylax ridibundus ↗Common frogOne pond, two very different menus.Rana temporaria ↗Moor frogA male’s blue breeding colour is a brief appearance, not its year-round coat.Rana arvalis ↗