THE ANIMAL FILES

Nile crocodile

Crocodylus niloticus

A closed mouth still leaves a clue.

Nile crocodiles have replaceable teeth and use rivers, lakes and wetlands beyond the river in their name.[1]

Follow the evidence ↓
Nile crocodile
Image: Tim Muttoo · Commons · CC BY-SA 2.0
A visible lower tooth
The fourth lower tooth fits an upper notch.[1]
Beyond one river
Rivers, lakes and wetlands provide habitat.[1]
Sharing the water's edge
Large predators can compete over carcasses.[1]

A visible lower tooth

An enlarged fourth tooth in the lower jaw remains visible when the mouth closes, fitting a notch above it. Broken teeth can also be replaced through much of the animal's life. This is a useful structural feature to study, although that visible tooth is shared with other true crocodiles rather than identifying this species by itself.[1]

Beyond one river

Despite its name, this crocodile is not confined to the Nile. Recorded habitats include rivers, lakes, marshes, dams and estuarine settings. Modern species boundaries also matter: many crocodiles formerly grouped with it in West Africa are now recognised as West African crocodiles, so an old map may mix distinct species.[1]

Sharing the water's edge

Crocodiles and large cats often avoid one another, but food can bring them together. Contests over kills and carrion near water have outcomes influenced by body size.[1]

A COMMON MIX-UP

Is the visible lower tooth unique to Nile crocodiles?

No. It is a shared feature of true crocodiles, so additional evidence is needed for species identification.[1]

TRY A LITTLE REASONING

Why should an old West African crocodile record be checked before labelling it a Nile crocodile?

Reveal the explanation

Species classification has changed. A record may refer to the separately recognised West African crocodile, so geography alone cannot repair an outdated name.[1]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 — Nile crocodile (cited revision)
  2. NCBI Taxonomy — Crocodylus niloticus

Last fact check:

One discovery leads to another

GharialA narrow snout meets less water resistance while catching fish.Gavialis gangeticus ↗American alligatorA predator can also reshape a wetland.Alligator mississippiensis ↗Spectacled caimanIts spectacles are bone, not a change in eyesight.Caiman crocodilus ↗