Aelian, Varia Historia 1.3:
The species of frogs in Egypt is a clever thing, and indeed they far outstrip frogs everywhere else. If one of these Egyptian frogs ever stumbles upon a water-snake in the Nile, it bites off a piece of reed and carries it sideways, and it holds it with closed teeth, and tries pretty hard not to let it go. The water-snake is not able to eat it with the reed. For the snake’s mouth does not open wide enough to encompass as much space as the reed opens up. Thus, the frogs use their intelligence to outstrip the strength of the snakes.
Σοφόν τι ἄρα χρῆμα ἦν γένος βατράχων Αἰγυπτίων, καὶ οὖν καὶ τῶν ἄλλων ὑπερφέρουσι κατὰ πολύ. ἐὰν γὰρ ὕδρῳ περιπέσῃ Νείλου θρέμματι βάτραχος, καλάμου τρύφος ἐνδακὼν πλάγιον φέρει, καὶ ἀπρὶξ ἔχεται, καὶ οὐκ ἀνίησι κατὰ τὸ καρτερόν. ὃ δὲ ἀμηχανεῖ καταπιεῖν αὐτὸν αὐτῷ καλάμῳ· οὐ γάρ οἱ ἐγχωρεῖ περιβαλεῖν τοσοῦτον τὸ στόμα, ὅσον ὁ κάλαμος διείργει. καὶ ἐκ τούτου περιγίνονται τῆς ῥώμης τῶν ὕδρων οἱ βάτραχοι τῇ σοφίᾳ.