Not that I find mule-breeding an interesting question per se, but it seems to me that this passage is a good yet mysterious example of intertextuality in Herodotus.
In the Odyssey, book 4, Homer mentions in passing mule-breeding in Elis. Herodotus, on the other hand, in the middle of his account of the Scythians, claims (Hdt 4.30) that mules cannot be bred in Elis; just before this, Herodotus has explicitly made reference (in Hdt 4.29) to another place in the same book of the Odyssey (about lambs growing horns straight at birth in Libya, 4.85 καὶ Λιβύην, ὅθι τ᾽ ἄρνες ἄφαρ κεραοὶ τελέθουσι). Why Herodotus should have an opinion so diametrically opposed to Homer in such a trivial matter as mule-breeding in Elis is a mystery to me, but it seems to me that some sort of intertextuality with the Odyssey is intented, although his motives remain totally opaque to me – perhaps he simply forgot to make his intentions more explicit?
The Oxford commentary doesn’t comment this in any way, nor could I find anyone else commenting this anywhere else.
Hdt 4.30
ἐνθαῦτα μέν νυν διὰ τὰ ψύχεα γίνεται ταῦτα. θωμάζω δέ (προσθήκας γὰρ δή μοι ὁ λόγος ἐξ ἀρχῆς ἐδίζητο) ὅτι ἐν τῇ Ἠλείῃ πάσῃ χώρῃ οὐ δυνέαται γίνεσθαι ἡμίονοι, οὔτε ψυχροῦ τοῦ χώρου ἐόντος οὔτε ἄλλου φανεροῦ αἰτίου οὐδενός. φασὶ δὲ αὐτοὶ Ἠλεῖοι ἐκ κατάρης τευ οὐ γίνεσθαι σφίσι ἡμιόνους, [2] ἀλλ᾽ ἐπεὰν προσίῃ ἡ ὥρη κυΐσκεσθαι τὰς ἵππους, ἐξελαύνουσι ἐς τοὺς πλησιοχώρους αὐτάς, καὶ ἔπειτά σφι ἐν τῇ τῶν πέλας ἐπιεῖσι τοὺς ὄνους, ἐς οὗ ἂν σχῶσι αἱ ἵπποι ἐν γαστρί· ἔπειτα δὲ ἀπελαύνουσι.
“In that land then this takes place on account of the cold; but (since my history proceeded from the first seeking occasions for digression) I feel wonder that in the whole land of Elis mules cannot be bred, though that region is not cold, nor is there any other evident cause. The Eleians themselves say that in consequence of some curse mules are not begotten in their land; but when the time approaches for the mares to conceive, they drive them out into the neighbouring lands and there in the land of their neighbours they admit to them the he-asses until the mares are pregnant, and then they drive them back.”
Od. 4.632: (Noemon wants to get his ship back in order to fetch one of his young mules from Elis)
Ἀντίνο᾽, ἦ ῥά τι ἴδμεν ἐνὶ φρεσίν, ἦε καὶ οὐκί,
ὁππότε Τηλέμαχος νεῖτ᾽ ἐκ Πύλου ἠμαθόεντος;
νῆά μοι οἴχετ᾽ ἄγων: ἐμὲ δὲ χρεὼ γίγνεται αὐτῆς
Ἤλιδ᾽ ἐς εὐρύχορον διαβήμεναι, ἔνθα μοι ἵπποι
δώδεκα θήλειαι, ὑπὸ δ᾽ ἡμίονοι ταλαεργοὶ
ἀδμῆτες: τῶν κέν τιν᾽ ἐλασσάμενος δαμασαίμην.
