ひき or 頭 for horses?

Question

Initially I'd thought ひき is for small animals and 頭 is for animals that are not small ("big" animals) however EDICT (http://www.csse.monash.edu.au/~jwb/cgi-bin/wwwjdic.cgi?1MUE%E3%81%B2%E3%81%8D) seems to claim that horses belong to the ひき group and not the 頭 group (yet of course I think we can agree that a horse is not "small" at all!).

1) Basically I was wondering is it true that "horses" is the exception where we ignore the "small" / "big" rule and they are always counted with ひき (regardless of the size of the horse) instead of 頭 ?

2) Are there any cases when ひき is used to refer to a non-small animal?

Answer 1

I don't personally know the answer, but exploring my way through EDICT:

a) In the definition, sense 3 - counter for horses - is listed only as "き only" (so not ひき); it is also marked as an archaic term.

b) Skimming the examples page for 馬, I could only find one example using a counter:

そのレースで争った馬は４頭だけだった。

Only four horses competed in the race.

Edit:

Actually, I found another one as well:

彼は牛を２頭の馬と交換した。

He exchanged his cow for two horses.

So both of the examples use 頭 for the counter.

Answer 2

Regarding 匹, the original sense was that which comes in pairs. As a counter, it referred to animals with asses which have a left and right half. Primary examples were horses and cows. Gradually it became used for other animals such as reptiles, fish and insects. Eventually, a desire to count large animals emerged and this was accomplished with 頭. Now 匹 generally refers to smaller animals.

There are several counters used for horses. The primary counter is 頭. Historically, the common counter was 匹, but this is now obsolete or at least archaic.

Other counters include 蹄 (tei), 騎 (ki), and 乗 (jō).

• A 蹄 a horseshoe and four 蹄 is equivalent to one horse.
• A 騎 is used for a horse that is being ridden.
• A 乗 is used to count horse-drawn wagons. One 乗 is expected to have four horses.