Wapiti is not a British English word, it is a Native American word for the American elk...most online dictionaries specify the Shawnee tribe. I live in Cody, Wyoming, next door to Yellowstone. The town next to Cody is named Wapiti. \
Added: That is interesting/a bit strange, hcarleton. Thank you for that clarification. But perhaps not so strange....Buffalo Bill Cody's Wild West Shows (featuring Native Americans) were quite popular in England, perhaps the word spread to the UK that way. The hotel in Cody he had constructed and named after his daughter (The Irma) features the beautiful back bar that Queen Victoria gave to him in appreciation for his tours.
No! "Älg" and B. E. "elk" refer to the same animal in Europe. The American "moose" is the same species, slightly different genetically. If it is correct that A. E. "elk" is the same species as "wapiti", then that would be translated as "vitsvanshjort" (literally "white-tailed deer"), which is a different species.
We have one word yes. There seems to be some confusion between North American English and British English but here's a quick explanation: http://naturetravels.wordpress.com/2007/10/29/what%E2%80%99s-the-difference-between-a-moose-and-an-elk/
The European elk is basically the same animal as the American moose (arguably the same species). The American elk (or wapiti) is basically the same animal as the European red deer (although not the same species). Then there is the American white-tailed deer. I have listed these in order of decreasing size. (There are also hundreds of other species of deer.)
That's what this course does. If you have any chance at all, try to access it from a computer and read the lesson notes before each lesson. They contain basic explanations.
PS strictly speaking you don't need a computer: you can see them if you access the site from a browser on your phone or tablet, rather than using the app.
I guess you would just say Varning för älgskylt or Älgvarningsskylt.
Here is the official name for the road sign: https://www.transportstyrelsen.se/sv/vagtrafik/Vagmarken/Varningsmarken/Varning-for-djur/