I lived in Tanzania for 2 years combined and I don't remember seeing a single sheep. I've seen a horse ONCE in some posh mzungu "high-class" place in Arusha.
I don't want to sound negative or anything, just trying to open valid discussion, but why are we learning these words? It's not something you would ever need. What's next? Polar bear?
My point is, I feel like there are far more important words for real-life situations (that I know from experience in Tanzania) then we are sometimes learning.
There are certainly sheep in Kenya. http://www.nation.co.ke/business/seedsofgold/My-two-decades-keeping-sheep/2301238-3489244-v644xy/
While I also wonder about some of the word choices (like eels), it's interesting that you picked sheep for your complaint. According to the FAO, sheep are the fourth most popular type of livestock in Tanzania, after chickens, cows, and goats. The organization estimates that there are over three times as many sheep in Tanzania as pigs. In Kenya, the FAO estimates there are as many sheep as cattle (18 million each). And only ~3 laki pigs. Should Duo scrub pig and pork from lessons too?
They might not be everywhere, but I've seen and eaten sheep in Tanzania. There are even indigenous sheep in East Africa. I wouldn't be surprised if you actually did see some sheep in the distance when you were in Tanzania, but just thought that they were goats.
this is old, but to whoever comes across this and is wondering the same thing, this is a course for Swahili for English speakers. There is no expectation that the people taking this course are solely doing so to go speak Swahili in East Africa Learners are from many different countries and seemingly out-of-context words will apply to some people and not others. In any case, there's no down side to coming across them; if you use it, great, if not, also fine.
Referring to your specific query, there's definitely a lot of livestock in some areas more than others, and I doubt you've covered all of Tanzania in your 2-year stay. Arusha is an urban place, so chances of you bumping into sheep are pretty slim
Arusha isn't just an urban place. In addition to Arusha town, Arusha can also refer to a rural district and a region. Arusha Region has historically led the nation in sheep production and, according to the Livestock Population Census of 2014, has almost as many sheep as goats or cows. And the districts surrounding Arusha town have the highest density of sheep in the region (and presumably at least near the highest density of sheep in the country).
So the odds of seeing sheep while in Arusha would actually be relatively high. Some of the most popular restaurants in the town, like Khan's BBQ serve lamb/mutton. And unless someone almost always stays in the city center itself and refrains from looking out of the window when driving elsewhere (to the airport, other towns, national parks, etc.), one would almost certainly see sheep during two years living in Arusha. But when all of your life you've seen sheep (in person or pictures) that look like this or this, you might not recognize these as sheep.