In many countries where males are valued more highly culturally, infanticide is depressingly common. On a similar note, many countries have outlawed doctors revealing the baby's sex during pregnancy appointments because too many parents would end the pregnancy if it was going to be a girl.
Qatar and UAE are small petro states with more immigrants than natives. Most of these immigrant laborers are men in their 20s which skews the gender ratio.
In general, for citizen it's 103:100 male/female ratio, it's only when added the whole population, including permanent resident and immigrant, the ratio skewed to 111:100, because there's more immigrant men coming in to work as blue collar than women. There's no widespread infanticide happening as far as i can tell, so it's very likely just happen naturally.
What happened in Qatar is very likely similar situation.
Qatar for instance is not very high (this is a ratio of number of male over number of female) on the "at birth" and "0-14" age bracket with 1.02. it's actually a bit lower than western countries.
The data is still concerning in some countries with notably larger "at birth" ratio and even an increase in th "0-14" age bracket.