Most baby burms hiss some of them grow out of it some of them dont. I have about 3 that dont hiss maybe 4. BUt the other 7-8 do. Usually only when I get them out or im messing in there cage but some of them hiss the entire time I handle them and everything. Its just like humans we have different personalitys some of us are nice as can be and some of us can be a bit snotty.