Porting models, be they props or rigged figures, from non-Poser formats can often be interesting due to wild scaling issues.

More subtly, different programs handle transparency / Alpha channels different ways. Usually, the original platform auto-loads such.

But, unless you delve deep into Cycles, Poser much prefers textures' Alpha channels to be 'saved out' and loaded separately.

Free Irfan View displays most formats' Alpha channel via 'Image, show channel', which may then be saved out. However, this does not yet work for DDS.

Free XN View can display DDS' Alpha Channel via 'Image, extract channel'. This route is more convoluted than it seems and, when you get there, the channel may be blank...

Sadly, neither App can 'batch extract' Alpha channels, which is a real nuisance when dealing with eg a scene's dozens of foliage textures. 
( Essential when texture is 'pasted' onto a triangle or rectangle 'flat' to keep poly-count very low compared to 'fully-drawn' leaves' mesh...)

So, is there any quick & easy way to spot if a DDS file has an Alpha channel ??

ImBatch from High Motion Software https://www.highmotionsoftware.com/products/imbatch can extract channels, and will open DDS images - although I'm not sure I have any to test. The interface is kinda clonky, but it's free for non-commercial use so it wouldn't hurt to try it out. I keep it around for the occasional task that IrfanView et al can't handle - it's very powerful once you've got to grips with it.

Thank you: I'll give it a go !!