Constructed or natural?

Does anyone know a way to distinguish conlangs from natural ones? I
know of a secret language, but don't know if it's a natural or
conlang. Some people tipped me that conlangers usually can tell by
some 'gut feeling'. I have made a group for it with some grammar and
a few sentences at the melanaq group. Hopefully some of you can help me
with this bizarre problem.

http://www.egroups com/group/melanaq

By the way, here's the Melanian translation of the text:

English:   Fight linguistic extinction... invent a language!

Melanian:  Heqit krakytlame uqy... ixami uqe she!
          fight-you extinction linguistic... create language one!