The strap of my Yashica Electro 35 appears to be a bit sticky. I am not sure if it is leather or something synthetic. It has a chrome clip like thing that locks the loop in the strap (used to adjust the length) and has slits that end with holes on each end. The ends of the strap go through the camera lugs and the holes are secured on plastic stubs.
The strap could be leather with a synthetic finish or completely synthetic, either way the rot is terminal. Keep the item away from other plastic/synthetic finished leathers as it could damage the surface finishes.
Sometimes wiping over with naphtha or alcohol can remove the stickiness for a while, but it soon comes back as the degradation/aging continues.
Do not store synthetics from this era in plastic bags or sealed containers as this seems to accelerate the problem. Somewhere on the web there is a very useful site that explores the degradation routes of these 'early' plastic finishes, unfortunately I cannot lay my hands on it at this moment in time.