When we reported on Relicanth’s difficult to find locations, we also reported on Zangoose and Seviper. They were only seen in opposing hemispheres. This made sense, given that the Pokemon are bitter rivals. Not long after pinpointing their locations, they’ve up and moved!
According to The Silph Road, a Pokemon GO online community, the two 3rd gen Pokemon have been far apart. Zangoose only was seen in North America, Africa, and the Arabian peninsula while Seviper could only be found in Australia, the Middle East and more remote areas of Europe. There are recent reports of trainers finding and catching Seviper in the States.
Some players state that they can still catch Zangoose in their area, while others are claiming that Zangoose is gone entirely, having been replaced by Seviper. This indicated that a nesting rotation may not be exactly aligned to each other. It’s a safe bet that you will rarely, if ever, see them both at the same time, however. This is good for those wanting to complete their Dex without having to traverse the entire globe. With the exception of the still-rare Relicanth. You’ll need to go to the Pacific Islands for that.