Sniffer hatching

I spent 4 hours finding a single sniffer egg, definitely not a 16% spawn chance, but onto the real issue. After I brought the eggs back to my base to hatch I spent an hour getting a pen ready then I waited and when they hatched..... The sniffles didn't spawn

Below is a link to the video of what happened

 

https://www.xbox.com/play/media/DDYKYFK7VZ