When standing underneath solid blocks with sniffers above you, they give off shadows through the solid blocks, even though there are no holes above you.
The shadow is visible when looking forward, but when looking downwards, the shadow will disappear (and reappear when looking back up).
This only seems to happen with fully grown sniffers. The baby sniffers don't have the issue.
(Sniffer_Looking down/forward.png are from a survival world. Recreated.png is an example in a creative world showing the sniffer compared to a cow.
Thank you for your report!
We're tracking this issue in MCPE-123540, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Bug Tracker Guidelines – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki