Unsure what this could be, help?

Unsure what this could be, help?

Observation - Unsure what this could be, help? - UK and Ireland. Description: Found upon heathland. Everytime I went near it, it's rear end would raise towards me as seen in the photo.

Found upon heathland. Everytime I went near it, it's rear end would raise towards me as seen in the photo.