This effect is most likely a composite rather than a straight photograph. A realistic glowing, translucent animal figure would normally be created in editing, unless you physically build a translucent subject and light it from inside or behind.

If you want an in-camera approximation, you could fake it with a silhouette on glass or translucent paper placed close to the camera, lit from behind, with the real landscape in the background. That creates a bright, glowing shape layered over the scene. A little diffusion, such as haze or a smeared filter, can soften the glow.

To keep both the foreground element and background reasonably sharp, use a wide-angle lens and a small aperture, and focus for the scene so depth of field covers both planes as much as possible.

So: for a convincing result, use compositing; for an experimental practical effect, try a backlit translucent cutout or model with forced perspective.