Small pests called Dermestids caused this damage.
Dermestids are beetle larvae that eat dead and dried tissue -- that
which makes up these moths. The can also infest taxidermy
mounts, animal hides and skeletal material. As you can
see in this picture, they are fully capable of destroying museum
specimens and we actively monitor for their presence. This
display was removed from a pest mitigation freezer a few months ago
and we now keep it as an example of what can happen if areas of the
collection go unmonitored for too long.