Two Soay sheep have been stolen from Sacrewell.
The sheep, one of which was hand-raised, were taken overnight between 6pm on Monday, 5 December and 7am on Tuesday, 6 December.
The farm is an agricultural education charity founded in 1964 to teach people about food and farming, but the Soay sheep on site were kept as pets.
Engagement Manager, Jack Pishhorn said: "Staff here are absolutely gutted.
"Solar and Luna were this year's lambs and Luna was rejected by her mother so was hand-reared by one of our rangers."
Jack added: "Most of this year's lambs have gone to market already and the only ones left are pets, which we keep here for agricultural education purposes.
"We've stepped up our overnight security and increased the presence of our staff on site to deter any further attempts."
Anyone with information can contact Sacrewell on 01780 782254.