foot print

Hello Fellow duck owners- I need some help. After having my ducks for the past seven years, I had something kill them last week. I am very frustrated, I can't figure out what got them. They were in a dog kennel that had a wire fence top. Attached to the back of the kennel is a wood house. That has a split roof that opens but, that was chained closed. Came up with the chains once we found out that the raccoons could lift bungie cords :) We live in the woods in western New York, it is attempting to be spring here and critters are waking up. I am attaching a picture of a bloody foot print that was from the scene of the crime. ? if it was from the murderer :) :(

I have just ordered six rouen ducklings and can't wait to get them. They will be inside with us for awhile. This gives us time to strengthen the existing pen. Please help with any info you can think of on what may have killed the last ducks or ways to protect the new babies. Thanks for any help. - DuckerMom