The answer lies with the individual swan and species. Whooper swans have a 6% divorce rate, higher than most swan species and they are the most aggressive of the European swan species.

The behavior he is exhibiting is not depression as animals are not going to grieve for the lengths of time that humans. If they did, they would ignore their young and themselves which would be extremely detrimental to their survival in the wild.

If he swan his mate get killed, he may be extremely scared for his safety. Trying to get him to go back to normal routines without freaking out everytime he sees or hears something out of the ordinary, is to take some time. You might try to frequently give him treats so that he comes out and spends more time on the pond.

Did the attack occur on the bank or near the hut? This is another question that needs to be considered. If it was on the opposite side of the lake, then, this is definitely why he is hanging around his little hut. Also, if the temperature is extremely hot and this is the only shade afforded to him, this would be a normal activity.

Male swans usually do not re-mate after losing their mate. However, you can try, but you will need a pen (1/2 in water and 1/2 on land with feeder inside). The pen needs to be covered from top to bottom in fencing so that no predator can dig under or climb into the pen and access the swan.

The pen will allow the two swans to get to know each other and the new swan will familiarize itself with its new habitat and feeding system. It will also allow it time to get to know you as its caretaker.

If any signs of aggression from either swan is exhibited, then you will have your answer and will need to find the new swan a new home. Also, the most important aspect is to make sure that you know the sex of the swan in your pond. Are you absolutely sure it is a male? This is just as important to know about the new swan. If both are the same gender, you will have a hurt and possibly even dead swan from territorial fights. The Regal Swan