The River Tees has streams and other rivers running into it all along its length. Many of these, nearer the estuary are tidal, just like the Tees. One of the largest is Greatham Creek on the North side of the river, really close to the mouth. The creek winds its way between lagoons and marshes that are often flooded at high tide. It is here that seals, both Common and Harbour Seals, make their home.
Seals are mammals that hunt in the sea but live much of their lives on land, especially the newborn seal pups. The whole area around the seal hide is named Seal Sands and historically there were lots of seals living here. However, during the late 19th Century, when pollution levels were at their worst, the seal population collapsed.
As industry began to clean up its act, and the quality of the river water improved, plants, fish and then the biggest predator in the local chain, seals, began to return. The population seems to have grown year on year and their safe haven of a nature reserve means that they are relatively safe on top of the food chain. The long channel connecting their lagoons to the estuary fills up and drains twice daily and if you stand alongside it you will often see multiple seals swimming just a few feet from the bank on their way to and from the sea.
Some of the seals also ‘turn right’ instead of left and swim further up the river. There is almost always a seal or two fishing near the barrage and from time to time they venture further up towards Yarm.