Maybe it was that extra sprat at lunchtime or perhaps a strenuous morning swim.
Whatever it was, Pablo the South American fur seal struggled to keep his eyes open at Bristol Zoo Gardens.
And as the early afternoon sunshine bathed him in warmth he dozed off.
The eight-year-old seal, who is one of five fur seals at Bristol Zoo, laid there on his back with the sound of water gently flowing nearby.
Then his mouth fell open and he started to snore.
Mikolaj Zybala, senior presenter at Bristol Zoo, said: “Seals often make snoring noises just like we do. But they do it when they are awake as well!”
South American fur seals are found on the coasts of Chile, Argentina, Brazil, Uruguay and the Falkland Islands.
But their numbers have suffered because they have been hunted for their warm fur.