Throwing a right hook as he launches onto his opponent with his gnarling teeth at the ready, this is the ruthless showdown between two otters.
The otter takes no prisoners as he battles it out with a rival in a war over food and territory.
The clash sees the feisty mammal raising his arm and swinging for his opponent, who falls back into the water from the force of the attack.
Clash: This otter was pictured throwing a right hook at his rival in a battle over territorial rights
Vicious: One of the otters is clearly on the backfoot as the pair fight it out
Battle: Neither of the otters were prepared to give up their fishing spot without a fight
In one picture, you can see his piercing teeth as he prepares to take a chunk out of his opponent.
Indonesian photographer Monica Anantyowati took the pictures while on a trip to Gembira Loka Zoological Garden in Indonesia.
Ms Anantyowati, 40, said: ‘This was an amazing moment for me — watching the two otters fighting.
‘When I first started watching them I thought the fight was primarily over food, but after studying them for a while I discovered it was about who was the strongest in the territory.’
The two otters were not prepared to give up the fishing spot without a fight and spent nearly three minutes battling it out, being dunked in and out of the murky waters.
Monica was lucky enough to get a front row seat for the match.
Victor: The winner of the battle goes on to celebrate by eating some fish
Take a bite: The otter uses his teeth to get stuck into his celebratory fish
Hungry work: The otter appears to attack his victory meal with as much gusto as he used when fighting his opponent
She said: ‘The otters fought for a good two and a half minutes straight, constantly bobbing under the water before throwing themselves back up.
‘In the end the winner ate and enjoyed the fish he won and the loser found a plastic sheet from somewhere to cover up his face.
‘I took this as a sign that he was ashamed to have lost the fight in front of a prying audience.’
The shame of it: The loser appears to cover his face in shame after losing the battle
Hide away: Photographer Monica Anantyowati said it seemed as if the otter was particularly ashamed at losing the fight in front of an audience
Many otters live in cold waters and have very high metabolic rates to help keep them warm. Otters must eat 15 per cent of their body weight a day, with sea otters having to eat 20 to 25 per cent, in order to stay healthy.
In waters as warm as 10 degrees, an otter needs to catch 100 grammes of fish every hour in order to survive, with most species hunting for three to five hours a day, every day.
The zoo in Yogyakarta is home to a variety of species from around the world and is a popular tourist attraction.