It's one of our most beloved mammals - but this otter was found with its neck caught in the jaws of a trap at the weekend.
Police are investigating a possible wildlife crime after the discovery of the carcass on the banks of the Sixmilewater River at Dunadry on Sunday.
The trap had been left openly on the riverbank, suggesting a deliberate attempt to target the otter, a scarce species which is protected at European level.
The shocking photos were posted on the Antrim and District Angling Association Facebook page and sparked a huge amount of interest, attracting 10,000 page views in just 12 hours. Viewers from Germany and the USA condemned the killing.
It is not clear whether the trap is an illegal gin trap or a legal clamp trap. But even if it were a legal trap, it was set in a way that is against the law, according to one member of the association who described the incident as "sickening".
"The main thing about these traps is that they have to be concealed. In this instance it was lying openly on the riverbank," he said.
The traps are usually designed to catch the animal by the foot, but in this case it appears that something was left to entice the otter to put its head into the trap.
"There must have been something there to provoke its curiosity," he said.
"There is a residential development backing onto that area. The field is popular with anglers and walkers as it gives direct access to Dunadry and Muckamore and is well walked. A cat or a dog or a young child could have been caught in that trap. Some of these traps have the power to take off a young child's hands or severely physically impair them.
"It could be a legal kind of trap, but where it was placed is no doubt illegal.
"Otters only eat what they can easily catch and most of their prey are fish, mostly the smaller, slower, weaker fish. So they do play an important role in maintaining the health of the ecosystem. It's a thing that we (anglers) look to have in the river as it's an indicator of good water quality and it shows that we are doing a good job in maintaining the health of the river."
The angler said it is an offence to deliberately capture, kill or injure an otter.
"I think this has really hit home. People don't often see otters as they're quite rare and this has hit home the reality that these traps are out there and people are using them to trap animals.
"People have been up in arms about it. It's shocked a lot of people. We spend a lot of time trying to create an environment where animals and humans can live together."
The PSNI said they received a report of an otter having been caught in a trap in the Dunadry Road area of Antrim on Sunday evening and inquiries are continuing.
Otters are good indicators of water quality - they need clean, unpolluted water with a large and varied supply of food. They are found throughout Northern Ireland in suitable habitats. Otters are shy, solitary animals that are active mainly at night. Otters can live for up to 10 years and feed mainly on fish, frogs and crayfish, though other prey such as small birds may be eaten.