Wildlife authorities in Florida are investigating after finding a manatee with the word “Trump” etched into its back.

The manatee was discovered in the small town of Homosassa Springs, north-west of Orlando, on Sunday by a local diver and boat captain named Hailey Warrington.

She has told how she was leading a tour when she recognised the female manatee as a regular in the area, based on its boat propeller scars.

But there was a new ‘scar’ on the huge marine mammal’s back.

Ms Warrington said she thought the scraped inscription was probably made with fingernails.

“It was an uncharacteristic thing for us to see,” she said.

“I was surprised when I saw it.”

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Animal advocacy group the Centre for Biological Diversity said on Monday it was offering a $US5000 ($6500) reward for information leading to an arrest for the “cruel and illegal mutilation”.

“It’s heartbreaking that this manatee was subjected to this vile, criminal act,” the centre’s Florida director, Jaclyn Lopez, said.

“It’s clear that whoever harmed this defenceless, gentle giant is capable of doing grave violence and needs to be apprehended immediately.”

A healthy manatee swimming in a Florida river. Photo: Getty

Manatees, which are also known as sea cows and are famously docile, are protected under state and federal laws in the US.

They migrate to the waters west of Florida every year, but are considered threatened in the area.

Federal officials said the manatee seen in the photograph is a subspecies of the West Indian manatee.

They said the mammal did not appear to be “seriously injured”, with the name apparently etched into algae on its skin.

-with agencies