Creatures including dolphins, monkeys, fruit bats and even ants are all capable of selflessly coming to the rescue of others, researchers found.
Dr Elise Nowbahari, from the University of Paris, said there is mounting evidence that willingness to go to the aid of others at personal risk is common in a range of species and far from a solely human trait.
Dolphins endanger themselves to rescue trapped dolphins, lifting an injured dolphin to the water's surface to help it breathe, she said.
Monkeys will drive away an attacker from a vulnerable female or infants and female fruit bats help other fruit bats in labour to ease the birth.
She also said that ants frequently help other ants from the same colony if they are caught in traps or by a predator – though their heroism does not extend to helping ants from other colonies whose actual cries for help are ignored.
One of the biggest internet hits is a film of buffalo fighting off lions that had attacked one of their young in the Kruger National Park in South Africa.
"We may be underestimating the extent of rescue behaviour in the wild," said Dr Nowbahari, whose work is published in the latest issue of Communicative and Integrative Biology.
"Reports of rescue behaviour in non-human animals are exceedingly rare but is far more common than thought."
She has drawn up a four-point model that could be applied to the behaviour of any creature, including humans, to identify heroic acts.
First, the individual being helped is in distress and unless it escapes on its own it will suffer severe physical harm.
Second, the rescuer places themselves in harm's way by helping.
Third, the rescuer's behaviour is suitable to the circumstances of the victim's distress.
And last, rescuing is not done for any inherent reward.
She said: "Human acts of heroism are often rewarded with medals and commendations, for example. But one needs to distinguish between the reward inherent in the rescuing someone and the reward that may or may not be given if the act is recognised."
Dr Nowbahari and her colleagues now intend to apply the four-point model to a range of non-human animal situations to determine if the rescuer's behaviour was indeed heroic.
By using this detached method she expects to be able to document an enormous range of animals being heroic.