A scientist based in the UK says she has proved that lions can count.
Lionesses seek bigger numbers to protect their cubs
Biologist Karen McComb of Sussex University used a big loudspeaker and recordings of lions in various numbers to experiment with African lions.
She then recorded the number and type of roars that came back from lions around.
"What they did was closely controlled by how many were roaring from the loudspeaker, and how many of themselves there were," Karen McComb of Sussex University explained to BBC World Service's Science In Action programme.
"Their likelihood of approaching increased as their own group size increased - and also decreased as the number of intruders roaring from the loudspeaker increased.
"Their behaviour was best predicted by a variable that we called odds, which was the ratio of number of defenders to number of intruders."
In other words, the lions were making decisions by working out the numbers they potentially faced.
The basis for this action - and the reason for their counting - varied according to the sex of the lions, Dr McComb found.
Females use this numerical ability to determine how many potential rivals are roaring back at them from competing groups.
However males quantify the size of groups of females to weigh up whether to try and take over the prides.
"Basically, a very potent force in lion society is infanticide," Dr McComb explained.
"Nomadic males, when they come in to take over a pride, actually kill the female's cubs.
"So the females in a pride are extremely worried if they hear strange males roaring, and will retreat if they can. But if they can't retreat they will stand and defend the cubs - and three females are more likely to defend the cubs than one would."
A male's response was likely to greatly depend on its assessment of female numbers, Dr McComb said.
"What we find is that males who are in a position to come and take over a pride seem to be aware of this greater threat," she confirmed.
"If it's one female roaring they'll actually come very quickly - they'll almost run towards the loudspeaker, they're so interested in the female - but if there are three of them they'll come much more slowly and be much more cautious."
Dr McComb said that although the lions were not counting cognitively - in a linear way up from one - they were very skilled at working out the exact numbers in other prides.
"They may be doing 'quite a few' from 'not many', however the way that they react is actually very accurately predicted by this number of us/number of them.
Lions are also able to count the numbers missing from their pride
"If that's the case, they're doing it in a very fine-scaled way, and they do actually appear able to work out somehow that ratio quite accurately."
Another finding was that they could actually tell when their own pride was not all present and accounted for.
"They seem able to assess whether the number in their own pride was at its maximum - whether all the females that should have been in the pride were there.
"They very rarely roared themselves after playback, but on the occasions when they did roar were the times when their pride size was less than maximum.
"Some individuals were missing, and it looks like they were roaring to recruit those individuals."