A recent study published in Nature looked at thousands of different mammal species, and worked out the percentage of cases where animal fatalities were caused by their own kind - a phenomenon called lethal violence.
The study, lead by Professor José María Gómez, had some unexpected results, including the fact that meerkats are the most murderous mammals of all.
This graph shows some mammals who kill each other a lot more often than humans do - and some may surprise you:
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