"Lions love meat."
Translation:אריות אוהבים בשר.
This is the comment from Walrosse that explains it:
This is one of these confusing nouns that have the "ות" ending but actually are masculine, so you would have to use the male version of the verb. And no, unfortunately there is no "אריים" (even though I have to admit it sounds pretty cool).
The female lion is called "לביאה" (le-viyah), just for general knowledge :)
There are just words that are exceprions. Usually you can find out the right gender from the singular form. And just memorize the correct plural.
Here are a few other exceptions: ביצה ביצים. Female
ציפור ציפורים. Female
מזלג מזלגות. Male
סכין. סכינים. Both genders
יין. יינות. Male
To the question why: Initially the plurals of the words had nothing to do with the gender and you needes to memorize all plurals. In modern hebrew the endings now are used for telling the gender. But some words still use the old forms that might not fit the gender.