Panda cub is adorably sleepy at the Toronto Zoo

In case you thoughtthe idea ofcute cubs at the Toronto Zoo hadgrown tired ... one of them yawns.

Zoo staff today released avideo of the adorably tiredtwincubyawning.

Toronto Zoo's twin panda cubs hang with mom Er Shun in new video

Toronto Zoo panda cubs outgrow their incubator, are somehow even more adorable

Twin panda cubs begin to open their adorable eyes at Toronto Zoo

The pandas are now 12-weeks-old and weigh more than 3.5 kilograms. The zoo says the cubs are getting stronger by the day and arebeginning the teething process.

The cubs are in the zoo's maternity den and not availablefor viewing by the public.

The twin cubs were the first-ever giant pandas born in Canada. Their mom Er Shun is one of two pandas on loan from China.

All of the pandaswill be at the Toronto Zoo until 2018, when they'll move to the Calgary Zoo forfive years.