This week's been pretty rough.

Luckily for our sanity, this Reddit thread in response to user AaronM97's request to be cheered up lists thousands of happy facts.

We science nerds picked out 10 of the happiest animal facts from the thread to brighten your day. We've even found the science to support them.

1. Rats and mice are actually ticklish. And they laugh. This study by Jaak Panksepp from Bowling Green University in Ohio, shows that rats have ticklish spots and will actually "laugh" when you tickle them. Tickle the nape of a young rat's neck and it will make lots of squeaking sounds — in this case the rat equivalent of laughter. (From Reddit user Smitsha516)

2. Some turtles can breathe out of their butts. Turtles have an opening on their butt where feces, urine, and eggs all come out. Some water turtles, according to this Google book, have a specialized cloaca that they rely on for oxygen when they're under water. While most turtles do not rely heavily on this kind of "butt breathing," one kind of turtle — the Fitzroy River turtle — gets almost two-thirds of its oxygen this way. (From Reddit user panamared78)

3. Crows are pranksters — they have been observed actually playing tricks on each other. A study published in the journal Science by University of Oxford Professor Alex Kacelnik tells us that crows are smart and can even make tools. Long-time bird watcher and nature writer Candace Savage has observed that these birds are so intelligent they can play pranks on each other. She describes her observations in this summary of her book "Crows: Encounters with the Wise Guys" (Greystone Books, 2005). (From Reddit user buttons_aren't_toys)

4. Honey Bees can communicate through dance. University of Munich Professor Karl von Frisch explains how honey bees talk through dancing. Worker bees rely on their "waggle" dance to tell other bees where the best pollen is. (From Reddit user Jackthastripper)

5. Every cow has a best friend and they hang out every day. Researcher Krista McLennan made this discovery when she observed that pairs of cows within a herd became stressed when they were separated. Being separated from their best pal can impact a cow's heart rate and may even affect how much milk they produce. (From Reddit user KHDTX13)

6. Most penguins only have one mate for life. In some species the male penguin even "proposes" by giving the female penguin a pebble. (From Reddit user BabyBlackout19)

7. A group of pugs is called a grumble. Some other great names for groups of animals include a parliament of owls, a prickle of porcupines, and a troubling of goldfish. (From Reddit user MaNamIsKahlfin).

8. Otters have a pocket in their skin to keep their favorite rock in. Otters have to use rocks to crack open the hard shells of mollusks they eat. Some otters keep the same rock their entire lives and store it in this skin flap. (From Reddit user Izzuriaren)

9. Cats will headbutt you to show their affection. Just to remind you that they love you, cats will often gently headbutt your leg, or whatever body part they can reach. This behavior may even be a type of Territorial marking — your cat wants everyone else to know you're taken. (From Reddit user bansheelust)

10. Dolphins sometimes try to rescue people who are drowning. There are several reports of dolphins guiding humans to the surface or alerting other humans to a distressed swimmer. Dolphins have even been known to protect swimmers and surfers from shark attacks. Professor Lori Marino, a zoologist at Emory University, says this behavior is probably linked to the fact that dolphins are one of the most intelligent animals on Earth. (From Reddit user CleanBill)

11. Squirrels will adopt other squirrels babies if they are abandoned. Nature doesn't always follow the ruthless "survival of the fittest" code. Scientists have observed squirrels caring for abandoned young. However, adult squirrels are much more likely to do this if the abandoned baby squirrels are closely related to them. (From Reddit user Ragdoll_Proletariat)