Nick Jonas & Lorde We're On Each Other's Team

3/27/2016 2:31 PM PDT BY TMZ STAFF

0327-nick-jonas-lourde-lady-gaga-birthday-leaving-AKMGSI-01Lorde picked up a tail at Lady Gaga's birthday party -- Nick Jonas was sticking close, as the singers left the bash together.

We're sure they were just looking out for the environment by carpooling Saturday night at No Name Club, They both looked so determined to ... save fuel.

We're not saying they hooked up -- however, 19-year-old Lorde and 23-year-old Nick are a lot closer in age than his on/off GF Kate Hudson.

Not that anyone's counting ... or hooking up.