The couple enjoyed an "unbelievable" visit to Wolf Mountain sanctuary in Lucerne Valley, California, to mark the actor turning 36 but admitted they wished they could stay longer, reported Ace Showbiz.
Alongside a picture of one of the animals, Lovato, 23, wrote on Instagram: "Spent the day at Wolf Mountain sanctuary ... It was unbelievable. I fell in love with the wolves there and wish I could spend more time with these beautiful, spiritual creatures."
On a picture of the "Minority Report" actor kneeling alongside a wolf, she wrote: "Look at how handsome the birthday boy is... #wolfpack #happybirthdaywilmer (sic).