Portner met Animal Collective’s Deakin (Josh Dibb), Panda Bear (Noah Lennox), and Geologist (Brian Weitz) in high school. For years, the four of them swapped homemade recordings, shared musical ideas and performed in different group configurations. Portner recorded the Spirit They’re Gone, Spirit They’ve Vanished album with Lennox, and initially released the recording on the band’s own Animal label in 1999. The album is commonly referred to as the first official Animal Collective release, with Tare writing the music and Lennox providing the ‘perfect percussion’ (as cited in the album’s credits).

From 2006 to 2008, Portner was married to musician Kría Brekkan. Afterwards he was in a relationship with Angel Deradoorian and moved to Los Angeles with her. He currently lives in North Carolina and is in a relationship.

Portner’s other projects and releases include Terrestrial Tones with Eric Copeland of Black Dice, a split 12″ with David Grubbs, and an LP with his then-wife Kristín Anna Valtýsdóttir (aka Kría Brekkan) called Pullhair Rubeye. He released his debut solo album “Down There” on October 26, 2010.

In April, 2013, it was announced that Portner had formed the group Avey Tare’s Slasher Flicks along with Angel Deradoorian, former member of Dirty Projectors, and ex-Ponytail drummer, Jeremy Hyman. Portner describes the band as “[a] group of three hippies on a road trip through the backwaters of 2013s rural music scene fall prey to a murderous cannibalistic band making…” Their debut album Enter the Slasher House came out internationally on April 7, 2014, and a supporting west-coast tour was announced soon after the album’s release. Ahead of the album they released a video for ‘Little Fang’ directed by Portner’s sister and featuring a puppet created by Jim Henson’s Creature Shop. In 2017, he appeared on Grateful Dead member Mickey Hart’s solo album, RAMU