The five most valuable startups in the US have achieved unicorn status many times over. They have also proven rather acquisitive along the way. Taken together, the elite group has completed nearly 50 M&A deals, according to the PitchBook Platform. As these companies mature ahead of—or, perhaps, even to set themselves up for—their hotly anticipated IPOs, their approaches to scaling their businesses have also matured to reflect a mix of organic growth and strategic acquisitions.

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5 Biggest Startups In The US Are Buying

Pinterest

The most prolific acquirer of the bunch had a banner 2016, completing six of its 16 M&A transactions last year, per PitchBook data. In March, it picked up Jelly Industries, the operator of an algorithm-based Q&A service that pairs questioners with experts. Jelly was launched in 2013 by Twitter co-founder Biz Stone and former Twitter engineering manager Ben Finkel, both of whom joined Pinterest as part of the deal. Jelly had raised a total of $11.5 million from investors including Spark Capital, Greylock Partners and SV Angel. The company was valued at roughly $76 million with an $8 million round in early 2014.

Other notable deals: Instapaper, a bookmarking service (2016); Punchfork, a recipe aggregator and Pinterest's first acquisition (2013).

Airbnb

Coming in a close second, the peer-to-peer rental platform is currently enjoying its most active year as an acquirer since 2012. Airbnb has completed four of its 15 M&A deals in 2017, including its biggest yet at around $300 million for high-end property rental platform Luxury Retreats in February. With its most recent deal for Trooly, Airbnb picked up the provider of an online background check platform. Founded in 2014, Trooly raised roughly $10 million in financing from the likes of Bain Capital Ventures and Milliways Ventures, including an $8 million Series A at a $30 million valuation in June 2016, about exactly a year before Airbnb's approach.

Other notable deals: Tilt, a social payment platform (2017); Accoleo, a Germany-based property rental platform and Airbnb's first acquisition (2011).

Palantir

For the infamously secretive Big Data company run by Alex Karp and backed in part by the CIA, 2017 has been a quiet year for M&A. Palantir completed its most recent acquisition last summer—a deal to pick up Dutch data visualization company Silk. Prior to Palantir's approach, Silk had raised roughly $3.7 million from investors including New Enterprise Associates and Atomico since launching its service in 2010.

Other notable deals: Kimono Labs, the developer of a web-scraping tool (2016); Kabless, the provider of a personal voice messaging service and Palantir's first acquisition (2013).

WeWork

At its recent pace, WeWork looks hell bent on catching up with the likes of Airbnb and Pinterest, completing three of its five deals just this summer. The co-working juggernaut most recently cut a check—its second this month—to buy Unomy, adding a sales & marketing intelligence platform in a bid to boost WeWork use by a growing base of enterprise clients. Before WeWork came a-courting, the Tel Aviv-based startup had raised $2.4 million in equity funding from Altair Capital, JANVEST Capital Partners and Leta Capital, among others.

Other notable deals: Welkio, a mobile guest sign-in platform (2016); Case, a building information and technology consultancy and WeWork's first acquisition (2015).

Uber

?Uber might be the most valuable startup in the world (for now), but all that backing has hardly driven the ridehailing giant to pick up many other companies. Uber has completed just five confirmed M&A transactions, three of which closed in 2016—including its $680 million deal for self-driving trucking company Otto. But along with that deal came Otto's founder Anthony Levandowski, who quickly became the head of Uber's self-driving car unit. A lawsuit soon followed alleging that Levandowski stole thousands of confidential files before leaving his job as an engineer at Waymo, Google’s autonomous vehicle arm, to start Otto and subsequently to develop Uber's self-driving fleet.

Other notable deals: Swipe Labs, a social product studio (2017); deCarta, a geospatial mapping company and Uber's first acquisition (2015).

Check out the latest class of unicorns. Or, if you're a PitchBook user, access the full data on the unicorn class of 2017.

Article by Adam Putz, PitchBook