Yahoo said today that it paid an undisclosed sum to acquire Bignoggins, maker of popular fantasy-sports apps, in a bid to ensure its leagues remain popular in a world where they are increasingly managed on mobile devices. Bignoggins, a one-person operation run by developer Jerry Shen, created the popular Fantasy Monster and Draft Monster apps for iOS and Android. The apps have been removed from the App Store and Google Play.

Yahoo, which introduced fantasy sports leagues in 1999, was one of the first big sites to harness the potential of online sports communities. Unlike some of its competitors, Yahoo's leagues are free, and they quickly amassed a large and loyal audience. In recent years Yahoo has drawn competition from ESPN, CBS, and the NFL, among others, increasing the pressure to add features.

The average fantasy player spends $95 on a league

The competitors are targeting fantasy's large and growing mainstream audience: 35 million people play fantasy sports in the United States and Canada, according to the Fantasy Sports Trade Association, up from 9 million in 2005. Players tend to be highly engaged, visiting league sites multiple times per day, and collectively they pay millions of dollars for apps, analysis and other fantasy-league services. The average player spends $95 a year on the hobby.

Those players are valuable to Yahoo, which under CEO Marissa Mayer has moved aggressively to improve its mobile offerings. In a blog post, Shen said features from his apps are coming to Yahoo's official fantasy sports products. "For years, players have used Fantasy Monster and Draft Monster to dominate their fantasy leagues," Shen wrote. "The great news is that the technology driving those apps will be integrated into Yahoo's own offerings."

The acquisition of Bignoggins is minor compared to Yahoo's monster purchase of Tumblr, or its rumored bid for Hulu. But it's a strategic move for a CEO looking to acquire technology that will draw in new users and get them using Yahoo services every day.