Discovery Communications, preparing for an over-the-top world, has signed up thousands of subscribers to its true crime channel offered via Amazon.

During Discovery’s earnings call Tuesday, CEO David Zaslav said that Investigation Discovery’s subscription VOD channel on Amazon—True Crime Files—launched in November is attracting 10,000 new net subscribers per month at $4 per month.

Discovery also launched Destination Unknown, based on its Destination American channel, on Amazon

“In niche categories where we have a dominant consumer and brand advantage, such as ID and Turbo Velocity, we see huge potential to expand these genres on and off the traditional TV screen” using content verticals, SVOD channels and through partnerships, like the one with Amazon, Zaslav said.

He said Discovery plans to launch several niche verticals “as we continue to monetize our library content on a direct-to-consumer basis.”

Kids and science were two other areas where Discovery has intellectual property that could be popular on a direct-to-consumer basis, he said. “We are learning more and more from the audience about what they like and what they don’t,” he said.

Discovery is also looking to capitalize on mobile with its TV Everywhere Go family of apps. Originally, Discovery tried putting all of its brands into one mobile app, but last year began giving each of its networks its own app.

“Today, Go, is available in more than 80% of U.S. pay-TV households, so to over 150 million people. And we have expanded our content portfolio to now showcase over 5,000 episodes,” Zaslav said.

“We are finding that Go is a great vehicle for reaching younger viewers with about 40% of our viewers ages 18 to 34, averaging one-hour length of tune-in,” he added, compared to about 40 minutes on cable. “With Go now super serving super fans and gaining momentum with viewers and younger viewers, we are undoubtedly directly connecting to our viewers and fortifying the pay-TV ecosystem.”

The apps help Discovery financially because ads on them generate premium prices. Zaslav said in the first quarter the Go apps will contribute more than 1 point of U.S. advertising growth to the company’s bottom line, and that should increase to 2% by the end of the year.

“I am very confident in our ability to continue monetizing this important and growing platform,” he said.