Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

MOSCOW — When governments award military contracts it's usually so they can obtain equipment such as guns, missiles and aircraft engines.

But this week Russia's Ministry of Defense bought some dolphins — and it won't explain why.

The ministry will pay $26,000 for the animals, at a price of 350,000 rubles ($5,200) per mammal, according to official records.

A bottlenose dolphin. David Goldman / AP file

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

It put the contract to supply the dolphins out to tender, but Moscow's Utrish Dolphinarium was the only bidder before the process closed Tuesday, according to the Russian website for state tenders.

The dolphinarium pledged that by August 1 it will supply three male and two female dolphins aged 3-to-5 years old, "with all teeth intact ... [and] no mucus from the blowhole," the website said.

Related: Russia's 'Extremely Aggressive' Flyby Alarms Experts

The state tender does not shed light on why Russia's military — in command of one of the world's most powerful armies — needs bottlenose dolphins.

The Ministry of Defense did not return NBC News' request for comment, and the dolphinarium could not be reached.

However, dolphins are historically no stranger to the militaries of global superpowers.

In the 1960s, the United States and Soviet Union ran competing programs to train the cetaceans for military uses, including torpedo and mine detection, and even the interception of underwater spies.

The five dolphins bought this week are to be delivered to Sevastopol in Crimea, a Ukrainian peninsula annexed by Russia in 2014.

The spoils of annexation included a Ukrainian military dolphin training facility in Sevastopol. However, Russia claimed that it had no militaristic plans for dolphins, which are also used for psychological and stress therapy.