ecosia search engine?

what bot do they use?

[SumGuy]

Got a web hit yesterday, the referrer was www.ecosia.org. Hit was legit human. Very rare referrer.

But have never seen a search bot. What do they use?

[not2easy]

They are one of the default search engines for Safari, the organization is ecology related. I am not sure about the UA but will try to look into that.

[brotherhood of LAN]

They've historically used the Bing API to get their results, I don't think they run their own crawler.