Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of oil and natural gas producer Ultra Petroleum Corp. (NASDAQ:UPL) got hammered another 10% today. The stock is down 32% since Nov. 1 and has been nearly cut in half since June 18:

UPL Chart

UPL data by YCharts

What's special about June 18? That was the 2014 peak for Brent crude, the global pricing standard for crude oil. 

So what: Brent crude fell another 4% today, and West Texas intermediate -- a pricing standard for domestic oil -- fell to $63 per barrel, the lowest price in five years. The bottom line is, there is a lot of fear driving investors in oil companies right now. Ad in the fact that at least some of the selling is probably end-of-year selling for tax purposes, and it's making for a very ugly market. 

Now what: Ultra Petroleum's name is a bit of a misnomer, as 90% of the company's 2015 production will be natural gas. The company has significantly increased its oil assets -- oil production has tripled over the past year -- but natural gas remains at profitable price levels, and domestic demand in industrial and energy applications is increasing. Ultra will be affected some by the decline in oil, but its strength is in natural gas. 

Do your own due diligence, but this looks like a serious overreaction by Mr. Market to me. 

Jason Hall owns shares of Ultra Petroleum. The Motley Fool recommends and has options on Ultra Petroleum. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.