CORVALLIS, Ore. (AP) -- Cows that survive a wolf encounter reportedly suffer symptoms similar to post-traumatic stress disorder. A study by Oregon State University found the stress decreases pregnancy rates and increases the number of lighter calves and the likelihood of getting sick. Weight loss translates into a financial loss for ranchers. KPTV reports researchers induced wolf stress by putting cows in a pen scented with wolf urine while playing recorded wolf howls on a stereo. The study was conducted by Oregon State University animal scientists Reinaldo Cooke and David Bohnert. The study was funded by the Oregon Beef Council and published in the Journal of Animal Science.