Sorry, but this isn't true. The only case of animals possibly even coming close to having a higher left appendage-ness is in Gorillas. Approximately 62% of of gorillas have left arms that are slightly heavier than their rights, indicating a possibility that those arms are the dominant ones.
There really is very little difference between lefty and righty mortality. The man who studied it thought lefties die sooner because of the dangers of using right handed machines. So this is a well known myth. [link]