An anecdote for future rodent researchers on extrinsic mortality. Learned a hard lesson today. I had three young Mus musculus in my practice lab last week and this morning I had one. In the wild it’s not uncommon for extrinsic mortality rates for house mice to soar. Still we abhor them. Few creatures have more predators.
Meanwhile, the lab environment was supposed to be a neutral environment free of all that extrinsic environment at least during the experiment. What I never imagined was that extrinsic mortality could slither into my mouse cage in form of rat snake, and take advantage of the fortified high rise nest.
Fortunately though even in such a confined environment one of the mus subjects managed to survive. He barricaded the tunnel and lived in terror for several days. I noticed he was changing up nesting tactics and seemed stress but still never even imagined there could be a rat snake in the cage.
Poor little mus. Talk about grit.