On our first fact-finding trip to the potash mine, we noticed this Tarantula spider keeping an eye on us from the wall of one of the electrical switchgear buildings. These large spiders occur worldwide, with the ones inhabiting Southwestern USA being a bit smaller than most, with a body length of about 2 inches. Tarantulas can live for 30 years or more and catch their prey by running it down rather than using a web like most spiders. Although not poisonous, its bite usually has the same effect as a bee or wasp sting and can be serious if it causes an allergic reaction. Just in case you are feeling brave, literature also reports that Tarantulas have "barbed, irritating hairs, called urticating hairs, that can be thrown by their back legs toward an enemy. These hairs can cause an allergic reaction in humans, being most serious if they get in the eyes". Luckily, we always wear safety glasses as part of our kit when working and, so far, nobody has had any bad experiences with these spiders!
During my visit to Carlsbad Caverns National Park, I had to make a wide berth around a rattlesnake sunning itself on the footpath to the cavern itself. There are also scorpions in the Carlsbad area that like dark places such as in shoes but they are also reported to be more of the 'ouch' type of sting rather than fatal. We have had 20-40 employees working in the area for months now and everyone seems to be surviving quite nicely.
Do NOT touch the limestone structures. With every fingertip of limestone, you destroy the work of hundreds of years.
Also, do NOT leave the paths. The cave system isn´t fully explored yet, and they might never find you.