There are many individuals out there that claim to be thrill seekers and pursue "life on the edge." The rush of adrenaline, the heightened sense of awareness as you face some dare-devil act head on can create an addiction leaving people wanting more. We may think ourselves clever and creative when we invent a new thrill (such as riding in a specialized plane that plummets to earth, creating the feeling of zero gravity) but once again the animal world has us beat. Not only do some animals experience these situations on a daily basis, many of them actually thrive and live in conditions that would make human habitation impossible.

Extremophiles, animals that love living in extreme conditions, are actually more common than many people realize. They range from the bizarre to the more mundane, but each has unique adaptations that allow them to survive in harsh and seemingly inhospitable places.

For example, claustrophobia, the fear of enclosed spaces, is a major issue for many people. Yet there are those individuals who enjoy the rush they get when they journey underground in pitch-black caverns and caves while spelunking. Some animals live deep underground their entire lives and never see the light of day. Cave-dwelling animals have adapted to a life of steady, cooler temperatures (55 degrees F to 58 degrees F), little disturbances from the outside world and, of course, no light. Because of the lack of light, no plants are able to grow. This means that the food chain is dependent on another energy source: bat droppings (otherwise known as guano). Bats travel outside the caves to eat insects and come back to caves to roost. Mounds of guano accumulate, and decomposers such as the giant cave cockroach and cave millipede eat the guano. These invertebrates are in turn eaten by other animals in the cave.

If you think animals that eat bat feces are weird, then try to imagine the troglobites, animals that have become so adapted to living in caves that they have lost their eyesight and all pigmentation and appear to be translucent blind ghosts. Cave crayfish, cave fish and blind salamanders all live in calm pools in underground caverns. Their bodies have extra sensitive organs that help to detect movement in the water and obstacles in their path.

Then there are the acidophiles: organisms that can survive in extremely acidic conditions. Mostly consisting of algae, fungus and bacteria, these creatures thrive in conditions that can be as extreme as a pH of zero or one (hydrochloric acid has a pH of one) and live in places such as sulfur springs and volcanic areas. Some organisms, while not acid loving, still can survive low pH environments such as that of our stomach (pH of 1.5 to 3.5). A great example is Escherichia coli (E. coli) that enjoys the neutral environment of many different foods but can survive the low pH of our stomachs when we ingest it and therefore make us sick.

Ever sit in a sauna and get overwhelmed by the heat? Thermophiles would really enjoy the extremely high temperatures (those 104 degrees F or above) and many live in hydrothermal ocean vents and in the boiling hot springs of Yellowstone National Park. Ocean thermophiles are not only bacteria but also consist of creatures such as clams, shrimp and giant tube worms. Some thermophiles are so extreme that they even use sulfur instead of oxygen to breathe! And speaking of lack of oxygen, some water systems (especially those that have lots of algae blooms) or high altitudes, such as the tops of mountains, have very little oxygen and these hypoxic conditions require special adaptations, as well. Animals that live in these areas have more efficient respiratory systems, higher blood volume and faster heart rates than those that live in places with sufficient oxygen.

The list of extremophiles can go on and on: bacteria that can live in extremely cold conditions and halophiles that live in extremely salty areas are two more examples. The ability to live in these seemingly inhospitable places is remarkable. Here at the zoo we have some animals that are adapted to live in some very difficult environments. Our Bactrian camels are experts at living in deserts, with long eye lashes that prevent sand from being blown into their eyes and the ability to fluctuate their body temperature so as not to overheat. Our snow leopard is better suited for colder temperatures, with fur on the bottom of their feet to act as snow shoes and bushy tails used for balance and warmth. So the next time you go thrill seeking, think about the animals who already have you beat!

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