Estivation: How Some Animal-People Chill Out

Most people have heard of hibernation – the period of inactivity that enables certain species to survive cold winters. But did you know a similar strategy protects us from extreme heat and lack of water in the summer? It is called estivation, and you will be surprised by how many kinds of animal-people use it. Some animal-people I know nap for just a few hours during the hottest part of each day, while others go dormant for weeks or longer.

Let’s consider, for example, lungfish-people. When swimming is no longer possible, lungfish-people begin breathing air from the atmosphere, hence their name. They burrow into the mud and cover themselves with a thick layer of mucus, which hardens into a cocoon. Protected from complete dehydration, they reduce their metabolism by 60% and wait. They remain like this until there is sufficient rain to restore their watery environment, usually a few months. But they have been known to estivate for up to four years when necessity demands.

The fat-tailed dwarf lemur-people of Madagascar are the only primates known to estivate. During the months when they are foraging, their heartbeats average 180 per minute, but while they are estivating, the rate drops dramatically to only eight or nine.

Another kind of sleeper is the species “Helix pomatia.” When the air temperature goes above 25 degrees Celsius, the little guys start looking for a place to hide. Once the weather cools off, their nap is over, and they resume foraging through the local vegetation.

Whenever topsoil is subjected to extremes of temperature or becomes too wet or dry, worm-gardeners typically respond by tunneling down. In places where the summers are very hot, certain types bundle themselves up into balls and secrete mucus as insulation. Thus, surrounded by moisture, they can chill out for a couple of weeks until circumstances improve.

Desert tortoise-people live in the hot and arid regions of the southwestern United States and northwestern México. When we want to estivate, we will either dig out a new home, return to a former one, or make a deal with a friend to stay with them. We remain subterranean for extended periods, sometimes months, but we monitor the situation on the surface and may venture out when it’s cool enough.