The Saguaro Cactus (Carnegia gigantea) is one of the images people bring to mind when they picture the South-western US desert - a tall, columnar plant with arms pointing upwards, rather like a character from a Western film who has just been told to 'Reach for the sky'. It's an extremely slow-growing cactus, and older specimens have been known to live for 250 years and reach a height of over 50 feet. As one of the few sources of moisture in the desert however, the Saguaro often comes under attack from desert fauna, despite its defence of sharp spines, and has developed an effective way of protecting itself against such damage.

The Boot

Contrary to being the uninhabited wilderness that people sometimes imagine, most deserts of the world are teeming with wildlife, and the Sonoran Desert of Southern Arizona and Northern Mexico is no exception. Several species of bird make this area their home, but as the desert climate can only support a small number of somewhat stunted trees, they need to find an alternative nest site. One in particular - the Gila Woodpecker - uses the Saguaro, and burrows through its tough outer flesh into the body of the plant where there is plenty of moisture, and a relatively cool environment shaded from the searing desert sun. Once through the skin, the bird makes a sharp downward turn and hollows out a space for itself. A cactus, being little more than a living water container would continuously lose moisture, and be open to infection if it didn't do something to protect itself, so the Saguaro begins to exude a resinous sap around the void which the bird has made. The sap gradually solidifies to form a hard, bark-like substance around the wound, rather like a scab on animal skin, only this scab doesn't go away. The woodpecker has learned to leave the newly excavated burrow for a while in order to let the sap harden, although other birds sometimes decide to make it their own before the woodpecker returns, particularly desert owls.

When the Saguaro eventually dies and falls to the ground, the leathery skin and soft inner flesh both rot away to leave the woody skeleton which the plant used for support, and the remains of the nest, which resemble a rudimentary boot from the way that the bird burrowed into the cactus in the first place. Even after the death of the Saguaro, the boot is still useful to desert wildlife. Snakes, rodents, lizards, scorpions, and spiders have all been known to use one as their home, and in the rainy season a boot may fill with water to act as a short-lived miniature oasis.

Human Uses of a Saguaro Boot

Although it is now illegal to collect boots from the wild, in the past they were used by the local Tohona O'Odham Indians as water containers, and have for many years been sought after by collectors, either in their natural state as a simple ornament, or carved into intricate creations, similar to the way sailors used to carve whalebone.

Saguaro National Park

In 1994, the former Saguaro National Monument in Southern Arizona was upgraded to full National Park status to become Saguaro National Park. A group of dedicated supporters - The Friends of Saguaro National Park - exists to help with keeping the Park as it should be, and much useful information can be found at this unofficial website.