By Neal Erickson
Mexico has more species of tarantula than any other country in the world except Brazil. The tarantula is, however, often maligned and misunderstood. Their bite is not fatal, and barely toxic to humans if at all, and most of the species in Mexico would rather flick hairs at you than bite you if they are threatened. That’s right. Flick hairs.
The tarantula has a two part main body. In North America it may range from the size of a fingernail, to 4 inches in length. The front section is the prosoma (or cephalothorax), and the back section is the opisthosoma (or abdomen). The connector between them, the pedicle (actually an extension of the prosoma), allows for the abdomen to move in fairly wide side to side and up and down range. There are eight legs, four on each side of the prosoma. At the front of the prosoma is what could be called the “face”, since the mouth and eyes are located there. On each side of the mouth are the chelicerae, two two-segment extensions that contain the venom glands and fangs. The fangs extend or fold back jacknife-style as needed. Next to these are the pedipalpi, six-segment leg-like appendages with, in most species, a jagged plate at the end for crushing and cutting food.
The tarantula has eight eyes, but they only sense motion and light variation. It is believed the hairs covering the tarantula play a strong part in detecting the slightest vibrations and determining direction of their source. Their sensitivity to vibration and sound is how they locate and pursue prey. The mouth is an opening only for sucking liquids as food. When prey is captured and disabled with venom, the tarantula pulverizes the prey with his pedipalpi, and actually has to spread digestive juices on whatever is not liquid in the body of the prey, in order to liquefy it for ingestion. A tarantula will eat almost any living thing smaller than herself, and sometimes even a little larger, so they often are a great pest control for humans to have nearby.
On the back of the abdomen of the tarantula grow fine, barbed hairs (called urticating hairs) that will irritate when they come in contact with the skin of a human or other animal. If a predator mammal gets close enough to sniff the spider, the hairs come off and cause great discomfort in the nasal passages. If the tarantula feels threatened, he or she will also use their back legs to fling these hairs at the suspected threat. If you happen to see a tarantula with a bald spot on his rear end, he has been defending himself. This is an example of the true nature of the tarantula species indigenous to Mexico; if threatened, they will try to discourage the attacker. Even when they are approached from the front, they will often first raise the front legs and “slap” at the attacker rather than bite, although the bite will follow if the threat does not back off.
Tarantulas do not see people as prey. They generally don’t even see them as a threat until the human comes too close in an aggressive manner, intentionally or otherwise. Many species are so docile that they are popular as pets. Their appearance belies their good nature, so it’s a novelty to have one at home to show friends. The big problem in Mexico is that people have collected them for sale almost to extinction in some regions.
Tarantulas like to burrow and live underground. Females spend most of their days inside their burrows and nights going out to hunt food. Males do pretty much the same thing until somewhere around their eighth year when they reach sexual maturity. Then they start to roam relentlessly, searching for females with which to mate. After reaching this point in their lives, males will generally live no more than a year to a year-and-a-half longer, where the females’ natural lifespan is usually 30 to 40 years. When poachers look for tarantulas, they wind up with a disproportionate number of the roaming males, simply because they are most active.
When too many males are taken from a region, it threatens the future of the species, since, with the loss of available breeding males, there are not enough new generations born to counteract both natural predation and poaching. Natural predators include skunks, coatis, raccoons, foxes, mountain lions, jaguars, lynxes, ocelots, jaguarundi, ring-tailed cats, possums, sables, weasels, and armadillos, and these are just the mammals. Many birds and most snakes and lizards will think the tarantula a fine lunch.
Another predator, the “tarantula hawk” is a large wasp that digs a hole not coincidentally just large enough for a tarantula, conceals the opening, and then goes hunting, specifically for a tarantula. When it finds one on the move, or lures one out of it’s burrow (sometimes even going in after it), the wasp paralyses it with a sting, drags it back to the hole it dug, and then lays an egg on it. The tarantula is still alive, but unable to move. When the egg reaches the larval stage, it begins to feed on the tarantula, but doesn’t eat anything essential until it’s almost ready to pupate, killing the tarantula right at the end of its larval stage. Ironically, the adult wasp only eats pollen; it’s the larva that’s carnivorous. Rodrigo Orozco said that he followed this process in the field, and after the wasp got caught up in some obstacles, he abandoned the tarantula before he could stash it in the burrow. Orozco took the spider home to observe what would happen, and after 3 months the tarantula slowly returned to life and gradually recovered!
Rodrigo Orozco admits he’s no biologist, but since getting a pet tarantula years ago, he found he was fascinated by them, and became aware of the perilous plight of the tarantula in parts of Mexico. His story is told on his website (www.tarantulasdemexico.com), but in a nutshell, he’s formed an organization to breed Mexican tarantulas in captivity in order to flood the pet market so poachers are discouraged. There are laws against capturing tarantulas in the wild, but enforcement has been almost non-existent, and the profit makes the risk acceptable. Orozco’s knowledge of the species is broad and deep and he has an unquestioned empathy for their plight in the world. One of his favorite statements about the tarantula is, “Ugly does not mean bad!”