Grammostola porteri

Physical description and identification

Grammostola porteri is a medium-sized, stocky terrestrial tarantula with none of the bold markings that make its relatives easy to name. It is grey to grey-brown overall, clothed in fine setae with pale or whitish tips that give the whole animal a frosted, dusty look, and the carapace usually carries a soft rose or coppery tint that is obvious in sunlight and invisible in shade. There are no leg bands, no red abdomen and no metallic sheen.

Adults

• Size: the figure of 15 cm quoted almost everywhere is the leg span, not the body length. The body itself measures around 5–7 cm. Females are heavier and more robustly built; males match them in span but are markedly lighter and longer in the leg.
• Colour: grey-brown base with pink, rose or copper overtones, strongest on the carapace and strongest of all in the weeks after a moult. Colour intensity varies enough between individuals that it is a poor identification character on its own.
• Urticating hairs: the abdomen carries a field of barbed urticating setae, and this species uses them readily. An individual that has kicked repeatedly develops a bald dark patch on the abdomen that is restored at the next moult.
• Sexing: mature males have swollen pedipalp bulbs and tibial hooks on the front legs; females stay bulkier. Before maturity, examining a shed skin is the only dependable method.

Eggs and egg sac

The female builds a dense silk sac inside her burrow and guards it, turning it to keep humidity and temperature even. Clutch figures for this species are often reported as "50 to 2,000", a range wide enough to be meaningless: the upper end is not credible for a tarantula of this size, and realistic clutches run to a few hundred eggs. The spiderlings emerge after their first moult inside the sac, roughly six to eight weeks after laying.

Spiderlings

Hatchlings are pale pinkish and plain, and take on the grey adult colouring gradually over successive moults. Growth is slow even by tarantula standards, with maturity several years away; juveniles moult a few times a year and adult females roughly once a year. Our guide to spider moulting explains why a tarantula stops feeding, lies on its back and must not be disturbed while shedding.

The web and hunting

No capture web is built. The spider digs a burrow in firm, dry soil or takes over a cavity under a stone, lines it with silk and lays a scatter of silk threads around the entrance that function purely as tripwires. It waits inside after dark with its front legs resting on that silk, feels an insect cross, lunges and drags the prey underground. In its dry habitat a sealed burrow is also a defence against water loss.

Where Grammostola porteri lives

This is a Chilean spider. Records come overwhelmingly from the arid and semi-arid scrub, matorral and grassland of northern and central Chile, on the dry western side of the Andes. Popular accounts often extend the distribution to Argentina and Bolivia, but those listings largely reflect the long-running confusion with Grammostola rosea, whose range does reach across the mountains, rather than confirmed records of G. porteri itself.

The habitat is hot, stony and seasonally very dry, with sparse shrubs, coarse grass and long rainless periods. The spider is strictly terrestrial and fossorial, sheltering by day in a burrow or a rock cavity and emerging at night, and it is sedentary enough that a female may hold the same refuge for a decade or more. Its nearest relatives on this site include the eastern, grassland-dwelling Brazilian black tarantula and the Chaco golden knee; the genus as a whole is profiled on our Grammostola page.

Is Grammostola porteri venomous?

Yes, like every tarantula, and like every Grammostola it is harmless to people in practice. The venom is adapted to insects; clinical reviews of theraphosid bites place New World ground species at the mild end of the scale, with local pain and swelling and no systemic effects. There is no antivenom because none is required, and no death has ever been attributed to this genus.

The defence that matters is the hair. As a New World species it carries barbed urticating setae on the abdomen and rakes them off with a hind leg when alarmed, and this species is more willing to use them than its famously placid cousin the Brazilian black. Old World tarantulas such as the king baboon tarantula have no urticating hairs at all and compensate with far more potent venom.

Can Grammostola porteri bite?

It can, though bites are uncommon. This is a slow, generally placid spider whose first response to a threat is to sit still or walk away, and whose second is to kick hairs. It is also known for abrupt changes of mood — long calm spells broken by sudden defensive displays — so "docile" should not be read as "predictable". Almost all recorded bites follow the spider being grabbed, pinned or startled at close range.

When a bite occurs, the puncture matters more than the venom. The fangs strike downward in parallel and leave two deep wounds with sharp immediate pain, some bleeding and local redness and swelling that settle within a day or two. Cramping in the bitten limb has been reported after theraphosid bites generally and is uncomfortable rather than dangerous. The realistic complication is a secondary skin infection at the puncture site.

Wash the wound thoroughly with soap and water, apply a cold pack, keep the limb raised and take an ordinary painkiller if needed. Seek medical advice if the site becomes hot, spreading and increasingly painful after a day or two, if you develop breathing difficulty, faintness or a widespread rash suggesting an allergic reaction, or if hairs may have entered an eye. Do not cut, suck or burn the wound.

Ecological importance and behaviour of Grammostola porteri

In the Chilean scrub this is a long-lived, low-energy ambush predator and a meaningful check on ground-living invertebrates around a single burrow. It hunts at night and takes beetles, crickets, grasshoppers, moths, cockroaches, millipedes and other spiders, with small lizards taken opportunistically. Its metabolism is remarkably economical: adults can go for months without feeding, an adaptation to a habitat where prey appears in pulses after rain.

Natural predators: birds of prey and ground-foraging birds, snakes, lizards and small carnivorous mammals take adults caught in the open. The specialist enemy is the pompilid spider wasp, which stings a tarantula into paralysis, drags it into a chamber and lays a single egg on the still-living body.

Prey–predator dynamics: because a female may occupy one burrow for twenty years, her predation pressure on the immediate area is steady and long-term, while very large clutches offset the heavy losses among dispersing spiderlings, only a few of which establish burrows of their own.

Seasonal behaviour: activity concentrates in the warmer, less arid part of the year. Mature males abandon their burrows, stop feeding and wander in search of females, which is when they are most often seen crossing open ground, and they seldom survive a year beyond that final moult.

Relationship with humans: the species is harmless and rarely met, since it stays underground. Its calm nature and long life made it the standard beginner's tarantula worldwide for decades, and for most of that period the demand was met by animals taken from the wild in Chile rather than bred in captivity — a heavy drain on a slow-growing species with a limited range. Captive breeding and export restrictions have since reduced that pressure, and habitat conversion is now the more serious long-term threat.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The species was described in 1936 by the Brazilian zoologist Cândido Firmino de Mello-Leitão, who also named the Brazilian black tarantula fifteen years earlier.
• Whether G. porteri and G. rosea are genuinely distinct species has been argued for decades, and the two have repeatedly been treated as one and then separated again. Reliable identification needs mature specimens and a microscope.
• The great majority of tarantulas sold and photographed as "Chilean rose hair" are G. porteri, which means a large part of what the public knows about the rose hair is really about this species.
• Adults can fast for months at a time without harm, an adaptation to an arid habitat where prey arrives in pulses — and a habit that alarms new keepers who assume the spider is ill.
• Being a mygalomorph, it belongs to the ancient spider lineage whose fangs strike straight down in parallel, which is why a tarantula must rear up before it can bite.

In summary, Grammostola porteri is a grey, rose-tinted, burrow-dwelling tarantula of the Chilean scrub: mild-venomed, extremely long-lived, defended by irritating hairs, and so easily mistaken for G. rosea that most of the spiders bearing that name are actually this one.