Mexican Red-knee Tarantula

Mexican Red-knee Tarantula battle analysis

On the dry, thorny hillsides of Colima and Michoacán, the Mexican red-knee tarantula spends most of its life underground. A female digs or remodels a burrow beneath a log, rock or tree root, with a tunnel leading to a molting chamber and a deeper room where she rests and eats. At dusk she waits near the entrance, feeling for the vibrations of beetles, crickets or the occasional mouse, then rushes out, pins the prey, bites, and drags it below.

Her defenses are layered. Threatened, she rears up to show her fangs, then turns and kicks a cloud of barbed hairs from her abdomen, hairs that irritate skin and can injure the eyes of mammals, people included. Only as a last resort does she bite, and her venom, though deadly to insects, is mild to people. She grows slowly, moulting once a year and regrowing lost legs, and can live for 25 to 30 years, while males mature, wander in search of mates, and usually die within a few years.

In battle terms, the red-knee is a small specialist. Its fangs, venom and hairs give it a high Special rating for its size, but it weighs perhaps 15 grams, moves slowly, and has a soft, easily crushed abdomen. It wins against insects and small prey at its burrow and loses to almost any vertebrate predator large enough to shrug off a few hairs.

Habitat & range

Endemic to Mexico on the Pacific slope of the Sierra Madre Occidental and Sierra Madre del Sur, mainly Colima, north-western Michoacán and southern Jalisco (Wikipedia; Fukushima et al. 2019). It lives in subtropical dry forest, mostly thorn and deciduous secondary forest, from the coastal lowlands into the foothills up to about 2,100 m, preferring undisturbed shaded areas and places near seasonal watercourses (Fukushima et al. 2019). ADW describes red-knee habitat as dry scrubland, desert, dry thorn forest and tropical deciduous forest, often at the base of thorny plants such as cacti.

Diet & hunting

Nocturnal sit-and-wait predator of ground-dwelling insects, arachnids and myriapods, and occasionally small vertebrates such as frogs and mice (Fukushima et al. 2019; ADW; Wikipedia). It sucks out the liquefied body contents and wraps the remains in silk. Predators include white-nosed coatis (Wikipedia), birds and lizards (ADW), and Pepsis tarantula hawk wasps (ADW).

Social life

Solitary. Each female keeps her own burrow; males leave their burrows to search for females in the mating season, when roads are a significant cause of male deaths (Fukushima et al. 2019).

Conservation

Vulnerable on the IUCN Red List (Fukushima et al. 2019 assessment, per Wikipedia), with an estimated extent of occurrence of about 13,000 km² and an area of occupancy of about 8,450 km², both declining through urbanisation, agriculture and roads (Fukushima et al. 2019). Listed on CITES Appendix II since 1985 (then under the name B. smithi). Illegal collection continues, especially around Colima, while legal captive breeding in Mexican management units supplies part of the pet trade (Fukushima et al. 2019). No protected area covers its range.

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