Mexican Red-kneed Tarantula

STATUSNear Threatened

COMMON NAME (SCIENTIFIC NAME)Brachypelma hamorii

DIETInsects, other spiders, small amphibians and small mammals

RANGEMexico along central-Pacific coast

HABITATDry to semi-dry scrublands, grasslands, and deciduous tropical forests

Mexican Red-kneed Tarantula

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Program and General Information

The Red Knee Tarantula is a type of burrowing tarantula that inhabits the scrub- forest habitats and semi-desert regions of the Pacific mountains of Mexico. They are a moderately large arachnid; a fully mature Red Knee can reach approx. 4-6 inches in its total leg span. They are a very stocky species of tarantula with a tan and black carapace and orange setae (hairs) on their legs and abdomen. Like most tarantulas, the Mexican redknee tarantula is covered in thin setae that they can use for climbing, sensing, and defense. Their diet primarily consists of arthropods, but they will also eat small amphibians and mammals. Breeding season occurs in the summer during the rainy season. The female constructs an egg sac and lays 200-400 eggs the following spring. Eggs hatch inside the egg case after about 3 months, and will remain inside for another 3 weeks. Spiderlings mature between 4-7 years.


Diet

Redknee tarantulas primarily eat arthropods, such as insects and other spiders, but will also prey on small amphibians and small mammals. Most tarantulas can go weeks without eating but water is necessary.

They are nocturnal hunters and do not spin webs to catch prey. Tarantulas carve deep burrows into soil banks not only to keep them protected from predators, but these burrows also enable them to easily ambush passing prey. The burrow is typically located in or not far from vegetation.

Redknee tarantulas are venomous and will inject their prey with this venom, which is full of digestive enzymes that break down the prey and turn it into nutritious soup. This venom is not fatal to humans.


Habitat and Range
Mexican redknee tarantulas are native to the Central Pacific coast of Mexico; can also be found in Southwest US and Panama. They inhabit the complex scrub- forest habitats and semi-desert regions where there is an abundance of food. They need to burrow, so they are rarely found on rock faces.

The entrance of the tarantulas burrow is just slightly larger than the body size of the spider. The tunnel, usually about three times the tarantula’s leg span in length, leads to a chamber which is large enough for the spider to safely molt in. Further down the burrow, via a shorter tunnel is a larger chamber located where the spider will rest and eat its prey. When the tarantula needs privacy, (when molting or laying eggs), the entrance is sealed with silk that is sometimes covered with soil and leaves.


Common Physical Features

Mexican redknee tarantulas are fairly large arachnids with a leg span of 4-6 inches. They are black or tan with orange setae (hair) on their legs and abdomen. Following molting, the colors are more pronounced. They have eight eyes, which are very small and generally not very strong. Tarantulas have four pairs of legs, or eight legs total.

Each of their 8 legs is also equipped with 2 claws that help them scale a variety of surfaces with ease. In addition to their legs, tarantulas have four other appendages near the mouth called chelicerae and pedipalps. The chelicerae contain the fangs and venom. A tarantula’s fangs fold under the body, meaning that it must strike downward to impale its prey. The pedipalps are used as feelers and claws, and are also used by the male as a part of reproduction. Both the chelicerae and pedipalps aid in feeding.

Adaptations: Tarantula’s digestive system is designed to handle liquid food. In order to be able to properly eat their prey, tarantulas will inject their prey with venom. The tarantula’s venom acts as a neurotoxin, affecting the nervous system, and a cytotoxin, breaking down tissues. The venom will act as a digestive fluid and work to break down the prey into a nutritious soup for the tarantula to easily eat. Although this tarantula’s venom has not caused any known fatalities to humans, people may experience a range of allergic effects and caution should be taken when handling a tarantula.

Like most tarantulas, the Mexican redknee tarantula’s body is covered with tiny hairs. These hairs serve various functions, from holding hairs to grip on varied surfaces and hairs for combing silk, to sensory hairs. When threatened tarantulas will do a short display where they will raise their front legs and present their fangs in preparation to defend themselves, after which they will beat a hasty retreat or will simply walk away. New World tarantulas (those that live in the Americas) have urticating hairs on their abdomens that can be used for defense. These spiders can rub their back legs together to flip these hairs and flick the urticating hairs off their abdomens, causing an irritating reaction in an attacker and even cause respiratory issues in smaller animals. High-strung specimens will often show a dark bald patch on their abdomens from flicking away the hairs.


Behavior and Life Cycle

Mexican Red Knee Tarantulas are solitary. They will only socialize during the breeding season; older spiders may readily cannibalize younger spiders.

Breeding begins in the summer during the rainy season. Males will signify they are ready to mate by approaching a female in her burrow and performing a “dance” by vibrating the abdomen and tapping the front legs. When this is successful, the female will be enticed to follow the male out of the burrow. Males will approach females with special hooks on their pedipalps, used to “lift” the female and bend her backwards. He then uses his other set of legs while collecting sperm with his pedipalps into a packet, which he inserts into the female’s spermatheca, which can store the male’s living sperm.

Spiders are oviparous, which means they lay eggs. Females will produce an egg sack, which contains 200-400 eggs, a few weeks after mating has occurred. Eggs hatch inside the egg case after about 3 months, and will remain inside for another 3 weeks. Spiderlings will molt 4 times a year until they are mature at around 4-7 years.


Conservation Messaging

Together with Nature
Habitat destruction and fragmentation are a major concern for Mexican redknee tarantula populations and have put them at risk. Human activities, such as residential and commercial development, farming and ranching, and construction of roads and railways have all led to the decline of tarantula populations. Tarantulas play an important ecological role because they prey upon insects. Spiders help keep gardens healthy by eating pest species that can destroy trees, flowers, and bushes. They can also help by catching mosquitoes in their webs which will create a happier outside oasis for you and your family. Even though tarantulas are not found naturally in Pennsylvania, it is still important for us to realize that arachnids are vital to our environment, even in our own backyard.

What can we do?: One thing we can do to help tarantulas is create a spider friendly garden! Planting natural areas around your house or community encourages wildlife into the area by providing food and shelter for those species. Keeping undisturbed areas under shrubs or in flower beds will encourage spiders to create their webs in these areas.

Never remove an animal from the wild! Some well-meaning people will trap and relocate “pest” animals but the truth is, trapping rarely ends well for wildlife and is not a long term solution. While you might be thinking you are helping that animal, most people don’t realize the amount of care and time that goes in to caring for these animals, and removing them from their natural environment can be detrimental to the wild populations. If wild animals are not causing damage or posing danger, the best solution is to coexist! If you come across injured wildlife please call your local wildlife rehabilitation center as they are better equipped to handle and care for that animal.

The most important thing that we can do to help sustain their habitats is to “Leave No Trace”. Once you leave nature, no one should know that you’ve been there. This means bringing out anything that you’ve brought in. Additionally, leaving the environment unaltered is equally important.


Fun Facts

  • While Mexican Red-Knee Tarantulas are not usually harmful to humans, people with allergies to other arachnids such as other spiders or scorpions may have a reaction. The tarantula’s hair-like setae serve them in many ways, but primarily as sensory structures. Some are sensitive to pressure, others to heat or air movement or vibrations.
  • As they outgrow their existing skin, all tarantulas regularly go through an extensive molt, shedding their entire skin as well as the linings of their mouth, fangs, respiratory organs, stomach, and sexual organs.
  • Tarantulas can regenerate a leg if one is lost.
  • There are over 800 documented species of tarantulas.
  • The most notable nemesis of the tarantula is the Pepsis wasp. Also known as the tarantula hawk, this wasp parasitizes the unfortunate arachnids, using them as a living nest in which to raise their young.

Bibliography

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