Grammostola grossa
Guarani Giant Tarantula: Advanced Care Guide
Keeper Snapshot: A terrestrial Grammostola whose care literature is unusually easy to contaminate with G. pulchripes because the two names were synonymized from 1994 to 2009. Build from the defensible common ground: a low enclosure, firm form-holding substrate, an anchored hide, a mostly dry exposed surface with a moisture reserve below or to one side, effective ventilation, and a shallow open water dish. No G. grossa captive optimum or sling schedule was verified. Type III/IV setal evidence is genus-level and eye-injury cases are family-level, but they still justify transfers only, tongs, a catch cup, eye protection during disturbance, and strict fall prevention. - Big Z
Group: TarantulasDifficulty: Spice 3: IntermediateSetup: Low terrestrial build on firm, structure-holding substrate with an anchored ground-level hideHandling: Not recommended. Catch cup transfers only, and treat the hair as the real hazard rather than the fangs.
Use This Guide Safely
- Confirm the exact animal. Match this guide to the species, locality, size, and life stage on your label. If the ID is uncertain, use the more conservative part of the range and ask before changing the setup.
- Change one thing at a time. Treat temperature and humidity as target zones, then watch posture, burrowing, drinking, feeding, and molt behavior before making another adjustment.
- Respect the handling boundary. If the guide says no handling, fast, defensive, or medically significant, plan transfers with catch cups, locked lids, and no bare hands. For serious bites, stings, or symptoms, seek emergency medical care.
Quick Snapshot
| Temperature | 72-82 F (22-28 C) is a Big Z starting band, not a published Grammostola grossa optimum or source overlap. Family-level captive practice and regional modeled climate provide context only. Maintain a gradient and avoid direct, uncontrolled heat. |
|---|---|
| Humidity | No species numeric RH % target was verified. Maintain a mostly dry exposed surface with a moisture reserve in the lower or side substrate, effective ventilation, and accessible open water. This physical method is Big Z house practice. The historical 30-50% table is not a G. grossa institutional target. |
| Setup Type | Low terrestrial build on firm, structure-holding substrate with an anchored ground-level hide |
| Substrate | Use firm, tamped, form-holding terrestrial substrate deep enough for safe footing and a retreat option, with an anchored ground-level hide. Exact mix and depth are family/Big Z house choices. Species burrow/seasonal ecology is available only through a secondary account citing Schmidt; the original source was not independently recovered. Avoid abrasive gravel and excessive fall height. |
| Feeding | Offer a small sling appropriately sized prey at a cautious Big Z house cadence, commonly once or twice weekly, and adjust from abdomen condition and intake. Remove leftovers and do not feed through molt. No G. grossa sling schedule was verified. |
| Care Difficulty | Spice 3: Intermediate |
| Handling | Not recommended. Catch cup transfers only, and treat the hair as the real hazard rather than the fangs. |
Humidity zones: Very Low under 30% - Low 30-60% - Low-Moderate 40-70% - Moderate 60-80% - Moderate-High 70-85% - High 80%+ - Very High 90%+
Enclosure Format / Size Class
- Sling (0.75-1 in as supplied): low escape-proof enclosure, firm substrate, anchored hide, moisture reserve, effective ventilation, and a shallow open water dish sized to prevent entrapment
- Juvenile: low enclosure with increasing floor area, form-holding substrate, hide, open water, and minimal fall distance
- Adult: published adult size is unresolved; size enclosure from the individual spider, preserving floor space, secure footing, a hide, open water, and low fall height
Warnings First
- Grammostola material carried type III and IV urticating setae in the primary morphology study, but the specimens were Grammostola sp. and G. rosea, not identified G. grossa. This is genus-level morphology, not a species incidence claim.
- Tarantula setae can cause serious ocular injury at family scope. Avoid face-level work, wash exposed skin, and use eye protection during disturbance; seek professional care for eye exposure.
- A 2025 captive-tarantula bite report described paroxysmal cramping for four weeks, but 2026 correspondence acknowledged that the photographed spider could belong to several genera. It is a family-level warning signal, not Grammostola- or G. grossa-specific evidence.
- Transfers only. A terrestrial fall can injure the abdomen; use a catch cup over a clear, low work zone.
- No G. grossa numeric RH target, captive optimum, sling schedule, adult size, growth rate, molt cadence, or lifespan was verified.
- The 1994-2009 pulchripes synonymy period contaminates older care and size claims. Do not import unscoped figures from that window.
Simple Care
- House one spider per enclosure.
- Use a low terrestrial setup with firm form-holding substrate and an anchored hide.
- Keep most of the exposed surface dry while maintaining a lower or side moisture reserve.
- Use 72-82 F as a house starting band, not a species optimum.
- Provide effective ventilation and a shallow open water dish.
- Feed slings at a cautious recorded house cadence and adjust from abdomen condition and intake.
- Keep fall distance short and avoid handling or free climbing.
- Use tongs and a catch cup for transfers; reduce setal exposure and protect eyes during disturbance.
Advanced Keeper Notes
Enclosure & Microclimate
- A 2005 Certificate III student husbandry manual relays Australian Reptile Park practice. It is family/historical analogue material, not a formal zoo guideline and not G. grossa-specific.
- The manual's historical 30-50% row appears under obsolete genus usage and is not a species RH target. Physical moisture cues, ventilation, and open water replace a gauge-driven claim.
- Firm tamped substrate and a ground-level hide are defensible family/house construction. The species ecology statement is a secondary account citing Schmidt; original source was inaccessible in this pass.
- Bare SoilGrids and Open-Meteo endpoints were not reproducible citations and their extracted numeric claims were removed. Regional model output is context, not a captive optimum.
- Use a shallow open water dish. Pebbles, cotton, or sponge are not required and can complicate cleaning.
Feeding, Growth & Maintenance
- No G. grossa sling feeding study was found. Once- or twice-weekly small prey is a Big Z house starting cadence, not validation from the student manual.
- Adjust from abdomen condition, intake, and molt behavior; remove leftovers and stop feeding through molt.
- Adult feeding examples in the manual are family/historical analogues, not a species schedule.
- Adult size, growth rate, molt cadence, and lifespan remain unverified rather than being filled from retailer claims.
Possible Origin / Range
- Likely native range: Brazil, Paraguay, Uruguay and Argentina, per the World Spider Catalog. Bolivia is unsupported and is not claimed. Public occurrence coverage is very thin: GBIF returned 22 records total, only 10 with decimal coordinates, and represented Brazil and Argentina but not Paraguay or Uruguay. That coverage gap does not narrow the four-country catalogue range, and a contaminated synonym-path record prevents treating the dataset as a clean range sample. Secondary ecology accounts place the species under roots, bark, stones and leaf litter and at pastures or forest edges. The supplier provided no locality.
- Habitat translation: A cautious terrestrial build based on family/historical analogue and secondary species ecology: firm form-holding substrate, an anchored ground-level hide, a mostly dry exposed surface with moisture retained below or to one side, effective ventilation, shallow open water, and minimal fall height. 72-82 F is a Big Z starting band. Regional modeled climate and soil products are context only, not a measured captive optimum.
Advanced Keeper Details
- G. grossa and G. pulchripes were treated as one species from 1994 until Gabriel separated them in 2009. Care, size, and lifespan claims from that interval may refer to either animal.
- Current WSC records no junior synonyms for G. grossa. Names often folded into it belong to other valid species or synonym paths and are not commercial aliases here.
- Public occurrence coverage is thin and contaminated: GBIF returned 22 records total, only 10 georeferenced, and one record demonstrates a G. grandicola/pulchripes synonym-path problem.
- Type III/IV setal evidence is genus-level; ocular case reports are family-level. No G. grossa clinical series was found.
- The 2025 four-week cramping case is taxonomically unresolved after the authors' 2026 reply and cannot establish a Grammostola-specific hazard.
- No reliable adult size or lifespan figure was recovered. Size the enclosure from the individual and preserve low fall height.
- CITES Appendix II now includes G. rosea, not G. grossa or Grammostola spp. G. grossa is absent from the appendices valid 5 March 2026; other legality and provenance questions remain unverified.