Size and growth
Adult Theraphosa blondi reach about 25–28 cm and are moderate growers. Adult Theraphosa stirmi reach about 25–28 cm (10–11 in) and are fast growers. That affects how quickly Goliath Birdeaters and Burgundy Goliath Birdeaters move through sling and juvenile enclosure sizes.
Do not use size alone to estimate age in either Theraphosa blondi or Theraphosa stirmi. Sex, feeding and individual variation can change the pace of growth even when two spiders began at a similar size.
Enclosure and lifestyle
Goliath Birdeaters are terrestrial, while Burgundy Goliath Birdeaters are terrestrial. Build the Theraphosa blondi enclosure for a terrestrial spider and the Theraphosa stirmi enclosure for a terrestrial spider instead of assuming two tarantulas need the same shape of setup.
For Theraphosa blondi, substrate depth, retreat position and usable space should match its terrestrial lifestyle. Apply the same rule separately to Theraphosa stirmi; the enclosure should make normal behaviour easy rather than forcing either species into a generic layout.
Temperature, water and moisture
A practical temperature range for Theraphosa blondi is 20–26°C; for Theraphosa stirmi, it is 22–26°C. Stable room conditions are more useful for both species than chasing small fluctuations within those ranges.
For Theraphosa blondi, use moisture-retentive substrate with very good ventilation; never swampy and never allowed to dry completely. For Theraphosa stirmi, use moisture-retentive substrate with strong ventilation; damp rather than waterlogged. In both enclosures, keep fresh water available and adjust substrate moisture to how quickly the setup actually dries.
Temperament and maintenance
Theraphosa blondi is a New World species, while Theraphosa stirmi is a New World species. That background is useful when planning maintenance, but individual Goliath Birdeaters and Burgundy Goliath Birdeaters can still differ noticeably in speed and defensiveness.
With both Theraphosa blondi and Theraphosa stirmi, locate the spider before opening the enclosure, use long tools when they make the job safer and keep a catch cup ready for rehousing. Handling is not required for routine care.
Male and female lifespan
Male Theraphosa blondi generally live roughly 3–6 years, while females can live 15–20+ years. Male Theraphosa stirmi generally live roughly 3–5 years, while females can live 12–18 years.
Those lifespan ranges make sex particularly relevant when comparing Theraphosa blondi with Theraphosa stirmi. A confirmed female of either species is normally a much longer commitment than a mature male, and the exact age of an older juvenile may be impossible to know.
UK availability and trade notes
In the UK hobby, Theraphosa blondi is currently classed as uncommon, while Theraphosa stirmi is classed as uncommon. Stock changes between specialist sellers, captive-produced batches and show weekends, so availability should be checked at the time of purchase.
For records and purchases, use the scientific names Theraphosa blondi and Theraphosa stirmi as the main identifiers. Current trade notes list Theraphosa blondi as 'Not listed' and Theraphosa stirmi as 'Check current CITES rules before cross-border trade', so check current requirements before any international movement where controls may apply.
Practical difference in day-to-day care
The practical difference between Theraphosa blondi and Theraphosa stirmi comes from the combination of lifestyle, adult size, growth and moisture needs. Those factors change how much substrate, vertical space and maintenance access each enclosure needs.
Whichever species you keep, let the individual spider settle into an enclosure designed for its own biology. That applies equally to Theraphosa blondi and Theraphosa stirmi: fresh water, secure housing and patient observation matter more than trying to make the two species behave the same way.