“What is the fastest-growing tarantula species?”

It’s a question that I’ve been asked dozens of times over the years, and one that I’ve strategically avoided answering. First off, although I’ve managed to keep over 130 different species, that’s only a fraction of the 900+ species of described tarantulas in the world. It would literally be impossible for me to comment on the fastest-growing species, having no experience with the majority of tarantulas out there.

Also, there are several factors that can impact tarantula growth, and while one keeper might experience super-fast growth with a species, another keeper may find that their specimen is taking forever to put on size. In my years of experience, I’ve had many folks come to me with differing opinions on a particular species’ growth rates. 

The fact is, a specimen’s growth can be impacted by several variables, including temperature, feeding schedule, and genetics. Someone maintaining their collection at 80 F (27 C) will likely experience faster growth rates than another person keeping hers at 70 F (21 C). A keeper may feed his slings once a month, while another keeper feeds his spider twice weekly, again leading to faster growth. Then, some specimens just seem to put on size more quickly than others due to genetics. How could I possibly assemble an accurate list when there was just so much to take into consideration?

However, after years of dodging the question, I finally decided that the best way to approach the topic wasn’t to make a list of the fastest-growing tarantulas in the hobby, but to talk about the species I have personally raised that have exhibited faster-than-average growth rates. And, as the temperatures in my tarantula room tend to run lower than some of the year, with winter temps often in the lower 70s F, it would mean that these species grew quickly despite not having high temperatures. Therefore, someone keeping theirs at higher temperatures should still experience even faster growth. So, how could one go about determining which species are “fast growing”? Kyle Shane Horner summed up the issues best with his comment: 

When assembling this list, I took a couple of factors into account. First, I looked at species in which males mature quickly, as mature males are adults nearing the end of their life cycle. In these instances, their female counterparts were not sexually mature but still qualified as “young adults.” I also looked at annual growth, as I found that my fastest-growing tarantulas usually gained several inches in the first 12 months of their lives. With the spiders on this list, one can expect their little sling to resemble a big hairy adult within a year while also reaching a large percentage of their max size. 

So, at long last, here is my list of the 14 fastest-growing tarantulas I have had the pleasure of keeping! 

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