I had thrown a locust into the enclosure, and I hung around for a little while to see if she would do it (as I usually do) but there seemed to be no sign and I had all but given up. I went to feed another spood, and when I came back, she was doing this:
This dance is often seen in Big Spoods species, although a lot of other species do it too. They are essentially spinning in circles, laying a web - a feeding mat - underneath them as they do so. I've read a number of theories as to why they do the "happy dance" when they feed, but there is no definitive answer.
Some of the most popular theories include:
Threat detection
Liquidising and slurping a critter takes a long time, and during that time, they are vulnerable if sitting out in the open. By laying a web underneath themselves they are better able to detect approaching predators. Vibrations from predator movement are more easily transmitted through the web silk, in the same way that orb weaving spiders are able to detect prey caught in their webs. This enables them to eat in relative safety, as if anything were to approach, they would get an earlier warning and can then scarper.
Hygiene
Another theory states that they lay the mat down for hygiene. There are two branches to this theory - one is that it helps them to keep their living area clean. It helps them to prevent their prey from falling apart during the liquidisation process, and any spillages can be wrapped up in webbing, carried away and disposed of elsewhere. This could carry some weight - I know Big Spood herself will only toilet in one particular place in her enclosure - specifically her water bowl - and I've seen her digging holes to bury unidentifiable things via Spood-cam. She is very particular about her home. The second branch to this theory is that it helps to protect her from contaminating her prey with bacteria. Spider silk is sterile when it comes out, so by laying her prey on a silk mat, she is able to prevent bacterial contamination from the environment. I don't know whether spiders are that aware of hygiene, but it's a cool theory.
Preventing escapes
According to this theory, if her venom were not kicking in fast enough and the prey were to try and escape, it would get caught in the sticky web underneath her and not be able to go anywhere. I can't speak for other species, but Big Spoods venom is pretty fast-acting, so I'm less convinced about this theory.
Territory/theft
On a similar note to the above theory, there is another theory that by laying her mat she is saying "This is my territory, back off!" and that by lightly wrapping her prey in silk, she is laying claim to her prey. This would be effective against scavenging predators like ants, for example. By using silk, she is preventing the ants from crossing into her feeding space and carrying her prey off to their nest.
Leftovers
The final theory that I'm going to mention here is that the silk helps the spider to wrap the prey up to later store any leftovers, just as a garden spider does in it's web. It's well known that a garden spider will kill any prey that lands in its web, whether it's hungry or not, because it can wrap it up in silk and store it in it's "larder" for later consumption. There's no reason why a tarantula couldn't do the same thing, though I have never seen any of my captive spoods do this. For the most part, they consume the whole prey item before dropping a carcass and moving on.
These are just a selection of theories, and no one of them has been studied for confirmation. They're pretty interesting to discuss, mind. So what is your favourite theory? Do you have any theories that haven't been listed here? I don't often ask for feedback, but this is something I'd love to know more about, so please leave any thoughts in the comments!
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