Just an update for the one or two folks interested.

15 November 2011

The female in the communal has been guarding her egg case for too long now. For about a week, I have noticed that it is in a bad state, so I finally decided that it will not hatch. No explanation, just the way it is.

The egg case from my forth female has hatched about a month ago. A rough count suggested about 70 slings. So the one mother has plenty, the other in the communal has none. This is just unbearable, so what to do?

With the help of my Frootbat and some serious objection from the first female, we were able to separate ten slings from her. I kept the ten slings in a glass while opening the female in the communals nest, then carefully gave her the ten slings. It will be spectacular if she "adopts" them, only time will tell. Strange things happen in a Tarantula burrow overnight, so tomorrow should indicate if she took them under her proverbial wing... I think she will.

Sorry to hear that Scarab, lets just hope she adopts the others as here own

Okay so I just found this post and have read it from page one. This is awsome now I know why most people speak of you with respect and awe. well done and good luck with the future communal hope it works out and thanks so much for sharing. :woohoo: :woohoo: :woohoo: :woohoo: :woohoo: :woohoo: :woohoo: :woohoo:

2 December 2011

It would be safe to assume that the female in the communal has adopted the babies from another female. The young are just as fat as their siblings next door, which in my mind is pretty freaken amazing. Although it is difficult to see into the nest, and equally difficult to see all ten at the same time, the occasional sighting of slings proves that they are getting fed. The female has intensified her webbing efforts, expanding the nest almost daily. As is the case with most young, her adopted babies come out mid morning until late afternoon, so when they do, it is clear that they are very healthy.

It is impossible to say whether this has been done in captivity before, but from what I have witnessed, M balfouri females are likely to adopt young from other females when introduced during the peak of her maternal cycle. A scenario like this is unlikely to occur in the wild IMO, I don't thing slings would survive should their mother die. In this experiment however, the female produced a dud egg case and was given young from elsewhere. To date, it seems to be with success.

This experiment is realy interesting. In your opinion if the female had produced a viable egg sac and you had introduced the 10 adoptee's do you think she would still have taken them in and then abondoned her egg sac? Or, my guess, do you think she would have chosen her own offfspring and rejected, maybe even kill these introduced slings?
Obviously this is all speculation but it would be interesting to know which scenario you think from your experience is more likely. Another scenario is if she was not on her maternal cycle and slings were introduced what would happen then???

Your first question sk27.
I don't think the female, or any female for that matter, would abandon her own viable egg sac and adopt other young. I think (with some certainty) that she would have continued guarding her sac while tolerating the foreign slings. Once her own has hatched, she would feed them all, irrespective of the genes. Just to give substance to my theory, this female was extremely reluctant to abandon her dud egg case. After I introduced the ten slings, she was still sitting on her own sac. It took about ten days for her to finally let it go. The introduction of new babies had no affect on her initial brooding pattern, but since she had no sac to take care of, she obviously feeds the adopted babies. I am also of the opinion that she would not reject individuals from another mother when combined with her own offspring. The only difference would probably be the size of the slings if they did not hatch in the same time frame. This could cause the stronger ones to dominate the distribution or availability of food, but I am 100% convinced they will be accepted by the female.

Your second question.
Should you introduce slings while the female is not in a breeding cycle, I am sure she would not eat them. She might not care for them as such, but I don't believe she will harm them. The presence of young in her burrow MIGHT delay the production of her own egg case, but this would be very difficult to prove.

The bottom line is that I can say with much certainty that M balfouri can cohabitate and has strong social bonds. Living communally in captivity suggests this already, so the behavior of these spiders is centered around this with a total lack of intolerance or aggression towards each other, young or adult.

If I can, I will add a few pictures soon.