You said shipped by usps...surely you mean overnight shipping, right, and not postal service (longer than next day)? Shipping even overnight in a small, stifling box can sometimes be stressful enough to do in any chameleon, even the most healthy. Shipping longer than overnight delivery certainly could have contributed to her female's demise, in my opinion. I recently received a DOA on an overnighted CB animal, for inexplicable reasons. Personally I still hold my breath every time I ship chameleons, even when temps and all other parameters are optimal. Chameleons are fragile beasts.
I am assuming your Senegal was WC, as CB are virtually nonexistant, and any reputable breeder skillful enough to have actually bred Senegals in captivity would hesitate in shipping a gravid female, and certainly not any route longer than overnight. The demands of being gravid sometimes overwhelm healthy CB stock---pregnancy is a highly consuming state for a little chameleon body. A WC chameleon who survives the rigors of shipping not once, but twice at least (from native country to US, then from supplier to you) has already endured much stress from just shipment alone. So yes, being gravid could definitely have contributed to your chameleon's death.
Senegals are a very timid and easily stressed chameleon. They are very much a hands-off species. WC specimens are often literally loaded with internal parasites (sometimes external, too). There may even be smoldering disease(s) lying dormant in these wild animals that are exacerbated from stress and overwhelm the chameleon's impaired and compromised immune system. That is why it is critical that all WC animals be quarantined upon arrival, even ones from the same shipment.
How do I know this?
My very first chameleon was a WC Senegal. If I had only known then that Senegals were such a difficult species to keep, I would have considered other species. I truly believe the only way Carly has survived to this day was by early intervention of my very helpful veterinarian, as Carly was full of worms and required several fecal checks and various medications to finally achieve a clean bill of health. Today she is probably one of the most robust chameleons I have, but it took several months of a petrifed, scrawny-looking chameleon in quarantine before she started to blossom. It is only just recently that I feel she has finally acclimated well enough to captivity that I may try to mate her, although I rather doubt I will be lucky again in acquiring a male Senegal and getting it to full health and maturity as I was with Carly. Below is a picture of "Carly", who was incorrectly sold under the label of "Gracilis" but who has only recently been correctly identified as a Senegal!
~Kerry
(PS: For what its worth, in my time keeping Carly I have found her to be very senstive to vitamin and mineral supplementation via dusting, considerably more sensitive than almost every other species I keep. She does much better with gutload only as a means to acheive vit/min supplementation. That is just something interesting I have observed in my time with Carly).
