This is a difficult situation, however when you advertise an animal for sale, whether it is yours or belongs to someone else, in my eyes you are responsible. It is your responsibility to get the animal to its destination alive and unless you get the buyer to put in writing that they accept that if the carrier is delayed and the animal dies, then you should cover that loss. I can understand that you cannot simply fork out $3200, however if that were I, I would be offering the buyer $3200 credit with my business. At least that way the buyer can hopefully recoup their money through either the sale of those animals or goods purchased on credit with you, or be happy with those animals.
Shipping through UPS is illegal regardless as they do not accept live animals. This was made abundantly clear a few years back when shipyourreptiles stopped shipping temporarily. Anyone with any knowledge of the reptile industry would be aware of that.
As I say, this is a difficult situation. I had something similar happen to me 10 years ago. In one of the shipments I had arranged from the US to the UK, when I lived there, the seller in the US screwed up. I had ordered three Boelens pythons for a customer who asked if I could get some. I was simply bringing in some boas and balls, but the seller (a large dealer in Florida) said it was not a problem. The buyer wired the money to me, and me to Florida. Well, lets just say the Boelen's never arrived. I was out around $10,000 and the dealer said he did not have it to return. What did he do, he reluctantly sent me a ball morph that was worth that value. Of course, the market in the UK was not interested in a 10 grand ball at the time and I had to take out a loan and pay it off to repay the buyer. Even thought the seller in Florida screwed me, because I was brokering the deal, I was the one that had to make it right. Thankfully Karma caught up to the dealer in Florida in a big way. Long story short, if you broker a deal, you are responsible. No matter what your ridiculous terms are on your website, unless the buyer said I agree, and unless you have no conscience to realize that your shipping method was wrong, and plain illegal, I believe that the Tortoise compound should make this right to the full extent of the value ($3200). The story of the tortoise dying several weeks later is irrelevant. It was alive when it arrived and the buyer/trader made no issue relating to its health.
Just my two cents as someone with experience in brokering a sale that went wrong.
ATC, make it right. (I was actually looking at your site last week considering buying some red foots from you).
Warren