Conclusions - 1
My hypothesis is that Typhlonectes natans is a dry season breeder, mating mid-dry season one year and giving birth early in the dry season in the following year. This would confer a number of advantages. The first being that the feeble new born young would be less liable to drown as would almost certainly happen in the flooded forests during the wet season. The second advantage is that food is plentiful and concentrated into small areas during the dry season, particularly for scavengers. The disadvantage is that the stress on the mother of such a long pregnancy (the mother in this case died four months after giving birth despite extensive care and treatment) makes it improbable that breeding would take place every year in the wild. Every second year seems more likely (it may be possible that a well fed captive female caecilian might regain breeding condition faster). Females of a relative of T. natans, Dermophis mexicanus are known to have a biennial sexual cycle while the males breed annually (Jared, Nava & Toledo, 1999). This would mean that the reproductive rate of Typhlonectes natans is very low. It therefore follows that the mortality rate of wild caecilians must also be low or they would long-since have become extinct (rather than persisting as a group for over 200 million years).
Why then, since Typhlonectes natans appears to take no steps whatever to avoid predation, does it not get decimated by the wide array of predators present in its habitat (fish, turtles, otters, snakes, cormorants, freshwater dolphins, herons & egrets to name a few)? There is good evidence for the toxicity of many caecilians, particularly members of the genera Ichthyophis and Dermophis, although the extent of toxicity in Typhlonetes species is less clear. References have been made to the toxic effects of Typhlonectes compressicauda on the predatory wolf fish, Hoplias malabaricus (Miller, 2003). My supposition is that, in common with many other amphibians, Typhlonectes natans is either unpalatable or positively toxic. I have, however, kept my caecilians with fish for 8 years now and none have suffered any ill effects. I would therefore assume that, in common with bufonid toads, it is necessary to either eat the caecilian or agitate it very severely before any toxins are exuded. I have not tried this and advise others not to do so, on both safety and humanitarian grounds. This supposition would be best proved/disproved at autopsy by a pathologist.