Field evaluation of alpha-chlorohydrin against the Indian mole rat: studies on toxic and antifertility effects

Field acceptance and efficacy of a toxicant-sterilant, alpha-chlorohydrin (α-CH), at its 0.5% concentration in bait were evaluated against rodents in sugarcane fields which harboured high populations of the Indian mole rat Bandicota bengalensis (Trap Index (TI) = 53.6 rats/100 traps/24 h) followed by that of the Indian bush rat Golunda ellioti (TI = 28.6) and soft-furred field rat Rattus meltada (TI = 1.8). Acceptance of the α-CH bait by rodents in the fields was evident from complete consumption of the offered bait at most of the baiting points. The treatment (72 h exposure to the poison bait) resulted in 63.7% to 82.9% rodent mortality. Survey of the mature sugarcane crop revealed that the percentage of rodent cut canes in the treated fields (7.6% to 16.2%) was significantly less than that of the reference fields (26.3%). Most of the surviving male B. bengalensis, captured after 15 days of the treatment, had developed sterility as revealed by the functional abnormalities in their testes and epid-idymides. They showed decreased thickness of the seminiferous tubules, lower population of spermatogenic cells, cauda epididymal sperm concentration, live sperm and sperm mortality. A nonsignificant positive correlation between the testicular weight and sperm motility in males from treated fields indicated the effect of α-CH at maturation level in the cauda epididymides. Overall, it was evident that a significant proportion of the surviving B. bengalensis had become permanently sterile as a consequence to the development of spermatocoeles in the caput epididymides and the remaining had significantly low numbers (< 30%) of motile sperm in their cauda epididymides which was, obviously, a handicap for successful fertilisation.