Effects of spraying the herbicides 2,4-D and 2,4,5-T on a population of the tortoise Testudo hermanni in southern Greece

A population of the tortoise Testudo hermanii near Olympia in southern Gree ce was studied by mark-recapture from 1975 to 1984. Part of the site was sp rayed with the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) each year from 1980, producing sympto ms of poisoning (swollen eyes, fluid discharge from the nose and immobility ) in tortoises. Survival rates of tortoises 10 cm or larger were significan tly lower in the affected areas, with extra mortality of about 34% year(-1) , against an annual survival rate of 0.85-0.90 in unaffected areas. Changin g population structures showed that juveniles were even more strongly affec ted, with the proportion of juveniles in samples decreased by half. The pop ulation in the sprayed area declined to near zero by 1984, due to mortality rather than to emigration, since more movements were recorded into than ou t of the affected area. There was no difference in body mass condition betw een sprayed and unsprayed areas, showing that effects were acute; mortality was not due to starvation from loss of food plants. The scale and pattern of mortality was similar to that from a severe scrub fire, spraying is pote ntially more catastrophic since often repeated at shorter intervals than bu rning. Possible physiological mechanisms of death are discussed. The suscep tibility of tortoises to 2,4-D and 2,4,5-T (or to associated dioxin impurit ies) presents a warning for conservation of these late-maturing animals. (C ) 2001 Elsevier Science Ltd. All rights reserved.