Reproduction and Survival of the Desert Tortoise, Scaptochelys agassizii, in Ivanpah Valley, CA

Turner, F.; Medica, P.; Lyons, C.

Eighty-seven adult desert tortoises (58 female, 29 males in Ivanpah Valley, California, were fitted with radiotransmitters in 1980 and 1981. All were marked, weighed, and measured and released. Tortosises were then recaptured, weighed and released about every two weeks in 1980 and weekly in 1981. The experiment concluded in the spring of 1982, when 62 tortoises were recovered. Survival of males and females did not differ, but the observed death rate in 1981-82 (18.4%) was significantly greater than that in 1980-81 (4.4%). Females>200mm in plastron length exhibited two periods of distinct loss of mass in 1980 (15-28 May, 12-25 June)when masses of males were essentially unchanged. Losses of >100 were interpreted as evidence of egg-laying. Eleven of 15 females for which we had season-long records in 1980 laid two clutches, two laid one clutch and two did not lay eggs. The mean number of clutches laid was 1.60. Of 40 females considered in 1981, 20 laid one clutch, 12 laid two clutches and 8 did not lay. The mean number of clutches was 1.10

Reproduction and Survival of the Desert Tortoise, Scaptochelys agassizii, in Ivanpah Valley, CA

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