Size-specific Fecundity of the Desert Tortoise (Gopherus agassizii)

We determined the annual fecundity of desert tortoises using x-rays from 1993 through 1995 at Yucca Mountain, Nevada. The smallest tortoise to reproduce was 209 mm carapace length (CL); eleven smaller tortoises did not reproduce. The mean age of first reproduction was estimated to be 19-20 years. Clutch size and annual fecundity were related to female size, but annual clutch frequency was not Clutch size ranged from 1 to 10 eggs; annual clutch frequency ranged from 0 to 2. Mean clutch size of tortoises with a single clutch was 0.9 eggs larger than that of tortoises with two clutches. Annual fecundity ranged from 0 to 16 eggs. Predicted annual fecundity was three eggs for a 208 mm CL tortoise and increased by one egg for each 7 mm increase in CL. Annual fecundity of tortoises in this study was compared with that of tortoises studied in Goffs, California, during 1983-1985. The regressions of fecundity on female size had similar slopes, but tortoises at Goffs produced an average of 4.5 eggs more than tortoises of the same size in our study. Tortoises at Goffs, however, were significantly smaller than tortoises in our study.

[1]  C. Tracy.  Estimating Age of Desert Tortoises (Gopherus agassizii) from Scute Rings , 1995 .

[2]  K. Rautenstrauch,et al.  The northern boundary of the desert tortoise range on the Nevada Test Site , 1994 .

[3]  Peter Kareiva,et al.  Modeling Population Viability for the Desert Tortoise in the Western Mojave Desert , 1994 .

[4]  A. Alberts,et al.  Seasonal Reproductive Cycle of the Desert Tortoise (Gopherus agassizii) in the Eastern Mojave Desert , 1994 .

[5]  J. Spotila,et al.  Non-Lethal Sexing Techniques for Hatchling and Immature Desert Tortoises (Gopherus agassizii) , 1994 .

[6]  T. Esque,et al.  Range and habitats of the desert tortoise , 1994 .

[7]  R. Bury,et al.  Research on North American Tortoises: A Critique With Suggestions for the Future , 1994 .

[8]  D. Germano.  Age and growth histories of desert tortoises using scute annuli , 1988 .

[9]  F. Turner,et al.  Age-size relationships of desert tortoises (Gopherus agassizi) in southern Nevada , 1987 .

[10]  K. Nagy,et al.  Physiological ecology of desert tortoises in southern Nevada , 1986 .

[11]  F. Turner,et al.  Reproduction and survival of the desert tortoise (Scaptochelys agassizii) in Ivanpah Valley, California , 1984 .

[12]  J. L. Greene,et al.  Variation in Reproductive Characteristics of Aquatic Turtles , 1982 .

[13]  L. Miller.  Further Observations on the Desert Tortoise, Gopherus agassizi, of California , 1955 .

[14]  G. Stuart.  Observations on Reproduction in the Tortoise Gopherus agassizi in Captivity , 1954 .

[15]  C. Grant.  The Southwestern desert tortoise, Gopherus agassizii , 1936 .

[16]  R. Breder.  Turtle trailing: A new technique for studying the life habits of certain Testudinata , 1927 .