BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 38 PT. 1(4)


de anidamiento consecutivas se chequearon 2,008 madrigueras en b6squeda de huevos. Menos de un 2% de
las madrigueras contuvieron huevos, y s61o dos de 18 hembras gravidas depositaron sus huevos en la entrada
de las madrigueras. El tamaflo promedio de la puesta en 1990, en medio de una sequoia regional prolongada,
fue significativamente diferente que el promedio de 1991 cuando la Iluvia caida fue cercana al promedio. El
tamafio de puesta estuvo positivamente correlacionado con el largo del caparaz6n de las hembras, adn
cuando el largo del caparaz6n explic6 una pequefia proporci6n de la varianza. Sin embargo, el hecho de que
existi6 una correlaci6n negative entire el ancho de las madrigueras y el tamailo de la puesta en nidos
localizados en madrigueras, sugiere que estos nidos fueron depositados por hembras no residents.


 INTRODUCTION


 Gopher tortoises (Gopherus polyphemus) occur in upland habitats in six
southeastern states (Auffenberg and Franz 1982). They excavate extensive
burrows that provide protection from predators, thermal extremes, and
environmental perturbations. Gopher tortoise numbers may have declined by 80%
in the past 100 years (Auffenberg and Franz 1982), largely as a result of habitat
alteration and human predation (Taylor 1982a; Means 1986; Diemer 1987). The
decline in tortoise populations is particularly important because gopher tortoise
burrows are used by many other wildlife species (Eisenberg 1983). Sixty vertebrate
and 302 invertebrate species have been documented to use tortoise burrows (Speake
1981; Franz 1986; Jackson 1989; Lago 1991).
 In north-central Florida, female gopher tortoises attain sexual maturity at a
carapace length of 220-230 mm (10-15 years of age) (Iverson 1980; Taylor 1982b;
Diemer 1986). Males typically reach maturity at a smaller size than females
(200-210 mm carapace length) (Taylor 1982b; Douglass 1986). Longevity
estimates range from 40 to 60 years, although growth rate declines with age
(Landers et al. 1982).
 Gopher tortoises rarely are encountered above ground. However, important
population characteristics can be described based on the size and number of
burrows. There is a strong positive correlation between carapace length of the
resident tortoise and burrow width (Hansen 1963; Alford 1980; Martin and Layne
1987). Carapace length is related to age in gopher tortoises (Auffenberg and
Iverson 1979; Landers et al. 1982); therefore, the general size-class structure of a
population can be evaluated based on burrow width. Gopher tortoise populations
typically are estimated by assessing burrow occupancy using visual cues such as
tracks or plastral slide marks. In a long-term study in north-central Florida,
Auffenberg and Franz (1982) found that an average of 61.4% of burrows were
occupied at any given time. Recent studies have shown that there is considerable
variation in burrow occupancy depending upon season, habitat, and geographic
location (Burke 1989; Breininger et al. 1991).
 Movement from the burrow is related to the diurnal temperature cycle
(McRae et al. 1981b). In northern regions, cold temperatures restrict tortoise
activity in winter months, whereas in south Florida, tortoises are active year-round