Study Species
The gopher tortoise is the only native tortoise found east of the
Mississippi River (Auffenberg and Franz 1982, Bury and Germano 1994,
Edwards et al. 2016). Its range spans the southeastern United
States, from Louisiana to South Carolina and south into Miami-Dade
County and Cape Sable in Florida (Kushlan and Mazzotti 1984, Enge et
al. 2004, Waddle et al. 2006). Gopher tortoises support over 350
commensal animal species that use their burrows (Diemer 1986, Lips
1991) and are known to forage on over 1000 plant species across
their range (Ashton and Ashton 2008).
Many studies have investigated the diet and foraging ecology of
this species (McRae et al. 1981, MacDonald and Mushinsky 1988,
Mushinsky et al. 2003, Ashton and Ashton 2008), classifying it as
an herbivore that engages in frugivory (Birkhead et al. 2005, Hanish
2018, Richardson and Stiling 2019a, 2019b). As such, it is a
widely-recognized seed disperser by ingesting the seeds of
fleshy-fruited (Hanish 2018, Richardson and Stiling 2019a), and
“foliage is the fruit” species (Carlson et al. 2003, Birkhead et al.
2005, Figueroa et al. 2021), oftentimes enhancing seed
germination (Falcón et al. 2020). The tortoises in this study
serve as a model for investigating how frugivory might fluctuate in a
seed-dispersing herbivore (Marques Dracxler and Kissling 2022, van
Leeuwen et al. 2022), providing an opportunity to quantify which
fleshy fruits are an important part of its diet, and whether its
functional role as a seed disperser changes temporally.
The tortoises in the study site are found in three aggregations
which we refer to as the East, South, and West sites – named after the
cardinal directions in which they are located across Zoo Miami’s pine
rocklands (see Fig. 1). These tortoises aggregations are due to a
combination of the species’ social behavior (Guyer et al. 2012),
as well as the geology of this ecosystem (Hoffmeister et al.
1967), which can limit the availability of deep sandy soils that
facilitate burrowing (Whitfield et al. 2022). During the study,
no tortoises migrated from one site to another, as we regularly tracked
individuals via radio telemetry, so each site has a perfectly nested
subset of individuals that occupy it. While formal surveys were not
conducted, the plant communities in both the South and West sites were
representative of healthy pine rockland while the East site had a
greater presence of invasive plant species such as Burma reed (Neyraudia
reynaudiana), showy rattlebox (Crotalaria spectabilis), and shrub
verbena (Lantana camara).