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Transcript
Gopher tortoises
• https://www.youtube.com/watch?v=o5FwvUD2e94
• https://www.youtube.com/watch?v=GQSZjgl6Iss
• https://www.youtube.com/watch?v=BF8UAEVWgwk
Tortoise facts
• Gopherus polyphemus
• 1 of 4 tortoise species in North America
Family Testudinidae
• Desert tortoise Gopherus agassizii
• Texas tortoise Gopherus berlandieri
• Sonoran Desert tortoise Gopherus morafkai
Gopher tortoise
• Range:
Gopher tortoise ecology
• Like other NA tortoises, inhabits relatively arid environments in its
range (sandhill, scrub, coastal scrub primarily here in FL)
• Often found in disturbed sites (retention ponds, roadsides)
• Not often found in association with sites with standing water/high
water tables, although they can swim.
• Limiting factors (other than standing water) include difficult soils
(compacted, clays), unbroken canopy, dense ground-level shrubby
vegetation
Gopher tortoise ecology
• Primary remaining native grazer in FL grasslands
• Higher densities often associated with higher density (ground cover)
of herbaceous vegetation
• Food items include broadleaf grasses, legumes, cacti (Opuntia),
wiregrass (early spring), and opportunistic foraging (seeds, fruits,
flowers)
• Potentially an important disperser for native grasses and other plants
Gopher tortoise biology
• Long-lived species (?)
• Females reach sexual maturity after 12-15 years
• Low fecundity (clutch size is ~ 5-6 eggs, single clutch per year)
• Mating and nesting occurs in the spring
• Eggs incubate over 100 days in the burrows
• Vast majority of eggs and young are killed (some reports estimate
populations may only produce young that survive beyond the first
year every 7 years or so.
• Racoons are primary nest predators, but lots of others
Gopher tortoise burrows
• Burrow depth limited by the water table
• Affect soil chemistry
• Serve as sites for plant recruitment
• Serve as key soil disturbance necessary for soil swimming vertebrates
(e.g. sand skinks)
• Serve as refuge for numerous species (indigo snakes, Florida mouse)
• Hundreds of commensal species (flies, beetles, etc.)
Reasons for decline/threats
• Primary factors: habitat loss, habitat degradation (fire suppression),
human predation
• Habitat loss: urban development is generally incompatible with
tortoise ecology
• Habitat degradation: roads (roadkill), dense vegetation (due to lack of
burning), loss of food plants (due to lack of burning) makes habitat
unsuitable causing abandonment and/or death
• Gopher tortoise has been a food item for over 4000 years for humans.
• Until recently, regularly taken as food. Now illegal.
• https://www.youtube.com/watch?v=eNknz8hYTRs
• Discuss issues of tortoise relocation (unexpected threats, problems)