Literaturdatenbank
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Hinderle, D. (2011). Desert tortoises (gopherus agassizii) and translocation : homing, behavior, habitat and shell temperature experiments. Unpublished thesis , San Diego State University, San Diego.
Added by: Admin (29 Jan 2012 12:38:50 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: Hinderle2011 View all bibliographic details  |
Categories: General Keywords: Gopherus, Gopherus agassizii, Habitat = habitat, Nordamerika = North America, Schildkröten = turtles + tortoises, Testudinidae Creators: Hinderle Publisher: San Diego State University (San Diego) |
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| Abstract |
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Testudinidae Translocation of threatened or vulnerable species is a tool increasingly used for conservation and management, and in some species the behavioral and physiological responses to translocation may undermine the success of translocation efforts. For the federally protected desert tortoise (Gopherus agassizii), translocation is a strategy used to manage declining populations, yet post-translocation responses in this species are poorly understood. Here, we radio tracked 40 tortoises in Fall 2009 and 40 tortoises in Spring 2010 to explore homing ability and movement patterns; we further considered differences in behavior and habitat use between translocated and non-translocated tortoises, and assessed how these differences affected carapace temperatures. Tortoises were randomly assigned to one of three treatment groups: translocated (displaced 2, 5, or 8 km from their source location), handling control (used to measure the effect of handling tortoises during experimental manipulation) or control (as a control treatment). After translocation, twenty percent of the translocated tortoises were able to navigate to their source location, and translocation distance had an effect on their ability to navigate home, with males and females demonstrating similar homing abilities. We found 44 % of tortoises in the 2 km translocated group returned home, whereas no tortoises in the 8 km translocated group did. We also found that translocated tortoises moved more than the control groups, with some individuals moving > 10 km from the translocation site. These patterns were persistent even accounting for seasonal and sex differences in movement. Further, we found that translocated tortoises exhibited different placement, position and activity patterns within their habitat than nontranslocated tortoises. We also found that while all tortoises showed an association with large shrubs in the landscape, the translocated tortoises showed a significantly closer association to shrubs and showed a stronger affinity to particular shrub species. Although there were no significant carapace temperature differences between translocated and non-translocated tortoises across all ambient temperatures, we found translocated tortoises had significantly higher carapace temperatures when the ambient temperature was >29°C. By identifying homing behaviors and quantifying post-translocation movement patterns and habitat associations in desert tortoises, this in-situ experiment addresses a key data gap that may have limited the efficacy of tortoise translocation efforts.
Added by: Admin |