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Reproduction and Growth in Relocated and Resident Gopher Tortoises (Gopherus polyphemus) on Reclaimed Phosphate-Mined Lands

 

03-105-145Final

The study objectives were to investigate the effects of relocation on growth rate, number of eggs (clutch size), egg size, and characteristics of hatchling gopher tortoise (Gopherus polyphemus), a Florida Species of Special Concern. A primary reason for this study was to provide insights into the suitability of reclaimed phosphate-mined lands as relocation sites for tortoises. Gopher tortoises were studied at three unmined donor sites and four relocation sites (four reclaimed mine sites and one unmined site). Relocation appears to be an acceptable form of conservation from the perspective of continuing reproduction by the relocated tortoise populations. The relocation event itself had no lasting effect on reproduction. Results indicate relocation site may affect reproduction. For example, relocatees to a ruderal phosphate-mined site had a significantly larger clutch size than relocatees to an unmined pasture site. Any effect due to the relocation event was discounted because no significant differences were observed between the remnant residents and relocatees. Larger female gopher tortoises produced larger numbers of eggs, larger eggs, and thus greater egg mass per clutch. Body size was factored out during the relocation event analysis. Growth rates varied by site but appeared to be more closely associated with the age distribution of recaptured tortoises than with site characteristics. Very young and very old tortoises tended to grow slower than moderate aged tortoise. Due to poor incubation conditions, we were unable to determine if there was a relationship between hatchling characteristics and relocation event or site. Researchers should not discount the reproductive ability of small female tortoises. Three recorded here are the smallest reported for the species, attributed to higher than average annual growth rates for their populations. In conclusion, from the perspective of reproduction and growth, phosphate-mined sites appear to be suitable relocation sites for gopher tortoises.