Graduate Thesis Or Dissertation
 

Control and biology of feral goats on Aldabra Atoll, Republic of Seychelles

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  • The control of feral goats (Capra hircus) and relevant aspects of their biology were studied on Aldabra Atoll, Republic of Seychelles, from October 1993 - May 1994 and November 1994 - May 1995. A total of 832 goats were killed on Aldabra using both the Judas goat technique and traditional hunting methods; a total of 28 Judas goats were used during the entire campaign. The remnant goat populations on Ile Picard (N=13) and Ile Malabar (N=19) were eradicated during the first season. On Grande Terre, a total of 798 (374 M: 424 F) goats were killed. The overall kill rate on Grande Terre was 0.37 goats killed/hour with 1.66 shots fired/goat. A total of 1,042 goats were encountered of which 26.1% escaped. Mean group size was 3.2 with a range of 1 to 20. Judas goat hunting became increasingly important over time with 18.0% (n=85) of goats killed in the first season being in the presence of Judas goats; 42.3% (n=126) of goats killed during the second season were in the presence of Judas goats. The overall kill rate for the project was almost 2 times greater for Judas goat hunting (0.61 goats killed/hr) than traditional hunting (0.32 goats killed/hr); Judas goat hunting was approximately 70% more effective than traditional hunting when compared using multiple linear regression. There was a significant relationship between Judas goat home range size and the number of conspecifics killed. Feral goats on Aldabra may be unique among feral goat populations by apparently not responding to population reductions in a density-dependent manner. For the first season, the intrinsic rate of increase (r) was 0.45; r=0.39 for the second season. Twinning rates were 30.7% and 37.5% in the first and second seasons, respectively. I subjectively estimated approximately 60-120 goats remaining on all of Grande Terre at the end of the project; 84 goats were estimated using the Leslie-Davis removal method of population estimation.
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