Abstract
In a TREE review, Courchamp et al. 1. Courchamp F et al. Inverse density dependence and the Allee effect. Trends Ecol. Evol. 1999; 14: 405-410 Abstract Full Text Full Text PDF PubMed Scopus (1227) Google Scholar illustrated the Allee effect, resulting from stochastic sex-ratio fluctuations in small populations, with the case of the Kakapo, Strigops habroptilus. This parrot is now considered extinct in its original quarters in New Zealand because of predation by introduced stoats and feral cats 2. Clout M.N Merton D.V Saving the Kakapo: the conservation of the world's most peculiar parrot. Bird Cons. Int. 1998; 8: 281-296 Crossref Scopus (50) Google Scholar . The historical wild population was male-biased (∼2:1), probably as a result of interacting sexual and natural selection processes 3. Trewick S.A On the skewed sex ratio of the Kakapo Strigops habroptilus: sexual and natural selection in opposition?. Ibis. 1997; 139: 652-663 Crossref Google Scholar , including a higher predation risk on females after the arrival of humans 2. Clout M.N Merton D.V Saving the Kakapo: the conservation of the world's most peculiar parrot. Bird Cons. Int. 1998; 8: 281-296 Crossref Scopus (50) Google Scholar . Of the last 60 surviving birds that were translocated two decades ago to predator-free islands, only 22 were females – only about nine of which have remained fertile in recent years 2. Clout M.N Merton D.V Saving the Kakapo: the conservation of the world's most peculiar parrot. Bird Cons. Int. 1998; 8: 281-296 Crossref Scopus (50) Google Scholar . This situation is even more critical if you consider that seven of the nine fledglings produced so far are males (3.5:1) 1. Courchamp F et al. Inverse density dependence and the Allee effect. Trends Ecol. Evol. 1999; 14: 405-410 Abstract Full Text Full Text PDF PubMed Scopus (1227) Google Scholar , 2. Clout M.N Merton D.V Saving the Kakapo: the conservation of the world's most peculiar parrot. Bird Cons. Int. 1998; 8: 281-296 Crossref Scopus (50) Google Scholar . Therefore, the probability of definitive extinction is high just because of the stochastic biases of the offspring sex-ratio 1. Courchamp F et al. Inverse density dependence and the Allee effect. Trends Ecol. Evol. 1999; 14: 405-410 Abstract Full Text Full Text PDF PubMed Scopus (1227) Google Scholar . However, I wonder, in light of the recent advances in our knowledge of avian sex-ratio allocation, whether this apparently stochastic skew could be managed and even reversed.
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