Crocs Crocked By Warming
By Sarah Gillham
As far as I was aware, the only time gender can be fixed or chosen is when the meddling hands of a plastic surgeon are involved. For most mammals (humans included), it’s just luck of the draw as to which chromosomes nature bestows upon you, XX or XY, a method which generally results in an even distribution of sexes. For some species however, this is not so straight forward as is the case with crocs, whose sex is determined not by genetics but by the embryo’s temperature during incubation.
Dr Alison Leslie of South Africa’s University of Stellenbosch and principal investigator of Earthwatch’s Crocodiles of the Okavango Delta project, has been studying this phenomenon for years. She states that a difference of 0.5-10C can result in markedly different sex ratios.
Research has shown that the optimum temperature for male hatchlings is around 32-330C while temperatures either side of this are better for females. It is possible for a nest to result in hatchlings of both genders, however, as nest temperatures can vary from the top the bottom.
The problem is, as global warming increases, so to will the incubation temperature of crocodile nests resulting in a situation where females rule the school.
This may sound the perfect scenario to us women – a few males at the mercy of the more abundant females. However for survival of the species this situation would be far from perfect and could result in their eventual extirpation. Whether this would really be from the lack of men or from the snappiness associated with too many women under one roof remains to be seen!
Dr Alison Leslie of South Africa’s University of Stellenbosch and principal investigator of Earthwatch’s Crocodiles of the Okavango Delta project, has been studying this phenomenon for years. She states that a difference of 0.5-10C can result in markedly different sex ratios.
Research has shown that the optimum temperature for male hatchlings is around 32-330C while temperatures either side of this are better for females. It is possible for a nest to result in hatchlings of both genders, however, as nest temperatures can vary from the top the bottom.
The problem is, as global warming increases, so to will the incubation temperature of crocodile nests resulting in a situation where females rule the school.
This may sound the perfect scenario to us women – a few males at the mercy of the more abundant females. However for survival of the species this situation would be far from perfect and could result in their eventual extirpation. Whether this would really be from the lack of men or from the snappiness associated with too many women under one roof remains to be seen!
Image: Peter Ong
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