See the link below.

In snakes the females are WZ and the males are ZZ. So the father always gives Z and daughters are caused when the mother gives W and sons when she gives Z. So the mother determines the gender on what should in theory be the long term observed 50/50 split.

However, the 16 females in a row works out to 1 in 65,536. The example of 45 females in a row 1 in 35 trillion. So, something is up here that looks to be a considerable deviation from the expected.

Where there many eggs that failed to hatch in either case? Maybe these males are homozygous for a "son killer" version of the Z chromosome (opposite of the article). Of course that bags the question of how are the fathers alive. Maybe it's only fatal when paired with a normal Z. But where the first homozygous "son killer" Z male came from would be a good question. Maybe there is some regional variation of the Z of these males that just isn’t compatible with the more common Z seen in the mothers.
ZW Species

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