I have over-simplified things here in order for easy understanding of the non-genetics inclined.

All of us have the genetic information(DNA) that makes each and every one unique in their own right. This genetic information is found throughout every cell in the body and is in the form of structures, called genes, which are a set(two copies) of units of genetic messages/codes that tell the cell what it needs to be, to what kind of enzymes, body processes it needs to make etc. These genes are then collectively packaged into structures called chromosomes. All of us humans, have 23 pairs of these chromosomes that carry a variety of genetic information. To now focus on the sex-linked chrmosomes- Females have two X-chromosomes and males have one X-chromosome and a Y-chromosome. This Y-chromosome in males is unable to carry any useful genes and thus the males are at the mercy of the single X-chromosome. Genes if highly expressed(produced), both on the internal and external bodily attributes, are termed dominant genes. If the gene is rarely produced it is termed a recessive gene. For a recessive gene to occur in males, thus it appears on the X-chromosome and the result in most cases is a recessive attribute internally and externally. On females, due to there being two X-chromosomes, she would have the option of either carrying the recessive gene on one X-chromosomes and a dominant gene on the other X-chromosome and hence she would always have dominant gene expression in her cells. For her to have a recessive gene, she needs to have the recessive gene on both of her X-chromosomes.

This color morph can be due to two types of processes: (1) A recessive inherited gene or (2) A mutation in the “normal male coloring” genetic information during the developmental stages of this chap.

In the case of (1), for him to be a male he needs to have one X-chromosome and a Y-chromosome on his sex-linked chromosome. Thus when his mother and father mated, during the cellular development of the fertilized egg, he receives some genetic information from his mother and some from his father. Therefore he could have received his X-chromosome (and Y-chromosome) from either his father or one of either of two X-chromosomes from his mother. I suspect that this type of coloring is a recessive trait as it is not commonly seen in the Nyala’s or most other antelope for that matter-however it does occur(I recall two other instances where I have come across these odd looking chaps-I have not heard of this in other antelope species though) over a certain population. The frequency of this is not known (I certainly am not familiar with the cause of frequency, however im sure a statistician could crunch some numbers for me and work out the exact occurrence of this gene morph)- Also some recessive genes occur more readily than others. Thus, his coloring is a recessive (rare) inherited gene from his mother’s genetic information.

In case (2), this chap could have received the “normal male coloring” genes during early embryo development in his mother’s womb. And naturally with Nyala males, during later “teenage” years we see the color change to that of his father, as you pointed out. During this development, either a mutation; that is a change in his original “normal male coloring” gene, could have occurred or the “normal male coloring” gene is functional but has been suppressed or blocked and hence the female coloring prevails.

So will his coloring change to his father over time? Well I highly doubt it, looking at his horns and estimating his age, he will remain this color. Does he over express/ produce high levels of estrogen? Well perhaps so, however; I am not sure if the gene relating to color development is solely influenced by testosterone/estrogen-could be, but I certainly am not aware of this. However this is a plausible explanation, Adam. Since he could be expressing the “normal male coloring” gene, and high levels of estrogen could be forcing his body to behave in some way as female attributes. One sees/hears about this in human males with higher levels of estrogen that they develop breasts etc… How would one test this estrogen factor? Well, one could take blood samples and test your question of “high levels of female hormones” (this would be an interesting and novel ecological study and certainly a unique one, considering that the occurrence of this abnormal coloring is quite rare) and an answer could be found. Alternatively, one could monitor his behavior amongst other males-does he exhibit his typical male behavior of ‘ground-horning’ (Nyala males will scrape at the ground/earth/mud in sign of his masculinity) or his ‘lateral-display’ (Slow lateral movement of Nyala males, always contracting their dorsal hairs-which according to some researchers, can increase the overall appearance of the Nyala up to 40%, this display is linked to territory and dominance amongst males) or ‘mock-fighting’. This information could also be an exciting ecological find to report on! I hope this helps, and look forward to hearing others opinions to shed some more light on this peculiar color morph.

We have seen a young Nyala, gender unknown that is almost white. Is this a well known colour mutation in Nyala?