What can we learn from buffalo?
In 2013, R40-million was paid for an African buffalo stud bull at a Vleissentraal Bosveld auction. This shattered the previous record of R26-million for a buffalo bull set in 2012.
Also in 2012, Deputy President Cyril Ramaphosa made an unsuccessful R19.5-million bid for a buffalo cow that was sold for R20-million. Wildlife breeding in South Africa is a lucrative industry.
But buffalo are not the only animals being sold for millions of rands at game auctions.
Sable and roan antelope are often sold in the range of R1-million to R10-million. Rare colour variants of springbok, impala and wildebeest regularly go for tens of thousands of rands.
This has caused people to ask whether the game industry is in an economic bubble with such inflated prices, or whether it is truly sustainable at these levels.
Arguably more important than the economic sustainability, is the genetic durability of the industry, which prizes certain characteristics, such as large horns or an unusual colouring. Your DNA (and that of all living organisms) is made up of four chemical building blocks, abbreviated as the letters A, T, C and G. This is your genetic alphabet.
In a sentence, the order of words conveys meaning to the reader. In the same way, the specific order in which the chemical letters of your genetic alphabet are arranged conveys a particular meaning to your cells. This ultimately affects you as a living being. These are your genes – the sentences hidden in your DNA.
Changing a letter in the order of a gene can improve, weaken or have no effect on its function – just like moving a word around in a sentence. In natural populations of a species there are many versions of each gene, differing only by a letter or two. These are called gene variants or alleles.
The more gene variants there are in a population, the better. When there is a drought, or a disease outbreak, a population with many gene variants (or high genetic diversity) is more likely to survive than one with only a few gene variants (or low genetic diversity).
This is because the population with high genetic diversity is more likely to have individuals that have the gene variant responsible for drought resistance or immunity to the disease.
Many individuals might die, but those with the gene variants best suited to the situation will survive and pass these variants on to the next generation. The population as a whole survives. The population with low genetic diversity dies out, because none of them has the gene variants that could help them survive. This is genetic durability, and survival of the fittest.
Intensive breeding practices select one or a few (economically) desirable traits. Wildlife breeders are particularly interested in rare coat colours of species such as impala, wildebeest and springbok.
These coat colours are relatively easy to breed and the animals are sold for huge sums to other breeders or trophy hunters. However, focusing on one characteristic may lead to a decrease in genetic diversity and increased levels of inbreeding in populations.
Decreased genetic diversity means that there will be fewer variants of each gene. To make matters worse, inbreeding increases the frequency in a population of rare gene variants that are often worse at performing their function than the common variants of that gene. There is probably a reason why these colour variants are rare in nature.
The blue wildebeest, for example, has developed its distinctive bluish grey colour because it is optimal for its environment in terms of camouflage, heat regulation and overall genetic durability. A different colouration could mean that it is not as adapted to its environment. One hypothesis is that rare, or weak, gene variants are inherited together with the unusual coat colour. A practical example is the case of golden wildebeest.
You could argue that just because something is rare in nature it does not mean that it is bad. The golden colour could help the animal to be better camouflaged in the savannah. The lighter colour also might help the animal reflect more sunlight and thus stay cooler. However, golden wildebeest are known to be more likely to die during and after transport to new environments. Scientists are not sure why.
It could be that they have rare, weaker variants of genes involved in stress response and adaptation than those variants found in normal blue wildebeest. In nature, animals with different coats are targeted by predators or are less adept at surviving droughts or diseases. This means that they are usually eliminated through natural selection, taking the weak gene variants with them. By choosing to breed only for certain colours, wildlife breeders could be decreasing the genetic durability of their herds.
However, the game ownership laws of South Africa mean that each breeder is allowed to deal with this issue in their own way and that the natural populations are kept genetically pure.
The case for selective breeding of Cape buffalo is a bit more positive. Breeders argue that trophy hunting has, over the years, removed those animals with the biggest horns from the population. Thus, breeding buffalo to obtain large horns is not believed to pass on weak gene variants, but simply to restore those genes that were removed by hunting and not natural selection.
A 2008 study by Vanessa Ezenwa and Anna Jolles, from the University of Montana and Oregon State University, respectively, illustrates this point.
They found that buffalo with bigger horns had fewer parasites on them. This suggests that buffalo with larger horns probably have stronger immune systems. Therefore, as long as big horns are not being obtained through inbreeding, breeders argue that private buffalo owners are in fact strengthening, or at the very least not weakening, the genetic durability of buffalo in South Africa.
This is all very good in theory, but is it actually happening in practice? To find out, we, in the Molecular Ecology and Evolution Programme in the Department of Genetics, and the Veterinary Genetics Laboratory at the University of Pretoria, investigated the genetic diversity and levels of inbreeding in privately owned populations of Cape buffalo compared to those in national parks.
Population genetics theory tells us that in large populations, such as those in the Kruger National Park, genetic diversity is often high, because the large number of individuals means many gene variants are present and there is random mating with little to no inbreeding. In our study we compared more than 1?200 buffalo from 12 private game reserves to just fewer than 80 buffalo originally from the Kruger National Park and now in Mokala National Park.
We found that the private herds had similar or slightly higher genetic diversity and lower inbreeding levels than the buffalo population in Mokala National Park. One reason for this is the practice of exchanging bulls between private game reserves, called outbreeding.
Outbreeding simulates the random mating that happens in large populations and also introduces new gene variants into each population or herd. This keeps inbreeding low and genetic diversity high. In other words, the private buffalo populations are at least as genetically durable as the natural population in this study.
The research suggests that no genes with negative effects are being passed on through the selective breeding of buffalo. However, this has not been specifically investigated and it is something that we will be testing in the future. Add to this the fact that most privately owned buffalo are disease-free and you have a situation that stands in contrast to the breeding of colour variants.
These private buffalo populations could even serve as back-up stock for the natural populations, if something like bovine tuberculosis were to put a serious dent in these populations.
Responsible wildlife breeding is thus an important aspect in conserving wildlife in South Africa for future generations to enjoy. Breeders would do well to follow the template of the buffalo industry with other game species and contribute to the genetic strengthening of wildlife in South Africa.
Deon de Jager attends the University of Pretoria.