Dr. Silber Studies Reproductive Habits in African Wildlife
African Wildlife Reproductive Behavior
We’ve been studying the complex ecology and reproductive behavior of African wildlife ever since 1992. As soon as you go into the African bush you realize you are at the birthplace of humanity and actually the birthplace of all complex life. Africa holds the key to understanding the modern human infertility dilemma. There is a constant struggle between predators and prey as well as predators and each other to survive in this rich environment. But it is not just a matter of their surviving for their own lifetime, but rather a constant struggle to transmit their genes to the next generation – not to become extinct. Even the herbivores like wildebeests and impalas and gazelles that don’t prey on other animals have to fight each other in order to determine the pecking order and which male gets to mate. Only the males who fight the hardest get to pass their genes on to the next generation and those will be the animals with the highest sperm count because testosterone level and sperm count are closely related in these animals and will determine who will win the battle to mate even among the relatively peaceful herbivores.
Reproduction in Primates
Reproduction in Gorillas
Gorillas have relatively tiny testicles and extremely low sperm counts because there is no sperm competition in gorillas. If the female is ever going to get pregnant it will be with her one male partner.
Reproduction in Chimpanzees
Chimpanzees, on the other hand, have huge testes and a prolific system of mating and that every female gets mounted by every male so that the male with the highest sperm count is the one most likely to become the father. So sperm count is prevented from going down by the mating system which allows sperm competition and male-to-male fighting and male competition. Because, otherwise, the y-chromosome would inevitably result in a much lower sperm count and extinction of the species over many many hundreds of thousands of years.
Seasonal Affect on Wildlife Reproduction
The change of seasons, although subtle, also presents tremendous challenges to animals. Here you see literally millions of wildebeest and zebra migrating together in gigantic numbers up to the northwest of Tanzania from the southeast in order to get to wetter ground where they can feed and not starve during the dry season of the east and southeast in the summer months. And during this whole time they are involved in the mating process the competition to see which male gets to be the leader of the herd both sexually and socially and that will determine the way his sperm count will continue to be passed on to the next generation.
Reproduction in Elephants
Elephants are extremely social and family-oriented animals. The young can be seen protected by the entire family as they are suckling on their mother. Interestingly, it is impossible to evaluate whether the male with the largest testicles, and therefore the highest testosterone level, is going to win such a battle because the elephant peculiarly has his testicles placed inside the abdomen and they are not hanging down like with most other animals and so we can’t evaluate them. But we would guess that the male bull with the largest testicles is probably going to wind up being the father of most of the offspring. During the rest of the year the males and the females the children of the babies all get along together as they migrate through the East African bush looking for thorns and ridiculous things to eat like trees and tree bark. But the males are subject to fighting fits at the time of breeding season and when the males fight, it is truly a Clash of the Titans. And we think the males with the highest testosterone level and therefore the best sperm count and the biggest testicles inside their abdomens are the ones that are going to win.
Reproduction in Hyenas
The hyena is probably the most vicious animal in all of Africa and in fact when hyenas team up they can easily kill a lion in order to steal the Lions own kill. Interestingly, the female hyenas are much more vicious than their docile male partners and it is impossible to sex these animals by appearance to determine which is male and which is female. The female dominates so physically the male hyenas and they have a much higher testosterone level than the males – unlike in almost all other animals. In fact, the male in the hyena family is just a creature that is tolerated for no other reason and that they need his sperm in order to have offspring and carry on. His testosterone level is much lower than the female partners and they’re the ones in control. He is just allowed to be around as an inseminator and he is clearly the non-testosterone side of the family.
Reproduction in African Big Cats
Reproduction in Cheetahs
For years, it was thought that cheetahs were going extinct because of a very low sperm count caused by a lack of genetic diversity. In fact, all cheetahs are basically identical twins, genetically, of each other. There is hardly any genetic dissimilarity at all between them. However, it is now known that despite a very low sperm count in virtually all male cheetahs, the only reason for the infertility of the cheetahs in our zoos is our intrusion on their habitat. Cheetahs need to have a large variety of other cheetahs available so that they can actually choose the personality of the one he or she likes the best. Without this diversity of cheetahs and a large enough population to choose from, they will only appear to be infertile because they don’t mate. But it is not because of the extremely low sperm count. The extremely low sperm count has no impact on their fertility.
Reproduction in Lions
In lions, like all cats, a female doesn’t actually ovulate until she has sex. Her eggs remain ready to ovulate but she isn’t going to ovulate until there’s a reason for her to ovulate – and that is having sex. However – like the grizzly bear – if she has cubs, she is not interested in letting a male mount her. And his job if he really wants to have sex with her is to kill her cubs and then she will go to heat and be ready to accept him. Still, she will fight to protect her cubs as will the actual father lion. Unlike the grizzly bears, the male lion stays around to protect the females and to protect his domain and his genetic progeny.
So by understanding the reproductive behavior of these African animals and how they function in the wild, it gives us a complete understanding of the evolution of infertility in all animals – and particularly the evolution of infertility in humans and the current epidemic of infertility throughout the planet for humans.