Coming around the corner to an open field, one can almost predict that there will be a lone wildebeest bull standing tall, with their long face held high as you approach closer. One of the more familiar spots is along the open grounds of the Londolozi Airstrip and observing this lone figure inevitably prompts the question: ‘Why is that wildebeest alone?’ More recently however the site of the lone wildebeest bull and the separately gathered herds prompted one of my guests to ask: ‘Does this mean there are fewer males in the population?’ The answers are more complex than one would think, so I thought I would dive a little deeper and explore the illusion of a skewed gender ratio.

A lone wildebeest male stands proud over his domain.

Why is that Wildebeest alone?

The solitary nature of wildebeest bulls is often attributed to their territorial behaviour. In many ecosystems, male wildebeests will fiercely defend their territories, marking them with their scent and engaging in vocal displays to deter opposing intruders. This territorial behaviour serves to establish dominance and secure mating opportunities during the breeding season. In the instance of the lone wildebeest on the airstrip, some would say he is securing a prime piece of real estate that provides a productive grazing area, nearby water, and thickets to take shelter and to lure in potential mating opportunities. Consequently, once you have observed the larger, tightly-knit female herds one may perceive an apparent imbalance between males and females. However, this can be a misleading impression of unequal distribution, as the solitary nature of male wildebeests primarily stems from their territorial instincts rather than indicating a scarcity of males within the population.

Two wildebeest bulls face to face, one already on its knees ready to engage as they challenge each other for territorial rights.

Nature’s Calculated Balance

The distribution of males and females in wild animal populations is not random but rather intricately balanced through evolutionary, ecological, and behavioural mechanisms. One such mechanism is the Fischer principle, which states that the sex ratio of offspring is determined by the relative investment of parents in producing each sex. In species where females invest more in reproduction, such as many mammals, there tends to be a slightly skewed sex ratio, with more females than males.

Safety in numbers as a herd of wildebeest cows and their calves gather together for protection on the airstrip. There was likely a dominant bull that lured them closer with this territorial gnu call and with the access to good grazing and water nearby.

The Fischer Principle in Action

Consider the example of the wildebeest. Female wildebeest invest significant energy in carrying and giving birth to calves, as well as nursing and protecting them. In contrast, male wildebeest contribute primarily to mating efforts. As per the Fischer principle, in species like wildebeest where females invest more in reproduction, there will likely be a skewed sex ratio, with more females than males. This ensures that the reproductive effort of females is optimised, contributing to the overall reproductive success of the species.

A newborn calf walking alongside its mother.

Chromosomal Dynamics

Another aspect of understanding the complexity of gender ratios is to delve into the fundamental mechanisms of sex determination – chromosomes. In many species, including humans, sex is determined by the combination of X and Y chromosomes. Females typically possess two X chromosomes (XX), while males have one X and one Y chromosome (XY). During reproduction, the male contributes either an X or a Y chromosome, determining the sex of the offspring. This chromosomal interplay forms the basis of the Fischer principle, wherein the relative investment of parents in producing each sex influences the overall gender ratio of the population.

The Kigelia female’s two cubs show off nothing but cuteness! Read Sean Zeederberg’s blog here which discusses the chromosomal dynamics and how they influence the sex of leopard cubs.

Balancing Acts

The social dynamics of other animals also showcase intriguing strategies for balancing male-female ratios. Impalas, for instance, exhibit a harem-based mating system where dominant males defend groups of females from rival males. This system ensures that most females are monopolised by the strongest males, leading to a more balanced distribution of males and females in the population.

Elephants provide another fascinating example. While elephant bulls may appear solitary, their solitary nature does not necessarily mean there are fewer males in the population. In fact, male elephants often roam over large territories, interacting with multiple female herds during the breeding season. This behaviour ensures genetic diversity and contributes to a balanced sex ratio within elephant populations.

Female elephants invest considerable time and energy in carrying and raising their young, forming close-knit family units that provide protection and support.

So next time you come across a lone bull, whether it be a wildebeest or elephant, remember that there is more to their solitary stance. While superficial observations may suggest unequal distributions of males and females, a deeper understanding reveals the intricacies of the evolutionary, biological mechanisms and social dynamics at play that maintain the delicate balance of gender ratios.

The imposing figure of a wildebeest bull silhouetted against the golden hues of the setting sun. Guests often encounter a solitary wildebeest standing apart from the herd, grazing the vast grasslands, or ambling along the open savannah.