A story of survival for Thomson’s gazelles
Across the savannah, animals seasonally engage in a long migration journey across the 30 000 km stretch of Tanzania and southwestern Kenya known as the Serengeti and the Masai Mara. Gazelles, wildebeests, and zebras represent what remains from a dwindling migratory species population. Animals like Thomson’s gazelles are one of the best known species of gazelles and named after the British geologist and explorer Joseph Thomson. They navigate the fluctuating climate to create patterns that ecologists are interested in mapping and predicting. Savannah ecologist T. Micheal Anderson attempts to interpret the movement of several gazelle populations to introduce a more scientific reasoning to their ambiguous nature. By merely observing the ascension of the migratory population from the Serengeti, the ecologist describes it as “breathtaking.”
Do Thomson’s gazelles and other species follow their instincts as their natural compass? Is making the long and uncertain trek across African savannahs in search of rich grassland the target of this journey? Or is it the search for a pack that will defend individual gazelles against predators?
Observing Thomson’s gazelles in the Serengeti was the first thing ecologists did to predict their transition to areas with abundant rainfall against the changing climate that started shaping the biodiverse savannah landscape. Ecologists documented several confrontations of Thomson’s gazelles with predators, droughts, and resource scarcity, and their response as a pack. Their effort to track gazelle’s mobility was made possible by using GPS trackers on the animals, as well as collecting feces to study how their diet influenced their trajectory. It turns out that the gazelle’s population size and diet predicts their movement across the great landscape.
Tall grass or young herbs…
As the dry season arrives, the availability of grazing land in the Serengeti declines. This drives Thomson’s gazelles to migrate toward the savannah plains that offer abundant foraging area fostered by seasonal rainfall. Seems simple, but the herd may encounter further obstacles, including finding enough quality nutritious plants to feed the pack. Compared to wildebeests and zebras, gazelles’ small stomachs and slow digestion force them to prioritize quality over quantity — the quality grass is young herbs that sprout after rainfall. To make their journey even longer, gazelles target areas with abundant young herbs with large quantities sufficient to feed their large pack. With varying degrees of vegetation across the savannah, they cannot find a good place to end their journey, which explains their constant mobility across the grassland.
Growing the herd…
It is a gazelle’s priority to be part of a large herd. By ensuring a place within a sizable population, gazelles secure protection against predators who become overwhelmed by the size of the herd, leaving the gazelles to graze in peace. In this game, the prey outwit their predators because collaborative grouping and teamwork enables them to detect dangers easily. Yet, their size simultaneously compromises their camouflage and makes it easier for predators to spot them in the wild. Not to mention how they can outnumber the available quality herbs and may fall short on resources. Here, Thomson’s gazelles embark on a new journey where they target safer plains with no obvious predators and promising vegetation.
To coexist with others…
In the absence of fires, Thomson’s gazelles travel jointly with wildebeests and zebras. Zebras and wildebeests begin consuming the tall grass and leave more promising herbs within the reach of gazelles who lack the freedom to choose their meal. Following in the footsteps of other herbivores may reduce the risk of predators’ attacks. However, climate change has created more fires, which change the available vegetation, thus changing the dynamics between different herbivore species. This makes the Thomson’s gazelles less dependent on large-sized grazers, which threatens the biodiversity species thrive on as they make seasonal odysseys across the land.