Every year, thousands of drowned wildebeest feed this African ecosystem

Summary

The annual migration of 1.2 million wildebeests across the Serengeti has a profound impact on the ecosystem, including the overlooked phenomenon of mass drownings during river crossings. Around 6,500 wildebeests drown each year, contributing significant nutrients—such as phosphorous, nitrogen, and carbon—into the rivers. These carcasses support a wide range of scavengers, including vultures, crocodiles, and fish. Despite the dramatic toll, this accounts for only 0.7% of the herd, with starvation, predation, and illegal harvesting having a greater overall effect.

Takeaways

• 🦬 The migration of 1.2 million wildebeests across the Serengeti is crucial to the ecosystem, affecting grass consumption and nutrient flow.
• 🌾 Wildebeests consume over 4,500 tons of grass daily as they travel 1,800 kilometers between Kenya and Tanzania following the rains.
• 🦁 Despite the competition for food, wildebeests benefit from herding due to protection from predators like lions.
• 🌊 Thousands of wildebeests drown annually during river crossings, often because of steep banks or overcrowding.
• 🦴 Around 6,500 wildebeests die in river crossings each year, contributing the biomass equivalent of 10 blue whales to the ecosystem.
• 🔬 Researchers have studied carcass decomposition and nutrient distribution in the food chain over the past six years.
• 💧 Wildebeest carcasses contribute about 13 tons of phosphorus, 25 tons of nitrogen, and 107 tons of carbon to the ecosystem annually.
• 🦅 Scavengers like vultures and storks feed on the carcasses, helping to distribute nutrients further inland.
• 🐊 Crocodiles and fish also benefit, with up to 50% of local fish diets coming from carcasses during this time.
• 🧫 Once the meat is gone, the remaining bones support microbial growth, which serves as food for river-dwelling creatures.

Q & A

What is the primary reason wildebeests migrate across the Serengeti?

Wildebeests migrate across the Serengeti following the rains to find fresh grass to graze on. This annual migration covers an 1800-kilometer circuit between Kenya and Tanzania.

How much grass do wildebeests consume daily during their migration?

Wildebeests consume more than 4,500 tons of grass every day during their migration.

Why do wildebeests rely on herding instinct despite competition for food?

Wildebeests rely on their herding instinct because there is strength in numbers, which helps them survive against predators like lions, even if it leads to stiff competition for food.

What is one of the dangers wildebeests face during river crossings?

During river crossings, wildebeests risk drowning, especially when the opposite banks are too steep or when too many attempt to cross at once.

How many wildebeests drown annually during the river crossings?

About 6,500 wildebeests drown each year during river crossings.

What impact do the drowned wildebeests have on the ecosystem?

The drowned wildebeests contribute nutrients such as phosphorus, nitrogen, and carbon to the ecosystem, with their carcasses supporting scavengers, fish, and microbes.

How long do the bones of drowned wildebeests take to decay?

The bones of drowned wildebeests take approximately 7 years to decay.

What percentage of the local fish's diet comes from wildebeest carcasses?

Up to 50% of the local fish's diet comes from wildebeest carcasses when they are present in the river.

What is the estimated biomass contribution from drowned wildebeests to the river annually?

The drowned wildebeests contribute the equivalent biomass of 10 blue whale carcasses to the river annually.

What portion of the wildebeest herd is affected by drowning during migration?

Approximately 0.7% of the total wildebeest herd is affected by drowning during the migration, a relatively small portion compared to other causes of death like predation or starvation.