Imagine, for a minute, that you're taking a stroll through the Kalahari desert under the unforgiving heat of a summer sun. Now imagine that stroll lasting for 5 days and covering an impressive 80 km. Finally, imagine undertaking this epic desert trek without a single break for food or water. For humans and many other mammals, this journey would be their final one, but for wildebeest, no imagination is required; this is their annual migration. Blue wildebeest (Connochaetes taurinus), also known as brindled gnus, are renowned for their ability to travel long distances in hot and dry environments, but it wasn't until recently that a research team from the University of London's Royal Veterinary College and the University of Botswana set out to investigate how they actually achieve this feat. This new study from lead authors Nancy Curtin and Alan Wilson not only explains how blue wildebeest are able to migrate without refuelling but also reveals that large mammal locomotor muscles are strikingly more efficient than was previously thought.
Much like their study species, the team's approach to the investigation was two-pronged. Firstly, they wanted to track the wildebeest using GPS collars to monitor their walking patterns and behaviours. Secondly, they wanted to examine the locomotor muscles of the wildebeest to see whether their physiological properties hold the key to their extreme endurance. From the GPS collar data, the team discovered that the wildebeest drank exclusively from a single river during the dry season and were capable of regularly going between 2 and 5 days without visiting the river for a drink, a feat that they were capable of repeating during their twice-yearly migrations through harsh waterless environments. The team were also able to extract locomotion speed data from the collars, which revealed that 97% of the distance covered by the wildebeest over a full year was completed at a slow walking pace close to the previously predicted optimum for reducing their energetic ‘cost of transport’.
In addition, the team collected minute muscle samples from each animal, which they electrically stimulated to investigate how the tissue contracted, while also measuring the heat they produced during contraction to reveal a crucial piece of the puzzle: the efficiency of the muscle. While previous mammal muscle efficiencies from small rodent studies have fallen in the range 20–30%, the average efficiency of the wildebeest's muscle was a staggering 63%. The only locomotor muscles that are currently known to be more efficient are those of the notoriously slow and steady tortoise. These super-efficient muscles play a pivotal role in the wildebeest's endurance by generating very little heat during locomotion, allowing them to conserve energy and water instead of using it for thermoregulation. The team also collected muscle samples from farmyard cows to compare the extraordinary muscle properties of the blue wildebeest with those from large mammals that haven't adapted to the nomadic lifestyle. This revealed lower muscle efficiencies of around 42% for the cows, suggesting that the wildebeest's impressive muscle efficiency is not purely due to their body size.
The team conclude that maintaining a low cost of transport is essential for long-distance trekkers that may need to travel during the hottest and driest times of day in order to avoid predators. For blue wildebeest, the solution lies in the surprisingly high efficiency of their specialised locomotor muscles, allowing them to undertake journeys that are truly gnus-worthy.
