Slopes more than 20° pose challenges for their conservation

New research finds that giraffes much prefer flat terrain and do not traverse slopes of more than 20°, which severely limits the areas in, and outside, protected reserves they can access. The findings, which are yet to be published, were presented at the British Ecological Society’s (BES) Annual meeting in Liverpool on the 13 December.

A study analyzing the movements of 33 GPS collared giraffes in South Africa has found that they avoid steep terrain and are unable to navigate slopes with a gradient of more than 20°, most likely due to the energy required and the risk of falling.

The researchers from the University of Manchester and the University of the Free State, South Africa found that giraffes will tolerate terrain of up to 12°, but only if it leads to favorable vegetation.

Jessica Granweiler, a PHD candidate at the University of Manchester, who presented the research at the meeting said, “We often think of giraffes roaming in large, flat grassland savannas in Africa, but that’s not really their true habitat. There are also rolling hills, deep riverbeds and high plateaus.

“Our study shows that giraffes much prefer flat areas. They will tolerate some steepness to access food, but simply cannot access areas above a 20° gradient. It’s quite shocking when you look at distribution maps.”

“Giraffes are tolerant animals and resilient to many things like food availability and human pressures, but this is a scenario where they simply may not be able to adapt due to physiological limits.”

The findings highlight a mismatch between the ideal, flat habitats of giraffes and the areas they’re being conserved in. Using the newly discovered 20° gradient threshold, the researchers were able to calculate the proportion of habitats in key African countries where giraffes are currently found that are inaccessible to the animals.

“In Namibia and Tanzania, there is approximately 8,000km² that may be unusable to giraffes, that’s nearly half of the size of Wales,” said Jessica.

“In Kenya and South Africa, there’s approximately 4,000km² that may be unusable. What’s even more worrying is that of all the countries we mapped, one in three had more unusable areas in protected areas than outside of protected areas.”

This issue is exacerbated when reserves are fenced, which many in South Africa are.

“If a reserve is say 200 hectares but has a large mountain in the middle, from a giraffe’s perspective, this reserve is not 200 hectares anymore,” said Jessica. “We need to start including topography in giraffe conservation planning and habitat assessments, especially for small fenced reserves.”

Professor Susanne Shultz, lead supervisor on Jessica’s PHD, further commented, “Steep and rugged environments are challenging for large-bodied animals, like giraffes. Unfortunately, natural and protected areas are more likely to be placed in such places, which can lead to a mismatch between the landscapes animals ‘want’ to use and the landscapes that we have ‘left’ for them.

“Incorporating geography and physical limitations in habitat assessments can help avoid conserving animals in inappropriate places.”

Giraffes are currently found in 21 African countries but despite their wide distribution, populations have been declining due to habitat loss, poaching, and human-wildlife conflict. Conservation initiatives are critical for their survival. However, traditional habitat suitability models primarily focus on vegetation distribution, predation, and human disturbance and overlook topography.

In the study, the researchers repurposed GPS data collected between 2011 to 2023 by Dr. Francois Deacon’s team at the University of the Free State, South Africa who fitted GPS collars to 33 giraffes (10 males and 23 females) across five reserves in South Africa. The researchers combined this data with topographic maps to work out the gradients that giraffes could and couldn’t navigate.

Dr. Francois Deacon, who was also part of this research, said, “The more awareness we can bring to giraffe ecology, the more research effort there will be on this species in the future. The fact that we are still discovering major limitations or drivers of their ecology and behavior is worrying. But research like ours helps close this gap in knowledge and will help better management and conservation of giraffes in the future.”