Study zooms in on giraffe movements

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Giraffes reduce their movements when human pressures are highest and when forage resources are richest, a new study has revealed. 

The findings of the study are published in Royal Society’s flagship biological research journal, Proceedings B. Dr Michael Butler Brown, an ecologist with the Giraffe Conservation Foundation (GCF) and Smithsonian’s National Zoo and Conservation Biology Institute in the USA, ran point on the study.

The study details that when resources and human pressures are less predictable in space and time, giraffes must cover much more ground.

This finding has conservation implications in a rapidly developing world. 

Giraffes live in incredibly diverse environments across 21 African countries.

These environments span impressive ecological gradients: from the hyper-arid deserts of northwest Namibia to the lush savannahs along Uganda’s River Nile.

They also vary significantly in the level of human impact: from the semi-arid pastoral landscapes of Niger’s Sahel to protected private reserves of Southern Africa. 

Dr Brown and colleagues collected Global Positioning System (GPS) tracking data from 148 animals of all four giraffe species from across 10 countries to understand how the animals change space use patterns in response to human pressures and the availability/predictability of forage resources. 

To achieve the aforesaid goal, the team designed and applied different types of GPS tracking units specifically for giraffes since traditional GPS collars do not work well on their long necks. These devices collected millions of locational fixes and relayed them through satellite networks so the researchers could track giraffe locations across some of the continent’s remotest environments. Overall, giraffes cover impressively large areas, with an average home range size of 360km2 and average daily movements of over 14kms.

“We found that in areas with consistently high availability of woody vegetation, giraffe don’t cover as much ground since they generally have most of the resources they need in close proximity,” Dr Brown said, adding, “Where the story gets more interesting is in the more heterogeneous systems where giraffes cover more ground as they navigate more patchy environments.”

Because giraffes live across diverse environments with measurably different conditions, they are an ideal study species to test these ideas.

To do so, Brown and colleagues used continental scale environmental datasets derived from satellite imagery, linking the giraffe locations to the exact conditions in space and time. Since the work drew from data collected throughout Africa, through different high resolution GPS devices, it required applications of novel statistical techniques so that results were directly comparable.

Using Continuous Time Movement Models and mixed effects meta regressions, the team developed and applied statistical methods that effectively allow for a comparison of giraffe space use metrics across various sites and tracking technologies.

These newly applied methods can be used much more broadly in other movement ecology studies to make robust comparisons of animal movement behaviours under diverse conditions.

Recent estimates suggest there are only 117,000 giraffes remaining in the wild of Africa.

“As human populations continue to grow and climate change renders the predictability of resources more uncertain, understanding how giraffes will spatially respond to these changes is critical to ensuring conservation strategies effectively account for different movement strategies,” said Dr Julian Fennessy, the co-founder and director of conservation at GCF.

GCF said giraffes have already become extinct in at least seven countries in Africa.