Mobility of wild animals, including zebra, reduced in human-modified landscapes, study finds

A zebra fitted with a Royal Veterinary College collar in Botswana. Photo: Tatjana Hubel
A zebra fitted with a Royal Veterinary College collar in Botswana. © Tatjana Hubel

Mammals on average move only a half to one-third of the distance in human-modified landscapes than they do in the wild, an international research team has found.

It is the first time this topic has been examined on a global scale and for many different species at once, including the zebra.

The authors say the results may have far-reaching consequences for ecosystems and, in turn, for society.

Most mammals are on the move every day while searching for food, to find a mate or to seek shelter.

Some larger mammals like zebra generally move longer distances, while smaller mammals, such as hares, usually cover shorter distances.

A team led by biologist Dr Marlee Tucker, of the Senckenberg Biodiversity and Climate Research Centre and Goethe University in Germany, has shown that the extent of these movements is significantly reduced in human-modified areas.

In the study, published in the journal Science, Tucker and 114 coauthors from various institutions collated movement data from 803 individuals across 57 mammal species from around the globe.

To do this they used the data portal, Movebank, which archives movement data from researchers across the world.

“Our study looks at everything from hares to wild boars to elephants. The scientists in our team equipped individual animals with a GPS tracking device that recorded each animal’s location every hour for a period of at least two months,” says Tucker.

Mammals, such as these bears on a street in Poland, tend to move much less in areas that are characterised by humans than in wilderness. Photo: Adam Wajrak
Mammals, such as these bears on a street in Poland, tend to move much less in areas that are characterised by humans than in wilderness. © Adam Wajrak

The researchers then compared these data to the Human Footprint Index of the areas in which the animals were moving. The index measures how much an area has been changed by human activities such as infrastructure, settlements or agriculture.

During a period of ten days, mammals cover only a half to one-third of the distance in areas with a comparatively high human footprint compared to mammals living in more natural landscapes. This is the case for the maximum distance covered within a 10-day time frame as well as for the average distance.

The analysis shows however, that at shorter time scales than 10 days, such as one hour, mammals do not move any differently across landscapes of varying human footprint. This means that the human footprint affects the ranging behavior of mammals over longer time frames, but does not affect their movements at shorter time frames.

Potentially, mammals move less because they have changed their behaviour in human-modified landscapes.

Co-author Dr Thomas Mueller, from the same institutions as Tucker, said: “In some of these areas there might be more food available so that animals do not need to cover such large distances. In addition, landscape fragmentation and barriers created by infrastructure might limit mammalian movements.”

The researchers are concerned that the reduced travel distances could affect ecosystem functions that hinge on animal movements.

“It is important that animals move,” continues Tucker, “because in moving they carry out important ecological functions like transporting nutrients and seeds between different areas. Additionally, mammalian movements bring different species together and thus allow for interactions in food webs that might otherwise not occur.

“If mammals move less this could alter any of these ecosystem functions. For example, the dispersal of plant seeds by animals between different habitats could be endangered.”

Dr Hattie Bartlam-Brooks, a postdoctoral researcher at Britain’s Royal Veterinary College, who contributed to the research, said: “By limiting animal movement we impede their ability to perform critical day-to-day functions and ultimately, in some species, constrain their long-term viability.

“To properly allow for the conservation of medium to large-sized mammal species we need to prioritise conservation at the landscape scale, such as the integrated management of land through national parks, wildlife corridors and community conservation areas.”

Tucker, M.A. et al. (2018): Moving in the Anthropocene: Global reductions in terrestrial mammalian movements. Science, Doi: 10.1126/science.aam9712

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