What effect do landscape changes have on animal migration?

Distances are two or three times shorter in changed landscapes

While several studies have analyzed the influence of landscape changes on the movement of one or more animal species, few have looked at a wide range of species across the planet. To achieve a global view of the situation, researcher Marlee Tucker[1], based in Germany, has partnered with 114 other researchers, including Björn Reineking at Irstea, to examine localization data for 803 individuals from 57 land mammal species fitted with a GPS tracker[2] and monitored continuously for at least two months. These observations were then cross-referenced with data from the Human Footprint Index, an index measuring population density, infrastructure, etc., for the areas in which the animals were moving. “We also took into account the quantity of available vegetation (using remote sensing), the size of the individuals and their eating habits and other variables involved in movement,” says Björn Reineking.

The results of this study published in Science[3] show that, over a period of 5 to 10 days, the distances covered by mammals in areas with a high human footprint (with an HFI score of more than 35, such as Albany in the USA) are two to three times lower than those covered in more natural landscapes. “This decrease in movement in areas with the most human activity may be explained by a change in individual behavior, linked primarily to greater availability of water and food resources, as well as to the fragmentation of the landscape due to obstacles (roads, railways, etc.),” specifies Björn. This is not without consequences for ecosystems and the services they provide. “When they travel, deer, roe deer and other mammals transport plant seeds to wherever they are going to settle, thus contributing to the biodiversity of their ecosystems.” This problem has been studied closely by the FONA team at Irstea. “The decrease in distances traveled may also have an impact on interactions between species and can change the trophic network [3] ,“ he continues.

Simulating behavior when faced with fragmented habitats

Alongside this project, Björn Reineking has also contributed to the analysis of a model[5] aiming to improve our understanding of the impact of habitat fragmentation on the movement of a single species within a virtual environment. The model is used to simulate the result of various movement strategies, habitat availability and quality, and the risk of death, on the expansion of the distribution area of a given population. It includes three migration phases: the decision to move, the movement phase and settling in a new habitat. The simulations show that a drop in the number of habitats does not necessarily increase the range of movement for a population before it settles in a new habitat. “In our simulations, some individuals chose a home in a habitat even before they encountered any obstacles to their journeys,” notes Björn.

Tracking the Common Frog

Elsewhere, as part of a project evaluating the permeability of skiable areas, Irstea researchers in Grenoble are using radio tracking to monitor Common Frog individuals (Rana temporaria) fitted with GPS trackers. “Very common in the mountains, this species is particularly sensitive to linear infrastructure,” specifies Björn Reineking. The aim of this project is to analyze their movements when confronted by obstacles and decide if ecological barriers exist at various points across a skiable area. The results will be particularly relevant to help improve our understanding of animal movements in significantly altered landscapes. 

 

For more information

[1] Senckenberg Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, 60325 Frankfurt (Main), Germany. Website: http://www.bik-f.de

[2] The data is stored in the Movebank portal.

[3] Marlee A. Tucker and al, Moving in the Anthropocene: Global reductions in terrestrial mammalian movements, Science  26 Jan 2018: Vol. 359, Issue 6374, pp. 466-469 DOI: 10.1126/science.aam9712

[4] All interlinked food chains within one ecosystem

[5] Greta Bocedi, Damaris Zurell, Björn Reineking and Justin M. J. TravisMechanistic modeling of animal dispersal offers new insights into range expansion dynamics across fragmented landscapes, Ecography 37: 1240–1253, 2014 doi: 10.1111/ecog.01041