Impact of behavioral change on migratory species

The herds of wildebeest like the crowded waterfall in the Serengeti field, bison crowded together along the northern plains - these iconic images interfered with the Hollywood film capital to the imagination. usually, common, normal. But there is the fact that such large-scale immigration has greatly reduced. People are skeptical that about a quarter of migratory species are no longer migrating, all because of man-made terrain changes. A recently published study highlights this global change and analyzes the decline in large-scale migration.

Grant Harris of the Biodiversity Conservation Center of the American Museum of Natural History, the lead author of the article in Endangered Species Research, said: 'Conservation science has a very poor understanding of activity. migration, and so many migration activities have completely disappeared. Migration barriers reduce the chances of migrating animals' food and water. Therefore, the migration activity stopped, or shortened, and the number of animals decreased. '

The migration of large herbivores (also known as ungulates) occurs when these animals move to areas with richer food or better quality. Ecologically there are two main effects on the availability of food. In areas with moderate temperatures, better quality food moves seasonally, and animals respond by moving along established routes. With steppe ecosystems, rain allows the development of higher quality foods. This is a more unpredictable change so animals have to search across vast areas of terrain.

Human activity currently prevents large groups of ungulates from pursuing their food. Building fences, agriculture, preventing water flow from changing terrain, and abusing animal exploitation undermines the number of migratory species.

Image of multiple branched antelope (Antilocapra americana) running on snow. (Photo: J. Berger / WCS)

To assess the impact of human activities on worldwide migration, Harris and co-authors have gathered information on 24 migratory (over 20 kg) large ungulate species. on a large scale. Animals in the study are distributed in areas such as the Arctic tundra (caribou reindeer), steppe and Eurasian plateau (Saiga antelope), North American plains (bison and elk), and African steppe (zebra and wildebeest). The number of large-scale migratory species in the Americas is the least, and this is where most data exist. Assessing human impact on migratory species in Africa and Eurasia is difficult because of the lack of scientific data: in Africa - where most migrations are on a large scale. exist - 3 species have no scientific publication of their status, and in Europe Asia half of the 6 migratory species have very little recorded data.

All 24 species in the study lost their migration pathway and the number of individuals in the species decreased. In North America, bison is still considered a migratory species, but their range is now limited to the Great Plains Plains to two small locations in Yellowstone and Alberta. Similar changes are found on other continents when human activity limits the ability of species to move to new sources of food. Limit detection analysis is more serious with 6 species. The South African antelope (Antidorcas marsupialis), the black wildebeest (Connochaetes gnou), another South African antelope (Damaliscus dorcas), and the mottled donkey (Equus quagga) of South Africa; kulan (Equus hemionus) of Central Asia; and Oryx dammah (North African horny antelope) in North Africa or no longer migrating or cannot be evaluated as migratory animals

Co-author Joel Berger of the Wildlife Conservation Society, and the University of Montana, said: 'If we want to preserve migration as well as these animals, we need to recognize the actions needed. set: where migration remains, how far away species are, needs for habitat, their location, threats. For some species, such as wildebeest and African antelope in Botswana, threats have been identified decades ago. However, we have not done much in our efforts to protect their migration. '

Harris said: 'An important part is the issue of awareness. People don't realize what we have and what we are losing. '

In addition to Harris and Berger, the authors of the study include Simon Thirgood and J. Grant of the Frankfurt Zoological Association in Tanzania, and Joris Cromsigt of the Institute of Mammal Studies at the Polish Academy of Sciences. Study the John D. and Catherine T. MacArthur Foundation, Frankfurt Zoological Association, Association of Wildlife Conservation, and the Marie Curie BIORESC knowledge transfer project funded.