Tracks We Leave Behind: Human Impacts on Mammal Movement

Summer Elsie explores how human activity influences mammal movement worldwide, revealing where we’re clearing paths and where we’re closing them. 

A fox running across a busy road. Image Credit: Wal (2020) on Pixabay

As cities expand and human populations spread, the results of global urbanisation have consequences for both humans and animals. While we benefit socioeconomically from the growth of industrialization, infrastructure, transportation, and a growing job market. But for animals, particularly mammals, this human influence has led to major shifts in how they move, migrate and survive.

Habitat fragmentation

With urban sprawl taking place across cities, seen clearly in London with its outward growth into Surrey, habitat fragmentation begins to take hold. Expanding transport networks, man-made dams, and the rapid development of infrastructure needed to house growing populations all divide habitats into smaller, isolated patches.

This issue affects most species of mammals found in urban areas; bats, foxes, badgers, deer and many more. Dormice (Muscardinus avellanarius) are a particular concern : their numbers have fallen by just over 50% since 1995, and continues to decline significantly as their habitats shrink. Habitat fragmentation also affects animals at a global scale. In North America, for example, research on , the swift fox (Vulpes velox), found that between 1998 and 2001, 48% (sample of 50) of the foxes monitored died in road collisions.

To prevent further declines, we can increase wildflower planting, along with aiding the development of treelined pathways – practical steps that create safer corridors for wildlife and offer a compromise for human needs and mammal conservation.

A city extending out into snowy lands. Image Credit: Andreas on Pixabay

An increase in resources

Population growth in rural areas, particularly those focused on farming, water collection and other primary sector jobs, creates an area concentrated with accessible resources that mammals tend to travel far for. This abundance reduces the need to travel long distances in search of food or water. Croplands provide plentiful prey, while local canals and rivers offer reliable water sources.

This behaviour is observed across multiple species. The plains zebra (Equus quagga), benefits from agricultural expansion, moving less due to the vast availability of their required resources. Similar trends are seen across North and South America and throughout Africa, where cropland has increased by 35% over the past two decades, to aid the rising human populations. Despite benefit to human needs, this expansion also alters animal behaviour and is one of the major contributors to both deforestation and climate change.

Zebra foal looking at the camera. Image Credit: Rolf Dobberstein on Pixabay

Species-specific effects

Some animals simply disappear from an area heavily modified by humans. This can result from habitat loss, anthropogenic congestion, increasing temperatures in micro-climates, and noise or light pollution. Such effects are seen in mega-cities and world-cities like Paris, New York, Tokyo, London and many more.

A wide range of species have disappeared over the years, a good example would be the Tasmanian Tiger (Thylacinus cynocephalus), also known as thylacine, a mammal that was classed as extinct back in 1936. Its disappearance was caused by human activities such as hunting, agricultural expansion and diseases introduced during the European colonization of mainland Australia.

To this day we still mourn the loss of the Tasmanian Tiger and  in recent years a myriad of animals are unfortunately following in its paw steps.; The snow leopard (Panthera uncia), for instance, declined to a population of ~6000 individuals (approx), a 20% reduction over the last two decades, due to pelt hunting and habitat loss caused by melting  permafrost linked to industrialization. Another example would be the hedgehog (Erinaceus europaeus), which has experienced a 75% decline since the early 2000s across rural areas in the UK due to similar reasons.

Fortunately, we now have resources to help prevent further losses. If you’d like to help, WWF allows you to donate monthly to support an animal of your choice. There are also local initiatives to keep an eye out for, such as The British Hedgehog Preservation Society who offer volunteering opportunities and hedgehog first aid training.

Snow leopard looking up close at the camera. Image Credit: Pixabay

Policy implications

A crucial factor in understanding mammal movement and behaviour is monitoring biodiversity and its losses, to ensure animals in protected areas are preserved. What we learn from monitoring is vital for informing policies that safeguard mammal populations.

Policies addressing this cover a range of schemes. One example is conservation translocations, the intentional movement of animals, fungi or plants to promote breeding and habitat safety. This approach has been used with Roe deer (caproelus caproelus) in both the UK and Spain, where relocating individuals into more concentrated groups helped populations recover and replenish areas where numbers had declined.

Another important policy area worth mentioning is the growing movement of wild animal welfare, which prioritises the wellbeing of individual animals within ecosystem management. A great example of this policy is the Wild Animal Welfare Committee (WAWC) which provides guidance for the public, covering topics such as garden wildlife health, tourism, wild animal control, and population monitoring. These policies and initiatives offer practical solutions to protecting the movement of mammals in the face of human interventions.

Children sat with a poster that says “I have a dream and it is green what about you…?”. Image Credit: Barbara Grzebulska on Pixabay

Humans have gained great social and economic benefits from urban growth and industrialization, but at what cost? Is expanding infrastructure and a growing job market worth the complete extinction of species like snow leopards and hedgehogs? Why should animals that occupied these habitats years before our rapid expansion have to be displaced to make way for our endless cities and roads?

About the Author:

Summer Elsie is the deputy editor of Wild Magazine and recent graduate from the University of Exeter - an aspiring zoologist, passionate about the interactions of urbanisation on ecosystems and even completing her dissertation on bats in urban areas.