Climate change and super furry white animals

The long read – by Carlos Bedson – COP26 Day – 31 October 2021

“I don’t run a car, have never run a car. I could say that this is because I have this extremely tender environmentalist conscience, but the fact is I hate driving.”  Sir David Attenborough

This is a long read summarising observations, charts and findings from the science literature. Here are things you probably wonder about, don’t have time to look up, yet really want to know. 

It is sobering to think about climate change, affecting super furry white animals like mountain hares

Climate change

COP26 has given us a chance to reflect upon how we are heating up and destroying our planet. 

The United Nations presents alarming views:

“A growing global population combined with the unsustainable use of natural resources is having a devastating impact on our planet – propelling climate change, destroying nature and raising pollution levels.”    


The effect on our climate is apparent to everyone.   In Britain we are enjoying warmer summers and milder winters.

The effects of climate change are felt most at the polar regions.

The National Snow and Ice Data Centre, a partner of NASA, reports daily how much the Arctic Sea Ice is melting. 

Polar sea ice has an important role in reflecting heat from the sun back in to space, helping keep global temperatures cooler. As the ice melts, climate patterns change, with warmer air temperatures, moving the jet stream and oceanic air currents, causing severe weather events.  The ice melt also causes sea levels to rise, which endangers coastal areas.

Undoubtedly climate change is already here. The IPPC forecasts dire prospects for the world.

Its Sixth Assessment report was written by 284 authors from 66 countries and states:

“Unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach…….Many of the changes observed in the climate are unprecedented in thousands, if not hundreds of thousands of years, and some of the changes already set in motion—such as continued sea level rise—are irreversible over hundreds to thousands of years.”


The World Wildlife Fund predicts imminent disaster.

“Global warming is likely to be the greatest cause of species extinctions this century….

A 1.5°C average rise may put 20-30% of species at risk of extinction.

If the planet warms by more than 2°C, most ecosystems will struggle.”


The IUCN describe specific consequences to ecosystems:

“The ways in which climate change is expected to affect species are multiple and complex, but are generally thought to include:

  • Loss or degradation of important habitats and microhabitats.
    • Changing of environmental thresholds e.g. temperature, water availability/quality beyond those that a species can tolerate.
    • Loss of important interactions between two unrelated species, or the arrival of new, negative ones e.g. disease.
    • The disruption of environmental cues (e.g. for breeding or migration).
    • The direct loss of individual organisms, or even populations, as a result of extreme events.”


The effects on ecosystems, plants and animals are varied, intricate and complex.

Let us consider how one group of animals are particularly badly affected.

Super furry white animals

Those animals which are adapted to cold climates, are especially vulnerable to the effects of increasing temperatures in the northern and polar regions.  This is particularly because of changes to the availability of their food sources.

Obvious examples are those iconic animals which wear furry white coats.

Polar bears suffer because the ice melts and so the bears cannot easily prey on seals which used to sit on the ice. Across the Arctic there are 19 groups of polar bears for which 4 populations are decreasing, 2 increasing, 5 stable and of the rest, data is uncertain. More information is at the IUCN polar bear specialist group. Source:

Arctic foxes are extinct in Finland, endangered in Sweden and Norway. They suffer because they inhabit tundra where lives their main food source, the lemming, whose numbers fluctuate substantially. Lemmings themselves are struggling with snow thaw-freeze cycles during warmer winters. As the ground re-freezes, lemmings can’t forage, they starve, there are less of them available as prey. Arctic foxes which lived in the southern parts of their Scandinavian range are moving north to coastal areas, where food sources are more reliable.  Source:

Mountain hares are Ice Age relicts. The number one threat to mountain hare populations is climate change.  At the Swiss Institute for Forest, Snow and Landscape Research, the talented ecologist Maik Rehnus explains

Mountain hares are the indicator species for Arctic-Alpine ecosystems… they react very sensitively to environmental changes.”  


Five climate change mechanisms affecting mountain hares

1          Mountain hares prefer a “climate envelope” of cold and snow

Of various animals of the genus Lepus, mountain hares evolved over the last 2 to 4 million years, as cold adapted species.  They emerged after the Pleistocene, the last Ice Age, and followed the movement and eventual retreat of glaciers.  

Map shows left: the current range of mountain hares in Europe; right where they were 18,000 years ago, when Europe was covered in ice. 
Source:  Thulin, C (2003). The distribution of mountain hares (Lepus timidus, L. 1758) in Europe: a challenge from brown hares (L. europaeus, Pall. 1778)?

Mountain hares benefit from winter-adapted  physiology: excellent insulating thick white coats,  which allow them to thrive in temperatures down to minus 30 degrees.  

The chart shows how mountain hare body temperature is stable, the hare is surviving, while the winter air temperature is at minus 30 or even colder.
Source: Solomonov et al. 2008 Ecological and physiological characteristics of the mountain hare (Lepus timidus) cold resistance in the northeastern Siberia
Photo: Mountain hare foraging in snow at minus 10C. from my camera trap surveys Holme Moss, Yorkshire UK 2018

Thus the mountain hare has a natural “climate envelope”: an upper and lower preference to temperature and precipitation.  Mountain hares want weather cold and at least sufficiently freezing that precipitation falls as snow.  This is not to say mountain hares do not occasionally enjoy a good sunbathe. Yet overall their preference is for a cold snowy environment.

The science literature consistently forecasts warming temperatures. Accordingly mountain hares are predicted to shift their ranges and head northwards or to higher colder elevations.

The map predicts the mountain hare range in Scandinavia and northern Russia, moving north. 
By contrast, European brown hare range is forecast to expand all over. 
Source  Hof et al. 2012 Future climate change with favour non-specialist mammals in the sub-arctics
The map on the left shows where mountain hare species are today.  The map on the right, where they will be in 2080.  Gradually they are moving northwards in Scandinavia. Those mountain hares in other parts of Europe may disappear e.g. Germany. 
Source: Acevedo et al. 2012 Parapatric species and the implications for climate change
The map shows mountain hare occurrence in Switzerland a) today b) RCP 4.5 climate scenario for year 2080 = 26% habitat loss.  Effectively mountain hares are forecast to climb up the Swiss mountains into little sky-island ecosystems and with meta-population processes become fragmented.
Source: Rehnus et al. 2017 Alpine glacial relict species losing out to climate change

Yet another paper was just published (Sept 2021), shows these predictions as already happening.

The chart c) shows that with fewer frost days, mountain hares have been moving up hill in Switzerland.  
Source: 2021 Schai-Braun et al. Temperature increase and frost decrease driving upslope elevational range shifts in Alpine grouse and hares

My recent investigations for the Peak District, UK, showed recent historic average winter temperature at minus 2 degrees.  Because of climate change, average winter temperature for the year 2050 is forecast at plus 2 degrees.  That means precipitation will fall as rain not snow.  And although winters are forecast to be wetter, overall annual precipitation will decrease by 25%.

The present average elevation for mountain hares is 490m. In the year 2050 it will be higher at 570m.  The range of mountain hares today is 168km2 . In the year 2050 it will be just ~20km2.  Mountain hares will occupy only Kinder Scout, parts of Bleaklow and a small area near Rishworth.  Those groups of mountain hares presently occupying Derwent Edges and Margery Hill will be gone.

This is a peer reviewed study, based on 16,000 mountain hare observations submitted by the public to biological record centres across northern England.  Analysis retrieved environmental data including climate values: temperature and rainfall from WorldClim.  Modelling was in R software with the sophisticated package called ‘biomod2’ which collated the environmental data from the mountain hare locations and applied advanced algorithms to identify the mountain hare climate envelope and distribution extent. Investigations used the cold temperature and wet precipitation values enjoyed by mountain hares today; then looked for areas with these same values in 2050: there were hardly any, just small patches on the hilltops.

2          Increased competition with European brown hares

“The effects of climate change on the distribution of mountain hares predicted for 2080, especially when combined with potential exclusion by European brown hares, should drive managers to consider global climate change as one of the factors involved in mountain hare decline in Europe”

Source: Acevedo et al. 2012 Parapatric species and the implications for climate change

Photo: Brown hare on grassy farm field, just 100 metres from the known mountain hare range, Peak District, UK August 2020

Brown hares (Lepus europaeus) are a sister species, physiologically similar and yet not the same as mountain hares.   Brown hares originated from central Asia and are steppe herbivores. They were not present in Europe during the Ice Ages, they arrived afterwards. They are suited to warmer drier climates and they forage on grasses.  Brown hares were introduced to Britain by humans either during the Neolithic period or definitely by the Romans. The two species are known to compete for resource, where the habitat is the same.  In other countries such as Ireland and Sweden, huge areas of mountain hare range have been ceded to brown hares. 

Map of Sweden showing gradual invasion of the historic range of mountain hares by European brown hares.
Source: Jansson & Perhson 2007 The recent expansion of the brown hare (Lepus europaeus) in Sweden with possible implications to the mountain hare (L. timidus)

However this interspecies competition might presently happen rather less in mainland Britain.  Why?

It is notable that the British mountain hare winter diet is 90% heather and summer diet 50% heather and 50% grasses.  However brown hares cannot digest heather very easily. This was proven through some interesting feeding experiments in the 1990s. Mountain and brown hares were kept in cages and fed pellets sprayed with resin, akin to woody heather. Brown hares suffered sodium loss, becoming dehydrated and slightly unwell; mountain hares coped fine.  There is something in mountain hare digestive detoxification chemistry which allows them to be more of a dietary generalist.  

Source: Iason & Palo 1991. Effects of birch phenolics on a grazing and a browsing mammal: A comparison of hares

Therefore we see as consequence in Britain with our partitioned landscapes, that mountain hares occupy upland bogs and heather moorland and feed mainly on heather; whereas brown hares occupy agricultural and arable fields where they feed on grass.

However, again based on temperature and precipitation preferences, the forecast range for brown hares under climate change is expansion.  The hills will be warmer and drier.  In the Peak District the brown hares will move up the hills, following the mountain hares.  

The present average elevation for brown hares is 298m. In the year 2050 it will be higher at 369m.  The range of brown hares today is 252km2 . In the year 2050 it will be more than ~760km2.  European brown hares will occupy and share all the ranges of mountain hares.

3          Changes to available food and moisture resource

Key for mountain hare survival is the presence of heather which they depend on.  If there is no heather, it is likely mountain hares may be outcompeted by brown hares, and die out.  

We do not know what the Peak District upland vegetation composition will be in the year 2050.  Presently on Bleaklow, Kinder Scout, Derwent Edges and Holme Moss, there are substantial amounts of wet blanket bog communities which include some heather.  Typically if these were to dry out they would give way to more extensive upland heather communities.  That might be good for mountain hares.  However, again, if soils enabling the heather plant dry out too much, this might mean a transition to grasses.  Thus we have seen large areas of heather moorland inadvertently superseded by acid grassland.  That pattern was reported in the 1980s, although was particularly caused by excessive sheep grazing.  See:  Anderson, P. & Yalden, D. (1981). Increased sheep numbers and the loss of heather moorland in the Peak District, England. Biological Conservation (20) 195-213

It is difficult to speculate how much heather will still exist in 2050.

Meanwhile if the moors are drier – such as we saw particularly in 2018 – there is less standing water (ponds) and the  vegetation turns dry, lacking moisture.  This may make it harder for dehydrated female hares to provide milk, when raising leverets.  

Photo: Stillborn mountain hare leverets, during an extremely hot summer August 2018, Bleaklow, Derbyshire UK

In the Peak District, one beneficial human intervention is moorland restoration conducted by Moors for the Future Partnership and RSPB Dove Stone.   These organisations were tasked with protecting the upland peat layers which are important for carbon storage.   Their investments in blocking gullies, raising the water table and revegetating the landscape, have yielded a verdant vibrant bog ecosystem with a wide variety of plants, shrubs and mosses.  These areas are now associated with substantial numbers of mountain hares.

It may be that bog restoration goes a little way to trapping carbon, reducing climate change; and a long way to providing a beneficial ecosystem to wildlife.

Photo: Blanket bog restoration on Bleaklow, with four mountain hares March 2017

4          Wildfires

Most years have seen consistent increases in wildfires in the Peak District.

“At face value these projections suggest things will remain much as they are at present for the next 20 to 30 years, but after that time, danger of wildfires increases sharply. Depending on the actual amount of greenhouse gas emissions worldwide, long, dry summers may become the norm rather than (as at present) the exception. Recreational users of Peak District moorland might welcome such weather, but the moors themselves are likely to suffer and, unless substantial extra resources are put into fire prevention and fire fighting, the cost to ecosystem services of climate change in this upland region is likely to be high.”
 Source: Albertson et al. 2010 Climate change and the future occurrence of moorland wildfires in the Peak District of the UK

In 2003 Bleaklow experienced a large wildfire over several km2. The estimated cost to society was £2.3m.   The fire engulfed mountain hare habitat. The estimated cost to the species was probably rather worse.  The mountain hares did eventually recover, this time.

Map of Bleaklow fire zone 2003
Source: Moors for the Future: Bleaklow fire report 2003

Like many animals, mountain hares do not know how to escape a fire. I saw this during the Saddleworth fire of 2018, as I retrieved some camera traps which were inadvertently caught up in the fire zone.  

During 2020, we all witnessed images from Australia of koala bears being burned in wildfires

Is it alarmist to speculate on a major moorland fire in the Peak District? 

Will such disaster come to pass for mountain hares?

5          Climate change coat colour camouflage conundrum

This is a subtle, ironic consequence of climate change.

Mountain hares evolved over thousands of years so that their brown summer fur moults to a white furry coat. This is a biological process triggered by autumn change of day(light)  length and air temperature, prompting the growth of thicker white fur with hollow insulating hairs.  

Being white, this coat should these provide mountain hares with excellent camouflage from predators when on snow. However now there is less snow, mountain hares stick out on a brown background.

There is more detail about this process, and as affects other white animals e.g. ptarmigan, arctic fox, in the following fascinating article. Zimova et al. 2018 Function and underlying mechanisms of seasonal colour moulting

Photo: Mountain hare climate change coat colour camouflage mismatch, Bleaklow, Derbyshire UK  2020

Recent important studies have shown that mountain hares may be colour mismatched by up to 35 days, compared to perhaps 60 years ago when we experienced more snow. This makes mountain hares vulnerable to being seen by predators: foxes, stoats, raptors, owls.

It might be argued that because there is substantial predator control on English Peak District uplands, that risk is reduced.  Nonetheless some predation does happen.

Photo: Predated mountain hare, Lawrence Edge, Peak District 2018

Notwithstanding this difficulty, a new study offers encouragement: it suggests that despite the vulnerabilities of coat colour mismatch, the benefits of a warm winter coat outweigh the costs. Kennah et al. 2021 Coat color mismatch improves survival of a keystone boreal herbivore

Cooling reflections

We reflect upon our human societies heating up the planet. As consequence we have unfortunately created five climate change mechanisms which are adversely affecting furry white animals, including mountain hares.  In truth we do not know the extent nor frequency of these mechanisms. The literature listed above undoubtedly proves they occur.  However it is difficult to measure to a fine degree their severity and impact upon animal populations, including most groups of mountain hares

We can do just three things:

1          Continue monitoring wildlife populations.

2          Think about COP26 and how we can help.

3          Care for and restore habitats like blanket bog.

It is up to each of us to act as leaders of our own society, reducing our own individual carbon emissions and helping furry white animals to survive.  

With best wishes, Carlos Bedson

Sunday 31 October 2021 COP26 Day

Photo: Mountain hare at home on snow, Holme Moss, Yorkshire, UK 2018