Tag Archives: wildlife

Animals with white winter camouflage could struggle to adapt to climate change

Animals that turn white in the winter to hide themselves in snowy landscapes could struggle to adapt to climate change, research suggests.

A new study finds that declining winter snowfall near the Arctic could have varying effects on the survival of eight mammal species that undergo a seasonal colour moult from summer brown to winter white each year.

Species most at risk of standing out against the snow include mountain hares, snowshoe hares and short-tailed weasels. Without blending into the background, these animals could find it harder to hunt prey or hide from predators.

However, there are some parts of the northern hemisphere where colour-changing mammals could have a better chance of adapting to climate change, the study finds.

These “rescue” hotspots, which include northern Scotland and parts of North America, should be protected by conservationists to give colour-changing animals the best chance of adapting to future climate change, the lead author tells Carbon Brief.

Turning white

Visual camouflage is a vital tactic used by both predatory animals, who must hunt while avoiding detection, and their prey, who must hide to avoid being eaten.

But in parts of the northern hemisphere, the changing of the seasons offers a unique challenge to those trying to camouflage with their surroundings.

In winter, when the landscape is snowy and barren, animals with white colouring find it easiest to blend in. However, when spring arrives and snow is replaced with brown soils and growing vegetation, those with mottled brown colouring tend to find it easier to escape detection.

One solution to this problem, used by a range of animals, is to undergo a seasonal molt from brown to white each year.

Scientists have recorded 21 mammal and bird species using this colour-changing tactic, including the Siberian hamster, the collared lemming and the willow ptarmigan.

The new study, published in Science, focuses on how climate change could alter the survival chances of eight of these species.

Climate change is causing a decline in winter snow cover in Arctic regions, along with the earlier onset of spring each year. This decline could be causing a “mismatch” between animals with white coats and the snowless ground, explains lead author Prof Scott Mills, vice president of research for global change and sustainability at the University of Montana. He tells Carbon Brief:

“All of these species literally live or die by the effectiveness of their camouflage, which evolution has exquisitely crafted to match the average duration of winter snow.”

This mismatch could make some animals, such as hares, more vulnerable to predators, he says. It could also make it harder for predators, such as the arctic fox, to effectively hunt their prey. Mills says:

“One thing to realise is that all 21 of these species, including the carnivores, are prey: Arctic fox get clobbered by golden eagles, weasels are killed by foxes, coyotes, and raptors. For the hares and rodents, tasty snacks for multiple predators, camouflage is everything.”

Arctic fox (Alopex lagopus) in snow, Churchill, Manitoba, Canada, North America. Credit: robertharding / Alamy Stock Photo

Charting colour change

For the study, the researchers first collected coat colour and location data for more than 2,500 live animals and museum specimens spanning 60 countries.

They then analysed this data using modelling to study the moulting behaviour of animals living in different parts of the world.

The researchers found that, within one species, not all individuals will moult in the winter.

The chances of an animal moulting depend on the landscape in which they live. The more snowy the landscape, the higher the chance an animal will turn white in the winter.

This is shown on the chart below, where the number of snow-covered days per year is plotted against the likelihood of turning white in the winter for the Japanese hare (dark blue), the white-tailed jackrabbit (light blue), the least weasel (yellow) and the long-tailed weasel (red).

The probability of a colour-changing mammal having a white winter coat in regions with 0-320 days of snowfall per year. Results are shown for the Japanese hare (dark blue), the white-tailed jackrabbit (light blue), the least weasel (yellow) and the long-tailed weasel (red). Source: Mills et al. (2018)

The chart also includes a “broad polymorphic zone”. A “polymorphic zone” is a term used to describe regions where the probability of having either a brown or white winter coat is close to equal.

In these “zones”, mammals could have the best chance of adapting to declining snowfall conditions, Mills says. That is because, in these areas, a proportion of each species do not turn white in the winter and are therefore more able to blend in with snowless environments.

These brown-coated animals will be more likely to survive winters with less snow cover and pass on their genes to their offspring. Over time, this would increase the proportion of animals with brown winter coats, allowing the population to adapt – and ultimately survive – in environments with less snow.

The maps below show where the polymorphic zone of two or more species overlap. On the charts, red shows where the zones of two species overlap, while brown shows areas where the zones of three species overlap.

Regions in North America (A) and Eurasia (B) with polymorphic zones in winter coat colour for more than two species (red) and more than three species (brown). Source: Mills et al. (2018)

The charts show that parts of the US, Canada and Scotland show the largest overlap.

These regions could be considered “evolutionary rescue zones” where a number of colour-changing mammal species could be able to adapt to declining snowfall, says Mills:

“Because areas with the most [coat colour] variation evolve most quickly, these ‘polymorphic’ zones emerge as hotspots for rapid evolutionary response to climate change. Here in the polymorphic zones the populations are most likely to rapidly evolve towards winter brown, and to disperse the winter brown genes out into the adjacent winter white populations.”

The species whose range most commonly fall into these zones include the arctic fox, the white-tailed jackrabbit and the long-tailed weasel, the research finds. These species may have the best chance of adapting to declining winter snowfall, Mills says, but it is still too soon to tell what their chances of survival could be:

“To really evaluate risk to various species will require a lot more fieldwork and genetic analyses for other species, like we’ve been doing with snowshoe hares. We’re starting to work with weasels and Arctic fox, but I really hope that this paper initiates researchers around the world to start investigating coat colour mismatch.”

Picture of change

The findings should provide “yet another push to policymakers” to reduce the “global carbon footprint”, Mills says:

“I hope that the picture of white animals on brown snowless ground ‘paints a thousand words’ that shows that with continued human-caused climate change and reduction in snow duration, winter white animals on a brown snowless winter background will be in trouble.”

The research also shows that conserving “evolutionary rescue zones” could help wildlife to survive future climate change, Mills says:

“I hope it also helps [policymakers] see that other short-term, yet effective, options are available for protecting wildlife in the face of climate change.”

The post Animals with white winter camouflage could struggle to adapt to climate change appeared first on Carbon Brief.

Polar bears could be struggling to catch enough prey, study shows

Polar bears could be failing to hunt enough seals to meet their energy demands, new research suggests.

A study tracking the behaviour of nine female bears from 2014 to 2016 over the Beaufort Sea found that some of the animals exerted so much energy during the hunting season that they lost up to 10% of their body mass in an 8-11 day period.

Polar bears live on a diet made up of ringed seals, which they hunt from the ice surface. However, sea-ice cover in the Arctic is falling at a rate of 14% per decade. This may be forcing some polar bears to travel further in order to find their prey, the authors of the new research say.

Female bears who lose large amounts of weight during the spring hunting season could find it more difficult to raise their cubs to maturity in the following months, the lead author tells Carbon Brief.

However, it is not yet clear how such changes could be affecting the long-term survival of adult polar bears, he adds.

Polar bear with a GPS-equipped video camera collar, lying on the sea ice of the Beaufort sea. Credit: Anthony Pagano, USGS.

Bear’s-eye view

Polar bears live across the Arctic and spend the spring and early summer months hunting ringed seals, which provide the animals with a high source of energy and fat.

When autumn arrives, pregnant bears will enter the “denning” season. At this time, females will build themselves a maternity den out of snow, which is where she will give birth to her cubs and nurse them until the following spring.

Though previous studies have looked at the hunting activities of polar bears during the spring months, the new study, which was published in Science, has revealed these habits in striking detail.

The research followed the behaviour of nine female bears living in the Beaufort Sea area for a period of 8-11 days at some point between 2014 and 2016.

To track the bears’ day-to-day activities, the scientists fitted the females with GPS-equipped video-camera collars and accelerometers. They chose to study females because male polar bears’ necks are “larger than their heads” and so they are unable to retain collars, according to the research team.

The video-camera collars allowed the researchers to collect a large amount of data, including how far each bears tends to roam across the ice, how much time they spend walking and swimming and how often they come into contact with other bears.

The camera footage also allowed the scientists to observe the techniques bears use when trying to hunt seals. Most of the time, polar bears catch their prey using the “sit-and-wait” tactic, says lead author Anthony Pagano, a PhD candidate at the United States Geological Survey (USGS) and the University of California, Santa Cruz. He tells Carbon Brief:

“Polar bears walk around until they find a breathing hole that a seal is actively using and they’ll typically stay there, they’ll either sit down or lay down or stand, and they’ll wait at that breathing hole. In some cases, they wait for hours.

“If they detect a seal has come out to breathe, they’ll stand up on their hind legs, raise their bodies up into the air and then pounce through the water as a way to try to stun the seal. If they’re successful, they’ll try to grab the seal around the neck with their jaws and pull them out of the water.”

The video below shows the polar bears in action:

In order to collect this data, the researchers had to capture the bears at the start and end of the study period. Catching the bears required the team to track the animals using a helicopter, Pagano says:

“The easiest way to catch the bears is from a helicopter. It’s the safest method both for the bears and for the biologists. It’s also the best way to try to locate bears as well. Bears occur over a pretty extensive landscape and so locating the bears is a serious challenge.”

Bustling bears

The recorded field movements of each bear over the two-year study period are shown on the diagram below, where each colour represents the movements of one bear. On the diagram, the black bear symbol shows where a bear was captured while the white bear symbol shows where they were recaptured.

Diagram showing the field movement of nine female polar bears in the Beaufort Sea area in April from 2014-2016. On the diagram, the black bear symbol shows where a bear was captured while the white bear symbol shows where they were recaptured. Source: Pagano et al. (2018)

The data collected by the researchers suggest that polar bears are more active than previous research has suggested, Pagano says:

“Previous modelling work has tried to guess what a polar bear’s energy expenditure might be and how many seals they might need to capture. They speculated that, because polar bears use the ‘sit-and-wait’ hunting tactic, they would be able to conserve energy.

“What we found in the study is that the activity rates of these bears are very similar to other terrestrial carnivores, despite this sit-and-wait approach to hunting. They are still quite active and they are still travelling long distances.”

In fact, the study finds that polar bears burn energy at a rate that is 1.6 times that of what previous research has suggested.

However, the activity rates of the bears may have been affected by the capturing process, the researchers note in their research paper:

“Admittedly, the activity levels…in the study may be biased low owing to the effects of recovery post-capture. On the basis of movement rate and activity sensor data, recovery post-capture for polar bears may last two to three days.”

Melting ice

Using the new estimate, the researchers predicted that a solitary female bear would need to eat, on average, either one adult seal, three subadult seals or 19 newborn seal pups every 10-12 days to gain enough energy to maintain her current weight.

However, in the study period, more than half of the bears did not eat enough seals to meet their energy needs and subsequently lost body mass. Four bears lost more than 10% of the 8-11 day study period, with an average loss of 1% per day.

Previous research also shows that, in recent years, female bears have been more likely to enter the “denning” season with inadequate fat reserves than in previous years, Pagano says.

The rate of Arctic sea-ice melt over the spring and summer has been increasing in recent decades. Pagano suggests that this could be forcing the bears in the region studied to travel further to find food, and, therefore, be causing them to lose body mass at a faster rate than previously observed. He says:

“In this area, 80-90% of the population is following the ice as it recedes to the north. They’re moving much greater distances than they had historically to follow the ice as it retreats hundreds of kilometres further to the north than it did historically.

“Once the ice returns in the fall and the winter, they’re following the ice back and making a long distance migration back to areas that are thought to have a higher variability of seals.”

Cub survival

Losing weight during the spring months could leave female bears without the adequate resources needed to raise their young in the “denning season”, Pagano says, which could be causing declines in cub survival:

“Some work has shown that they are emerging from their dens in lower body condition and they are not able to locate as much food as they have done historically. Basically, they’re not able to provide for their young at an adequate level and that’s driving declines in cub survival.”

The threats facing polar bears in this region are likely to worsen as climate change continues, he says:

“The concern is that as the ice breaks up earlier each year, the bears will be impacted in three ways: they’ll be less successful at catching seals because they’re being displaced from their primary foraging habitat earlier; they’re putting on less weight than they would have done historically; and then they’re also moving greater differences. If that trend continues, we would expect continued declines in reproductive success.”

However, it is less clear how these changes could impact the survival rates of adult bears, he adds:

“From what we’ve seen so far there doesn’t seem to be large decreases in adult survival, it really seems to be a function of females to be able to produce offspring and successfully raise them.”

Research from the International Union for the Conservation of Nature (IUCN) polar bear specialist group shows that polar bear populations in the southern Beaufort Sea are “likely to decline” in the future. Carbon Brief has previously published an article examining how climate change could affect polar bear population numbers.

Polar bear wearing a video camera collar, hunting for seals on the sea ice of the Beaufort sea. Credit: Anthony Pagano, USGS.

‘Brief’ study

The findings could tell scientists more about how “polar bears are responding to climate change”, says Prof Charlotte Lindqvist, a biologist from the University at Buffalo in New York, who was not involved in the research. She tells Carbon Brief:

“The sample size is small, but what can you do when you sample rare and wild polar bears on the sea ice? If half of the studied bears are already showing signs of energy deficiency on the spring sea ice, we can only imagine a likely gloomy outlook for polar bears as sea ice continues to decline.”

The “major strength” of the research comes from the integration of several different methods to gain greater insight into the behaviour of polar bears, says Prof Andrew Derocher, a polar bear biologist from the University of Alberta, who was not involved in the current study. He told Carbon Brief:

“One challenge with the study findings is that we know that feeding varies widely over space and time with polar bears and the study period used was, by necessity, quite brief. Some of the results could be rather different a few weeks or a month later. However, none of this detracts from the study’s findings, but context is useful.”

The research highlights that the challenges facing polar bears are “complex” and scientists are “yet to fully understand them”, he adds:

“Arctic sea-ice loss is a global issue and there is no quick fix: no protected areas, no habitat modification, or other standard conservation approach could significantly alter the threats facing polar bears in a warming climate. Only the reduction of greenhouse gases can slow the rate of loss of polar bear habitat and improve the conservation outlook for the bears.”

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Rainforests: Scientists concerned climate change is altering the tropical life cycle

Climate change could be causing shifts to the natural cycle of life in the tropical rainforest, scientists have suggested.

A rise in global temperatures may be driving trees and plants to produce fruit and flowers earlier or later than before, researchers have found. This could have large consequences for a diverse range of animals that rely on tropical rainforests for food and shelter.

The animals most at risk include those that rely on flower nectar for survival, including bees and hummingbirds, as well as animals that feed on the fruit of tropical trees, including great apes, monkeys and parrots.

However, a lack of historical data and ongoing research in the tropics means that the scale of these changes is yet to be fully understood, scientists told Carbon Brief at a Royal Society conference held in Buckinghamshire earlier this month.

Changing seasons

In every part of the world, plants rely on cues from their environment, including changes in sunshine, temperature and rainfall, to determine when to start producing leaves, flowers or fruit. The study of this phenomenon is known as plant “phenology”.

Primary rainforest Langkawi Malaysia. Credit: David Noton Photography / Alamy Stock Photo.

In temperate regions, including the UK and North America, plants tend to time their natural cycles to the changing of the seasons. For instance, plants respond to warming temperatures and increasing daylight hours in the spring by sprouting new leaves.

However, rainforests do not have well-defined seasons, such as spring, summer, autumn, and winter, says Prof Patricia Morellato from São Paulo State University in Brazil. Morellato chaired a session on the possible future of tropical phenology research at the conference. At the sidelines of the event, she told Carbon Brief:

“In the tropics, we don’t have sharp seasons, so it’s more difficult to track changes. Instead, we have to know the cycle and, over time, see if the cycle is changing.”

Most rainforests have a wet and a dry season, which is caused by annual changes in rainfall. But many tropical plants do not time events, such as flowering, in accordance with these seasons, says Dr Joseph Wright, from the Smithsonian Tropical Research Institute in Panama. At the conference, Wright presented a talk on the environmental controls of leaf fall and flowering in tropical rainforests. He told Carbon Brief:

“I work on a 16 sq km site in Panama with 2,000 plant species. Every month of the year, there are several hundred species flowering. At the peak month, there’s probably a thousand species flowering. But even in the minimum month, there’s 200 species flowering.”

Because tropical plants do not time their life cycles according to the seasons, it is more difficult to work out what environmental cues could be causing the plants to begin flowering, Wright said:

“It could be unusually low temperature. It could be the beginning of the rainy season. Or it could be sunlight. These hypotheses are very vague.”

Data drought

Another limitation in the tropics is a lack of long-term climate and plant data, the researchers said.

In Europe and North America, scientists and nature enthusiasts alike have been recording the date of the first bud, leaf and flower for thousands of species for more than a century.

This long record has enabled researchers to track how plants are responding to global warming. Recent research (pdf) from the Met Office finds that spring is currently advancing at a rate of 2.5 days per decade across Europe.

However, in the tropics, there are very few known historical records and little funding available for research to be conducted, Wright said:

“There’s an incredible north-south divide. The northern hemisphere is rich and there’s tonnes of excellent universities and national research councils and so, as a consequence, in the northern temperate zone we have an incredible knowledge base. There’s tonnes of scientists and there’s very few species.

“You go to the tropics, we have the opposite situation. Countries are poor, each country might have one national university and the vast majority have no national research programme. But there’s thousands of species, there’s a hundred times more species and three orders of magnitude fewer scientists.”

Measuring mismatch

Despite a lack of historical knowledge, a growing number of researchers are trying to find new ways of understanding how climate change could affect the natural cycle of tropical rainforests.

One key area of this new research is to understand how shifts in forest cycles could affect the unique community of animals that live in the tropics.

It is still unclear how climate change may affect rainfall patterns in much of the tropics, but research (pdf) suggests that rainforests could experience longer dry periods by the end of the century.

A research paper published by Morellato and her colleagues in 2016 in the journal Biological Conservation attempts to evaluate how a longer dry season caused by climate change could affect the timings of key events in the rainforest.

It suggests that a longer dry season could cause plants to start flowering later on in year. This is shown in the chart below, where blue bars show the amount of monthly rainfall, while blue lines show the percentage of plants that are producing flowers. Red lines show the percentage of plants producing fruit.

On the chart, red-dashed arrows show how a longer dry season caused by climate change could lead to later plant reproduction via flowering. Later flowering could lead to less time available for plant pollination, which will result in fewer plants producing fruit the following year.

Schematic diagram showing the effects of climate change in tropical rainforests. On the top chart, blue bars show monthly rainfall, blue lines show the percentage of plants flowering and red lines show the percentage of plants producing fruit. The bottom chart shows the overlap (black) and non-overlap (striped) of the activity timing of flowers and pollinators (blue) and fruit and fruit-eating animals (red). Caption: Morellato et al. (2016)

Beneath the chart, a diagram shows how a later flowering period caused by climate change could lead to a smaller overlap between the activity time of flowers and their pollinators (shown in blue).

This “mismatch” could greatly threaten the survival of pollinators, including insects and birds, who rely on flowers for both food and shelter.

The animals most at risk are those which feed on the nectar of just a small number of plant species, such as many bees and hummingbirds, the study notes:

“The reliable and continuous availability of floral resources in the tropics has enabled strong and diverse adaptations in flower visitors, maintaining rich assemblages of highly specialised floral foragers, such as bees and hummingbirds.”

On top of this, a reduction in fruit availability in the following year as a result of climate change could cause a “mismatch” in the activity time of fruit trees and fruit-eating animals, which are known as “frugivores”. The paper reads:

“Frugivorous animals critically rely on fruits, and fundamental aspects of their ecology – including diet, population size, social behaviour reproduction, and movements – depend on fruit abundance and seasonality.”

A wild, young male orangutan climbs trees in the rainforest to find red berries to eat. Credit: Lillian Tveit / Alamy Stock Photo.

Such animals include great apes, smaller monkey species, as well as a range of tropical birds, including parrots, the paper adds.

‘Critical to every organism’

Although recent research outlines the species most at risk from shifts to the tropical cycle, it is likely that such changes will affect almost every animal found in the rainforest in some way, Morellato said:

“In the tropics, almost all species rely, at some point in their lives, on a plant in flower or in fruit. Changes in phenology will affect the animal community in forests, that’s for sure.”

Fully understanding how climate change is affecting plant phenology will be key to protecting rainforest wildlife, Wright said:

“Primary producers [plants] are critical to every organism, every animal, every consumer in the forest. The more we’re able to get some understanding on what the link between what climate and the plant response is, the more we’re going to be able to make predictions about their chances of survival.”


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The Goat Effect: A reflection on creative ways to bring more people to the conservation table

During my first full year in extension, I spent a lot of time at field days. There’s a constant debate among folks that organize field days about the recipe for a successful event. Timing matters. So does location. Advertising and promotional efforts make a difference. And of course food—everyone knows that free food fills seats. […]