Image: © Randy van Domselaar/Stock.adobe.com
Dr Isabella Capellini’s research revealed that wild boars and young deer sleep less in hot temperatures, causing concern for all mammals on our heating planet.
Wild boars are fairly easy-going about where they live. They’re native to Asia, parts of North Africa and most of Europe, but now live on every continent except Antarctica. They’ve adapted to all sorts of habitats, including forests, grasslands, wetlands and they even brave farms and built-up areas to forage. They’ll eat almost anything too, munching on fruits, crops, roots, nuts, insects and small animals. And they’re big, getting to 3-6ft long, with females weighing 70-77kg and males averaging 90kg.
Together these attributes make wild boars an ideal animal to help Dr Isabella Capellini with her research.
Capellini is an ecologist who works at Queen’s University Belfast. She’s interested in animal behaviour and how it’s affected by environmental factors. A topic she is particularly focused on is sleep. As she explains to SiliconRepublic.com, a lot of work has been done studying sleep behaviours in labs, but not so much in the wild. There are practical reasons for this – it’s much trickier and more expensive to study animals in the wild (especially if you don’t want to disturb them), and, particularly, if you want to study them at night.
This is where Prof Luca Börger at Swansea University comes in. Börger and his team have developed a high-tech animal movement and tracking tag that captures various data, including motion, direction, light, temperature and barometric pressure. The tags are made by the university spin-out company Wildbyte Technologies. Until recently, tech like this didn’t have the capabilities to capture the kinds of data Capellini needs, nor could it last for the length of time she requires.
Now, Capellini and her team can put tagged collars on wild boars, who as mentioned above are big enough and laid back enough not to get too stressed by the intrusion or find the tag too uncomfortable (though they always have a vet with them to make sure the animals are safe during collaring). They can then monitor the animals for months at a time in what she describes as “ecologically meaningful conditions”. For three years, the team monitored individual animals for up to 12 months at a time.
This generated so much data, they needed a supercomputer to process it all. To make sense of it, they used what Capellini describes as “intense computational analysis” and also validated data from the tags using video footage of animal behaviours, including sleep posture.
And the results have shown a clear link between higher temperatures and less and lower quality sleep among the wild boar population.
“We found that essentially when boars are sleeping on hot summer days, they sleep less well in the sense that you sleep less overall,” Capellini explains. “Their sleep is more fragmented and the longest bout they have, which generally is the most restorative as you can spend more time in deep sleep if you sleep longer, then that bout is shorter.
“In the wild boar population, all of the three metrices show that hot days are no good and quality is particularly affected by also having high humidity.”
This finding was replicated across the three years of the study. On average wild boars sleep 17pc less during hot summer days.
In the context of the climate crisis, with extremely high temperature events becoming longer and more frequent, this could have negative implications for wild boars in the long term. Capellini notes the particular significance for animals such as wild boars because they reproduce during the summer months.
“So, they already have a trade-off between having to look after the newborns and sleeping. (And we know this lack of sleep is something that is not unique to female boars.)
“We know that these females are already sleep-deprived. We know that hot temperatures impair sleep from our research. So, we suggest that if spells of hot weather and extreme heat events become more frequent, all these animals will face even greater stress. More generally, female mammals that reproduce during summer in temperate ecosystems will be the ones that probably face the most sleep loss.”
Capellini also carried out the tagging and tracking process with a fawn population and, even though they are tiny in comparison to boars (the smallest tagged animal was a little over 2kg), the results were the same. Though Capellini notes that the study period was much shorter because they didn’t want to leave the tags on the smaller animals for too long. And while the boars were studied in the Czech Republic, which gets very high temperatures in the summer, the fawns were studied at Dublin’s Phoenix Park in Ireland and still struggled with increases in temperature.
Sleep research is no snooze fest
But why study sleep in wild animals?
Capellini emphasises the importance of sleep for health. During sleep you build your immune system, your brain gets cleared of any metabolic by-products and your memory is consolidated, she says. “Sleep is a self-maintenance behaviour … Sleep is self-care.
“But because it’s so difficult to study in the wild, we really do not know how sleep fits within the ecology of a species.
“And this is particularly important because conservation is always focusing on where the animals are, where the animals go, what the animals do. And we never really care about downtime, but that too is important.”
A herd of deer in Dublin’s Phoenix Park. Image: © alekampo/Stock.adobe.com
Because sleep might require specific sleep sites and sufficient time in a particular environment for an animal to get deep sleep, it’s important for conservationists to understand animals’ sleeping patterns to help protect them.
The role of sleep in building up the immune system also leads Capellini to wonder whether animals that are sleep-deprived are more prone to get or transmit diseases.
“I think those are important question that ecologists haven’t really had the chance to address.”
There’s also the applied learning we can get from the studies of other mammals. “Studying sleep in wild animals is useful to humans too, because we live in a very modern and artificial environment where, you know, often you hear the suggestion from some (not all) sleep scientists that you need to sleep eight hours a day all year round. And more or less that’s the same for everybody. But is it?
“Our research already shows no, probably not.
“You sleep less in summer and you are adjusted to that, but we don’t know how much is good for us because we don’t have a reference point and animals can help us identify the reference point because they live in natural environments.”
One of the interesting things that Capellini found among the wild boars was the huge differences in sleeping patterns between individuals. The boars that slept for longer also tended to get deeper, more restful sleep, whereas those that slept for less time, even if they took many naps, had less deep sleep.
“So that tells me that in the wild boar population, we have good sleepers and bad sleepers and that is natural.
“And so, the question is, are these short sleepers the ones that are really going to be affected by climate change?”
And if they get a disease, will they be less able to fight it, or will they be able to have longer bouts of sleep when they are sick?
“These are open questions I would like to investigate in the future.”
Capellini has been interested in animal behaviour for as long as she can remember. “I wanted to find out why animals did what they did,” she says of her childhood curiosity. She recalls an incident where her pet hamster killed her litter. “It does happen in nature and is often stress relating to being in a captive environment.
“I wasn’t upset in the sense I wasn’t angry, and I understood, even as a child, that the animal is doing something that they perceive is the right thing to do. But why does it perceive it’s the right thing to do?
“So, this is the kind of question I was fascinated by.”
As for the challenges of studying animals in the wild, it can be difficult to get funding because as Capellini explains, there’s a “reluctance to believe it could be done”. Luckily, she says, she has a supportive environment at Queen’s and great collaborators, including the team in the Czech Republic, the team in Swansea who have developed the sophisticated tagging tech, and her PhD student – now postdoc Dr Euan Mortlock, who is the first author on two of the papers to come out of this research. “He has been absolutely brilliant,” she says of Mortlock.
Capellini recalls when she first started studying sleep, even she thought maybe there are more interesting aspects of behaviour to study. But she soon came to realise just how important it is.
“You know that downtime is really important, and you feel better [after sleeping] and we should have more appreciation of the role of sleep in our lives.”
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