We're Up All Day to Get Lucky

One of the key characteristics that's often listed for the behaviour of a mammal species is what time of day it tends to be active. There are four basic options here, of which the most obvious are diurnality and nocturnality. The others are crepuscularity if it's most active around dawn and dusk but not in between, and cathemerality if it really doesn't care - often because it lives underground. But, either way, it's natural to assume that this behaviour is relatively fixed in an animal; either it's nocturnal or it isn't.

In reality, however, it turns out that this can have a lot to do with the circumstances. And, in the modern world, those circumstances are most likely to be shaped by... what else, but humans? 

The issue, of course, is that humans are for the most part diurnal. Which isn't much of a problem for animals that are naturally nocturnal, but can be if they, too, would prefer to be active during the daylight hours. What we see time and time again across the world, and across different mammal species, is that where humans are most likely to encounter wild animals, those animals shift their behaviour towards nocturnality to avoid the stress of meeting us too often.

To be sure, it's not a universal rule, and it probably applies more to large animals that we might hunt than it does to smaller ones that can stay out of sight or hide in our cornfields. But one study in 2018 looked at 62 medium to large mammal species from across the globe, ranging from coyotes to deer, lemurs, elephants, and porcupines and concluded that in areas with high "human disturbance", on average these animals were over one third more likely to be active at night than they would otherwise.

What sort of "human disturbance" you might ask? Well, the study showed that it really didn't matter. You might think that actively being hunted or persecuted would be the biggest driver of switching to nighttime behaviour but it turns out that simple agriculture and even living in a wild area frequented by hikers have just as much of an effect. Not to mention that living near a busy road is quite possibly as deadly to a wild animal as being on the hunting menu. Nor, at least from this study, did it seem to matter whether the animal was a predator or a herbivore, although the largest and most visible animals did seem to be more strongly affected than the others.

There is, on the other hand, a flip side to this. Things like agriculture and road building are expanding across many parts of the world, and leading to declines in many animal populations. But, in recent decades, the pattern of human development has tended to follow a different path in Europe and North America than elsewhere. Here, we see increasing urbanisation, something that clearly brings its own problems, but that does have the effect of depopulating rural areas. This means that, outside of those concentrated urban areas, wildlife is less likely to encounter humans, and can reassert its preferred behaviour. 

This isn't merely theoretical. Eurasian otters, for example, used to be nocturnal where humans were present, but researchers can now sit around and watch them fishing even in artificial reservoirs. An additional factor here may be that our relatively urbanised, modern, populations are likely to see wild animals less as competitors or threats to livestock but as something to be preserved and cherished.

But those changing attitudes and population shifts may only go so far. It's one thing to reduce the threat to, say, deer or badgers but it might be another to change the attitudes of the people who still do live in rural areas to animals they see as an active threat. In many parts of North America and Europe, one of the prime examples of this is surely the grey wolf (Canis lupus).

Wolves have been persecuted throughout human history, seen as a menace to our livestock and even to humans directly. Frankly, it's a wonder we ever domesticated them; in the wild we've done pretty much everything we can to get rid of them. The last wolf in the British Isles is generally said to have been killed in 1680, although later claims exist. Of course, there we had the advantage of being an island, making it difficult for new wolves to wander in to replace those killed.

The French had no such advantage when it came to wiping out all the wolves in their country, but that didn't stop them trying. Charlemagne set up the louveterie, a specialised corps of wolf-killers, in the early 9th century. It took them over 1,000 years (handicapped by being briefly abolished after the Revolution) to finish the job, but they finally managed it in the 1930s. Even then, in an example of our changing attitudes to such things, wolves were granted legal protection in the country in 1993, a year after one was spotted sneaking across the Italian border into the Mercantour National Park just north of Nice. There are now thought to be about 500 wolves living in France, mostly around the Alps.

There are similar stories from other parts of Europe, with the Balkans and Carpathian Mountains having held on to the largest populations. In western Europe, the largest surviving population is probably that in Spain, where it is estimated that there could be as many as 2,000, living in about 350 packs, all in the northwest of the country. Some researchers describe these as a distinct subspecies (Canis lupus signatus) as they diverged from the Italian population 10,300 years ago around the end of the Last Ice Age, but, even if they don't quite earn that honour, they are genetically distinct.

Despite their comparatively large numbers, wolves have been persecuted just as much in Spain as in other countries. Legal protection was only brought in at a national level in 2021 (it was earlier in Portugal, but there is only a tiny remnant population there, along the northern border) and there are efforts from some political parties to reverse that. So one would expect that Spanish wolves, like those elsewhere, are probably still cautious and try to avoid angry farmers with guns - and humans more generally - as much as they can.

Would they behave differently if there were no humans around to bother them or they naturally nocturnal anyway? It's the sort of thing that's difficult to test. We'd need two sizable areas, relatively close to one another, in one of which humans are present, doing the sorts of things they normally do, and in one of which human presence is essentially banned. The best example of the latter in recent years is probably the area around Chernobyl, but there are sound reasons why it's difficult to do too much wildlife research there. 

A recently published study, however, took a look at the wolves living in a smaller and less dramatic example of such an area in the north of Spain. The As Pontes coal mine was closed in 1985 and, over the next 20 years, the debris dump around it was rewilded by planting native vegetation and fencing it off to prevent human access. The process was completed in 2009, leaving a 1,120-hectare (4.3 square mile) area that it is difficult - and generally forbidden - for humans to access, but that animals can still enter. It is now home to several deer, wild boar, foxes, and, yes, wolves.

Using camera traps and checking their results by radio-tagging a couple of wolves and following their movements on GPS, the researchers began by looking at a more typical area to the south, a hilly region occupied by a mix of cattle pasture, scrubland, and pine plantations. Here, the wolves were, as we'd expect, nocturnal, spending 80% of their activity time between the hours of 8 pm and 8 am. This fits with how we'd generally expect wolves to act, consistent with other studies that show wolves as a generally nocturnal animal - for example, in Croatia and Minnesota. 

So, nothing unusual about Iberian wolves compared with those elsewhere, then. But, when it came to look at them, it turned out that the wolves living at the human-restricted nature reserve were not the same. While they were often still active at night, they continued their activity right through the morning, not going to sleep until around 2 pm, and actually being most active shortly before noon. Not really what you'd expect from a "nocturnal" animal.

It's plausible that, as predators, part of the reason for this shift in wolf behaviour was due to the local deer being less afraid of hunters, and therefore more active during the day themselves. The wolves were clever enough, for instance, to sneak out of the nature reserve at night to hunt the feral horses in the surrounding terrain, and then slink back again before dawn. But, on the other hand, they did seem relatively unafraid of humans (such as the researchers) on their home ground so it's likely that they're simply more comfortable being awake in the morning if only people aren't going to try and shoot them. Plus, the local deer and wild boar, unlike the wolves, are culled from time to time so they may still prefer coming out at night when they can.

The site had been fenced off for nine years at the time of study, so we don't know how long it took for the wolves to adapt to their new freedom. But the researchers point out that wolves were sometimes seen prowling Italian streets in broad daylight during the COVID lockdowns, so it may be quite quick. 

Few places are as free from humans as a fenced-off nature reserve but the general depopulation of rural areas across much of western Europe, not to mention any hunting bans that might be coming into place, may well be good news for wolves across the region. Quite how humans might react if they saw wolves around more often during the day and realise that the animals are more common than they thought is another matter. It is not, after all, as if wolves are entirely harmless, and those who wish to, for example, photograph them in the wild might not be in a majority. 

How we manage those expectations and provide safety for those still living in or travelling through depopulated rural areas might be something we have to think about in the coming decades.

[Photo by Tudela de Duero, from Wikimedia Commons.]