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Archive for the ‘Thoughts and Musings’ Category

For anyone who has any questions about wildlife in Britain there is a fabulous resource that’s free and available to anyone.  This is the Wild About Britain website, and in particular the forums there.  You can ask any question and get an answer from a huge range of experts and enthusiasts.

I asked the question about badgers being able to see the infra-red light from my night vision scope, and one response seemed to match my experiences exactly.  This is from a WAB member called stripee:

Yes they can see it and always react. Some more nervously than others. I have a night vision scope with infra red. The badgers, foxes etc don’t like it shone in their eyes. I try to shine it for short periods and not directly at them.

If you look at your scope when the red light is on from the front it can be seen for a long distance at a certain angle. I had heard that badgers don’t see red light, but it just isn’t true.

This is good.  This backs up what I have observed.  It isn’t scientific proof yet, but it adds to the anecdotal evidence.

I’ll keep searching and see what else I can find out.  In the meantime I’ll also try some informal experiments  and see if I can get some more evidence.   There are more formal experiments that could be done to prove the matter one way or another (I’m thinking of a version of the Skinner Box with an infra-red stimulus) but I’d need a fairly captive population of badgers to try it on.  If any biology students are looking for an idea for a project, let me know…

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This is an open question to any and all badger experts out there.  Can badgers see infra-red?

I’ve used my night vision scope twice now (see Fieldnotes: 25th July 2009 – First night vision session and Fieldnotes: 6th March 2010 – A frosty night at the badger sett).  On both occasions the badgers have been visibly spooked, presumably by the infra-red light.  Of course, this is purely anecdotal evidence – I haven’t done any sort of scientific study – but I’ve spent enough hours watching badgers to know when one is disturbed by something, and all the ones I’ve seen through the night vision scope have indeed been disturbed.

Of course, it might not necessarily be the infra-red.  The night vision scope (it’s a Bresser, by the way) may be doing something else to frighten the badgers.  It may make a noise that is inaudible to us but audible to badgers, for instance.  I don’t know.

So, has anyone had experience of using a night vision scope to watch badgers, particularly with an infra-red torch?  Did you notice any signs that the badgers were aware of it?  Does anyone know of any research or literature on the subject?  Does anyone know if any other animals can see in the infra-red end of the spectrum?

If you have any ideas or experiences, please do let me know.  I’ll keep searching myself and let you know if I find anything.

Thanks

BWM

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Badgers in a social group- but why?Following my thoughts on the evolutionary significance of delayed implantation, Pablo asked the very good question why (if my theory is correct)  badgers stopped being solitary and started living in clans.  Fortunately, I think I can answer this one.   What follows is not my own thinking, but based on the work of Hans Kruuk, a giant of badgerology upon whose shoulders I gratefully stand.  His The Social Badger is highly recommended reading for anyone interested in the subject.

Kruuk looked at the evolutionary advantages for badgers of living in social groups.  Social living is relatively common in mammals.  The usual benefit it gives is increased vigilance against predators (think of meerkats or rabbits – one or two individuals can keep watch while the others feed).  Social carnivores are more rare.  Lions, wolves, dogs and hyenas gain an advantage from hunting in packs – wolves and hyenas, for instance, can bring down prey much larger than themselves by attacking as a group.

Badgers don’t fit neatly into this scheme.  They are social carnivores but they do not hunt in packs.  In fact, for social animals they are actually not very sociable at all.  Badgers live together in a sett, and they will play and groom and interact with each other outside the sett, but once they leave the immediate area of the sett they forage as individuals.  For most of the time they are above ground they are alone, gaining the advantages of neither mutual vigilance nor pack hunting.  So why do they live in clans?

Kruuk’s theory is based on defending territory.  Badgers, in the UK at least, are omnivores.  They predominantly eat earthworms but will happily feed on anything from wheat and barley to rabbits and dead lambs.  Kruuk observed that badgers take advantage of different sources of food depending on weather conditions and time of year.  Success, for a badger, means making full use of these different ‘food patches’.  In order to have a guaranteed supply of food, the badger must have access to a wide enough range of food patches so that if one is not productive there will be others that are.

In order to have access to these food patches, the badger needs a large territory.  The problem is, a territory large enough to be productive is too large for a single badger to defend.  Hence, so the theory goes, badgers join together so that collectively the clan is able to defend a territory large enough to cover sufficient food patches.  Each badger plays a part in marking and patrolling the boundaries.  This makes perfect sense – many people have found a relationship between the size of badger territories and available food resources.  The territories in my fairly lush Bedfordshire landscape of woods, arable and pasture seem to be quite small, reflecting the good supply of available food.  Those in more sparse areas (such as Scotland, where Kruuk did a lot of his work) are much larger.

The theory accounts for why badgers live in clans today.  If my thinking is right, this clan living is a relatively recent evolutionary adaptation.   This does raise the question of why it should occur in the comparatively food-rich environment in Britain whilst badgers in other, poorer environments are solitary.  One would imagine that the advantage of defending food resources would be more pronounced where the is less food available.  Instead, the opposite seems to be the case.

Sorry Pablo – the answer to your question ended up a bit longer than I thought.  As ever, once I start to think that I understand badgers, I realise that actually I really don’t.

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Badger - one of the mammals that practices delayed implantationAs I write this I can be quite confident that in badger setts across the country, female badgers are either giving birth or getting very close to doing so.  Up to mid-February is the peak time for badger births.

The reason I can be so confident is that badgers have amazing control over their reproduction via a process called delayed implantation.  The badgers can mate at any time of year (spring and late summer seem to be particularly favoured times) and yet give birth in February.

What happens is that the egg gets fertilised in the normal way.  Egg and sperm combine and the cells start to divide.   But the fertilised egg does not implant itself into the uterus and continue to develop as would be the case in most mammals.  Instead, the small ball of cells, called a blastocyst, stops developing and goes dormant, drawing just the small amount of oxygen and nutrition it needs to survive.  In late December the blastocyst attaches itself to the wall of the uterus and starts to develop into a full foetus, to be born in February.  This is delayed implantation.  It means that the badger mating I witnessed in August (see Fieldnotes: 8th August 2009 – Sex) could result in cubs being born now.

Delayed implantation is not unique to badgers.  It occurs in a number of other mammals such as stoats, bears, Roe Deer and Grey Seals.  The evolutionary advantages of the process are clear – it means that the young are always born at the optimal time to take advantage of the best food resources in spring.

For badgers, there a few interesting implications.  Ernest Neal speculates that delayed implantation allows the badgers to mate throughout the year, which may help to strengthen clan relationships.  Hans Kruuk makes the point that multiple matings with different males could result in multiple blastocysts, meaning that each cub in a litter could have a different father.  Badger families must get complicated sometimes!  This is even more interesting when you remember that the dominant female badger may kill the cubs of other females to maintain her position.  This control over the genetic make-up of the clan is very much a female thing.  It must be related to the fact that you can never be sure who the father is, but there’s never any doubt about the mother.

Now, I’ve been thinking about badgers, and about delayed implantation, and I’ve got my own little theory.  This is just my own idea, so if it’s wrong then I take full blame.  My line of thinking goes like this: most of the mammals that practice delayed implantation are solitary by nature.  This means that the males and females come into contact only irregularly.

Delayed implantation offers an evolutionary advantage to these species because it means that a male and female can meet up at any time of year, mate, and still have the offspring born at the best time.  It is a way of compensating for geographical and territorial dispersion.

But badgers are different.  Badgers live in social groups where males and females come into contact every day.  For clan-living badgers, delayed implantation offers no great advantages.  Why don’t female badgers simply come into season in December and have cubs via direct implantation?  Neal’s theory about the regular mating strengthening group bonds is one plausible explanation, and there may be a further advantage gained by the genetic diversity of litters sired by different fathers, but I think it tells us something about the evolution of badgers.

I think that delayed implantation is an evolutionary throwback to a time when the Eurasian Badger was a solitary animal.  I think it points to a period in the history of the badger when they didn’t live in social groups and therefore gained an advantage from it much as stoats and seals do today.  In turn, it suggests that clan living is a relatively recent development for badgers.

It isn’t as wild a theory as it sounds.  Other badgers around the world are still solitary – the American Badger, the Honey Badger, the Indonesian Stink Badger, and so on.  Even our own Eurasian Badger is solitary across large parts of its range.  In Mediterranean regions, where food is scarce, badgers are virtually solitary.  Rather than this being an adaptation to the dry conditions, it’s my belief that delayed implantation shows that this is their natural state, with clan living a relatively recent adaptation to the conditions of North West Europe.

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Loch Ness from Fort Augustus

Loch Ness from Fort Augustus

For more years than I care to remember I’ve celebrated the summer solstice in true and outrageously pagan style at one of the great stone circles of Avebury and Stonehenge.  This year, however, I swapped the ritual of standing slightly bleary-eyed and hungover, waiting for the Wiltshire dawn to peep over the horizon, for the celebration of a friend’s wedding.

The wedding festivities took place near Inverness in Scotland.  The main venue was an enormous old country house, where we had the run of the place for three whole days.  It was a great place and a great wedding – the toasts were drunk in decent scotch whisky, which gives you an idea of the kind of night it was.

Despite my hopes of running into red squirrels or scottish wildcats, it was not to be.  I did take a stroll around the estate on the morning after the wedding to get a breath of fresh air while most of my fellow guests were still slumbering away.   In the woods of the estate I came across a pristine set of badger tracks on a muddy path, and I was able to follow these back and locate the sett – a grand affair with at least half a dozen active entrances.  It just goes to show that you can dress me up in a suit and try to make me civilised but once a tracker, always a tracker!

But for me, a trip to Inverness had to involve a visit to Loch Ness.  I borrowed a car (thanks Sam!) and spent a day there.

When I was much younger I was fascinated by the idea of the Loch Ness Monster.  As I grew older and developed faculties of critical thought I realised that there wasn’t actually a plesiosaur in a lake in Scotland – come on guys, what on earth were you thinking! – but the story is still a great one.

The Horseshoe Scree on Loch Ness where Torquil MacLeod saw the monster

The Horseshoe Scree on Loch Ness where Torquil MacLeod saw the monster on the shore

The best time to be at Loch Ness must have been in the late 60s and early 70s, when it was home to an assortment of different expeditions.  There was a tremendous enthusiasm about the place, a feeling that there was a genuine discovery to be made, and that if established science was not interested then it was up to the amateurs to show them the way.  It must have been great – the shores of the loch manned by student volunteers with cameras, binoculars and surplus World War II searchlights, while on the water a strange assortment of boats fussed around, playing tapes of mating whales on underwater speakers or ferrying American technicians as they tested their latest sonar gear.  In those heady days anything must have seemed possible.

Where Tim Dinsdale filmed the Loch Ness Monster

Where Tim Dinsdale filmed the Loch Ness Monster

I’ve never been to Loch Ness before, but I have read almost every word ever written about it.  I took my poor, long-suffering wife on a trip around the loch, stopping at obscure places of interest.  I found the layby where in 1960 Torquil MacLeod watched the monster as it basked on the Horseshoe scree on the opposite shore.  I found the approximate location from which Tim Dinsdale filmed the monster in April of the same year, and I was able to follow the route of his thrilling dash to the loch shore in a desperate attempt to get closer to the beastie.  I travelled the road where the Spicers had their classic 1933 land sighting, although it has changed out of all recognition now.

I enjoyed my pilgrimage to the loch immensely, but isn’t it all a bit sad?  I mean, people don’t really believe in it any more, do they?

Ironically, even though the enthusiastic volunteers of days gone by used to battle against mainstream science, they turned to mainstream science and in so doing they proved that the monster doesn’t exist.  Adrian Shine, monster-hunter turned respectable scientist, has spent years building up a picture of the ecology of the loch, starting from nutrient levels and plankton and working up the entire food chain.  The results of this work show that the loch cannot support a single large monster, let alone a breeding population of them.

Although I’d secretly like the monster to be real, I think I am reassured by this.  It shows what amateurs can do.  They didn’t find a plesiosaur, but the slow, patient study – starting from first ecological principles, establishing facts and building on them – has finally answered the question of the beastie in the loch.  In the process it has shown what enthusiasm, resourcefulness and some basic scientific principles can achieve.  It is a story that I, as a very amateur naturalist, still find inspirational.

There may not be a monster, but the story of the search for it deserves to be remembered.

Don’t worry – back to the badgers later this week…

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OK.  Time to bare my soul a little.

Most people in Britain have never seen a badger.  Many have seen a dead badger by the side of the road, but few ever see a live one.  Of those that do, I suspect that most are content to enjoy the experience, to enjoy the badger as an impressive yet endearing part of our wildlife.  As I’ve said before, once people see a badger they seem to become hooked.  Even Ernest Neal, the undisputed authority on badgers, first came across one by accident and this led to a lifetime of work studying these creatures.

But for me it is not enough to just watch badgers.  I’ve gone past the “wow – there’s a badger!” phase.  I want to understand them.  I think I’m becoming obsessed.

Now don’t get me wrong – it’s not a bad obsession to have.  It’s quite healthy.  I could be addicted to drink or drugs, but instead I’m becoming addicted to badgers.  It’s a pleasant diversion from work, it keeps my mind active and stops me getting up to mischief, and most importantly it encourages me to get out and enjoy the countryside on my doorstep.

What started out as a good excuse to go for a walk in the woods has now got me learning about animal behaviour, territoriality, social bonding and the whole ecology of woodlands.  As soon as I think I’ve understood how badgers work, I discover something new and realise I actually don’t know very much at all.

All of this philosophical musing has been triggered by a short walk in the woods this morning.  I wanted to go out and have a look at the Pine Tree sett, specifically to see if there was any more evidence of badgers eating the sycamore bark.

Sycamore with gnawed bark

Sycamore with gnawed bark

When I got to the sett I found that there was a lot more evidence of bark eating.  Another tree had been ‘attacked’ and more bark was missing from the original tree.  But from what I’ve seen, I’m not sure that badgers are the culprits.

The bark shows clear toothmarks – lots of them and quite small – rather than a few large claw marks that I’d expect from a badger.  More conclusive was that the damage to the bark now extends to about 8 feet off the ground.  Badgers are actually surprisingly good at climbing trees (and they seem to enjoy it as a game) but I think that this height is beyond them.  I now need to research squirrel feeding, and see if that fits the bill.  Even better, I need to spend an evening here and see if I can catch the culprit in the act.

Bark damage close up

Bark damage close up - scale in cm

Acting on suggestions from people on the Wild About Britain forum, I examined the badger dung in the latrine nearby.  It seemed a bit more green than usual but there were no clear signs of bark in it.  And no – I didn’t bring any home for analysis.  I’m not that obsessed yet!

Badger Dung

Badger Dung

Walking back through the woods, I came across more puzzling animal signs.  For want of a better word I’ll call these ‘nests’.  They were substantial piles of grass that had been pulled up and shaped into a mound, sometimes with a hollow in the middle.  They are undoubtedly the bedding of some animal.

I’ve come across these before, and I wondered if they were piles of bedding that a badger had collected and then for some reason abandoned on the way back to the sett.  After seeing more of them today I think that they are more likely to be nests in their own right, where an animal sleeps.  I found them in dry, sheltered spots.  Here’s one under a fallen tree:

Badger Nest 1

Here’s one under the shelter of a pine tree:

Badger Nest 2

The nests were associated with paths, but whether these were badger paths I could not say.  The whole area is criss-crossed by badger paths and deer paths, and to confuse matters the badgers use deer paths and the deer use badger paths.

Are these nests made by badgers?  What other animals deliberately gather bedding from distance?  If they are badger nests, why are they there?  Why are the badgers not safely underground in their sett?  Are they used as temporary shelter?  Are these badgers part of a sett, or are they some sort of homeless, ‘hobo badgers’, sleeping rough?  If so, how do they fit into the territories of the other badgers?

Do you see now how this whole badger business can become obsessive?  If anyone has any answers, please do let me know.

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Buzzard over the pasture field

Buzzard over the pasture field

I’ve tried to make a point of watching one group of badgers rather than flitting around here, there and everywhere, the idea being that I should be able to learn more by getting to know one group very well.

OK.  Today I changed my mind slightly, and decided to go and have a look at the neighbouring badger sett.

Regular readers may remember that I found this sett a little while ago (see Fieldnotes 7th September).  I hadn’t forgetton it.

In fact, this sett has been central in my efforts to understand ‘my’ group of badgers.  I was able to predict its position by mapping latrine sites, badger latrines being sited on the boundaries of their territories.  When I followed the badger tracks in the snow in January I was able to see how badgers from both of these setts interacted on the boundary between them.

A great deal of badger behaviour is related to establishing and maintaining a territory, so understanding the relationship between neighboring clans is important.  For instance, last year I wondered what happened to the ‘excess’ badgers at the sett, since as a group they seemed to reproducing faster than they were dying.  After reading Hans Kruuk’s The Social Badger I now know that the non-dominant males leave and typically mate with females from another sett, but only ever with those from a neighbouring sett.  They don’t seem to travel any further.  The females almost always stay in their home territory.

(Interestingly, this happened to me too.  I grew up in the north of England, but I left there and married my wife.  My wife is from Bedfordshire, where we now live,  so I migrated away from my clan whilst she stayed in her home territory.  Perhaps the principle works for humans as well…)

Anyway, I digress.  Today, I decided I fancied a bit of a change so I went to see the other sett.  It needs a name to distinguish it from the main sett I watch, and since there are pine trees around the entrance let’s call it the Pine Tree sett.

The Pine Tree sett is not as big as the main one.   Like the main sett it adjoins

The Pine Tree sett

The Pine Tree sett

the pasture field, so the badgers have access to the main food resources (hence the territorial boundary that divides the pasture field between them).  There are three entrances spread out over a hundred yards or so, with a well-used path between them.  The entrances are the classic sideways D shape, with large spoil heaps and used bedding outside.  Nearby were fresh dung pits.  In short, it was as badgery a place as you could ever wish for.

The only problem was that although I watched it for three hours, I didn’t see any badgers.  Very frustrating.

The holes are quite far apart and not intervisible, so it is only possible to see one of them at a time.  I chose to watch at the hole with the largest and freshest spoil heap, but perhaps the badgers were at another one.

It’s a mystery.  It is obviously a badger sett, and obviously in use, so the badgers must be somewhere.  I was at the sett from 6.30pm to 9.30pm, so I imagine the badgers would have come out during that time.  In the other sett half a mile away they’re coming out consistently between 8.00pm and 8.30pm.

I think I need to put in a few more trips to this sett and try watching the other holes.  Hopefully that will clear up the mystery.

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