Denizens of Decay

 A closer than normal view of a woodlouse's face, showing the simple clustered eyes. 

Beyond the busy and considerably important boundaries of the human world, there exists a hidden army. An army which is largely so insignificant and neglected that it is often only noticed when one of its ranks breaks and runs across the lounge carpet. This group of organisms is pivotal to the natural world in which we all enjoy and is as essential to the noctule bat roosting in the veteran oak as it is to the bumblebee pollinating the foxglove, growing at the trees base. Decomposition is natures answer to putting your glass bottles, empty cans and cardboard boxes in a blue bin and waving goodbye (not literally I hope). The list of organisms which help in decomposition is impressive and ranges from fungi to fruit flies. They are so important to ecosystems that earth would probably not contain life without them. Essentially they recycle dead matter and turn it into nutrients which support the food webs we are more familiar with.

Slugs perform an important role within ecosystems and are not just an unwanted garden pest.  

Two groups of decomposers can be quite easily found in and around the house (well maybe not one of them unless you have a very damp house), these are the woodlouse and the slug, yes slug, they don't just eat all of your favourite garden plants.

Woodlice are perfectly adapted to living in tight gaps and a life feeding on decaying organic matter. 

Take the woodlouse as an example, evolutionary perfection or a common creature of insignificance? Woodlice live under bark, logs, stones and rocks and typically feed on decaying leaves, bark, fruit and similar herbivorous matter. They clean up decay and reprocess it through their droppings into nutrients in the carbon dioxide cycle. Their droppings also contain fungal spores which are incredibly important to the continual breakdown of leaf litter and health of the forest. This speeds up the entire decomposition process, important for vegetation. They are exceptionally flat which allows them to live in small cracks, gaps and crevices where they can shelter and feed, away from predators. This has resulted in the evolution of a small, relatively hard, armour plated, flat crustacean which has evolved to do what it does to perfection.

A miniature tank. 

The flat profile, woodlice have 10 legs and are crustaceans not insects. 

Woodlice live for about 2 years but have been recorded living up to 4 years which is quite cool considering they are only about 1cm in length. Mating often occurs at night, when the male will climb on the females back, drum her with his forelimbs and lick her head (and who said romance was dead). The females lay about 25 eggs (species dependent) and broods the young in a pouch on its underside (no quite like a kangaroo but similar). She will then look after them until they are small adults ready to continue the everlasting job of decomposition. The species in the photographs Oniscus asellus can frequently be found in moist leaf litter, in gardens and around houses. It is one of Britain's most common species (of which we have approximately 45 species in the UK and over 3,000 in the world).  

I dint realise photographing slugs would be so difficult, the eyes are difficult to get in focus with the head, and the body has no real form. 

The second creature is the slug (for the record I am not a slug fanatic they just seem to get a lot of bad press so YETI is going to change that). Slugs are usually regarded as a garden pest or a none descript blob, but slugs need love too. Slugs are important components within ecosystems and provide food for a large number of species including hedgehogs, frogs, toads and slow worms. They are also very important decomposers, something not that widely known. They don't just feed on living plant matter but on a whole diversity of things (see Snail's Pace post) from fruit, wood, fungi, algae and even other slugs and carrion.

Limacus flavus an occasional species or just an under recorded species? 

This species is somewhere around number 600 for the YETI 2013 challenge and is appropriately known as the "Yellow Slug" (Limacus flavus) and is quite a looker as slugs go. It is described as occasional rather than common and another interesting record for the year. I would honestly have never even considered looking at slugs if it wasn't for the YETI challenge (this an intense but enjoyably serious learning curve). So although not quite a breeding record for a declining farmland bird, all of our records great and small will hopefully help build an important picture of our local wildlife, especially concerning overlooked species. Back to the slug, this species is a ravenous feeder of fungi, decaying organic matter, namely dead plant material and sorry folks vegetables. So it contributes to the overall decomposition, returning nutrients to the soil. It also breaks things up into smaller bits for the woodlouse, which also feed on its droppings, sweet. So next time you see a woodlouse or a slug just think, this guy is actually doing me a favour and give it a break.

A slugs eye view, slugs have such amazing eyes, which can be retracted back into their heads. This one is just opening.                                   

The Brown Blight and the Baby Snatcher

Perhaps the last sight that any nestling (except a jay) wants to see looking over the rim of its nest, look at those hungry eyes.  

It's human nature to anthropomorphize and nowhere is this more prevalent than in how we perceive the natural world (and in my blog post titles). Some animals are viewed as respectable heroes and heroines, others as evil villains. It is almost an innate sense, just mentally compare a rook and a robin, or a butterfly and a spider. In reality attributing human traits to animals is, as I have mentioned on the blog before, an unwise way to look at our wildlife. Every species plays a part and to appreciate and understand how an ecosystem works, or doesn't work, one must appreciate the part each species plays. You need predators to balance the prey, seldom do predators drive population declines, unless they are outside of their natural range.

Hate them or love them, your never far from a brown rat. 

Brown rats, like many of the mammals we have featured in the blog so far are not actually native. Before we go on, it is worth pointing out that it was the (also none native) black rat which was the key carrier for the bubonic plague, during the black death (1348-1350). The brown rat is considered to be less of a carrier for the species of fleas which carry the disease. There was even some (false) speculation that the colonisation of Britain and out competition of black rats helped combat the spread and intensity of the disease.

The brown rat first reached Europe from Russia (its native range being china) during the 18th century. This was noted by the German naturalist, Peter Simon Pallas during 1727 (The Pallas Warbler Guy). Initially it was believed that this species came to Britain in timber vessels from Norway hence its other name Norwegian rat and the norvegicus part of its Latin name. In fact it first arrived in 1728-9 from Russia. The species was not recorded in Norway until 1762.

Brown rats, are extremely adaptable burrow dwellers. 

Regardless of your opinion of rats they are responsible for extensive damage to stored products and to a lesser extent growing crops. Brown rats can cause extensive damage to seabird colonies, especially where they occur on offshore islands. Also as somebody who spends a lot of time working in freshwater Leptospirosis is a ever in my mind, a disease carried by brown rats, better known as Weils disease in its human form. In addition to this they carry Q fever, Toxoplasmosis and hantavirus.

The big bulging eyes and long whiskers help brown rats navigate in the dark in their tunnels and at night time.  

However despite this they appear to have occupied a bit of a niche in Britain and are a prey species for a wide variety of birds including barn owl and tawny owl locally. They also produce micro-habitats (their burrow systems) which can be utilized by other species like hibernating amphibians and reptiles, when disused. Not a species I would want near my house but if they stay away I remain on the fence.

There is something about the look in a jays eye, which screams intelligence. 

Close up, you can see the bright blue eye

The Jay on the other hand has historically been persecuted by gamekeepers, but its shy nature and the blind animosity towards magpies (deflection dislike) has probably helped its public opinion remain quite high. In addition to its striking colours, the jay must be one of Britain's most striking birds. Jays like the other corvids are partial to raiding nests for young birds and eggs. However it has been widely scientifically proven that they do not cause any lasting impacts on prey populations. Jays rate as one of my personal favorite British birds, they are incredibly intelligent and colourful.  

Unfortunately the dull dark sky results in dull dark, characterless photos, what a difference a little sun would make. Male Kestrel.  

The local sparrowhawks were displaying early today over their likely breeding location (a small Scots pine dominated plantation).  

A rather awkward Tree sparrow who opted to sit on the other side of the hedge. Still its great to see this species locally, away from the coastal populations.  

And finally ANOTHER brown hare, I am brown hare crazy at the moment. 

Mad World

The skies are constantly dark with snow heavy clouds, the sea is battering the coast and the north easterly wind bites the skin. It's hard to believe that we are days away from April a time of year one would expect lambs in the fields, daffodils in bloom, ponds full of frogspawn and a whole host of creatures and creepy-crawlies waking up to the summer after a long winters slumber. Seems like many of these have had to endure a rather forced lie-in. However I did manage to find common toad, common frog, smooth newt and great crested newt earlier in the week whilst at work. I will get some artistic amphibian shots this year, when it warms up. Reluctant to get soaked and blown away on the cliff-tops or travel far in the poor dull weather, I have made the farmland which surrounds my house my own once again, rekindling the childhood spirit which originally got me hooked on natural history. A very real sign of spring was present today however despite the mad march weather and that was the sight of mad march hares, one of nature's super spring spectacles.

Boxing is generally the result of a female warding off a males sexual advances, by rearing up and boxing him with her forepaws. This is usually seen in unreceptive females which are near oestrus but not quite ready to mate. Each female at this time of year is guarded by a male or a small number of males (as seen in the photo 3). These will remain with the female and generally stay within 5 metres from her daytime form (resting place). Males naturally chase and fight each other for breeding rights. We tends to see dominant males guarding near-oestrus females and attacking sub-ordinate males, thus having a higher breeding success rate. Subordinates are bitten and chased off, although boxing is unusual between males.

The term "mad march hare" is somewhat misleading as hares often mate as early as January, with births between February and October, brown hares have about 3 litters per year. These tend to consist of 1-4 leverets (young hares), early and late litters tend to have lower numbers of leverets, possibly linked to female condition and food availability. Interestingly females occasionally exhibit superfetation in which two different aged embryos are present together in the uterus. Prior to giving birth female tend to become shy and retire away from male attention, staying close to the place in which they want to give birth for about two weeks.

Unfortunately the pheasant and partridge culture of the region means foxes are controlled quite regularly (although my own scat counts reveal populations remain stable with territories more or less saturated in the area). This control probably helps the hares as foxes are their key predator in Britain, and have been shown to limit population growth and productivity. In extreme cases foxes can predate 80-100% of leverets in a season. I managed to find a fox skull recently which gave me a good opportunity to take a closer look at the species structure.

A bit of simple maths (Cough) using the Lynch equation and we can sex red fox skulls.

D = (2.114 x GL) - (1.874 x PO) - 27.478

I am not much of a fan of maths so I will get to the point the skull is from a male. Other ways of telling is the presence of a prominent sagittal crest, which is suggestive of a slightly older male. However the good condition of the teeth suggests it was not that old at the age of death, probably c.12 months or more. Red fox skulls tend to have narrow muzzles and longer canines in comparison to domesticated dogs (the only real confusion species in Britain). They also show a concave upper surface to the post-orbital process (bone which sticks out above the eye), this is convex in dogs.

Another hare predator which is prominent within this region is the buzzard, although perhaps less of a problem to hares than foxes. Common buzzards will no doubt take leverets, as well as rabbits. One was wheeling around in the snow above the hares, but certainly locally these buzzards tend not to close enough to be photographed. Although I did manage to see one with an extremely young rabbit, a lagomorph similar to the brown hare but more productive in terms of breeding and equally one which starts to mate early in the year.

The little owl seems to be getting a bit more approachable, but with the almost imminent onset of the breeding season, I will avoid any close interactions with these birds which are easily spooked and can abort the nest site early in the season prior to the egg/nestling period. Always nice to see this species though. Hopefully we will remain snow free and these birds will persist into the spring. I have been looking for other nest sites as undoubtedly other birds will be in the area but have only found jackdaws thus far.

       

It wasn't only the hares which were fighting in the fields today but also the male pheasants were getting a little shirty with one another.

Snails Pace

With MORE rain and MORE cold weather over the weekend continuing to suppress spring, there was little else to do than slug it out looking for molluscs. The un-seasonally cold weather is certainly holding the team back and the almost continual cloud cover is certainly making photographing some of the species very difficult.    

 Arion circumscriptus a member of the Arion fasciatus group, a species with quite a distinctive black head when it is extended. Also note the springtail (Probably Dicyrtomina saundersi) near the slugs head. 

 Arion fasciatus showing much reduced yellow on the flanks, a common feature of this species. On a more distinctive individual the flanks tend to be brighter yellow, this chap showed it towards the base, suggestive ID (just not seen in the photo).  

Arion silvaticus the the third member of the group complex, these guys are like the warblers of the slug world, in terms of being tricky to ID. This and the two species above can be incredibly similar to newcomers, especially to somebody like me, new to slugs, driven into slug induced coma, due to a lack of other invertebrates.

Quite attractive as slugs go, this is a young Arion subfuscus another variable species, which tends to be a brighter orange then the above three species. A species fond of fruits and fungi as well as young shoots from plants. 

Red form

Black form

The two common forms of the garden slug Arion ater agg. (a species complex), a species frequently encountered in and around gardens on damp days. These slugs grow quite large and provide food for a range of amphibians and hedgehogs. These slugs are omnivorous and feed on vegetation as well as dung and carrion. Slugs are quite important decomposes, despite worms getting all of the credit.  

Deroceras reticulatum another frequently seen slug in and around gardens. This species is a key component in the diet of slow worms. This is perhaps the most common species across Europe and can be a significant pest to crops such as lettuce. 

A young Limax maximus (Leopard slug), One of Britain's largest species. This is an omnivore which acts as a decomposer feeding on deadwood and fungi. It will also predate other snails and slugs. 

We cant have all these slugs without showing any snails, these are Trochulus striolatus. 

Slugs aside I managed to get some more good views of the local barn owls and brown hares, despite poor light and the hare choosing to sit behind a wire fence.

The Voice of Reason: Badgers and BTB

With cold wintery weather and regular snow showers, this week has felt more like December than March. A combination of this unseasonable weather and days of hard graft (depending on one's definition of what hard graft is) I have had little time for YETI'ing. Fortunately I have been undertaking a number of badger surveys (which has dangerously got me thinking. . .) and thought with not a lot happening let's take a look at what is one of Britain's most iconic mammals and the well documented association with BTB.

A question very much on every ones lips at the moment is the proposed cull of badgers in Britain with experimental trials having occurred in some places i.e. Gloucestershire. Recent news suggests that the government is about to give the green light to a full scale badger cull in England, which could see in excess of 100,000 animals slaughtered. As someone familiar with badger ecology and biology, I thought I would give my opinion and look at the facts while things remain quiet on the Yeti front. DEEP BREATH . . . . . (Sorry . . . .I don't have any photos of actual badgers).  

Active badger sett showing, small amounts of bedding in entrance (probably caught on the animals fur). 

So what exactly is Bovine TB? Well, Bovine Tuberculosis is a bacterial disease caused by the bacillus Mycobacterium bovis and is similar in many ways to Mycobacterium tuberculosis the human counterpart of the bacterium. In-fact these two diseases are very similar and it is likely that M.bovis evolved from M.tuberculosis and was originally spread from humans to cattle following their domestication, as early as the Neolithic period. Cattle then passed what was now a mutated disease back to humans and on to other mammals, including badgers. The disease basically consists of the formation of tiny tubercles on internal organs, most often found within the lungs. Within these tubercles the bacteria quickly multiply. When one such tubercle bursts it spills the bacteria out spreading the disease around the remainder of the hosts body.

TB often causes the animal to become weak, lethargic and eventually die. What makes it complex, certainly in the case of  the badger is some animals appear not to show signs and suffer, where the disease lays dormant, resulting in the animal acting as a reservoir for the disease. Badgers seem to have a remarkable tolerance to the bacterium and generally between 50% and 80% of tuberculous individuals have no observable lesions. In some studies badgers with TB and ones without it co-exist in the same sett over years without it spreading between them. Some animals do succumb to it and often leave the sett in a very poor condition, to live their remaining days alone often above ground. Approximately 35,000 cattle are slaughtered each year as a result of Bovine TB, making it one of the key issues currently facing British cattle Farmers.

Badger fur caught on barbed wire. Badgers have distinctive cream fur and longer guard hairs which are black/grey with cream tips. 

So why are badgers such an issue in regards to BTB? People often argue that mammals other than badgers carry TB and could contribute to the spread of Bovine TB and act as reservoirs. This is true, however the significance of this is unlikely to be high in most species as they do not interact with cattle, are not social and are poor hosts for the disease. One of the exceptions is perhaps deer. A host species needs to be able to carry the infection and interact with cattle regularly. Deer populations are on the increase and could certainly become a more significant reservoir for the disease in the future, especially given that they are capable of ranging further more quickly in comparison to badgers, which are relatively sedentary especially in areas with high population densities. However deer have not always been as numerous in comparison to how prevalent bovine TB has historically been, especially the large species like red deer and fallow deer, which is suggestive that they are not a significant player in this saga.

Badgers are undoubtedly a key reservoir for the disease as they are relatively vulnerable to infection and their biology means they often come into closer contact to cattle, in comparison to many other wild mammals. Badgers regularly feed in grazed pasture where they are directly close to cattle, they also urinate on the pasture causing an indirect risk, they regularly feed on stored cattle food, drink from water troughs and some radio-tracking studies have even noted them as physically interacting with cattle. In Britain, badgers are the only known maintenance host for M. bovis, although there are some “spill-over hosts” (i.e. populations in which infection will persist only where a maintenance host is present in the ecosystem), including Red foxes. Despite this the exact transmission from badger to cow and back from cow to badger is still poorly understood and may involve a number of transmission route ways. It is widely accepted that cow to cow routes are the most significant way in which cattle spread the disease, although cattle are less likely to act as long term reservoirs due to regular health checks.       

Badger footprint, showing the typical bear shape. Four (five) parallel toes with a kidney shaped pad behind. 

So what do we know about culling badgers as a means of protecting cattle from TB? With the evidence suggesting that Bovine TB was linked to badgers, the idea of culling as a control measure was investigated. This has occurred almost continually in one way or another since the 1970's, usually in the form of local trials. Thankfully unselective and inhumane methods such as the use of hydrogen cyanide to gas setts was soon outlawed and is no longer used as a culling method. This was replaced by live trapping and shooting, which still operates to an effect today. In the 90's Professor John Krebs began a Randomised Badger Culling Trial, this trial had a key aim to determine the extent to which the removal of badgers reduced TB in cattle. The trial used two culling regimes, Proactive - where badgers were eliminated as far as possible from the area and Reactive - where culling occurred in a small area as a direct result of a TB outbreak. In addition areas used as a control where no culling took place, were also studied, something which previous trials had not investigated in sufficient detail.

The results of this trial offered conclusive and interesting evidence, which appears is being consistently overlooked. The Reactive culling resulted in an increase in the rate of TB in cattle by on average 27 per cent. The proactive cull resulted in a lower rate of TB in cattle in culled areas, than in control areas, showing the removal of badgers did reduce TB. However only by a rather low 20%, not a lot given the time and money spent culling. What makes matters even more interesting is the rate of bovine TB actually increased by 25% (on average) in a 2km band around the culling area. The increase in TB surrounding the cull area effectively cancels out the results of culling inside the cull area.

The reason for this is known as the perturbation effect. Culling alters the spatial social organisation of badgers, which results in abnormal behaviour, not only in culled areas but in areas surrounding the cull site. Badgers are territorial animals which more of less constantly remain within the territory, or in close proximity to its boundary. Culling causes badgers to increase their territories size, range further and disperse more frequently. Larger territories often have more poorly defined boundaries increasing the (indirect and direct) interaction of animals from neighbouring setts. All of this moving around also causes TB to move around and spread at an increased rate, which is what the data from the trials found.   

In my opinion this is conclusive enough data to abort a national cull and look at other ways forward, and look at a genuine ways to control the disease in cattle. Culling trials in Ireland did however show that by culling 100% of badgers in an area you can reduce TB, this is unethical and not a practical solution to the problem.

So how do we go forward? I personally think the most realistic way of reducing the disease in cattle is to deal directly with the cattle rather than badgers. Cattle are easier to work with, easier to conduct research on and easier to access. Research into vaccinating cattle needs to be continued and looked at as a realistic way forward. However it is not as straight forwards as it would seem in that so-far no 100 effective vaccine has been found. Vaccinating cattle would also mean that you would no longer be able to conduct TB tests on vaccinated herds as they would be diagnosed as TB-positive. So any development of a vaccine would also require the development of a new TB test. Recent promising advances have been made using Bacille Calmette-Guerin (BCG), the vaccine used on humans. To make things awkward however, EU Legislation forbids vaccination of cattle as it may increase the spread of the disease, as vaccinated cattle cannot be reliably tested. Trials are ongoing in Gloucestershire to test the efficiency of vaccinating badgers.

In my opinion administering drugs to a wild animal like a badger would be very difficult, it would involve applying an oral vaccine to bait, which would be impractical as it would be impossible to ensure the whole sett had fed on the relative quantity of vaccine. This would then have to be regularly carried out to vaccinate young animals weaned after the initial bait was set up and animals new to the sett/area, which have dispersed from other areas. In addition to cattle vaccination, increased bio-security of stock sheds and food stores would help reduce the risks of infection i.e. increase ventilation and have lower numbers together, as would better fencing where possible (a method much cheaper than a national cull believe it or not). Certainly stricter farm bio-security, continued research into a more efficient vaccination for cattle and tighter measures of cattle movement would be positive steps forward. 

Regardless to the economic implications of the disease, do we not have a duty in protecting our wildlife from disease spread from our livestock? 

Latrine site showing droppings. This feature is typical of badgers and are used to mark territory boundaries and provide social messages between individuals.        

Tomorrows Child

Ruby Tiger caterpillar, sunning itself on a tree stump today.

Spring is still neither here nor there, cold nights and warm days lead to a false impression that there should be flowers, insects, reptiles and amphibians all over the place, but in reality it is still too cold here. No doubt there are signs of a change with the year's first bumblebee today (a Queen Bombus lucorum). I've almost run out of patience in terms of invertebrates, so I decided to do a little pond dip, without wanting to cause to much disturbance. This was actually a lot less productive than I had hoped, but a by-product of deep upland pools, still partially frozen. The usual high number of palmate newt efts were likely in the deeper sections (with a more stable water temperature) beyond my reach. 

 Large Red Damselfly nymph, partially encrusted in debris. 

It was a really pleasant surprise to a number of large red damselfly nymphs. This is the first species within the region on the wing and it won't be long until these little beauties are turning into bright red aerial predators. Interestingly anecdotally they are also a species which tends to be more active in lower winter water temperatures compared to other species. This makes complete sense given their earlier flight time. 

Large Red Damselfly Nymph

Large red damselflies are one of Britain's most widespread species, reflective of the ability to breed in a wide range of water bodies including slow flowing and still water with brackish, acidic and calcareous water chemistry. Higher populations as expected occur in un-shaded, fish free, ponds with an abundance of marginal, submerged and emergent vegetation. The species typically emerges and remains close to the water's surface when it turns into an adult. Like other damselflies nymphs they are ferocious predators and feed on small invertebrates such as daphnia and chironomid midge larvae. Hopefully over the coming weeks we will be able to take a close look at a number of different species of nymphs. Large red damselfly nymphs are quite distinctive and have black markings on the abdominal projections (Caudal Lamellae), which are quite pointed. These are usually a black X shape but are highly variable. The squat abdomen, long wing sheaths and rectangular head are also quite distinctive together.  Hopefully it won't be long until we see some photographs of adults on here.