Seasonal Update - July 2019


June was a month of weather contrasts across Europe. Scotland and Northern Ireland experienced persistently wet weather for much of last month. An occluded front brought heavy rain and gusty winds to southern and eastern England during late May and early June. The cause of this unseasonably wet weather was an area of low pressure that stalled over France, and the unsettled and inclement weather with below average temperatures affected most of western Europe. Indeed, France was the recipient of some serious hail storms that damaged buildings and destroyed crops, causing the French Prime Minister to declare a state of emergency. Here in the UK several areas experienced localised flooding, and Pennerley in Shropshire attained the unenviable record of having 150mm (6 inches) of rain, about three months’ worth, in only four days. The second half of the month was a mixture of warm, dry spells and heavy, thundery storms, particularly across the east of England, ending with some very hot weather for the final weekend.

By contrast to Britain, much of western Europe spent June in the grip of a relentless heatwave, with temperatures consistently in the mid to high 30s Celsius (90s Fahrenheit). In the final week of June, a “Spanish Plume” arrived in western Europe, bringing warm air up from the African continent and resulting in temperatures in the low 30s C for southern England and mid-40s C for France, Spain and Portugal. France broke its all-time highest temperature over the final weekend of June.

Cracks between sheets of Arctic sea ice photographed from the DMS instrument during an Operation IceBridge aerial survey in March 2011. NASA and the National Snow and Ice Data Center announced in August 2012, that the ice cap covering the Arctic Ocean is now smaller than ever recorded since consistent satellite measurements of the ice began more than three decades ago. - Credit: NASA Goddard Space Flight Center (CC BY 2.0)

Against this backdrop of fluctuating weather patterns, the Arctic spring thaw has seen extensive melting of the Greenland ice sheet and sea ice loss several weeks ahead of normal, scientists at the Lamont-Doherty Earth Observatory reported last month. A stagnant high-pressure airmass over Greenland in early June resulted in an influx of warm air from the south, increasing temperatures just over 4C (7F) above the seasonal average. The Observatory have been monitoring the onset of the spring thaw since 1979 and this year has seen the earliest start to the thaw on record. The average sea ice extent in May was almost half a million square miles below the 1981-2010 average, according to the National Snow and Ice Data Center.

The long range forecasts for Europe are currently predicting another very warm July and August, rivalling the temperatures we saw last year. Hot summers are invariably good news for some, but last year’s record-breaking temperatures resulted in deaths from heatstroke, a decline in crop yields, the closing of some nuclear power stations, and wildfires even inside the Arctic Circle. Indeed, recent devastating weather has prompted several countries, including the UK, to declare a “climate emergency”, which is triggered in the event of life-threatening climate situation.

The Gardenwatch Beyond the Back Door survey is still running and the BTO, Open University and BBC Springwatch are after information about your garden. Other surveys running this month include the British Deer Society’s Deer Distribution Survey, which is looking for deer sightings across the UK, and the People’s Trust for Endangered Species’ stag beetle survey. As usual, the Wildlife Trusts have a series of nature-themed events up and down the country, as do the RSPB. If you feel like being proactive this month and live near the coast, Surfers Against Sewage is looking for people to organise cleans of their local beaches – details here. The Forestry Commission is running a series of events this month – full list here.

Interested in the wildlife to be found this month? Check out my Wildlife Watching - July page.

Discoveries of the Month

Habitat heterogeneity affects red deer response to disturbance

Britain’s deer populations appear to be booming, with more and more deer being recorded in urban areas. This trend towards “urbanisation” even includes some of the more unlikely species, with a mature red stag photographed walking through a housing estate in Fort William, Scottish Highlands last month. With very few wild predators in Britain and pressure from ever-increasing development, there is an increasing need to understand how deer use the different habitats, particularly those heavily dominated by or modified by people, in order to best manage the populations at a sustainable level. One element of this is understanding how deer adapt to large-scale disturbance such as large winter storms and forest fires, which are an increasing threat associated with climate change. New research from Poland suggests that the way red deer use altered habitat is strongly influenced by human disturbance but not, interestingly, by hunting pressure.

A Red deer (_Cervus elaphus_) hind in the New Forest. - Credit: Marc Baldwin

In 1992, a wildfire burnt 42 sq km (16 sq mi) of the Rudy Raciborskie Forest District in south-west Poland. In the four years following the fire, the area was planted with various trees, including Scots pine, birch and larch. About a decade later, 16 red deer were caught and fitted with radio-transmitters, and their movements were followed by a team of researchers led by Julien Fattebert at the University of KwaZulu-Natal.

The tracking data showed that the red deer selected for the interface of the burnt and unburnt areas, the former offering poor feeding opportunities but good cover, the latter good feeding but poor cover. The deer could be found feeding out on the unburnt areas at night, before retreating to the burnt areas for cover during the day. Perhaps more interesting, though, was that when the researchers controlled for hunting risk (i.e. they factored in the behaviour during the peak hunting season), they found no correlation with the deer’s movements. In other words, the risk of being shot by a hunter didn’t appear to cause the deer to spend longer in the cover of the burnt areas as they expected them to. In their paper to the Journal of Zoology last month, the researchers suggest:

Non-lethal human disturbance therefore appears to be a strong driver of red deer habitat selection in the no-hunting season in this human-dominated landscape. In general, there is growing evidence that non-lethal human disturbance has significant impact on wildlife behaviour …”

This study is an important contribution to our understanding of how red deer use habitat because not only did it show how this species may anchor their home ranges to interface zones between habitat, it also suggests that red deer can respond differently to different types of human disturbance.

Reference: Fattebert, J. et al. (2019). Safety first: seasonal and diel habitat selection patterns by red deer in a contrasted landscape. J. Zool. 308: 111-120.

Predicting badger visits for farm yards

Many readers will be familiar with the controversy that has surrounded badgers and the role they play in the transmission of a bacterial disease called bovine tuberculosis. The infection, caused by Mycobacterium bovis, is, as the name implies, a disease of cattle, although badgers, like most mammals, can also contract it. In the case of badgers, however, there are additional complications.

A wet badger in Scotland. Badgers often opt for pasture in which to forage, which can bring them into conflict with farmers. - Credit: Pauline Mellor-Greenhalgh

Firstly, when most mammals contract the infection, they succumb relatively quickly, limiting their ability to spread it. Badgers, by contrast, seem able to live with a low level infection for many years, during which they can excrete the bacteria in their urine and faeces. This opens up the potential for them to transmit the disease to cattle. There’s a lot we still don’t understand, but badgers do appear to have a role in the sustenance of this disease in Britain. Secondly, badgers are often attracted to the very same areas in which cattle are kept. They forage across pasture looking for worms and other invertebrates and are well known to visit farmyards where they will eat cattle feed and stored grains.

Under the assumption that badgers can transmit bovine tb to cattle, an important element in assessing the potential risk to a given herd is understanding how likely they are to come into contact with badgers. In pasture this can often be approximated by surveying the local badger setts to establish their proximity to the herd, but predicting whether a farmyard is likely to attract badgers is more difficult. Recent work by a team of researchers led by Andrew Robertson at the University of Exeter has shed some light on this by developing a model to help predict a farmyard’s attractiveness to badgers.

The researchers studied 155 beef, dairy and mixed farms covering Gloucestershire, Devon, Cornwall and Wales between 2012 and 2013 during which they surveyed the area within 500m (~ 1/3 mile) of a central point in the farmyard for setts. They then set up camera traps to monitor badger activity around the farm buildings and did a general survey of the farm looking at potential attractants, such as palatable crops and accessibility of cattle feed. With the data collected they subjected them to a series of generalised linear models, a type of statistical analysis that looks for direct association between factors, and based on the results they created an interactive app called the “Badger Farm Assessment Tool”. The app allows landowners to estimate the probability that badgers will visit their farmyards by plugging in a series of information about their property.

Badgers captured on trailcameras visiting farmyards during Robertson et al's study. - Credit: Andrew Robertson / University of Exeter / PLOS One

The results of the study found that several factors predicted badger presence in farmyards. As expected, the presence of badgers in the 500m zone was one correlated factor, as was the number of badger setts on the farm. Interestingly, the cattle capacity also had an effect, with badgers less likely to visit farmyards with high stock densities. Curiously, however, on the few occasions where badgers did visit busy farms they tended to visit more often, possibly because high stock density often meant high feed availability and thus increased foraging opportunities. Overall, however, it seems that badgers were less inclined to visit busier farms, as their visits were also negatively associated with the presence of occupied buildings. While there are a lot of variables at play here, the team’s model was relatively successful at predicting badger visitations and in their paper to PLOS One in May, Robertson and his colleagues noted:

Our models could predict badger presence with 73% accuracy, with overall sensitivity and specificity of 63% and 81% respectively …”

Reference: Robertson, A. et al. (2019). Predicting badger visits to farm yards and making predictions available to farmers. PLOS One. 14(5): e0216953.

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