Seasonal Update (March 2021)

We really start to notice the lengthening days during March and the increase in both strength and duration of solar radiation can boost our mood. - Credit: Marc Baldwin

In southern England, Wales and Ireland, February began on the same mild-cold-mild theme on which January ended, while the north remained under Arctic influence. At the start of the first week a north-easterly airflow developed, courtesy of a large blocking high between Greenland and Scandinavia, and extensive areas of northern England and Scotland were hit by heavy snow - up to 20cm (8 in.) on high ground, but several centimetres fell even at low levels. It took a day or two for this to push south, and the split of air masses across the country during the first half of the week was reflected in the staggering temperature contrast: 3-6C (37-43F) in Scotland and Northern England and the bizarrely mild 12-14C (54-57F) in the south.

On the boundary of these masses, north-east England saw significant rainfall overnight Thursday into Friday, causing some localised flooding. This split held for the first week, before a north-easterly took over overnight Friday into Saturday, dropping temperatures widely into single figures and signalling the arrival of what the media branded the “Beast from the East II”. This airflow change was nowhere near as dramatic as the original “Beast” that hit in 2010, but the Met Office did issue a yellow weather warning for snow in south Lincolnshire/Yorkshire and along the east coast, particularly East Anglia.

The first weekend of February was cold across the board in the UK, with some heavy snowfall in the east, especially in the south-east of England. A strong easterly wind, gusting to 50mph (80 kmph), put an edge on the temperatures and dropped the “feels like” temperature to -6C (21F) in East Anglia on Monday, despite the air temperature hovering around 3C (37F). Tuesday night saw the temperatures fall widely – most areas dropped well into minus Celsius, but Altnaharra in the north-west Highlands saw -17.1C (1.2F).

Early February saw some significant snowfall in the east of England. - Credit: Scott Robinson (CC BY 2.0)

The high pressure started to ridge down over the country on Wednesday, so winds lightened and it dried out with only the odd snow flurry, mostly in Midlands and north. Wednesday night recorded the coldest overnight temperature of the winter, with Braemar falling to -22C (-7.2F). Thursday was bitterly cold, with most places remaining at or just below freezing thanks to a south-easterly wind. The UK did, however, remain largely dry, while the Republic of Ireland saw periods of significant snow through Thursday. Temperatures picked up a little towards the end of the second week and into the third weekend but remained cold in low single figures, 4C (39F) being the high.

Things changed dramatically at the end of the second weekend when a mild Atlantic system pushed the Arctic airmass back to the east, bathing the whole of the UK in balmy double figures – even Edinburgh had highs of 10C (50F) during the third week. In the south-west temperatures were back to mild day and night. Newquay in Cornwall saw daytime highs of 12C, while London hit 14C during the day and fell to only 10C overnight on Monday 15th. The seasonal average for London at this stage in February is 8C (46F). The mild, wet and windy (particularly in Scotland) weather continued through the third week and into the penultimate weekend as several low pressures swept across the UK. We saw heavy rain on Wednesday that, coupled with melting snow, led to localised flooding in the north and east. Friday was wildly wet and windy across the country with temperatures holding around 10C overnight into Saturday.

After the wet and windy start to the penultimate weekend it brightened up and in the south-east temperatures picked up into the mid-teens Celsius. Another large low pressure system brought heavy rain and gale-force winds to the west and north of the UK to start the final week. Once this cleared the weather settled down and we saw yet more surprisingly mild temperatures, courtesy of a long stretch of southerlies that brought up air from north-west Africa. Overnight Tuesday into Wednesday, for example, Birmingham dropped to only 13C (55F), about 6C (7.2F) above what we'd expect for a daytime high in February. On Wednesday, Santon Downham in Suffolk hit 18.4C and Coningsby in Lincolnshire 18.2 (65F), 10C (12F) warmer than the seasonal average. Things cooled down a little to end the month; daytime highs remained in low double Celsius but night-time temperatures fell to low single figures. Mild, dry and sunny days followed by clear and cold nights gave a spring-like feel to the end of February.

Outside of the UK, the temperature anomaly was 10C below average through northern and central Europe, while southern Europe was at or above average for the first half of the month. Greenland and Iceland were unseasonably mild. The second half of the month, when the mild sub-tropical air pushed Britain’s cold weather east, parts of the Mediterranean as far south as Greece saw unusually cold conditions, including rare snowfall. A similar split was seen in the US, where eastern states were warm while central and western states fell under a “Polar Plunge” bringing temperatures of -18C (-0.4F) and heavy snow to Texas. For Texans, this was the coldest weather they’d seen for nearly four decades, and tragically resulted in the loss of 22 lives. Besides Texas, weather-related emergencies were also declared in Alabama, Oregon, Oklahoma, Kansas, Kentucky and Mississippi. By the middle of the month, some 150 million Americans were under a winter storm warning.

Daffodils are one of the quintessential spring flowers. - Credit: Roger Powley

At the time of writing, it looks like March is continuing on a dry and settled note, with temperatures back down to around the seasonal average for most of the UK, although the predominance of high pressure is likely to result in some severe night frosts. Some models are suggesting this may only last until the middle of the month as an Atlantic influence takes over with the potential for stormy weather.

If you’re interested in the wildlife to be found this month, including a look at brown hare boxing behaviour, the peak of the fox birthing season, and the season of the arum lily, check out my Wildlife Watching - March page.

In the news

Some of the news stories that caught my attention over the last few weeks include a new more pessimistic estimation of climate warming, intelligent invertebrates, and the regenerative powers of the world’s largest sharks.

New research suggests cuttlefish have episodic memory and can plan ahead. - Credit: Xynalia (CC BY-NC-ND 2.0)
  • Nowhere to hide. Mountain hares rely on their camouflage as snow covers their high altitude homes, but new research by biologists at the University of Michigan suggests that the colour change is becoming progressively out of sync as snowfall declines. In North America, the weekly survival of snowshoe hares declined by up to 14% when mismatched with their background, and the concern is that the same fate may befall mountain hares in Europe.
  • Warming window narrowed. New models that include a more precise method of projecting the Earth’s temperature suggest that the threshold for dangerous global warming is now likely to be crossed between 2027 and 2042, at least 10 years earlier than that predicted by the IPCC.
  • Clever cephalopods. A study by researchers at Normandie Université and Cambridge University found that when cuttlefish knew they were going to be given their favourite food of shrimp at dinner they’d eat less at lunchtime to save room. This is the first example of episodic memory (remembering what they’re going to have for dinner and planning in advance) in an invertebrate.
  • Sanative sharks? A great many shark species are under threat from the activities of humans, but new data from the University of Southampton suggest that the world’s largest shark species, the whale shark, heals remarkably quickly from contusions caused by nets and boat strikes and even found evidence of partially-amputated dorsal fins regrowing.
  • Re-making memories. As we get older our brain loses the ability to produce new neurons, resulting in a decline in overall memory function. New research at the University of Zurich has revealed the mechanism behind this stem cell ageing mechanism and, more importantly, suggests it is reversible, offering hope for the treatment of Alzheimer’s disease.

Discoveries of the Month

Man’s best friend helping to monitor Mrs Tiggywinkle

It’s not uncommon these days to hear people lamenting how they’ve not seen a hedgehog in years, despite having often encountered them as children. Comments such as these are supported by several mammal surveys, all suggesting hedgehogs are suffering the same fate as much of our wildlife: numbers are falling, despite the best efforts of an army of dedicated and overstretched hedgehog carers across the UK. The latest State of Britain’s Hedgehogs report, published by the British Hedgehog Preservation Society in 2018, talks of a population decline of between one-third and one-half in some rural areas. In urban areas there was some cause for celebration because the survey data suggest, despite a sharp fall in sightings between 2004 and 2012, populations do appear to be recovering.

Henry, one of Conservation K9 Consultancy's wildlife detection dogs, taking a break from the hedgehog location study at Hartpury University's campus. - Credit: Louise Wilson (Conservation K9 Consultancy)

A big problem associated with surveying any animal is finding it in the first place, and this can be especially challenging when it comes to hedgehogs. Granted they’re not the stealthiest of animals—crashing around in the undergrowth, making a lot of racket during courtship and getting into fights—but they are small, nocturnal mammals that spend a lot of their time in cover. Consequently, it is sometimes difficult to know whether you have hedgehogs in your neighbourhood or not. Footprint tunnels, camera traps/trailcams and thermal scopes are all great allies when it comes to knowing what’s about, but each comes with its own limitations.

The use of domestic dogs to help the police track down fugitives is now a familiar part of our history, having been “officially” used by both the Metropolitan Police and police in Belgium since the late 1800s. In recent years, however, we’ve started to investigate the possibility of using dogs to help locate animals of conservation concern, and they have proved highly successful, finding a variety of species from the blunt-nosed leopard lizards in California to koalas in the Australian bush. Indeed, in one study, conservation dogs were just over 150% faster at identifying koala droppings than experienced human surveyors. Now, new research from a multidisciplinary team from Reading and Hartpury universities and the Conservation K9 Consultancy in Wrexham suggests they can also sniff out hedgehogs.

Across 18 nights in 2019, areas of mixed commercial farmland on the Hartpury University and College campus in Gloucestershire were surveyed for the presence of hedgehogs. Plots were searched using a CB2 Clubman spotlight, a FLIR E53 thermal imaging camera or a conservation dog (followed by someone with a thermal camera). In total, 54 surveys were carried out between May and October, covering three habitat types (amenity grassland, pasture and woodland). Over the course of the survey, 17 hedgehogs were found, with each being located about three times. No hedgehogs were found in the woodland, a few were on the pasture, and most were located on the amenity grasslands.

The results of the experiment, published in the Journal of Vertebrate Biology at the end of last year, show that the male springer spaniel found all the hedgehogs that were also identified by the thermal scoping-follower and both the thermal camera and spaniel were more effective at finding hedgehogs than spotlight surveys. The thermal camera could spot the hogs from the greatest distance (50m / 164 ft.), although the dog managed to locate one animal 30m (98 ft.) away. Most spotlight surveys found hedgehogs within only 10m (33 ft.). In the 6-10m (20-33 ft.) range, the camera found eight hogs, the dog seven and the spotlight only one. The detection dog was the only method able to locate hedgehogs in taller vegetation, in which he found four animals. The research team, led by Lucy Bearman-Brown at Hartpury, concluded:

This study has demonstrated that detection dogs can be trained to successfully and safely locate free-ranging hedgehogs, with a performance comparable to, or greater than, current technologies, although they are associated with markedly higher costs.”

Hedgehogs are small, nocturnal mammals that spend a lot of time in undergrowth, making them difficult to survey. - Credit: Marc Baldwin

In their paper, they go on to suggest that dogs may be useful in helping to locate hibernating or nesting hedgehogs.

Reference: Bearman-Brown, L.E. et al. (2020). Comparing non-invasive surveying techniques for elusive, nocturnal mammals: a case study of the West European hedgehog (Erinaceus europaeus). J. Vertebr. Biol. 69(3): 20075. doi: 10.25225/jvb.20075.

Using deer distraction to decrease damage

For me, living near the New Forest, deer are high on my list of photographic subjects, and a great many of us enjoy seeing them. Over the past couple of decades Britain has seen something of a surge in its deer numbers and, in their 2018 assessment of mammal populations, the Mammal Society note that all six of our wild deer species have expanded both their range and number in recent years and, with the exception of the roe deer, are expected to continue to increase. There are no “official” figures, but the Mammal Society conservatively estimate there to be as many as 1.1 million deer in Britain.

While deer are fascinating to study and offer an excellent source of wild protein, their presence is not without controversy. One significant issue is the impact their herbivory has on commercial agriculture and forestry interests. Again, we don’t have any nationwide data on this, but a 2004 project to assess the impact of deer in Eastern England concluded that they caused just over £3.2 million (US$4.5m / €3.7m) of damage to agriculture per year, mostly to cereal and root crops. A further £700,000-worth (US$975,000 / €807,000) of damage was suffered by the forestry industry through browsing and bark-stripping damage, plus the costs associated with culling and fencing.

A Red deer (_Cervus elaphus_) stag stripping conifer bark. Many deer species will remove bark from trees either to feed on the bark itself or to access the sap underneath. At high densities such bark stripping can have an impact on timber yields. - Credit: Marc Baldwin

Culling can reduce deer numbers locally, or at least alter their distribution, to relieve some pressure assist with reducing damage at critical times. Additionally, deer fencing can be erected to exclude deer from certain key plantations, but is expensive, costing £9,000-10,000 (US$13,000 / €11,000) to fence small woodlands, and fencing then requires maintenance. In an attempt to find potentially cheaper or more effective methods of reducing deer damage, researchers and deer managers have begun to look at alternatives, and an option that has recently shown promise is that of distraction. Can you keep deer off your crops/trees by keeping them busy somewhere else? The answer, in some circumstances at least, appears to be yes.

During the spring of 2012, a team of ecologists led by Maria Bobrowski at the University of Hamburg used a grid survey to assess an area of woodland in the Lower Saxony area of Germany for signs of deer presence (i.e. pellet counts) relative to the vegetation type and anthropogenic landscape features such as mineral licks, distance to roads/paths/villages and the location of elevated hunting towers. Just over 1,300 plots were surveyed and subjected to statistical analysis, the results of which were published in the journal Wildlife Biology last month.

The proximity to footpaths negatively affected the occurrence of red deer (Cervus elaphus), while mineral licks and bilberry ground cover (the latter being slightly more important than the former) seemed to attract them. Young rowan were also attractive, as were mature beech, but both less so than licks and bilberry. Roe deer (Capreolus capreolus) weren’t bothered by footpaths and were attracted to young beech, bilberry and mineral licks as well as blackberry bushes; birch and spruce were much less important. As with red deer, bilberry was slightly more of a draw for roe than the mineral licks. Overall, the presence of both species was strongly correlated with the presence of vegetation dominated by bilberry and young deciduous trees, which commonly showed signs of browsing, as well as by the presence of a mineral lick. Interestingly, the vicinity of settlements and hunting towers didn’t influence the presence of either species. Based on these observations, the researchers suggest that it might be possible to distract deer away from key forestry interests by the maintenance of relatively low value areas where bilberry and blackberry dominate:

We therefore recommend the maintenance of open sites with ground vegetation such as bilberry and with young non-target deciduous tree species like rowan and birch as feeding sites. This could be useful ‘decoy’ to draw deer away from trees of high value to the forest industries and thereby enhance biodiversity. Our results show, that these young open forest stands should be interspersed with dense islands of young coniferous trees to offer shelter. Additionally, mineral licks could also be useful to attract deer and lure it to the created feeding sites.”

Reference: Bobrowski, M. et al. (2020). Nothing else matters? Food as a driving factor of habitat use by red and roe deer in winter? Wildl. Biol. 2020(4): (2020). doi: 10.2981/wlb.00723.

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