Seasonal Update - June 2020

May was a particularly dry month, with most areas of the UK receiving well below the expected rainfall.

Much of May saw the kind of heady balmy weather that most people dream of for their summer holidays. Temperatures reached the high 20s Celsius (81F in places) with virtually wall-to-wall blue skies. All this came as a welcome change for many following the wettest February on record and as “lockdown” restrictions put in place by the UK government in response to the COVID-19 pandemic were relaxed. Indeed, official stats released by the Met Office just ahead of the final weekend of the month revealed what many of us could probably have guessed: that the spring of 2020 has been the sunniest on record, with 573 hours of sunshine recorded up to the 27th. The previous record was set in 1948, which clocked up just over 555 hours. If affirmation were required, chatting to my Dad on the final Friday of the month, he noted how his solar panels generated almost 700 kwh last month - ordinarily, he’d expect about 4,000 kwh over the whole year.

Despite the recent sunshine, the first half of the month did produce some very cold nights, courtesy of an Arctic airflow. Katesbridge in Northern Ireland, for example, reported their coldest May night since 1982, the mercury dropping to -6.1C (21F). Around the middle of May, however, high pressure built over the Nordic region and this brought much warmer air in from the Atlantic. Along with the sunshine and warmth there was a distinct lack of rain, particularly for most of England and, according to the Met Office’s blog:

Spring 2020 has been very dry, and May in parts of England has been exceptionally dry. As it stands up to May 27, for England, May 2020 is the driest May on record since 1896, with less than 10mm rain falling across England on average.”

Newborn Roe deer (_Capreolus capreolus_) kids. Please remember that deer mothers leave their young lying up in vegetation. If you come across a baby deer, please do not touch it, just back away and leave it where it is. Unless it's in immediate danger, it doesn't need rescuing. - Credit: Patricia Ware

At the time of writing, Northamptonshire holds the dubious record of the driest English county this spring, having received only 1.5mm of rain. To use the Met Office’s analogy, that’s less than the thickness of a 20p coin.

Unfortunately, this lack of rain, which looks set to continue for much of the summer, along with the above-average temperatures, has meant that most of our forests and heathlands are at high fire risk, the vegetation being tinder dry. Indeed, there was a devastating fire in Wareham Forest in Dorset last month, destroying just over 200 hectares (about one square mile) of woodland and heath; firefighters remain on the scene as I type this, nearly two weeks later. We don’t know for certain, but fire officials strongly suspect a barbeque (several of which were found) started the blaze. Please, if you head into your local forest for a day trip this summer, leave the barbeque at home.

As well as the danger that fires pose to forest wildlife at the moment, if you’re out and about please remember that we’re in the peak of the deer birthing season. It is perfectly normal behaviour for the mothers to leave their young lying up in vegetation while they’re off feeding. They haven’t been “abandoned” and they don’t need rescuing unless they’re in immediate danger. Please, if you find a deer calf, fawn or kid lying up just back away and leave it where it is – please, do not touch it. It’s also very wise to have your dog on a lead as the mothers can be fiercely protective of their young.

If you’re interested in the wildlife to be found this month, check out my Wildlife Watching - June page.

In the news

A few headlines making the conservation news this month include microplastics in sea spray, how “lockdown” can be both good and bad for wildlife, and “super worms” that can eat plastic.

A black rhino with her calf. Poaching appears to be on the rise under the cover of lockdown. - Credit: Marc Baldwin
  • Ocean breeze may contain microplastics: Nobody knows for sure how much plastic finds its way into the oceans each year, although 8 million metric tons is a commonly-cited figure based on an estimate of population and waste data published in Science in 2015. Until recently, we assumed that the plastic remained in our seas unless recovered by us, but new research led by scientists at the University of Strathclyde suggests that some plastic particles could be leaving the sea, entering the atmosphere along with other particulate matter (e.g. sea salt, bacteria, viruses and algae) on the ocean breeze. Analysis of samples of air collected during onshore and offshore winds along the French coast found evidence of microplastics and the researchers extrapolate that as much as 136,000 tons of microplastics may be blown on shore from the ocean globally each year.
  • Poaching blossoms during pandemic: A dramatic drop in tourism caused by the CV-19 global pandemic has resulted in a surge in reports of poachers taking advantage of the lockdown to kill endangered wildlife. Conservation organisation Panthera has warned that poachers in Colombia have been killing more cats, including jaguars, pumas and ocelots, while reports have also been received of increased killing of tiger and deer poaching in India, and at least 15 rhinos have been killed in Africa since the lockdown began. Indeed, some illegal wildlife traders are apparently cashing in on a rhino horn CV-19 ‘cure’.
  • Britain’s “lockdown” may be good for wildlife: Many of us have noticed more wildlife around since the movement restrictions were put in place by the UK government back in March. Recently, however, the National Trust have released data showing that species records have increased at many of their sites. The Trust’s rangers and gardeners have reported peregrine falcons nesting at Corfe Castle in Dorset for the first time since the 1980s, English partridges roosting near a now-empty car park near Cambridge, and a cuckoo calling at Osterley Park in west London, having not been heard there for 20 years. A buzzard was even photographed tucking into its lunch in a deserted orangery at Felbrigg Hall.
  • Mealworms employ bacteria to help them eat plastic: Readers who have ever owned reptiles or worked in animal care will likely be familiar with the giant mealworms Zophobas atratus that are sold by most pet shops as animal food. It turns out, however, that these beetle larvae harbour something of a ‘super power’. New research by scientists at the American Chemical Society has found that these larvae have a strain of Pseudomonas aeruginosa bacteria in their gut that allows them to digest polystyrene. Fifty of these ‘worms’ were placed in a chamber with only polystyrene to eat by the researchers and, three weeks later, they’d eaten 70% of it.

Discoveries of the Month

Vampire bees: hungry bees bite plants to make them flower earlier.

It’s becoming increasingly clear that as our climate changes, so our seasons shift. We know, for example, that many animals were recorded breeding up to 11 days earlier in 2005 than in 1976, while every 1C (1.8F) increase in temperature causes plants flower around five days earlier. This earlier flowering season is concerning some scientists and naturalists because it has the potential to disrupt the synchronicity in many ecosystems, putting already vulnerable species under greater pressure. Back in September on this blog, for example, I covered some research suggesting that many of our pollinators face a “nectar drought” during the summer owing to changes in flowering times, planting regimes and tidier gardens. Now a new study has revealed that bumblebees appear to have found a unique way to tap into nectar reserves early.

A bumblebee on a Dahlia. New research from Switzerland suggests bees can trigger flowers to produce nectar early by biting their leaves. - Credit: Marc Baldwin

While observing bumblebees (Bombus terrestris) visiting a collection of flowers, researchers at ETH Zürich in Switzerland noticed that the insects were using their proboscis to cut small semi-circular holes in the leaves. Curiously, the bees didn’t appear to either feed on the leaves or carry the leaf material away, which made the scientists wonder if this “stressing” of the plant might promote flower production. To test this theory, an experiment was setup to look at the impact this damage had on black mustard (Brassica nigra) and tomato (Solanum lycopersicum) plants.

A team led by Foteini Pashalidou at ETH placed the plants in mesh cages and let pollen-deprived worker bees loose on one batch, removing them once they’d made five or ten leaf holes. Each bee-damaged plant was then paired with a plant subjected to equivalent mechanical damage inflicted by tweezers and a razor blade and an undamaged specimen.

Remarkably, the bee-damaged plants of both species did indeed flower sooner than the undamaged plants – a month earlier in the case of the tomato plants. More interesting still was that whatever the bees were doing was more effective than the scientists’ attempt to imitate them. The mechanically damaged plants also flowered earlier than the undamaged individuals, but less significantly – mechanically damaged tomato plants flowered only a week earlier than undamaged plants. The difference for the black mustard was less striking, but still significant; bee- and mechanically damaged plants flowered 16 and eight days earlier than undamaged mustard, respectively.

A bee covered in hollyhock pollen. - Credit: Marc Baldwin

The researchers then looked at the difference in damage caused by pollen-sated and pollen-deprived colonies, finding that those bees deprived of this important protein source inflicted significantly more damage to plants than well-fed bees, and that biting behaviour increased after only three days of a pollen drought. We don’t yet understand what it is about the way bees inflict the damage that causes the plant to respond so dramatically, but these data provide a fascinating insight into a mechanism by which bees and plants may be able to compensate for climatic shifts.

Source: Pashalidou, F.G et al. (2020). Bumble bees damage plant leaves and accelerate flower production when pollen is scarce. Science. 368(6493): 881-884. DOI: 10.1126/science.aay0496

Traffic noise disrupts bat feeding behaviour

One of the things that many people have commented on in the immediate aftermath of the “lockdown” in Britain was how much more bird song they could hear without the relentless drone of traffic. According to the Organisation for Economic Co-operation and Development, while the number of roads in its 36 member countries (including the USA and UK) only increased by 10% between 1990 and 2011, the traffic density has increased by 55% during the same period. In other words, as many of us will testify, our roads are getting busier. This increase in traffic presents a plethora of problems for wildlife, both direct (e.g. acting as a physical barrier between habitats, a substantial source of mortality, etc.) and indirect (e.g. decreased air quality, increased noise, etc.).

With increasing traffic volumes comes increased noise pollution, which new research suggests may adversely impact bats. - Credit: versageek (CC BY-SA 2.0)

The impact of noise pollution, particularly that generated by traffic, on wildlife is becoming increasingly well understood. Back in May 2018, I featured a study that found roe deer living near busy roads exhibited higher levels of stress hormones than those in quieter habitats and, more recently, in January I covered research suggesting that noise pollution interferes with the ability of robins to compete with rivals. Indeed, there is now a sizeable body of evidence illustrating the negative consequences of noise pollution on birds and how this has led both to the evolution of louder songs and more singing at night. Similar data are, however, lacking for bats, which many scientists suspect are highly susceptible to noise levels given their dependency on echolocation for foraging and navigation. Now a new joint study by the Vincent Wildlife Trust and University of Sussex suggest that bats may suffer as traffic volume increases.

Trust scientist Domhnall Finch and colleagues measured and recorded the noise (both sonic and ultrasonic frequencies) along a 50m (165 ft.) stretch of the A38 dual carriageway running through Devon in south-west England. The recordings were then played back at seven sites around four greater horseshoe bat (Rhinolophus ferrumequinum) feeding areas in the county between May and August 2017, and a further six bat feeding locations in Sussex and Dorset between June and August 2018. Different combinations of the sonic and ultrasonic recordings were used to assess the impact on the bats’ behaviour versus a control site at least half a kilometre (one-third mile) away. Bat activity was measured using Kaleidoscope software that assesses the number of bat passes per survey window.

Over the course of the surveys, four species were identified – greater horseshoes, common pipistrelles (Pipistrellus pipistrellus), soprano pipistrelles (Pipistrellus pygmaeus) and noctules (Nyctalus noctula) – along with some uncertain Myotis species. Significantly lower levels of bat activity were recorded at the experimental sites while traffic noise playback was underway than at the control sites. The activity did not vary between the sites when traffic playback was switched off, strongly suggesting that it was the noise that was putting the bats off and not some habitat difference.

Both the sonic and ultrasonic frequencies reduced activity overall, although detailed analysis revealed that some species were affected more than others; soprano pipistrelles and those passing Myotis species seemed unaffected by ultrasonic noise, but were put off by sonic frequencies. Finch and his co-workers suggest that their results point to roads having a general deterrence/avoidance action on bats, rather than masking or interfering with their echolocation. The impact of the traffic noise was evident up to 20m (66 ft.) from the source, suggesting the impact of roads can permeate well beyond roadside verges.

A _Myotis_ bat in flight. Contrary to initial speculation, road noise seems to have a general deterrence effect on bats, rather than interfering with the echolocation sense that's so vital for their hunting and navigation. - Credit: Srikanth Vk (CC BY 2.0)

Writing in the journal Environmental Pollution, the researchers suggest that new strategies are needed to address the impact of noise pollution on bats, many of which are of high conservation concern, but do concede that there may not be a ‘quick fix’:

Although the transition to electric vehicles may reduce road noise within urban centres, it is unlikely to have a material impact for most roads because at speeds >75 km/h [46 mph], sound is generated primarily by the contact between the tyres and road surface rather than by engines. Alterations to tyre composition and structures are therefore a more promising route to reducing traffic noise.”

Source: Finch, D. et al. (2020). Traffic noise playback reduces the activity and feeding behaviour of free-living bats. Environ. Poll. 263(B): 114405. DOI: 10.1016/j.envpol.2020.114405

Related reading