After a gloriously sunny and warm Easter bank holiday, the early May public holiday was less impressive, being a mostly cloudy and damp affair for most of the UK. The most significant rain was further north, so southern Ireland, southern England and much of south Wales remained dry or drizzly with temperatures around average. The cloudy and showery weather continued through the first week, a band of heavy rain moving south on Thursday and Friday, before high pressure built into the second weekend.
The second week was again dry for most of England, while Ireland, Scotland and north-west Wales saw some very heavy rain over the first couple of days. Almost everywhere, however, it was mild by night and warm by day, with temperatures widely into the low to mid-20s Celsius (50s F). The middle weekend saw some much-needed rain for southern England, with all but the far southeast missing out, although a rash of thundery showers brought a little relief on the Sunday night. Into week three and we saw unsettled but warm weather. A succession of low-pressure systems brought heavy rain to the west, Ireland in particular, but most of England, Wales and Scotland was kept dry by high pressure over the continent, and London saw temperatures into the high 20s (mid-60s F). The second half of the week saw rain spreading east and high pressure building in behind.
The second half of May started on a warm and dry note but ended cooler and more unsettled one as a series of low pressures passed across. This brought more rain and at times some very gusty winds, Scotland seeing winds touching gale force towards the end of the fourth week. Still, after such a dry April and start to May the rain was welcome. Indeed, last month the Met Office released their official stats pointing to April having had 32% less precipitation than anticipated for the month. April was also 0.2C (0.4F) above average. Globally, according to NASA, April saw a temperature anomaly of 0.2C above the 1991-2020 norm (0.82C/1.5F higher than the 1951-1980 average) and was the seventh warmest on record, behind 2020, 2016, 2019, 2017, 2018 and 2010. April was very hot in the Middle East, Central Asia and Pakistan, and colder than normal in Canada, eastern Europe and South Africa.
Outside of the UK, some quite intense heat starting to build across western Europe during May. Come the third weekend Spain and France had recorded several days in the mid- to low 30s Celsius. Further east, Pakistan hit a staggering 49C (120F) on 30th April, one of the hottest temperatures ever recorded on Earth in April. (The world April record is 51C/124F in Santa Rosa in 2011.) The Asian heatwave continued into May, with temperatures pushing into the low 50s Celsius. At the start of last month, the Hassanabad Bridge on the Karakoram Highway collapsed after an outburst flood from the Shishper glacial lake. Come the middle of the month, Pilani and Rajgarh both hit a new monthly record, 47.7C (117.9F) and 47C (117F), respectively, while Naliya recorded 46.1C (115F), their highest temperature on record for any month.
The first half of May saw record heat in parts of East Africa and the Middle East: Aswan in Egypt hit 46.8C (116F), Makkah in Saudi Arabia reached 47C, while on the coast Yenbo and Wejh each recorded 46.8C. Bet Haarva in Israel reached 45.5C (113.9F). Russia also saw intense heat, some areas 18C above average come the middle of May. We also saw the Arctic 0.7C (1.3F) above average last month, while Antarctica was 0.1C (0.2F) below average for May.
If you're interested in getting out and about this month to look for wildlife, check out my June wildlife overview. Additionally, the British Deer Society are running their Deer Distribution Survey and I would strongly encourage readers to record their sightings of wild deer either via the app or by e-mailing the Society directly. The PTES Great Stag Hunt is back up and running for another year, with nearly 1,100 beetles recorded already - if you see one in the next few months, please take a moment to map it. Hedgehogs are also well and truly out of hibernation now, and if you have them visiting your garden it would be great if you could record them on the British Hedgehog Society's Big Hedgehog Map. You can also use the map to see if there are any hogs reported in your neighbourhood and if you're looking for advice on making your garden hedgehog friendly, check out my wildlife friendly gardening blog.
In the news
A few of the news stories that caught my attention this month include how farming and climate change represent a double-whammy for insect populations, sharks getting smaller and the cost of tail regeneration for lizards.
- Insect apocalypse? Insect populations are thought to have declined by 50% in some parts of the world in recent years and a new study by University College London scientists suggests that a combination of intensive farming practices and global heating has largely driven this.
- Shrinking sharks. Sharks are keystone predators in our oceans and some freshwater systems, a healthy shark population indicating a healthy food web. Recent work on sharks in Onslow Bay by researchers at the University of North Carolina suggests, however, that they may be getting smaller. Data for 12 species across nearly five decades indicates that not only were 11 species less common in the bay now than at the start of the study, but all species showed a decrease in body length; silky sharks about 10% smaller, while sandbar sharks were, on average, 35% smaller.
- Decoding dogs. A new genomic study by an international team of geneticists has found that dingoes are genetically distinct from domestic dogs, and appear to be an early offshoot of the modern dog lineage.
- Tall tails. We've known for decades that lizards are able to regenerate parts of their tail when lost, but recent data from University of Oviedo biologists suggests that such regrowth can affect the egg production of females. In the short term, regenerating female wall lizards exhibited reduced clutch mass and higher incidence of egg failure.
- Flying insect freefall. Many of us of a certain age will have observed how we rarely need to clean our cars and windscreens of squashed bugs any longer, despite it being a common occurrence only a few decades ago. Now analysis of data collected as part of the Bugs Matter survey supports these preliminary observations, although repeated sampling is needed. The results from some 5,000 journeys made by members of the public in the summer of 2021 were compared with those from 2004, the decline greatest in England (65%), followed by Wales (55%) and Scotland (28%).
A few tweaks have been made to the badger, squirrel and hedgehog articles over the last month, the latter about sexing hedgehogs and the mammals and birds in their diet in particular. Mostly, however, the focus has been on the Chinese water deer article and new sections on longevity, covering ageing methods and lifespan, now online.
Discoveries of the Month
One for the road: interplay of road configuration, vehicle type and season on wildlife-vehicle collisions
We've discussed many times before how road traffic can have a significant impact on wildlife populations, not only in terms of direct mortality, but also through the pollution and noise they generate. Across Europe, death on the roads is nonetheless the main source of mortality for several species and is considered a significant threat to conservation efforts for some, such as wildcats. Owing to the significant economic damage they generate, we have a reasonably good understanding of the associated factors, such as how larger species of deer respond to traffic. Much less is known about the responses of smaller species to the approach of vehicles.
Part of generating a holistic approach to wildlife-vehicle collision management is understanding how roads and traffic are viewed by animals and how it affects collision risk. In order to try and build a picture of this, a team at the Forest Research Institute of Baden-Wuerttemberg in Germany analysed 28,400 hours of video data of just over 2,800 animal-vehicle encounters. The data included thermal network cameras at 14 road sections in south-west Germany and involved classifying the behaviour before and during contact with a vehicle of nearly 2,000 roe deer (Capreolus capreolus), 700 red foxes (Vulpes vulpes) and 185 wild boar (Sus scrofa). The data were then subjected to statistical modelling to look for patterns in the behaviour that might help anticipate or even prevent these types of vehicle collisions.
The results of the study, published in the journal Accident Analysis and Prevention, show how the species' own behaviour, access to cover, vehicle type, road layout and biological seasonality were important predictors of how an animal responded to oncoming vehicles. Roe deer, foxes and boar all showed species-specific differences in their default reaction to the approach of traffic. Roe were more likely to respond to a vehicle by making a short dash away from the road, this being more pronounced (i.e. further) when large vehicles (e.g. lorries and coaches) approached. Overall, this default behaviour resulted in a decreased likelihood of vehicle collision, but they were frequently observed crossing immediately in front of oncoming vehicles and the risk remained high. The rut and gestation increased risky behaviour in Roe, while the likelihood of a collision was reduced by the presence of nearby cover.
Red foxes were unpredictable in their response to vehicles, but typically carried on with whatever they were doing when one approached unless they were non-attentive at the time (e.g. searching for food). The probability of them being involved in a collision was, however, slightly higher while they were raising their cubs than at other times of the year. The observation that foxes seemed to use the roadsides to hunt and search for carrion, and crossed roads frequently, did make them quite likely to be involved in an accident. The picture for wild boar was similar to that of foxes. In fact, boar appeared least affected by the approach of vehicles. They are a gregarious species, and the researchers found that if the lead sow decided to cross, the rest of the group was highly likely to interrupt whatever they were doing and follow, regardless of whether a vehicle was approaching. Riskier behaviour among the boar was more likely during periods of food shortage, which seems to correspond with previous studies showing a peak in vehicle collisions during winter.
In their paper, the research team propose:
“Studies on vehicle velocity show that lower speed clearly reduce the risk of [wildlife-vehicle collision]. Thus, we suggest the usage of temporal speed reductions to enable both an earlier detection of animals by the drivers as well as vice versa. This may be paired with physical alterations to the road (e.g. signs, speed bumps) in high-risk areas and during time periods when animals are more active and thus cross roads more frequently (e.g. during spring and rut or at night).”
Reference: Brieger, F. et al. (2022). Behavioural reactions to oncoming vehicles as a crucial aspect of wildlife-vehicle collision risk in three common wildlife species. Acc. Analy. Prev. 168: 106564. doi: 10.1016/j.aap.2021.106564.
Squirrelled away in Ireland: genetic diversity of the Emerald Isle's grey squirrels
Despite being a North American native, the Grey squirrel (Sciurus carolinensis) is a very familiar - sometimes a little too familiar - species in Britain and increasingly in Europe. Greys are a highly invasive species in Britain and Europe, replacing Reds, spreading pox virus, and causing damage to commercial forestry. One 2011 estimate of the forestry impact across the island of Ireland, for example, put the damage from Greys at €45 million (£38m / US$48m).
In Britain, there are reports of Greys being released as far back as 1828, although the first verifiable record of which I'm aware is the pair released in Cheshire by Thomas Brocklehurst. In a note to the Irish Naturalist in 1923, Hugh Watt recounted the first known introduction to Ireland: the Earl of Granard releasing “some dozen Grey squirrels from the stock at Woburn, Bedfordshire” at Castle Forbes in County Longford during 1911. By 1999, they had become established in 22 of 32 Irish counties, their spread westward only impeded by the River Shannon and patchy habitat. Populations seem to have declined in rural areas in recent years, although urban populations appears to be doing well. A recent study by a team of researchers in Galway and Knoxville (Texas) that analysed the genetic profile of Grey squirrel populations in Ireland has shed light on their introduction, evolutionary history in Ireland, and their potential vulnerability to management strategies.
One hundred squirrels were sampled from nine sites, eight in Ireland and one in Tennessee. Assessment of eleven species-specific microsatellite loci revealed low to moderate genetic diversity across the Irish population as a whole, along with the suggestion of inbreeding. Intriguingly, two clusters were found in the Irish population, with squirrels in County Kildare significantly differentiated from all other Irish populations. This suggests either genetic isolation from other squirrels on the island or, perhaps more likely given the short period that the species has been in Ireland, having been the site of a hitherto unverified second introduction.
The low genetic diversity observed within the Irish population, consistent with a single introduction (or very small number of introductions), suggests that the population may be more susceptible to management and even eradication than it is in Britain, where diversity is higher owing to many more releases. In their paper, currently in press with Biological Invasions, the team, led by Hannah McLaughlin, explain:
“Deficiency in heterozygosity of grey squirrel populations could negatively affect their potential to adapt to changing conditions and lessen competition with the red squirrel. Poor genetic diversity could be implicated to some extent in the recent collapse in grey squirrel populations in the midlands. Though this decline in grey squirrels in the midlands area is associated mainly with increased pine marten Martes martes presence, it could also be augmented by low genetic diversity in Irish grey squirrel populations, or the low genetic diversity may be hindering the grey squirrels from adapting to this recovering native predator.”
Reference: Dominguez, H. et al. (2022). A genetic analysis of grey squirrel (Sciurus carolinensis) populations in Ireland. Biol. Invas. In Press. doi: 10.1007/s10530-022-02782-x.