Seasonal Update (July 2022)

July can impose some very hot days, but if temperatures drop overnight the dawns can be sublimely misty and dewy. - Credit: Marc Baldwin

Meteorological summer started on a widely dry and warm note, with some glorious weather for the first day of the Jubilee bank holiday weekend and temperatures into the low 20s Celsius. Unfortunately for many street parties in England and Wales, this settled spell didn't last the week, with heavy and thundery showers pushing in from the near continent for the first weekend and start of the following week. Scotland and Northern Ireland, however, remained largely wet under high pressure into the start of the second week, with only some patchy cloud to contend with thereafter.

The second week was a predominantly showery and windy affair, touching gale force along the English Channel coast and north-west Scotland, although temperatures remained around average for the time of year, albeit with some muggy nights. For England and Wales things settled down towards the end of the week and into the weekend, with virtually wall to wall sunshine in the south for both Saturday and Sunday. Northern Ireland and much of Scotland, less happily, saw some heavy rain and strong winds. As we moved into week three, the rain in the north and north-west fizzled out into some drizzle and cloud, while England and Wales were mostly dry with some patchy cloud during the first half of the week. High pressure built in as the week drew on and Republic of Ireland, Wales and England saw some very warm weather, temperatures in the south-east nudging just over 33C on Friday. Northern Ireland and Scotland continued to see bands of rain as fronts moved around the top of the high-pressure system.

As temperatures rose and remained high during late May and much of June, many countries battled wildfires. - Credit: Mike McMillan / Pacific Southwest Forest Service, USDA (CC BY 2.0)

Despite initial forecasts that the high pressure would breakdown during the penultimate weekend, temperatures remained high and the air humid for the first half of the following week. We saw widespread thundery showers moving north on the Thursday, and by Friday and into the final weekend temperatures were back to the seasonal average. The final week was showery and windy for most of England, almost everywhere seeing heavy showers, but the heaviest of the rain was in Ireland and the west of England, Wales and Scotland.

In Europe, Pissos in south-west France hit 43.4C (110F) on 18th June, which is a record for the earliest in the year temperatures have climbed to 40, while firefighters were struggling to control wildfires in Spain as temperatures also climbed to 43C. On the 18th June Germany was up to 37.1C (98.8F) at Waghäusel-Kirrlach and Bad Kreuznach, with several long-term June records broken: 36.5C (97.7F) at Wolfach; 36.4C at Mullheim; and 34C (93F) at Hilgenroth. Poland was also up into the mid-30s Celsius.

Intense heat returned to India and Pakistan, too, with 49C (120F) recorded at Jacobabad in Pakistan and 47.5C (117.5) at Ganganagar in India early in the month. The heat was intense and more humid in eastern India, with up to 45C (113F) at Titlagarh and 44C (111F) at Vijayawada. Temperatures climbed above 45C in the south while Israel saw 43.8C at Eilat, on the Red Sea coast, and 47.6C (117.7F) at Yenbo on the north-west Saudi coast. The Iranian station of Mehran rose to 51.6C (124.9F) on 19th June. At the same time, 3.1 million people were displaced in Bangladesh by the worst monsoon floods in recent history.

A new intense heat wave took hold in Xinjiang, north-west China. The city of Turpan rose above 45C during mid-June, with overnight minimums above 30C. After its hottest May on record, Turpan experienced its hottest June on record, with a high temperature of 46.5C (114F). In the US, on 11th June, the station of Badwater in the Death Valley recorded a scorching minimum temperature of 37C. For the first time in 2022, no stations in lower 48 states dropped below freezing.

If you're interested in getting out and about this month to look for wildlife, check out my July 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 entering its final month, with nearly 9,000 beetles recorded already - if you see one in the next few weeks, please take a moment to map it. Hedgehogs are also very active now, many with hoglets, 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 over the last month include cats learning names, the dam fine work being done by beavers in Cornwall, and plastic-eating worms.

Eurasian swifts appear to be in decline, with numbers have fallen significantly in recent years. - Credit: pau.artigas (CC BY-SA 2.0)
  • What's in a name? A study of 48 cats living either in “cat cafés” or in households with at least three other felines, by scientists at Kyoto University found that they recognised their own names and those of their housemates. The research, published in Scientific Reports earlier this year, found that cats showed signs of confusion when the name called didn't match the photo of the cat they were shown, suggesting that cats learn the human names of their friends.
  • Swift decline. The latest Breeding Bird Survey, carried out by the British Trust for Ornithology, suggests that Scotland's population of swifts has dropped by nearly 60% in the last 25 years, with a decline of almost 50% since 2019. Europe's crashing insect populations and a lack of suitable nesting spots are among the reasons suggested for the decline.
  • Cornish Castor. Since their reintroduction to Woodland Valley Farm near Truro in Cornwall, beavers have dramatically reduced flood risk with their dam-building, which has also created habitat for 13 species that were locally extinct. Researchers at the University of Exeter found that the ponds created by the rodents dramatically changed water flow in the area, increasing the time water took to flow through the area from 15 minutes to more than an hour, allowing more to be absorbed in the floodplain and reducing the height of the river during periods of heavy rain by 30%.
  • Plastic proclivity. Scientists at the University of Queensland have found a species of beetle known as the “superworm”, otherwise Zophobas morio, produces an enzyme capable of digesting polystyrene. The researchers identified several bacteria species in the guts of the worm that reduce the plastic molecules into water and styrene monomers, which are then broken down inside the bacteria cells. The hope is that it will be possible to mimic the activity of the worms to help break down plastic waste.
  • White-out. Megatooth sharks, such as the infamous Otodus megalodon (formerly Carcharocles megalodon) or “megalodon”, were impressive sharks that grew to at least 20m (66 ft.) in length and swam the oceans up until about four million years ago. Now, new data from a team of US and German researchers suggest that competition with great white sharks might've played a hand (fin?) in driving megalodon to extinction. Using a new method of isotopic analysis, the scientists found a substantial trophic overlap between white sharks and meg.

Website news

I am continuing to progress with the breeding section of the water deer article. On the website, some updates have been made to the hedgehog and squirrel sections and a new water deer section is now online covering non-predatory mortality.

Discoveries of the Month

Chatty chiropterans – batters natter in the roost

Most of us know that bats use echolocation to hunt their prey and that different species echolocate at different frequencies. We've only known about this biological sonar for a relatively short time, however; it was first been identified by a young Donald Griffin and eminent Harvard University physics professor George Washington Pierce during the late 1930s. When they pointed the parabolic horn of the sonic detector at a cage of bats the loudspeaker erupted into life. Griffin coined the phrase “echolocation” for this vocalisation in 1944. It was much more recently that neurophysiologist Jagmeet Kanwal demonstrated that bats used this vocalisation to find their way around.

A brown long-eared bat (_Plecotus auritus_). A new study suggests this species engages in social chatter at their roost sites. - Credit: Kevin Witts

Echolocation isn't the only vocalisation that bats make. At least one species, the False vampire bat (Megaderma lyra) sings. Dominant males engage in a ritualised flight pattern during which they constantly vocalise that appears to be part of their courtship routine. We've known for some time that bats also chatter at the roost; a kind of “dusk chorus” if you like. This low frequency chattering can be quite loud and picked up by the ear of a human observer standing at the entrance to a roost. Recently, researchers at Wroclaw and Bristol universities set out to try to understand the purpose of this pre-emergence chatter.

Joanna Furmankiewicz and Gareth Jones studied a colony of brown long-eared bats (Plecotus auritus) at four sites in south-west Poland. Three were in the attics of churches in the villages of Bożnowice, Jabłów and Krajanów and contained maternity colonies, while the fourth was in a forest in Muszkowice, where small congeneric groups roosted in tree holes. The social and echolocation calls were recorded at the church roosts between August and September 2007 and played back to bats returning to maternity roosts during 2008 and 2009 in order to assess the bats' response.

When the data were subjected to analysis using a statistical method known as generalised linear mixed modelling, the researchers found that bats performed more inspection flights and produced more social calls when the recordings were being played than when “noise” was pumped through the playback system. Interestingly, playback of social calls also resulted in the bats producing more echolocation calls than playback of echolocation calls did. Writing in the journal Mammalian Biology, Furmankiewicz and Jones suggest that social calling by these bats as they return to maternity roosts is a means of maintaining contact among roostmates, and hence the social calls function as contact calls:

The recognition and affiliation processes in brown long-eared bat can be mediated by social calls that may function in this species as contact calls to maintain associations between roostmates.”

Reference: Furmankiewicz, J. & Jones, G. (2022). Bats (Plecotus auritus) use contact calls for communication among roost mates. Mamm. Biol. 102: 51-60. doi: 10.1007/s42991-021-00190-7.

Temperature-sensitive tawnies. Climate change a bigger threat to owls than urbanisation

Climate change is one of the most significant and serious threats humankind currently faces. As the climate broadly warms, we see shifts in well-established weather patterns resulting in more frequent and intense heat, cold, and flooding events. Given the truly global scale of this problem, however, it is not just humans who are feeling the effects. Virtually every species with which we share this planet is at risk, adding to the problems already created by our rampant pollution and destruction of habitat.

New science suggests that climate change may pose a greater risk to tawny owls on the edge of their ranges than urbanisation. - Credit: Sue Cro (CC BY-NC 2.0)

For several decades now, scientists have been monitoring animals and plants to see how they are reacting to the changing climate in order to model thresholds where species are lost or distributions shifted. Such statistical modelling helps us predict what we might expect under a range of different climate warming scenarios. One way of getting a handle on the response of a species to changing conditions is to study their natural history at the extremes of their range, as it is here that they tend to exhibit the lowest stability.

Between 1987 and 1998, a team of scientists led by Orr Comay at Tel Aviv University studied the distribution, nesting success (including the provisioning and development of the chicks) and diet of tawny owls (Strix aluco) in Israel's Upper Galilee, on the raptor's southern range limit. The data were then subjected to a species distribution model to predict relatively likelihood of occurrence. The results of their comprehensive dataset and analysis were published in the journal Animals earlier this year.

Comay and his team found that nesting success was temperature and precipitation dependent. Brood size was positively associated with higher rainfall and also with the minimum temperature during the early spring. In other words, brood size increased in mild springs, but, overall, fewer nestlings were recorded during hot springs, so hotter seasonal maximums from March to May were associated with lower nesting success. Generally, the owls seemed to prefer relatively cool, damp and wooded areas within Israel, and occurred more often in and around villages than in open fields. More owlets were raised in pine forests, especially when spring temperatures were moderate and following wet winters. The authors suggest that climate change, which trends towards higher spring temperatures and reduced rainfall in the Middle East, is likely to represent a threat to the breeding success of this ubiquitous woodland owl:

“... Tawny Owls are regularly observed in European cities with no negative impacts on breeding success. On the other hand, our results suggest that as the local climate warms and becomes more arid, breeding success will decrease. Taken together, our study suggests that while the Tawny Owl can survive rural development trends, climate change presents a real threat to its survival in its southern edge of distribution.”

Reference: Comay, O. et al. (2022). In its southern edge of distribution, the Tawny owl (Strix aluco) is more sensitive to extreme temperatures than to rural development. Animals. 12: 641. doi: 10.3390/ani12050641.

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