Seasonal Update - August 2018


Looking back, it feels like a long time since Britain had what might be described as a “decent” summer. Sure, it’s been hot the last few years, but for a couple of weeks at a time; hot, dry weather punctuated by a week or two of cooler and wetter conditions. Indeed, entomologists were beginning to despair about the impact this was having on some of our invertebrates – wasps and butterflies in particular. This summer has been different. Very different.

June and July saw Britain in the grips of the longest heatwave in 42 years, with a mere 47mm (1.85 in.) of rainfall during the first half of the season (1st June to 16th July). This made 2018 the driest start to summer since 1961 when modern records began. The UK has endured temperatures averaging 20.9C (69.6F) across the country so far this summer, only fractionally below the 21C (69.8F) average recorded for the famous summer of 1976, which saw standpipes in the street and people reporting water wastage to dedicated government hotlines.

A female stag beetle (_Lucanus cervus_). We know very little about the distribution and population of this insect and the People's Trust for Endangered Species are urging people to report their sightings via their online survey. - Credit: Marc Baldwin

Of course, not everywhere has had wall-to-wall sunshine, and the second week of July brought significant periods of wet weather across Northern Ireland and western Scotland. Nonetheless, here on the south coast it’s been mostly dry, and our garden in Southampton hasn’t seen any significant rain for almost nine weeks now.

So, what does all this mean for our wildlife? It’s too early to say what long-term impacts it will have, but we know that prolonged warm, dry spells are good for flying insects, so it’s likely to be a good year for butterflies, bees and wasps. Deer fawns/calves also tend to do better in dry summers than wet ones. It also seems to have been a good year for stag beetles - I’ve personally seen more this summer than I can recall ever having seen in a single year before. With that in mind, if you’ve seen one, please log it with the People’s Trust for Endangered Species – their Great Stag Hunt survey provides valuable “citizen science” data on the distribution of these endangered insects.

On the other side of the coin, many mammals really struggle in this weather – badgers, foxes, hedgehogs and moles find the baked earth puts earthworms and other invertebrates out of their reach. Lactating females can also quickly become dehydrated, so a bowl of water left out in your garden in this weather, day and night, can literally be a lifesaver. I’ve noticed on my trailcam that the visiting hedgehogs spend much more time at the drinking station than usual at the moment. River levels have also fallen, which affects a great many species, and there have been several heathland fires that have killed a great many beetles, reptiles and amphibians. One particular blaze on Saddleworth Moor in Yorkshire made the news last month, burning for nearly four weeks and decimating an area of 18 sq-km (7 sq-mi.).

Leaving water out during these periods of prolonged warm, dry weather can be vital for our garden wildlife. If possible, a couple of small bowls is the best option as it can reduce aggression between animals. - Credit: Natasha Weyers.

If you want to get out and do something positive this month, 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 are looking for people to organise cleans of their local beaches – details here. The Forestry Commission are running a series of events this month (full list here).

Discoveries of the Month

Conservation contradiction and conflict – a survey of public perception of grey squirrel management strategies in Britain

Britain’s landscape has been subject to change for thousands of years and part of this progression has been the introduction of species not historically resident here. Humans, often considering themselves removed from nature, label species as “native” or “non-native”. Typically, a species considered to have made it to the UK under its own steam since the last ice age (about 8,000 years ago) is “native”. If an animal or plant was brought here by people, deliberately or accidentally, it is “non-native”. If a non-native species is subsequently found to be detrimental to the natural history of our island, i.e. negatively impacting our native species, it is further classified as “invasive”. In 2008, a collaborative venture by DEFRA and the Scottish and Welsh governments called the Non-native Species Secretariat was formed to coordinate the response to non-native species in Britain. The resulting online Non-native Species Information Portal holds a catalogue of non-native species in the UK, and members of the public are able to log sightings to help better understand their distribution. There are now just over 3,000 species on the list.

The British government has a legal obligation to conserve native species and a big part of the challenge is to reduce or remove “alien” species. In order to accomplish this, however, public acceptance is required, and many proposed management strategies have failed to gain the necessary support. When it comes to getting members of the public on-side, the methods to be employed during management as well as how the need for control is communicated can have a significant impact on the outcome. Recently, a team of forestry biologists assessed the public acceptance of a plan to cull grey squirrels in the UK.

Introduced to the UK by the Victorians, the Grey squirrel (_Sciurus carolinensis_) is a controversial addition to the British landscape. - Credit: Marc Baldwin

The grey squirrel (Sciurus carolinensis) is a highly controversial species in Britain, having expanded its range rapidly and widely since initial introductions in the late 1800s. The expansion of the grey appears concomitant with the decline in both range and abundance of our native red squirrel (Sciurus vulgaris) and there are data to suggest they can also have a significant impact on commercial timber stocks and the nesting success of some song birds. The situation is by no means clear cut, as discussed elsewhere on this site, and many are quick to point out that reds and greys have been known to coexist and that the red squirrel was considered a pest to forestry and killed in significant numbers as recently as the mid-1940s. Many people also gain great joy and a connection to nature by watching and feeding their local grey squirrels and many of these would never see a red even were they still widespread in Britain. Hence, the management of this species is controversial and offers a unique insight to the factors affecting public perception of such schemes.

In a paper to Biological Conservation last month, a team led by Mike Dunn at the Northern Research Station in Midlothian presented the results of their national survey on squirrel control strategies. The 30 question survey was completed by 3,758 adults, roughly evenly split by sex. The results paint an interesting if somewhat conflicting picture. Reds were consistently more desirable to the respondents than greys, and most considered that they had a more positive impact on the local economy than greys. Additionally, 82% agreed that reds were endangered and 62% agreed that greys should be controlled if they were impacting red populations. However, almost 60% also considered that we should conserve both red and grey squirrels. Indeed, one-quarter of respondents considered that nature should be allowed to take its course and that there should be no management of squirrels.

Interestingly, despite this being a widely-discussed topic, only 6% considered themselves to know a lot about the subject, with 22% saying they were completely unaware of the two species’ interactions. Moreover, there was a clear trend in the sources of information people chose to believe, with 60-80% saying they trusted the information provided by forestry and conservation bodies, scientists and animal welfare groups, while only 28% and 33% said they considered governmental and media sources, respectively, reliable.

In terms of control strategies, lethal control was broadly unacceptable (for example, poisoning with warfarin was considered unacceptable by almost 70%), while non-lethal options were more likely to be tolerated (e.g. only 14% of respondents considered contraception unacceptable). Men, and particularly older men, were more likely to accept any form of control methodology than women. Overall, the researchers found that education appeared to be the key, with a knowledge of red squirrel conservation activities in respondents' area positively associated with acceptability for five of the control methods. The biologists concluded:

To foster more fruitful collaboration, wildlife professionals should raise awareness of why particular control methods are preferred, highlight the damage grey squirrels cause to other valued species, and offer local communities a variety of roles which contribute to the wider goal of native species conservation.

Grey squirrels are the only mammalian wildlife some people see in their gardens and many of us derive great pleasure watching and feeding them. - Credit: Peter Trimming

Source: Dunn, M. et al. (2018). Public attitudes towards “pest” management: Perceptions on squirrel management strategies in the UK. Biol. Cons. 222: 52-63.

Grey squirrels “stress out” reds

Globally, the Eurasian red squirrel is widespread, from the UK in the west to Japan in the east, and it is for this reason that the IUCN list it as a species of least concern. In Britain, however, the species has undergone a substantial contraction in both range and number in the last 80 years or so, and the red squirrel is now listed on Appendix III of the Bern Convention, requiring “Special protection through appropriate and necessary legislative and administrative measures”.

While not the complete picture, the introduction of the grey squirrel - a native of the hickory forests on the east coast of the USA - by Victorian collectors in the nineteenth century is thought to have played a significant role in the decline of the red. For the past few decades, a great deal of research has focussed on trying to understand the ecology of both species and the factors that mean they are rarely able to coexist. It was once believed that greys, being larger and often more aggressive than reds, physically attacked and chased them out of an area when they arrived, but we now know this is not the case. The displacement is subtler. We know, for example, that greys are better adapted to broadleaf woodlands than reds, are able to subsist on a diet of acorns and eat hazel nuts before they’re fully ripe, and also that some carry a pox virus (sometimes mislabelled as parapox) that is largely fatal to reds. New research suggests that the presence of greys may also stress out local red squirrels and that this might have further consequences for their reproduction and survival.

In some areas, Reds and Greys have persisted for many years before Reds have started to decline, suggesting the relationship is complex. - Credit: Peter Trimming

In a paper due to be published in the Journal of Animal Ecology shortly, Francesca Santicchia at the Università degli Studi dell’Insubria in Italy and her colleagues present the findings from their biochemical analysis of Nutkin. The researchers trapped red squirrels at five sites in the Lombardy region of northern Italy and collected samples of urine and faeces for analysis. Two sites were colonised by greys during the course of their sampling, allowing them to see what impact the arrival of the greys had on red squirrel physiology. The biologists were looking specifically for a group of chemicals known as faecal glucocorticoid metabolites (FGM), which give an idea of adrenal gland activity and thus long-term stress responses.

Based on 260 samples from 166 different animals, Santicchia and her team found that FGM concentrations were three times higher in red squirrels living in areas that contained greys than in woodlands without them. There was no significant impact of sex, reproductive condition (e.g. lactation), body size or time of day on the FGM levels, but concentrations were higher during the autumn than in spring-summer. Over the course of the experiment, the FGM concentrations of squirrels in the red-only forests remained consistent, while that of those animals in areas invaded by greys increased twofold following colonisation by greys. Perhaps most interestingly, removal of the greys resulted in a 1.5-fold decrease in FGM concentrations, implying the “damage” is repairable. In their paper, the researchers conclude:

Our FGM data suggest that red squirrels are chronically stressed by invasive grey squirrels. Although there are wild species in which chronic stress may be an evolutionary response to stressors such as predation pressure and is not necessarily deleterious, we believe this is not the case in our study system. Our results indicate that red squirrels have a physiological stress response to a threat posed by an invasive competitor to which they show no evolutionary adaptation. Therefore, the observed increase in glucocorticoid concentrations is likely to have detrimental consequences for red squirrels.

Source: Santicchia, F. et al. (2018). Stress in biological invasions: Introduced invasive grey squirrels increase physiological stress in native Eurasian red squirrels. J. Anim. Ecol. doi: 10.1111/1365-2656.12853

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