Seasonal Update - October

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At the beginning of September, the jet stream – a fast-flowing ribbon of air winding like a giant serpent some 10km (6.5 miles) above us – started to amplify. The result was a series of low pressure systems passing across the northern half of the UK, bringing heavy rain and, at times, gale force winds. The southern counties remained relatively unscathed for the first couple of weeks, with mild air dragged up from the continent giving the second week of the month an unseasonably mild feel. Indeed, when I went out to bring the trailcam in from the garden just before 6am on the 11th, it was 16C (61F). One result of this mild weather was that grasshoppers and crickets, as well as many moths and the bats that feed on them, remained active throughout the night here in the New Forest.

The mild weather did not last, however, and two deep areas of low pressure passed through during the middle of the month. The first was storm “Helene”, which hit Wales on 16th September, bringing 80 mph winds that caused damage and power outages. And worse was to come in the form of storm “Ali” that struck northern counties on the 18th. Ali brought Northern Ireland its strongest September winds on record, with gusts reaching 102 mph (164 kph), and caused the tragic deaths of at last two people. In the Scottish mountains, winds reached a staggering 115 mph (185 kph). Bad luck comes in threes, they say, and on the penultimate weekend of the month storm “Bronagh” brought rain and more strong winds to the Midlands and parts of the south-east.

The powerful storm that hit the UK in October 1987 brought down a great many trees. The storm arrived early in the season and many trees still had their leaves. - Credit: Backinpompey (CC BY-NC-ND 2.0)

Strong winds always have the potential to cause problems for us, but the timing of these storms was particularly unfortunate because they were very early in the season. There’s no denying that autumn is a stormy season in Britain, but November tends to be our “stormiest” month and, for good reason, most deciduous trees have lost their leaves by then. Leaves act like sails, catching the wind and increasing a tree’s surface area, hence increasing its wind resistance. Like a boat lowering its sail in a storm, trees drop their leaves (partly) to streamline themselves in windy conditions. Consequently, when storms come early, while trees are still in leaf, more are likely to be brought down. The “Great Storm” of 1987 was so devastating to our parks and woodlands because it was early and most trees still had their leaves.

The final week of September saw high pressure develop briefly over the UK before moving off to the continent, leaving its influence only in the south. The result was settled, sunny weather in the south, although the northerly airflow made it feel distinctly chilly to begin with, while Northern Ireland and Scotland (particularly the western coasts) continued to be battered by strong winds and heavy rain. England experienced an “Indian Summer” for a couple of days in the middle of the week, with temperatures peaking at 24C (75F) in the southeast, before low pressure brought cooler air across the whole country to kick off October. September ended with temperatures generally back to the seasonal average of 17-18C (62-64F).

Despite being a chillier start to autumn than many were hoping for, the northerly airflow appeared to stir many deer into action; I saw several posts on Facebook early in the week showing rutting activity among red deer. With that in mind, many people are attracted to deer parks this month to watch and photograph the deer rut, and they can provide some superb views. If you’re among the crowds this season, please remember that “relaxed around humans” does not mean “tame”. These animals are not tame. I saw a photo of a lady stood with her young son trying to hand-feed a red stag some leaves last month and behaviour like this is just crazy. Granted, in 90% of cases nothing may happen; but stags are het up on testosterone and, weighing up to 260kg (570 lbs), they can be very dangerous to fragile primates. Please, for your sake and theirs, keep your distance and watch through binoculars or a long lens.

Deer parks, such as Richmond on the outskirts of London, offer an excellent opportunity to watch the deer rut. Please remeber, however, that just because they're in a park setting DOES NOT mean the deer are tame. They're big animals het up on testosterone, which makes them unpredictable. Please keep your distance. - Credit: Marc Baldwin

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). Following on from their point tetrad survey I mentioned last month, the British Trust for Ornithology have now launched their tawny owl calling survey. This survey is much more relaxed than the point survey. Essentially, all they need you to do is stand in your garden, local allotment, park, wood, etc. for 20 minutes one evening a week and record whether you hear a tawny owl calling. The survey runs between 30th September and 31st March and the more weeks you can record for the better, but you can do as many or as few as you like – it also doesn’t matter if you miss some weeks. No calling is as valid a result as any other, so even if you’re pretty sure you don’t have tawnies in your neighbourhood I urge you to get involved and submit your findings.

Discoveries of the Month

Even sharks eat their greens

If you were anything like me as a kid, your Mum was forever trying to think up ingenious ways to get you to eat more fresh vegetables – blitzing a whole load of veg into a brown mushy soup, grating onion or carrot into cottage pie filling, slicing and hiding in sandwiches, even surreptitiously baking in innocent-looking cakes. How things change! These days, some [mind your own business] years later, I feel deprived if I haven’t had at least one portion of veg in a day and have even ordered a side of veg instead of chips as an accompaniment to a pub sandwich.

We know that fruit and veg provide us with a host of vitamins and minerals that are important for body function while also providing all-important fibre. That said, humans don’t have a gut that’s well adapted to digesting plant material, and we need to cook the veg to get the benefits, particularly cruciferous veg such as broccoli and cabbage. Cooking partially breaks down the fibre (particularly cellulose) in the cell walls, allowing our digestive system to do the rest.

Seagrass is an important marine habitat, providing shelter and food for a wealth of marine animals. New research that sharks may also be capable of expoliting the grass for food. - Credit: Dugong Seagrass Conservation Project

Most of us are familiar with the classification system used to group animals according to how well they can extract energy from different types of food. Herbivores are those that can subsist on a diet of predominantly vegetable matter. They typically have long digestive tracts containing a suite of microorganisms capable of breaking down plant cell walls to release the nutrients. Carnivores, by contrast, have much shorter digestive tracts containing concentrated stomach acids adapted to break down animal tissue. Some species, polar bears for example, also have hypertrophied gall bladders, producing vast quantities of bile that break down their fatty meals and allow them to eat quantities of blubber that would give a human a heart attack. In the middle are the omnivorous species, which have a “hybrid” digestive system, that’s not particularly specialised and can handle plant and animal tissue, albeit processing both with lower efficiency than either of the other groups.

Conventional wisdom told us that those species well-adapted to eating plants don’t digest animal tissue very well and vice versa. Nonetheless, herbivores have sometimes been observed eating meat and carnivores vegetable matter, and recent research at Florida International University’s Biscayne Bay campus suggests carnivores may be able to digest plant material better than we thought.

A Bonnethead shark (Sphyrna tiburo). - Credit: Ross Robertson (Smithsonian Tropical Research Institute)

University of California-Irvine biologist Samantha Leigh and her colleagues fed bonnethead sharks (Sphyrna tiburo) housed at Biscayne a diet of carbon-13 (13C) labelled seagrass and squid at a ratio of 9:1 (i.e. 90% seagrass, 10% squid) for three-weeks, taking periodic blood samples and collecting faecal samples. At the end of the study, the researchers had uncovered something remarkable. The sharks had all gained weight on their primarily plant-based diet and their hind guts showed signs of elevated β-glucosidase activity – this is an enzyme that breaks down cellulose. More interesting still was the clear increase in the 13C signature of the blood and liver samples by the end of the study, suggesting that the sharks were extracting and absorbing nutrients from the seagrass. Writing in the Proceedings of the Royal Society last month, Leigh and her co-workers concluded:

We provide conclusive evidence that bonnethead sharks, animals previously thought to be solely carnivorous, can assimilate nutrients from seagrass. This is the first species of shark ever to be shown to have an omnivorous digestive strategy.
Samantha Leigh et al. (2018)

Source: Leigh, S.C. et al. (2018). Seagrass digestion by a notorious 'carnivore'. Proc. Roy. Soc. 285B: 20181583.

The complicated picture of badger/hedgehog distribution in Britain

Most of countryside now devoid of hedgehogs, study finds” read the depressing headline in The Guardian early last month. Damian Carrington’s article was referring to the publication of an open access article to the journal Scientific Reports on 6th September. In the paper, a multidisciplinary team from six institutions, led by Ben Williams at Reading University, presented their analysis of hedgehog occurrence at 261 randomly-chosen sites across England (243) and Wales (18) between 2014 and 2015.

The researchers used footprint tunnels—triangular plastic tubes that are lined with paper, have an ink pad on either end and are baited with food (the idea being that the animal walks through the ink, leaving footprints on the paper from which the species can be determined)—to assess the presence or absence of hedgehogs at these sites. At the same time, students searched the areas, under the supervision of the authors, for evidence of badger setts. The hedgehog distribution data were then analysed statistically to look at countrywide distribution patterns and any potential correlations with either badger presence or local road ratings (i.e. motorway, A road, B road and minor road).

A fox, two badgers and a hedgehog feeding in the same garden. - Credit: Feathers Allan

Hedgehogs were found to be widely distributed across England and Wales, but the occupancy rates were low – hedgehogs being present in only 12-33% of land classes. In the south-west of England, no sign of hedgehog activity was observed at any of their rural sites. They were found in some suburban areas of The Dutchy, but the authors caution that these populations are isolated and vulnerable.

Overall, hedgehog occupancy correlated negatively with badger sett density (i.e. more setts meant fewer hedgehogs) and positively with urban areas. The authors were quick to point out, however, that the hedgehog-badger relationship was not a simple one. Indeed, just over a quarter of all sites had neither hedgehogs nor badger setts, suggesting that there are significant areas of England and Wales that are unsuitable for both species. Indeed, their statistical model predicted that even when badgers weren’t present in an area, the likelihood that hedgehogs would be found was only 31%. Conversely, at many sites both species coexisted and, in their paper, Williams and his colleagues explain:

“… of those 55 sites where hedgehogs were present, badgers were also present on 49.1% of these sites. This demonstrates that badgers and hedgehogs can, and do, coexist at the 1 km2 scale. The extent to which the ranging patterns of the two species overlap in space and/or time is, however, not known, although this does not appear to be a simple case of hedgehogs “hiding” in built environments, as footprint tunnels were placed in rural habitats.
Ben Williams et al. (2018)

This implies that suggestions that reducing badger numbers in response to the bovine TB crisis in Britain will also help boost the hedgehog population may be unfounded. Instead, the authors suggest farming practices need attention if the decline is to be tackled:

Collectively, this suggests that intensive management of rural areas is negatively impacting both these generalist terrestrial insectivores.
Ben Williams et al. (2018)
Connectivity between gardens is vital to allow hedgehogs and other wildlife entry and exit. - Credit: Marc Baldwin

The final word, for now, goes to hedgehog biologist Hugh Warwick, who is quoted in Carrington’s article:

This fascinating piece of research reminds us of how vital a habitat our back gardens can be and one we can easily improve with a few small actions. The most important is to ensure that hedgehogs can get into your garden, and a small hole – 13cm – will do.
Hugh Warwick (2018)

The link in the quote takes you to the Hedgehog Street website, which contains hints and tips on making your garden hedgehog-friendly. Additionally, you can check out my Helping Hedgehogs article.

Source: Williams, B.M. et al. (2018). Reduced occupancy of hedgehogs (Erinaceus europaeus) in rural England and Wales: The influence of habitat and an asymmetric intraguild predator. Sci. Rep. 8: 12156.

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