Seasonal Update - December 2019

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October blended almost seamlessly into November, a chilly, wet and windy start to the month. Indeed, gusts in excess of 90mph were recorded at The Needles, just off the Isle of Wight on the first weekend of the month. The first week saw flooding and small landslides, followed by more widespread and devastating flooding in the midlands and north of England. At the same time, temperatures hovered just below the seasonal average for most of the month, resulting in the first snowfall of the autumn/winter early on in November in parts of Scotland and the hills of north England and Wales. A blocking pattern establishing itself over the Arctic resulted in the jet stream being pushed to the south of the UK, allowing more Arctic air to spill into the north Atlantic.

After a cold and frosty couple of weeks, low pressure moved back in, bringing with it milder, wet and windy weather before a brief ridge of high pressure brought further frost to see autumn out everywhere except the south coast and southwest of England. The current long-range forecasts are split. One suggests this pattern is likely to continue through Christmas and into the new year, resulting in an unsettled festive period for most of us, with temperatures probably above the seasonal average and little chance of frost or snow. Alternatively, a small (by weather system standards, at least) change in direction of a pool of cold air in central Europe could see an easterly airflow develop, bringing a much cooler Yule. If the models predicting the first scenario are correct it will be interesting to see what impact that has on the Chinese water deer rut, hedgehog hibernation and the population of molluscs and ticks; all of these enter a crucial phase during December and January and appear very sensitive to mild, wet winters.

In November and December The Woodland Trust was urging people to plant trees as one strategy to help combat climate change and reduce flooding. - Credit: Alex Indigo (CC BY 2.0)

Despite what was happening in the UK, and as if to illustrate an element of climate change that many people find confusing and counterintuitive, the Copernicus Climate Change Service, a European organization that tracks global temperatures, released a report showing that, on the back of the warmest June, July and September on record, 2019 also claims the dubious crown of hottest October. According to the National Oceanic and Atmospheric Association, overall, 2019 will be the hottest year on record. If, incidentally, you spotted the media scrum a couple of months ago about a paper entitled “No Experimental Evidence For The Significant Anthropogenic Climate Change”, which boldly claimed that human activity was responsible for negligible warming (only 0.01C), you might want to see the critique.

A few conservation stories that caught my attention this week include the sad news that Paulo Paulino Guajajara, a 26-year-old member of the “Guardians of the Forest” group, was killed by suspected illegal loggers in the Amazon’s Maranhão state. Also, a new study by New Jersey-based researchers, published in Nature Communications, suggests that, come 2100, some 200 million people will be living below sea level, assuming a 2C (3.6F) increase in global temperatures, with a further 360 million suffering annual flooding.

Work by biologists at the Lebanese University in Beirut suggests that hyenas, Lebanon’s “national animal” are in under threat in the country thanks to a campaign of fear and myth that has resulted in frightened people poisoning and shooting them. Canadian scientists have engineered an artificial leaf that can absorb carbon dioxide from the atmosphere and convert it to methanol, which can be used as a fuel source. Finally, two new species were discovered this month: a new species of shark, the Ambon catshark (Akhelios suwartanai), from Indonesian waters, and a tiny soil beetle found in a sample collected in Kenya in the mid-1960s that has been named Nelloptodes gretae, after teenage climate activist Greta Thunberg.

If you’re up for getting outside for the start of autumn, 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 is looking for people to organise cleans of their local beaches – details here. The Forestry Commission is running a series of events this month – full list here. Remember, too, that December is the month when many of our hedgehogs will be entering hibernation, and I implore you to help if you can by leaving food and water out overnight and by keeping an eye out for very small animals that may not have time to put on sufficient weight before hibernation. Find out more about how you can help your local hedgehogs on my blog.

The new species of catshark, Akheilos suwartanai, discovered off the Indonesian coast, based on a specimen held at the Indonesian Institute of Sciences' Center of Deep-sea Research. - Credit: William White & Simon Weigmann / Zootaxa

Interested in the wildlife to be found this month? Check out my Wildlife Watching - December page.

Before we look at a couple of recent science discoveries, I wanted to take this opportunity to thank all my readers for their support over the past year - it is truly appreciated - and wish you and your families a very Merry Christmas and Happy New Year.

Discoveries of the Month

Talking the talk: human voices reduce predator activity

Predator deterrence has been something of a Holy Grail to humans for centuries. Whether it’s aimed at keeping tigers off your back while you’re washing clothes in a jungle river or protecting your chickens from the local fox, many deterrent approaches have been tried, with varying success. Given that humans are the most significant predator in most ecosystems on Earth, it has been suggested that even the sound of our voices is enough to make predators think twice. It was once considered something of an old wives’ tale that farmers used something as simple as a radio to keep foxes away from their livestock, but we now know that almost any “talk station” can be very effective at deterring vulpine intrusion. Likewise, as anyone who hikes regularly in the North American mountains can testify, making noise while you walk is a necessity during the autumn to reduce the risk of startling a bear. As if to add an empirical stamp to these observations, new joint research from the University of California in Santa Cruz and Western University London in Canada suggests that non-threatening human voices can elicit profound changes in the behaviour of carnivores both large and small.

Playback studies in the Santa Cruz mountains found that the sound of human voices caused mountain lions to avoid the area. - Credit: Marc Baldwin

A team of researchers led by Justin Suraci of the University of California looked at the response of various predators and their prey in two private areas (i.e. closed to public access) in the Santa Cruz Mountains. For five weeks between May and August 2017, the biologists played recordings of a person reading a poem through a grid network of 25 speakers and monitored the impact on GPS-collared mountain lions (aka the cougar or puma, Puma concolor) and a variety of other species with the aid of remote camera traps. Overall, movement data were collected for mountain lions, bobcats (Lynx rufus), skunks (Mephitis mephitis), opossums (Didelphis virginiana), mice (Peromyscus spp.) and woodrats (Neotoma fuscipes).

The results of the experiment were striking – puma, skunks, bobcats and opossums all avoided the area. The GPS tracks for the mountain lions showed them spending 30% less time inside the playback zones versus the controls and giving the speakers a wide berth. The puma also moved more cautiously through the playback areas, moving 34% slower than they transversed the control plots. Interestingly, bobcats also became progressively more nocturnal in response to the disturbance, a trend that we’ve seen in medium-sized carnivores here in Europe, particularly badgers. This relative reduction in predator activity at the playback sites had a knock-on impact on prey species. Deer mice increased their range by 45%, while both mice and woodrats visited feeding sites much more regularly – equating to a 17% increase in foraging intensity. This phenomenon, where prey prospers when people keep predators away, is known as the “human shield” and, writing in Ecology Letters last month, Suraci and his team explain:

If similar human shield effects for small mammals are common where human activity is high, this could ultimately lead to increased small mammal abundance in wildlife areas frequented by people, a potentially undesirable consequence of ecotourism.

While the cat's away? In the absence of predators, small mammals such as deer mice (Peromyscus maniculatus) increased their activity. - Credit: Christa R. (CC BY-NC 2.0)

In other words, reducing the activity of predators could lead to an increase in the density or activity of “pest species” that might throw the ecosystem, and potentially livelihoods that depend on them, out of kilter. Given that several medium-sized carnivores, such as skunks, seem to thrive in close proximity to us, despite our noise, Suraci and his team are now looking at the trade-off between benefitting from living in cities and the risk of potentially lethal encounters with people.

Reference: Suraci, J.P. et al. (2019). Fear of humans as apex predators has landscape-scale impacts from mountain lions to mice. Ecol. Lett. 22(10): 1578-1586.

The Perturbation Effect revisited: culling badgers changes their movement patterns

Anyone who has followed the tumultuous debate around bovine TB in Britain will be aware that badgers are frequently at the heart of the discussion. Specifically, the subject of whether shooting them to reduce the population density offers a solution, or part of the solution, to the stubborn problem of Mycobacterium bovis infection in Britain’s cattle herds.

New tracking data from the West Country shows that culling badgers affects their movement pattern and activity, which may have implications for TB transmission to cattle. - Credit: Marc Baldwin

The first attempt to assess the impact of culling badgers on rates of bTB was the Randomised Badger Culling Trial, or RBCT (sometimes also called Krebs Trial), that ran between 1998 and 2007. The experiment looked at culled and control sites in 30 areas of England with a high bTB prevalence and one finding was that while culling badgers reduced TB incidences within the cull zone, it appeared to increase incidence in neighbouring areas. This scenario was dubbed the “perturbation effect” and was believed to have been caused by infectious badgers, disturbed by the culling operation, moving out of the area and infecting nearby farms/badgers outside the cull zone. The perturbation effect is still a widely-cited reason for not culling badgers, despite considerable criticism, and new research has reignited the discussion.

Between 2013 and 2017, a team of researchers, led by Cally Ham at London’s Institute of Zoology, collected data on badger movements on 20 cattle farms in four areas of Cornwall. A culling licence was issued for one of their study areas in 2016 and culling took place in one of their study farms between September and October in 2016 and 2017, providing an opportunity to monitor how the badgers responded. Sixty-seven badgers were GPS collared and tracked during 8,243 nights, including 69 during and 244 after the culling had finished, and seven of the tracked badgers resided in the cull zone.

The GPS data revealed that the culling and its immediate aftermath resulted in disruption to the badger clans. During the “culling” and “post culling” periods, badgers increased their home ranges by 61%, moved almost 40% further from their setts each night and travelled more quickly than in the “pre cull” period and at “no cull” sites. With this increase in ranging activity, the researchers noted that badgers disturbed by culling, on average, visited 45% more fields and were almost 20 times more likely to trespass on a neighbouring clan’s territory than unperturbed badgers. The badgers also left up to an hour later in the evening and returned an hour earlier in cull areas than in unperturbed areas. Writing in the Journal of Applied Ecology last month, the biologists caution:

Our finding that badger behaviour changed while culls were ongoing may have important implications for TB control. Even if an individual is culled during the latter stages of a cull (which under current policy last ≤6 weeks), the behavioural changes exhibited by the individual prior to death may mean that even individuals which are ultimately killed may contribute to increased transmission risk while culls are ongoing.

The authors are also quick to point out that:

In contrast to the behavioural changes described in this study, badger vaccination has been shown to generate no such changes in individual ranging behaviour …”

Reference: Ham, C. et al. (2019). Effect of culling on individual badger Meles meles behaviour: Potential implications for bovine tuberculosis transmission. J. Appl. Ecol. 56(11): 2390-2399.

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