Seasonal Update - November 2018


October started on a chilly but bright note in the south, with more wind and rain in the north. The cool conditions were short-lived, in the midlands and south at least. Like waves lapping at a shoreline, swathes of mild air washed over the UK during the first half of the month, courtesy of high pressure systems in the north Atlantic and over Europe. The result was unseasonably mild and humid air dragged up over most of England and the Republic of Ireland from the Canary Islands by tropical storm Leslie in the western Atlantic.

The middle two weeks of the month saw an Indian Summer courtesy of warm air from Africa. Despite storm Callum - the third named storm to arrive in Britain this season - passing across in the second week of the month, it remained very mild for the time of year, with temperatures reaching 24.6C (76F) in North Holt in the south-east of England, about 11C (20F) above the seasonal average. Indeed, this was the hottest October day for almost a decade. Scotland, Wales and Northern Ireland, by contrast, were subjected to fits of heavy rain and, at times, gale force winds, but slightly cooler temperatures. Libanus in Wales saw 218mm of rain fall over three days during the second weekend, more than they’d expect in a month.

Things didn’t start to cool down until the final week of October when warm air was forced into Alaska, disrupting the jet stream and bringing an Arctic airflow to the UK. Overnight temperatures were widely only a degree or two above freezing on the final weekend of the month, and parts of Scotland and northern England, along with parts of continental Europe, saw their first (very early) snow. The early hours of Halloween saw temperatures drop to -6.4C (20.5F), although much milder conditions were on the horizon for the start of November, with daytime highs of 15C (59F) and 13C (55F) overnight forecast - several degrees above the seasonal average. Another topsy-turvy month, weather-wise.

The early hours of Halloween saw temperatures drop to a chilly -6.4C (20.5F) in the north-west. - Credit: Marc Baldwin

The big weather story last month was probably that of hurricane Michael, a Category 4 hurricane that hit the east coast of the USA at the start of October, leaving devastation in its wake. When the storm made landfall in Florida, it subjected America’s panhandle to sustained wind speeds of 155 mph (almost 250 kmph), making it the strongest storm to hit the east coast since the mid-1800s. Meanwhile, on the other side of the world, Australia continues to struggle through the worst drought in living memory, following the driest September on record.

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). The British Trust for Ornithology’s tawny owl calling survey is underway now. This survey is much more relaxed than the point survey they ran during September and October. 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.

Interested in the wildlife to be found during November? Check out my Wildlife Watching - November page.

Discoveries of the Month

Climate change is already causing species declines around the globe

Many mammal species are at risk from climate warming; from marine tutle populations that could see proportionally fewer males as a result of temperature-dependent sex assignment of eggs; to elephants facing pressure on the water supplies, an issue for an animal that drinks upto 300 litres per day. - Credit: Marc Baldwin

This autumn has been an uncomfortable season for conservationists and all those who care about the state of our planet and its wildlife. At the end of October, the World Wildlife Fund, in collaboration with the Zoological Society of London, produced their latest Living Planet report, and it  made grim reading. Living Planet reports a decline in wildlife populations of 60% between 1970 and 2014, with the destruction most pronounced in South America, where there has been an 89% loss since 1970. One key observation of this report was that the loss of animal populations and habitats isn’t taken as seriously by global leaders as climate change is. A separate report, also from ZSL, suggests, however, that climate change is already having detrimental impacts on our wildlife, with not enough being done to address it.

In a report published in Global Change Biology, the ZSL biologists assessed 987 populations of 481 different species across the globe, looking at whether their population trends could be linked with climate change and the impact people are having on the landscape. The results indicate that species populations were declining more rapidly in areas where the rate of climate warming was greatest. The impact was twice as strong in bird populations as it was among mammals, possibly because their breeding cycles are more closely linked with temperature, so even small changes have the potential to disrupt their normal reproductive activities.

Under the highest warming prediction of climate change, the RCP8.5 model, the report predicts annual population declines of about 4% for birds and 1.5% for mammals. In their summary, the report authors note:

The research is worrying stuff, as, if species are unable to adapt to rising temperatures, local extinctions of animals will only become more frequent. So, unless we can find ways to reduce future warming, we can expect these declines to become much worse in future.

Source: Spooner, F.E.B. et al. (2018). Rapid warming is associated with population decline among terrestrial birds and mammals globally. Global Change Biology. 24(10): 4521-4531.

Far out! New data shows sharks are moving further than we thought

Connectivity of populations is of huge importance in both ecological and genetic terms. For a population to thrive, it is widely accepted that it needs a free exchange of individuals with neighbouring populations. Population mixing ensures that new genes arrive and allows for the dispersal of the population’s genome, as well as physically boosting numbers in the event of a natural disaster or disease epidemic. As populations become increasingly isolated, the potential for inbreeding (i.e. having offspring with close relatives) increases dramatically, and this contributes to the population being at risk of extinction. This is the reason there has been a big conservation drive from the likes of the British Hedgehog Preservation Society and RSPB to connect gardens by making small holes in fences, allowing access for hedgehogs, frogs, mice and non-flying insects.

An identification tag (green plastic) being inserted into the fin of a thornback ray (Raja clavata). These simple tags allow individuals to be monitored as part of catch-mark-release schemes. - Credit: C.V. Vick (CC BY-NC-ND 2.0)

We have several methods of assessing how well connected a population is: we can simply follow the animal or track its movements using field signs (droppings, footprints, etc.); we can look at population genetics, comparing the genes in our target population with those in neighbouring groups; we can mark (tag) individuals of the population and note when and where we see them again, which is how we learned where swallows go in the winter; or we can fit animals with small radio or GPS devices that allow us to track their movements in real time over long periods and, in the case of the latter, with unparalleled resolution. Each method has pros and cons, and some are more useful than others depending on the species in question. Sharks are a group that pose particular challenges for researchers.

Catch and release schemes are now common practice among anglers fishing for sharks. The first large scale tagging studies began in 1941, targeting dogfish in the strait of Georgia between Vancouver Island and the mainland coast of British Columbia. Researchers used Petersen disc tags, wired through the animal’s dorsal fin, to individually mark the animals before they were returned to the water. This method, albeit with a different type of tag, is still used today, although the advance of technology is allowing us a greater insight into patterns of movement and has revealed that sharks travel further than we thought.

The whale shark (Rhincodon typus) is the largest living shark species and new GPS data suggests they roam vast distances in our oceans, possibly using major currents as migration pathways between oceans. - Credit: Jon Hanson (CC BY-SA 2.0)

Whale sharks (Rhincodon typus) are the largest shark species on Earth and are well-known to undertake long journeys. Between 1994 and 1998, Scott Eckert and Brent Stewart tracked a 15m (49 ft.) long female in the Pacific Ocean, during which time she moved some 13,000km (8,077 miles) from the Sea of Cortez into the western north Pacific. Subsequently, in 2013, Bob Heuter and colleagues published details of a 7,200km (4,470 mile) journey, from the Caribbean to the Atlantic Ocean, undertaken by a 7.5m (25 ft.) female in only five months. A more recent dataset has dwarfed both these distances.

In September 2011, Hector Guzman and colleagues tagged three female whale sharks at Wahoo Rock in the Coiba National Park, off the Pacific coast of Panama, with satellite trackers. One of the sharks, named “Anne” by the researchers, travelled a record-breaking distance of just over 20,140 km (almost 14,000km straight-line distance) from Panama to the Marianas Trench. Reviewing their tracking data against that of the previous studies, Guzman and his co-workers note:

The tracks show a potential passageway via the NEC to reach the Philippine Sea and move into the South China Sea. The results also are consistent with recent genetic studies that suggest a single Indo-Pacific population that is separate from a second Atlantic population.

In other words, it looks like these sharks may use the North Equatorial Current as a corridor to migrate between the two ocean basins and as a route out into the South China Sea. Why does this matter, though? So what if animals move around a lot and migrate vast distances? Well, studies like this illustrate that we need a holistic approach when it comes to designing a conservation and management approach for species that cross geopolitical boundaries. Unfortunately, Guzman and his colleagues point out that protection and conservation measures for sharks in this area are mostly focused at local level, rather than across the Pacific. We need a more integrated approach.

Source: Guzman, H.M. et al. (2018). Longest recorded trans-Pacific migration of a whale shark (Rhincodon typus). Marine Biodiversity Records. 11: 8.

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