December 2015 While the Bovey Valley’s barbastelle bats are well into hibernation, the study of this rare species carries on in the laboratories of the University of Bristol. One morning in December, some of the bat tracking volunteers assembled in the Life Sciences building to find out how the information gathered in Devon during the summer was being analysed.
Having now recovered from the semi-nocturnal part of the study, Andy Carr explained how his PhD was continuing and what had been discovered so far. Having found 12 roost trees in the Bovey Valley he had been transferring radio tracking data onto maps to locate the actual positions of the bats in flight. This stage showed clearly that the foraging activity was focussed on the edges of broadleaved woodlands and hedgerows, generally between Becky Falls and Chudleigh Knighton Heath, but sometimes further.
Having charted their routes and the range of foraging flights, Andy needed to know more about the actual diet of the bats. There are two ways to do this; the long established one being a morphological analysis of droppings. This is done with a microscope to study the fragments of undigested prey left in the dry droppings of bats. From this, the basic proportions of prey type can be recorded but with one catch, the accuracy of identification is limited to the “order” of the invertebrate prey and cannot detect the actual species. The main prey of barbastelles is generally known to be the order of Lepidoptera (moths) with a smaller proportion of Diptera (flies) but other species of bat are found to consume Neuroptera (including lacewings) and Coleoptera (beetles).
The University of Bristol is a world leader in this research and Dr Matt Zeale was on hand to explain how the DNA barcoding technology is being used. Within each living cell the mitochondria contains an individual DNA pattern which can be compared with animals of all other species. There is a reference library of the DNA sequences of many species around the world, but to extract this information from fragments of insects that have been degraded in the digestive system of a bat is a problem. Barcoding processes have been developed to overcome this and are capable of using shorter sequences of DNA.
Andy and Matt also explained the process of PCR (polymerase chain reaction) where a small sample of extracted DNA can be replicated, or grown to increase its size. This is cutting edge science and has the effect of unzipping DNA before replicating them and zipping them up again in a precisely controlled heated environment. One of the benefits of this method has been to understand the precise diet of barbastelles. It was previously believed that they preyed on micro-moths but Matt’s earlier work showed that, in fact, they feed on many larger species and, to confirm this, many of those species were trapped in the Bovey Valley during the study. Some of these larger moths have hearing organs which is why the barbastelle is a quiet echolocator – the evolutionary arms race in action!
The conversation continued in one of many open-plan break-out rooms of the brand new university building. The shafts of sunlight on the architectural steel and sparkling glass surfaces were a long way from the wild night time woods of Devon, as is the technology that has become a significant part of this project and continues to develop at a fast pace. DNA barcoding is a more accurate method to find out exactly which species of moths the barbastelles have been consuming in the Bovey Valley and this would be used to analyse the bats’ diets. Andy aimed to answer questions such as “does the diet of a bat change when it experiences additional energy demands during pregnancy or when raising young?”
Later in the day the volunteers had a chance to learn laboratory techniques to analyse the droppings of a greater horseshoe bat. These samples were taken from a colony at Woodchester Mansion in Gloucestershire where the bats have been studied for well over 50 years, a world record for any mammal. Droppings were hydrated and broken apart before using microscopes to study their contents. This is the less advanced, but widely used, method known as morphological analysis and the volunteers quickly got to grips with the techniques.
It soon became clear that a whole dropping was entirely made up of dry insect fragments including wings, legs, whiskers, scales, eggs, antennae and even compound eyes. Once the volunteers’ eyes began to tune in they quickly differentiated between beetle and fly and identified the moth scales and other defining fragments. While studying different samples, the month to month changes in diet were also clear depending on the availability of prey through the foraging period of the year.
Before the end of the day Andy gave the volunteers an opportunity to visit the laboratories where the actual DNA barcoding work is going on. He explained that he would be practising his technique on some greater horseshoe bat droppings before attempting to extract the DNA from the “precious” and rare barbastelle droppings. This had been a precious and rare treat for the volunteers who went home happy, eagerly awaiting Andy’s final PhD report.
Words and images for the Barbastelle Tracking Diary are by Matt Parkins
The Bovey Valley barbastelle tracking project is managed by the Moor than meets the eye Landscape Partnership comprising Dartmoor National Park Authority, the Woodland Trust and Natural England.