Dr. Arati Iyengar is from the School of Forensic & Applied Sciences at the University of Central Lancashire (UCLan), who have recently developed a forensic DNA kit, SkydancerPlex, which allows individual hen harriers to be identified from tiny samples of blood or feathers. To celebrate this research, UCLan have sponsored one of this year’s satellite-tagged hen harriers, Hermione, who was named via an online poll.
What is the SkydancerPlex?
This exciting new development is an extremely accurate DNA based identification kit for hen harriers. In humans, DNA is routinely used to match an evidence sample collected from a crime scene to a sample from a suspect, thus linking the suspect to the crime scene. In wildlife species, there are very few DNA based identification kits, particularly ones which have been tested to the rigorous standards needed for forensic casework. The SkydancerPlex is the first such kit, making it a real step forward in the fight against wildlife crime.
Hermione, the young female hen harrier from Mull, named by UCLan, and satellite tagged by RSPB's Hen Harrier LIFE Project. Photo: Paul Haworth
How was it created?
Unlike in the case of human DNA where extensive information is available, there was nothing at all available for the hen harrier when we started. It’s one thing to distinguish hen harrier DNA from that of other species but identifying individual hen harriers was a much bigger challenge.
To do this, we needed to look at areas of DNA called short tandem repeats (STRs). These are where short stretches of DNA are repeated and it’s that pattern of repetition which is different among individuals, like genetic fingerprints. The more of these STRs you analyse, the more accurate the identification.
After much hard work from a research intern and some MSc students, we selected 8 STRs along with another section of DNA to tell us the sex the bird. These were then all combined into a single identification kit, or an a STR multiplex. Hence the name 'SkydancerPlex'.
How does the SkydancerPlex work?
By focusing on these specific areas of hen harrier DNA and simultaneously analysing several such areas, we can create a DNA profile for each bird using very small samples of biological material. Here's one we made earlier:
What you see as coloured peaks are called alleles. An individual has 2 alleles at each STR region. Here we can tell that this bird is female since there are two peaks in the sexing region (see middle panel in area between HH11-G7 and 22316 where two peaks are visible). This tells us that there are Z and W chromosomes as opposed to only Z chromosomes found in males.
If two DNA samples (e.g. a sample taken from shot bird and one obtained from a suspect) have the same alleles across all STRs, what you have is a ‘match’. Of course, without DNA from every single hen harrier out there you can never be 100 % certain that a DNA profile is from a particular hen harrier. So instead, what we do is to calculate the probability of the DNA profile being present in a random unrelated individual in the population. The smaller this probability, the more likely it is that the sample came from the individual concerned. By calculating the frequency of the various alleles within the hen harrier population you can then calculate the probability of this match.
Using the Skydancerplex, the probability of matching a DNA profile to the wrong bird can be as small as 1 in 188 million. So if a DNA sample had been recovered as evidence and matched to a suspect, it would be hugely powerful evidence against him indeed.
What next?
The development of the SkydancerPlex is certainly not the end of our interest in hen harriers. It is very much the beginning of more exciting projects. What we really want to do next is use the SkydancerPlex to understand the population dynamics of hen harriers from across the UK and Europe. Analysing DNA from hen harriers from across this range will tell us about their movements and breeding patterns which is vital information to inform future conservation efforts.
Find out more about UCLan's exciting research by visiting their website here and can download the abstract from their published research paper here. From the end of this summer, you can follow Hermione's movements on the Hen Harrier LIFE Project website at rspb.org.uk/henharrierlife.