Stools of the trade

Developments in genetics have made DNA a cost-effective and efficient tool in studying wildlife. Poo is a valuable commodity, writes ANTHONY KING

In India, waste, or “scat”, is brought to the lab, and tigers can be identified through their DNA “fingerprints”, as they can be in forensics. “This way of obtaining information on specific individuals is far less expensive and time-consuming than, say, capturing or recapturing marked individual tigers,” according to US wildlife biologist James Nichols. It’s also safer.

Ten years ago it cost millions of dollars to sequence the DNA of a single individual; today scientists are working towards the $1,000 genome. The gains mean it is now efficient and cost-effective to use DNA to study wildlife.

Irish scientists are ahead of the posse in this regard. An all-Ireland census of pine martens is published in the journal Mammalian Biology this month. The count for this rarely seen carnivore relied on a scat survey and on DNA analyses.

Ecologist Dr Declan O’Mahony reports an estimated population of 2,700 pine martens in the Republic and 300 in Northern Ireland. “It is probably our rarest terrestrial mammal,” says O’Mahony, who adds that the official figures for the Republic of 3,000-10,000 individuals can now be considered unrealistic.

The pine martens’ “favourable conservation” status should be revisited, he says, given the results, and a conservation plan put in place. They are very susceptible to human persecution and are slow to breed, he adds, and common in just half the country.

The geneticist Dr Catherine O’Reilly of the molecular ecology group at Waterford Institute of Technology developed the technique to identify pine martens through scats by looking at a small piece of DNA from the mitochondria, a structure inside cells.

She can also sex them by looking at differences on the X and Y chromosome using a technique called real-time PCR. “With scat, you isolate pine marten DNA from the epithelial cells that are flushed off the gut,” she says.

Trapping mammals can be difficult and time consuming, so O’Reilly has developed DNA tests for otters, foxes and small mammals such as shrews and mice. Last month a volunteer reconnaissance of churches returned bat droppings to her lab. This will allow the resident species to be identified without any disturbance or stress to the animals themselves.

O’Reilly says there are currently 10 pine martens in Portlaw Forest in Waterford. Most people who walk in the woods would be amazed that pine martens are about, she says, and she rarely sees them. “Pine martens love blackberries. At this time of year you will find purple scats all over the place.”

The small mammals that pine martens eat also turn up in their scat, and O’Reilly recently used molecular techniques to identify this prey. She also studies otters and other mammals as part of the Mise project ( miseproject.ie).