On a wild dog chase

Scientists from Wildlife Conservation Society–India, National Centre for Biological Sciences, Kerala Veterinary and Animal Sciences University, University of Florida and Stanford University have estimated the number of dholes in Wayanad Wildlife Sanctuary in Kerala using genetic methods.

The study found that Wayanad has 12–14 per 100 sq km, with around 50 individuals estimated within the sanctuary’s administrative boundary. Dr Arjun Srivathsa, the lead author of the study, said, “This is relatively high density for a large carnivore.”

The International Union for Conservation of Nature places them in the “Endangered” Category because experts believe there may be approximately 10,000 dholes left globally, of which 1,000-2,000 are adults. According to co-author Prof Uma Ramakrishnan, “For species like dholes that do not have individual markings, genetic methods are the only way we can get statistically robust estimates of population size.”

The scientists conducted field surveys across 350 sq km of Wayanad Wildlife Sanctuary (Kerala, India) to collect dhole scats (faecal droppings) in 2019. They extracted DNA from the scats and used a novel approach involving Single Nucleotide Polymorphisms (SNPs) to identify unique dhole individuals. Uma said they sequenced whole genomes from three dholes (two individuals from the zoo and one from the Western Ghats) and added data from two additional dhole genomes that were already online. The scientists then identified positions in the genome that differed between these individuals. These single base pair changes or SNPs were then collated. They picked the ones that contained information and worked experimentally, and then picked a set of SNPs that could be used for individual identification.

Finally, they designed experiments that would read 150 of these SNPs. Combining this with sophisticated statistical methods called Spatial Capture-Recapture models, the researchers were able to estimate and map dhole numbers and density across the sanctuary. Uma said, “We have used a similar approach for tigers and have been using it extensively. We are in the process of developing similar approaches for elephants as well.”