Tigers' scent spray may be better way to track them

Scientists have demonstrated a new technique to non-invasively survey tigers using their scent sprays that can be detected much more frequently in the wild than scat.
The findings show that DNA taken from tiger spray is just as good or even better than scat DNA in identifying individual tigers and their gender, and have the potential to increase the power of conservation surveys and management.
It is the first time a technique has been developed specifically for the use of sprays in genetic analysis, researchers said.
"Genetic monitoring of tiger source populations is a conservation priority," said Anthony Caragiulo, a postdoctoral researcher in the American Museum of Natural History's Sackler Institute for Comparative Genomics.

"The utility of this new method is really impactful because it will let us dramatically build upon the number of tigers that can be surveyed and, consequently, increase our understanding of these elusive animals - hopefully before they are gone," said Caragiulo.
Despite intense conservation efforts, there are fewer than 3,200 tigers (Panthera tigris) in the wild, living in less than seven per cent of their historical range.

When a population is confined to small islands of wilderness, as are tigers, there is a higher risk of inbreeding and loss of genetic diversity, leaving the species with weaker young.
"Tracking" individual cats using genetic markers lets researchers map movement within and between populations.

Genetic tracking has traditionally relied on extracting DNA from scat collected in the wild. But in humid, tropical landscapes - like those in Sumatra, where a number of tigers live - scat often degrades before researchers can find it.
Scent sprays left by tigers on trees and overhanging leaves degrade less quickly, and can be detected by researchers between two and eight times as frequently as scat.
To boost the effectiveness of genetic monitoring of tigers in warm regions, the team questioned whether DNA could be extracted from sprays.
The researchers collected spray samples from three captive tigers in Ontario with cotton swabs that were then stored in tubes of buffer to help preserve the DNA.

Tiger spray is a combination of anal gland secretions - said, surprisingly, to have a floral scent like citrus - and urine, which contains DNA in the form of cells from the urethra.
The researchers were able to amplify microsatellite loci, which are noncoding DNA sequences with unique numbers of repeated nucleotides providing enough information to "fingerprint" individual tigers, and portions of the sex chromosome to determine whether they are male or female.
The finding was published in the journal Conservation Genetics Resources.