Scientists have demonstrated a new technique to non-invasively survey
tigers using their scent sprays, which are detected much more frequently
in the wild than scat--the 'breadcrumb' that researchers have
traditionally used to track the endangered animals. The findings show
that DNA taken from tiger spray is just as good or even better than scat
in identifying individual tigers and their gender, and have the
potential to increase the power of conservation surveys and management.
"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."
Despite intense conservation efforts, there are fewer than 3,200 tigers (Panthera tigris)
in the wild, living in less than seven percent 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. To combat this, the
Museum has been working with the global wild-cat conservation
organization Panthera to establish "genetic corridors" that allow tigers
to seek new territory for prey and new populations for breeding.
"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. So, to
boost the effectiveness of genetic monitoring of tigers in warm regions,
the research 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.
"We recently spent weeks looking for tiger scat in the field with
very little luck," said Rob Pickles, monitoring specialist for Panthera.
"Although this new spray technique wouldn't replace scat studies
entirely, we now know that we can use both methods in conjunction to
drastically increase our monitoring abilities."
The next step for the researchers is to test the technique in the
field, where it also could be used to monitor other scent-spraying
animals, like lions.
This Story is taken from Science Daily
