Wild chimpanzee infant urine and saliva sampled noninvasively usable for DNA analyses

In many genetic studies on the great apes, fecal or hair samples have been used as sources of DNA. However, feces and hairs are difficult to collect from chimpanzee infants under 3 years of age. As alternative DNA sources, we investigated the efficiency of collecting urine samples from infants compared with fecal samples, as well as the validity of the DNA extracted from urine and saliva samples of well-habituated M group chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania. We collected 40 urine and 3 fecal samples from 10 infants under 3 years. Compared with feces, the urine samples were relatively easy to collect. The saliva of infants, which remained on the twigs sucked by them, was collected using cotton swabs. The average amounts of DNA extracted from the 40 urine and 6 saliva samples were 3,920 and 458 pg/mul, respectively. The rate of positive PCR was low and the allelic dropout rate was high when using less than 25 pg of template DNA in the PCR mixtures. Based on the amounts of DNA, 50% of the urine samples and 100% of the saliva samples were judged usable for accurate microsatellite genotyping. For infant chimpanzees in particular, collecting urine and saliva as an alternative to fecal and hair samples can reduce the effort invested in collection in the field.