1 Tahrcountry Musings: Otter fecal genotyping studies and population estimation – Guidance for wildlife managers

Monday, October 10, 2011

Otter fecal genotyping studies and population estimation – Guidance for wildlife managers

The first river otter reintroductions in US occurred in Missouri and it is regarded as one of the most successful carnivore recovery programs in history.

The sticking point is that abundance estimates for river otter populations are difficult.  Here the researchers assessed the value of latrine site monitoring as a mechanism for quantifying river otter abundance. Analyses of fecal DNA to identify individual animals were tried.

The researchers say they optimized laboratory protocols, redesigned existing microsatellite primers, and calculated genotyping error rates to enhance genotyping success for a large quantity of river otter scat samples. The also developed a method for molecular sexing.

As a next step the researcher extracted DNA from 1,421 scat samples and anal sac secretions (anal jelly) collected during latrine site counts along 22–34-km stretches. These stretches represented 8–77% of 8 rivers in southern Missouri.

Error rates were low for the redesigned microsatellites. They obtained genotypes at 7–10 microsatellite loci for 24% of samples, observing highest success for anal jelly samples (71%) and lowest for fresh samples (collected within 1 day of defecation)

The team identified 63 otters (41 M, 22 F) in the 8 rivers, ranging from 2 to 14 otters per river. Analyses using program CAPWIRE resulted in population estimates similar to the minimum genotyping estimate. Density estimates averaged 0.24 otters/km.

The researchers used linear regression to develop and contrast models predicting population size based on latrine site and scat count indices, which are easily collected in the field. Population size was best predicted by a combination of scats per latrine and latrines per kilometer.

 The researchers contend that their results provide methodological approaches to guide wildlife managers seeking to initiate similar river otter fecal genotyping studies, as well as to estimate and monitor river otter population sizes.

Journal reference 

River Otter Population Size Estimations using Noninvasive Latrine Surveys

 Rebecca A. Mowry, Matthew E. Gompper, Jeff Beringer, Lori S. Eggert
pg(s) 1625–1636 Journal of Wildlife Management Volume 75 Issue 7

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