DNA-based approach to aging martens (Martes americanaandM. caurina)

Abstract

Demographic structure is central to understanding the dynamics of animal populations. However, determining the age of free-ranging mammals is difficult, and currently impossible when sampling with noninvasive, genetic-based approaches. We present a method to estimate age class by combining measures of telomere lengths with other biologically meaningful covariates in a Bayesian network. We applied this approach to American and Pacific martens (Martes americana and M. caurina) and compared predicted age with that obtained from counts of cementum annuli. Using telomere length and the covariates sex, species, and estimates of population density obtained from commercial trapping records, we assigned martens to juvenile (,1 year) or adult (1 year) classes with 75-88% accuracy. In our analysis for live-captured martens, for which information on body size and whether animals were juveniles or adults would be available, we achieved 90-93% accuracy when assigning individuals to 5 discrete age classes (0-4+ years). This general approach could be extended to other species for noninvasive estimation of age class, or in place of invasive aging methods, and enable demographically based population analyses that have heretofore been impossible. Aging, or senescence, is the result of processes that are progressive, irreversible, and unavoidable. Although the exact physiologic and evolutionary mechanisms underlying senescence remain unclear (Williams 1999), the impacts of aging on individual fitness are well understood. Age alters an individual's physiological state and ability to respond to environmental conditions; aging reduces cognitive ability, physical stamina (MacNulty et al. 2009), and immunocompetence (Clark 2004). Because population growth is a function of age-specific fecundity and survival, accounting for age structure of sampled populations is essential. However, determining the age of free-ranging mammals is difficult. Traditionally, field biologists have used several approaches to approximate the age of animals: weighing eye lenses, measuring skeletal and cranial characteristics, and counting cementum annuli of teeth (Schroeder and Robb 2005). Although useful, these techniques are highly invasive, some requiring the sacrifice of animals, which is particularly problematic when studying threatened or endangered species.Further, such traditional approaches are unviable for the growing number of biologists using noninvasive sampling on the basis of deoxyribonucleic acid (DNA) analyses of fur, feather, skin, or scat samples. Lacking an aging technique, noninvasive studies thus far have been limited by the inability to quantify age-specific fecundity, survival or dispersal, or demographic structure.Biomedical scientists have identified a relationship between the length of telomeres-repetitive, highly conserved DNA sequences ([T 2 AG 3 ] n ) that cap the ends of eukaryotic chromosomes-and senescent processes in individuals (Frenck et al. 1998). Past work indicates that telomeres can be useful not only in understanding sene...

Estimating cougar densities in northeast Oregon using conservation detection dogs

“…Age determination would result in more accurate density estimates and the ability to identify population size of independently aged animals. Similar work in aging animals based on DNA telomere length has been done with American and Pacific martens (Martes americana and M. caurina; Pauli et al 2011). Given the small study area size relative to a cougar's home range, transients were likely available for capture.…”

Telomere length is a strong predictor of foraging behavior in a long‐lived seabird

“…Telomere degradation occurs when cells divide, and loss rates are accelerated by DNA damage, especially oxidative damage (von Zgli-nicki 2002, Monaghan 2014. Traditionally, telomeres are associated with the biology of aging (Holmes andMartin 2009, Dunshea et al 2011) and have been shown to shorten with age in many species (Haussmann and Vleck 2002, Haussmann et al 2003, Pauli et al 2011, Mü ezzinler et al 2013, but see (Francis et al 2006). However, in long-lived birds a large telomere loss with chronological age is not the norm (Hall et al 2004, Foote et al 2011.…”

Remote biopsy darting and marking of polar bears

“…Remotely collected genetic information has been used in other animals to examine population structure and movements (Baker et al 1993, Witteveen et al 2009), examine genetic diversity (Schmidt et al 2009), determine sex ratios (Curtis et al 2007), and estimate abundance (Palsbøll et al 1997, Woods et al 1999. Other studies have used remote biopsy darts to collect tissues to test for contaminants (Ross et al 2000, Wiig et al 2000, conduct stable isotope and fatty acid analyses (Hooker et al 2001, Witteveen et al 2009), and estimate individual ages (Herman et al 2008(Herman et al , 2009Pauli et al 2011).…”