Quinn E. Fletcher

Measures of physiological stress: a transparent or opaque window into the status, management and conservation of species?

We discuss the methodological issues associated with measuring stress hormones in wild animals. We discuss five questions that we think should be considered about the use of stress hormone measurements in conservation physiology. We present a meta-analysis showing that human activities consistently increase stress hormone levels across vertebrates.

Telomeres shorten more slowly in slow-aging wild animals than in fast-aging ones

Research on the physiological causes of senescence aim to identify common physiological mechanisms that explain age-related declines in fitness across taxonomic groups. Telomeres are repetitive nucleotide sequences found on the ends of eukaryotic chromosomes. Past research indicates that telomere attrition is strongly correlated with inter-specific rates of aging, though these studies cannot distinguish whether telomere attrition is a cause or consequence of the aging process. We extend previous research on this topic by incorporating recent studies to test the hypothesis that telomeres shorten more slowly with age in slow-aging animals than in fast-aging ones. We assembled all studies that have quantified cross-sectional (i.e. between-individual) telomere rates of change (TROC) over the lifespans of wild animals. This included 22 estimates reflecting absolute TROC (TROCabs, bp/yr, primarily measured using the terminal restriction fragment length method), and 10 estimates reflecting relative TROC (TROCrel, relative telomere length/yr, measured using qPCR), from five classes (Aves, Mammalia, Bivalvia, Reptilia, and Actinopterygii). In 14 bird species, we correlated between-individual (i.e. cross-sectional) TROCabs estimates with both maximum lifespan and a phylogenetically-corrected principle component axis (pcPC1) that reflected the slow-fast axis of life-history variation. Bird species characterized by faster life-histories and shorter maximum lifespans had faster TROCabs. In nine studies, both between-individual and within-individual TROC estimates were available (n=8 for TROCabs, n=1 for TROCrel). Within-individual TROC estimates were generally greater than between-individual TROC estimates, which is indicative of selective disappearance of individuals with shorter telomeres. However, the difference between within- and between-individual TROC estimates was only significant in two out of nine studies. The relationship between within-individual TROCabs and maximum lifespan did not differ from the relationship of between-individual TROCabs and maximum lifespan. Overall, our results provide additional support for the hypothesis that TROC is correlated with inter-specific rates of aging and complement the intra-specific research that also find relationships between telomere attrition and components of fitness.

Roost Selection and Roosting Behavior of Male Common Nighthawks

Abstract Many studies to date have documented clear energetic costs and benefits of avian roost selection. Male Common Nighthawks (Chordeiles minor) spend at least half of each day during the summer on a day-roost. Therefore selection of roost-sites likely has implications for survival and long-term fitness. Our objective was to identify characteristics of day-roosts used by male Common Nighthawks in Cypress Hills Provincial Park, Saskatchewan, Canada. We measured features of roost trees and monitored behavior of roosting birds. Nighthawks preferred trees situated on north facing slopes surrounded by trees with significantly lower canopy height compared to randomly measured trees. Roost trees were taller than random trees and occurred in less dense patches of forest. Birds always roosted parallel to branches and adopted a motionless posture. There was a non-significant trend for birds to roost on branches facing east. Birds typically roosted in a direction pointing away from the sun and away from the roost tree trunk. Roost trees emerging from the canopy may provide landmarks for birds as they search for suitable day-roosts, whereas a low tree density surrounding roost trees likely reduces flight costs associated with maneuvering. Our results suggest that roosts chosen by male nighthawks may provide selective benefits in terms of microclimate, energetics and predator avoidance, but further studies are needed to determine which is the most important.

The impact of reproduction on the stress axis of free-living male northern red backed voles (Myodes rutilus).

Activation of the hypothalamic-pituitary-adrenal (HPA) axis culminates in the release of glucocorticoids (henceforth CORT), which have wide-reaching physiological effects. Three hypotheses potentially explain seasonal variation in CORT. The enabling hypothesis predicts that reproductive season CORT exceeds post-reproductive season CORT because CORT enables reproductive investment. The inhibitory hypothesis predicts the opposite because CORT can negatively affect reproductive function. The costs of reproduction hypothesis predicts that HPA axis condition declines over and following the reproductive season. We tested these hypotheses in wild male red-backed voles (Myodes rutilus) during the reproductive and post-reproductive seasons. We quantified CORT levels in response to restraint stress tests consisting of three blood samples (initial, stress-induced, and recovery). Mineralocorticoid (MR) and glucocorticoid (GR) receptor mRNA levels in the brain were also quantified over the reproductive season. Total CORT (tCORT) in the initial and stress-induced samples were greater in the post-reproductive than in the reproductive season, which supported the inhibitory hypothesis. Conversely, free CORT (fCORT) did not differ between the reproductive and post-reproductive seasons, which was counter to both the enabling and inhibitory hypotheses. Evidence for HPA axis condition decline in CORT as well as GR and MR mRNA over the reproductive season (i.e. costs of reproduction hypothesis) was mixed. Moreover, all of the parameters that showed signs of declining condition over the reproductive season did not also show signs of declining condition over the post-reproductive season suggesting that the costs resulting from reproductive investment had subsided. In conclusion, our results suggest that different aspects of the HPA axis respond differently to seasonal changes and reproductive investment.

A New Species of Chigger Mite (Acari: Trombiculidae) from Rodents in Southwest China

This paper describes a new species of chigger mite (Acari: Trombiculidae), Gahrliepia cangshanensis n. sp., from rodents in southwest China. The specimens were collected from Yunnan red-backed voles, Eothenomys miletus (Thomas, 1914), and a Chinese white-bellied rat, Niviventer confucianus (Milne-Edwards, 1871) in Yunnan Province. The new species is unique mainly in its number of dorsal setae (n=21), and it has the following features: fT (formula of palpotarsus)=4B (B=branched), fp (formula of palpal seta)=B/N/N/N/B (N=naked), a broad tongue-shaped scutum with an almost straight posterior margin, and 17 PPLs (posterior posterolateral seta) with a length of 36-43 µm. This chigger mite may also infect other rodent hosts and may be distributed in other localities.

Aging in the wild: Insights from free-living and non-model organisms

Aging ismost commonly defined as a decrease in physiological function that leads to an age-related decrease in fitness. The manifestations of aging are apparent at all phenotypic levels, from declining performance at the level of the whole animal, all the way down to ageassociated damage to, and dysfunction in, individual cells, organelles and molecules. Unfortunately, most of us are only too well versed on the effects of aging. Similarly, we are all acutely aware that the worlds population comprises an ever higher proportion of elderly individuals, with age being the primary risk factor for a number of pathologies that significantly affect late-life health and well-being. As a result, understandingwhywe age, and howwe age, is amajor research challenge in science.Muchofwhatwe knowabout the biological processes underlying aginghas been obtained from studies of ‘model’ organisms, such as Caenorhabditis elegans, Drosophila melanogaster and laboratory mice; animals that are easily maintained under standard laboratory conditions, relatively short-lived, genetically homogenous and have genomes amenable to manipulation. Using model organisms in biogerontology has undeniably generated critical insights into the aging process. We now know that many aging phenotypes and aging-relevant genetic pathways are conserved across wide evolutionary distances, and that both aging and late-life health can be extended through a number of dietary, genetic and pharmacological interventions (Vijg and Campisi, 2008; Gems and Partridge, 2013; Selman, 2014). However, and as detailed elsewhere (e.g. Monaghan et al., 2009; Austad, 2010b; Selman et al., 2012), limiting aging research to model organisms may cause us to miss important factors that help explain how and why we age. A second, complimentary, approach to understanding how andwhy we age is through studying aging in free-living animals and non-model organisms (Austad, 2010a,2010b; Nussey et al., 2013; Roach and Carey, 2014). This approach is gaining significantmomentum and there is now a large body of empirical evidence that clearly demonstrates that animals in the wild experience aging (Bronikowski and Promislow, 2005; Nussey et al., 2013; Roach and Carey, 2014). While a large proportion of free-living individuals within a population is likely to succumb to the various challenges of living in the wild long before they exhibit clearmanifestations of aging,many studies have now shown that reproductive performance, aspects of physiological and cellular function, and survival probability all decrease with advancing age free-living animals (for detailed reviews seeNussey et al., 2013; Roach and Carey, 2014; but see also Jones et al., 2014). Similarly, studies using comparative approaches and non-classical model organisms have already, and will continue, to provide important insights into the aging process

Independence between coping style and stress reactivity in plateau pika

The concept of coping style represents the way individual animals react to a stressful situation, both behaviourally and neurophysiologically. Over the last decades coping style has been linked to the development of research on animal personality. Based on this concept, we should find a proactive-reactive continuum in animal populations, with proactive individuals being fast explorer, bold, aggressive, and show high sympathetic reactivity (higher heart rate), as well as low hypothalamus-pituitary-adrenocortical (PHA) axis reactivity to external stressor (higher plasma glucocorticoid level). At the other extreme, shy, lowly aggressive, reactive individuals should be slow in their exploration, and show a low sympathetic reactivity and a high HPA axis reactivity. However, a recent two-tier model proposed that coping style and stress reactivity should be independent of each other. In this study, we tested the two-tier model in a wild plateau pika (Ochotona curzoniae) population on the Tibetan Plateau, by quantifying the associations between several behavioural and physiological traits at the among- and within-individual levels. We repeatedly measured exploration, docility, boldness, heart rate and plasma cortisol concentration in individuals between April and September of 2013. All traits tested were repeatable. At the among-individual level, all behavioural traits were correlated with each other and with heart rate, but were independent of both basal level and variation of plasma cortisol concentration. Most correlations were negligible at the within-individual level. In support of the two-tier model, these results suggest that coping style (i.e. behaviour and heart rate associations) is independent of stress reactivity (i.e. glucocorticoid reactivity) in that species.

Viral Richness is Positively Related to Group Size, but Not Mating System, in Bats

AbstractCharacterizing host traits that influence viral richness and diversification is important for understanding wildlife pathogens affecting conservation and/or human health. Behaviors that affect contact rates among hosts could be important for viral diversification because more frequent intra- and inter-specific contacts among hosts should increase the potential for viral diversification within host populations. We used published data on bats to test the contact-rate hypothesis. We predicted that species forming large conspecific groups, that share their range with more heterospecifics (i.e., sympatry), and with mating systems characterized by high contact rates (polygynandry: multi-male/multi-female), would host higher viral richness than species with small group sizes, lower sympatry, or low contact-rate mating systems (polygyny: single male/multi-female). Consistent with our hypothesis and previous research, viral richness was positively correlated with conspecific group size although the relationship plateaued at group sizes of approximately several hundred thousand bats. This pattern supports epidemiological theory that, up to a point, larger groups have higher contact rates, greater likelihood of acquiring and transmitting viruses, and ultimately greater potential for viral diversification. However, contrary to our hypothesis, there was no effect of sympatry on viral richness and no difference in viral richness between mating systems. We also found no residual effect of host phylogeny on viral richness, suggesting that closely related species do not necessarily host similar numbers of viruses. Our results support the contact-rate hypothesis that intra-specific viral transmission can enhance viral diversification within species and highlight the influence of host group size on the potential of viruses to propagate within host populations.