Life Sciences Commons^™

Telomeres And Longevity: Testing An Evolutionary Hypothesis, Robert Mauck

Robert Mauck

Identifying mechanisms that underlie variation in adult survivorship provide insight into the evolution of life history strategies and phenotypic variation in longevity. There is accumulating evidence that shortening telomeres, the protective caps at the ends of chromosomes, play an important role in individual variation in longevity. Given that telomeres generally shorten with age, it was surprising to find that in a population of a long-lived seabird, Leach's storm petrel, telomeres appear to lengthen with age. This unique finding suggested that the longest lived individuals are able to elongate telomeres, an interpretation we call the “elongation hypothesis.” Alternatively, the “selection hypothesis” …

Physiological And Behavioural Correlates Of Life-History Variation: A Comparison Between Tropical And Temperate Zone House Wrens, Robert Mauck

Robert Mauck

Summary

• 1 We studied physiological, behavioural and demographic traits of House Wrens (Troglodytes aedon) in tropical Panama and temperate zone Ohio to explore the hypothesis that tropical birds with higher adult survival rates invest less in annual reproduction than their temperate zone counterparts.
• 2 Compared with wrens from Ohio, Panamanian wrens invested fewer resources in a given reproductive episode, as quantified by lower parental field metabolic rate (FMR) and water influx rate (WIR), a smaller number of feeding trips to the nest, and fewer chicks per brood.
• 3 Whole organism FMR and WIR were only 13–15% lower in …

Changes In Plasma Hormone Levels Correlate With Fledging In Nestling Leach’S Storm-Petrels, Robert Mauck

Robert Mauck

Leach’s storm-petrels accumulate large amounts of body mass throughout the nestling period. Approximately 4 days before fledging, nestlings weigh 50–100% more than adults. In order to shed this excess mass, nestlings engage in behavioral anorexia, and leave the burrow when they are light enough to fly. During this prefledging period, we measured several plasma hormones (corticosterone, thyroxine, andtestosterone) to determine whether the behavioral changes associated with fledging are correlated withendocrine changes. In several species, including petrels, corticosterone levels are known to increase near fledging. Reduced food consumption has been shown to elevate corticosterone levels and …

Incubation Failure And Nest Abandonment By Leach's Storm‐Petrels Detected Using Pit Tags And Temperature Loggers, Robert Mauck

Robert Mauck

The nocturnal activity of burrow-nesting seabirds, such as storm-petrels and shearwaters, makes it difficult to study their incubation behavior. In particular, little is known about possible differences in the incubation behavior of adults at successful and unsuccessful nests. We combined the use of passive integrated transponder (PIT) technology and nest-temperature data loggers to monitor the incubation behavior of 10 pairs of Leach's Storm-Petrels (Oceanodroma leucorhoa). The mean incubation bout length was 3.31 +/- 0.59 (SD) days for individual adults at successful nests (N = 4) and 1.84 +/- 1.16 d for individuals at unsuccessful nests (N = 6). Mean bout …

Increase In The Constitutive Innate Humoral Immune System In Leach's Storm-Petrel (Oceanodroma Leucorhoa) Chicks Is Negatively Correlated With Growth Rate, Robert Mauck

Robert Mauck

1 Using a simple technique for assessing constitutive innate immune function recently adapted for use in wild populations, we characterize changes in avian immune system development by repeated measurements of individuals over the period of nestling growth in a wild population of Leach's Storm-Petrels (Oceanodroma leucorhoa). 2 We measured levels of natural antibodies (NAb) during the early, middle and late phases of storm-petrel development and related these levels and NAb rate of change to mass and wing length growth. We used natural variation in nestling growth to assess the influence of nutritional status on the development of innate immunity. 3 …

Asymmetrical Incest Avoidance In The Choice Of Social And Genetic Mates, Robert Mauck

Robert Mauck

Mating with close relatives generally results in reduced reproductive success (inbreeding depression) because it increases the risk that rare deleterious recessive alleles will be expressed in offspring. None the less, incest may occur when animals have incomplete knowledge about relatedness or when the costs of avoiding inbreeding are high. Over a 17-year period, Savannah sparrows, Passerculus sandwichensis, in an island population rarely paired incestuously (9 of 1110 pairs, 15 of 1609 nesting attempts). All but one case of close inbreeding (coefficient of inbreeding, F ≥ 0.25) involved 1-year-old males breeding for the first time, whereas more than half of …

Experience Versus Effort: What Explains Dynamic Heterogeneity With Respect To Age?, Robert Mauck

Robert Mauck

Age-related patterns of survival and reproduction have been explained by accumulated experience (‘experience hypothesis’), increased effort (‘effort hypothesis’), and intrinsic differences in phenotypes (‘selection hypothesis’). We examined the experience and effort hypotheses using a 40-year data set in a population of Leach's storm-petrels Oceanodroma leucorhoa, long-lived seabirds for which the effect of phenotypic variation has been previously demonstrated. Age was quantified by time since recruitment (‘breeding age’). The best model of adult survival included a positive effect of breeding age (1, 2, 3+ years), sex (male > female), and year. Among-individuals variation (fixed heterogeneity) accounted for 31.6% of the variance in …