Meeting Abstract
P1.16 Monday, Jan. 4 The Prudent Parent Meets Old Age: Senescence in Thick-billed Murres ELLIOTT, KH*; GASTON, AJ; U. Manitoba; Env. Can. urialomvia@gmail.com
The “rate of living” theory suggests a tradeoff between metabolism and survival. It is supported by inverse correlations between metabolic rate and survival rates, however charadriiform seabirds are exceptional in having long life spans despite high sustained metabolic rates. To investigate the tradeoff between metabolic rate and survival in a long-lived charadriiform seabird, the Thick-billed Murre, we monitored foraging behaviour, reproductive success, survival, metabolic rate, and corticosterone levels. Reproductive success increased with age between 7-11 y before leveling off, with experience being a better predictor of reproductive success than age during the first 12 y. Reproductive success was lower during the final year of life compared to previous years, suggesting that death may be related to health effects evident in the last year of life. In support, baseline corticosterone levels were elevated for birds 17+ years old. Hematocrit and metabolic rate appeared to decrease linearly with age, perhaps as a strategic adjustment to reduce blood viscosity and forestall potentially effects of high blood pressure on the vascular system in old age. When foraging conditions were experimentally worsened, time spent at the colony increased with age, with 33% of the youngest adults abandoning their chicks, and corticosterone response levels to handling were higher in younger experimental birds. Although foraging ability and dive efficiency was independent of age, older birds appear to be more willing to sacrifice future reproductive success for current offspring leading to an increase in reproductive success with age, although this may also be related to experience occupying a cliff breeding site. Meanwhile, the increase in baseline corticosterone levels, lower metabolism, lower reproductive success and lower apparent survival for birds over 20 years old suggest that murres show signs of deteriorating health when they are 20-25 years old.
